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AUTOCLAVED AERATED CONCRETE (AAC): AN
ALTERNATIVE SUSTAINABLE CONSTRUCTION
MATERIAL
BY
DELE ROGER SIMEON
MATRIC NO: 100504043
A THESIS SUBMITTED TO THE SCHOOL PF
POSTGRADUATE STUDIES, UNIVERSITY OF LAGOS IN
PARTIAL FUFILMENT OF THE REQUIREMENTS FOR THE
AWARD OF THE DEGREE OF MASTER OF SCIENCE (M.Sc.)
IN CONSTRUCTION TECHNOLOGY
JULY, 2021
ii
CERTIFICATION
This is to certify that Simeon Dele Roger with the matriculation number 100504043 of the
Department of Building, Faculty of Environmental sciences, University of Lagos, carried out this
project to the best of its standard.
………………………………… ……………………………
Student’s name Date
Dele Roger SIMEON
………………………………… …………………………….
Project Supervisor Date
Dr. O.J. OLADIRAN
………………………………… ……………………………
Head of Department Date
Dr. O.J. AMEH
iii
DEDICATION
I dedicate this project to God most high, the owner of my soul and the creator of the universe.
iv
ACKNOWLEDGEMENTS
I would like to express my sincere gratitude to God Almighty for His guidance and mercies
throughout the period of this project.
I acknowledge with enormous gratitude the inspiration, encouragement, valuable time and
guidance given by my project supervisor, Dr. O.J. Oladiran.
I highly recognize the contributions of Prof. E.E. Ikponmwosa of Civil & Environmental
Engineering department and Prof. O.A. Adenuga of Building department for his moral supports
and encouragements. I equally appreciate Dr. A.A. Soyingbe for sharing some of the study’s
materials with me and for his continuous mentorship throughout the preparation of this study, my
gratitude equally goes to my supporting wife (Mrs. Celestina) and my lovely daughter (Vera) for
their understanding and cooperation throughout the preparation of this master thesis.
Many thanks to my colleagues of Construction Technology in the department of Building who
have contributed immensely to the success of this project. How can I forget my ever active HOD,
Dr. O.J. Ameh (Associate Professor) for his fatherly advice, supports and words of
encouragements.
May God Almighty bless you all (Amen).
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TABLE OF CONTENTS
TITLE PAGE ............................................................................................................... ………. .i
CERTIFICATION………………………………………………………………………………. .ii
DEDICATION…………………………………………………………………………………... iii
ACKNOWLEDGEMENTS……………………………………………………………………. iv
TABLE OF CONTENTS ................................................................................................ ………v-ix
LIST OF TABLES……………………………………………………………………………..x-xi
LIST OF FIGURES……..……………………………………………………………………….xii
LIST OF ABBREVIATIONS………………………………………………………………xiii-xiv
ABSTRACT…………………………………………………………………………………… xv
CHAPTER ONE
1.0 INTRODUCTION ............................................................................................... …………1
1.1 Background to the study ........................................................................................ ……….1-3
1.2 Statement of research problem .............................................................................. ……….3-4
1.3 Research questions ............................................................................................. …………5
1.4 Aim and objectives of the study ............................................................................ …………5
1.5 Research hypotheses .............................................................................................. ……….6-7
1.6 Significance of the study ....................................................................................... ……….7-8
1.7 Scope and delimitation of the study .................................................................... …………8
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1.8 Operational definition of terms ............................................................................. …………8
CHAPTER TWO
2.0 LITERATURE REVIEW ................................................................................... …………9
2.1 Introduction ........................................................................................................ …………9
2.2 Definition of AAC and sustainable construction materials ................................... ……...9-11
2.2.1 Classification of Aerated concrete......................................................................... …….11-13
2.3 Constituent material and manufacturing process of AAC Block .......................... ……13-16
2.3.1 Mixing of raw materials ....................................................................................... ………..16
2.3.2 Addition of expansion agent ................................................................................. ………..17
2.3.3 Pre-curing and cutting .......................................................................................... ………..17
2.3.4 Curing process ..................................................................................................... …….17-18
2.3.5 Packaging and transporting .................................................................................. ………..18
2.4 Awareness of Autoclaved Aerated Concrete block variants ................................ …….19-21
2.5 Adoption level of Autoclaved Aerated Concrete ................................................. …….21-23
2.6 Drivers to the adoption of AAC ........................................................................... …….23-26
2.7 Barriers impeding AAC block adoption .............................................................. ….…26-28
2.8 Strategies that can improve the usage of AAC on building projects………………….28-32
CHAPTER THREE
3.0 RESEARCH METHOD ...................................................................................... ………. 33
3.1 Introduction ........................................................................................................ ………..33
3.2 Area of the study .............................................................................................. ………..33
vii
3.3 Research design................................................................................................... …….33-34
3.4 Population of the study .................................................................................... ………..34
3.5 Sample size and sampling techniques ................................................................ ….…34-35
3.6 Instrument for data collection ............................................................................ ….…35-37
3.7 Data distribution and collection procedure ........................................................ ….…….38
3.8 Types of data used in the study .......................................................................... ………..38
3.9 Validity of Research Instrument ........................................................................ ………..38
3.10 Procedure for data processing and analysis ....................................................... ………..39
3.11 Constraint to the study ....................................................................................... ………..39
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION OF FINDINGS ............................................... ………..40
4.1 Introduction ........................................................................................................... ………..40
4.2 The response rates………... …………………………………………………………….…40
4.3 Demographic profile of the respondents ............................................................. ….....41-45
4.4 Results of the stated objectives of the study………………………………..…….……….46
4.4.1 Awareness of AAC block variants…………………………………………………….46-47
4.4.2 Prospect for adoption of AAC block in the Nigerian Construction industry ………..…....48
4.4.3 Adoption level of AAC blocks on building projects in the South African Construction
Industry …………………………………………………………………………………….........49
4.4.4 Important drivers for the adoption of AAC on building projects……………...………50-52
4.4.5 Barriers impeding the adoption of AAC block for building projects…………….........52-54
4.4.6 Important strategies that can improve the adoption of AAC for building
projects………………………………………………………………………………………..54-56
4.5 Test of hypothesis………………………………………………………….…………… 57
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4.5.1 There is no significant difference among ownership of organisations on the awareness of
AAC block variants in the Nigerian construction industry.….………………………………57-58
4.5.2 There is no significant difference on the level of adoption of AAC block among the
ownership of the organisations…….………………………………………………………….59-61
4.5.3 There is no significant difference in the perception of Nigerian and South African
professionals on the level of awareness of AAC block variants.………………………….. …61-63
4.5.4 There is no significant difference on the prospect for adoption of AAC block among the
ownership of the organisations……………..………………………………………….…….......63
4.5.5 There is no significant agreement among South African professionals on the adoption of
AAC block variants on building projects.………………………….………………....………….64
4.5.6 There is no significant difference among the respondents on the drivers of AAC blocks in
the Nigerian construction industry.……….…………………………………………………..64-66
4.5.7 There is no significant difference in the perception of South African respondents on drivers
of AAC blocks among the ownership of the organisations.………………………………….66-67
4.5.8 There is no significant difference between Nigerian and South African professionals on
drivers of AAC blocks.……………..…………………………………………………..…….68-69
4.5.9 There is no significant difference in the perception of the Nigerian professionals on barriers
impeding adoption of AAC blocks on building……………………...…………………..........70-71
4.5.10 There is no significant difference in the perception of the South African professionals on
barriers impeding adoption of AAC blocks on building.……………………………………...72-73
4.5.11 There is no significant difference in the perception of Nigerian and South African
professionals on barriers impeding AAC block adoption.……………..……………………..74-76
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4.5.12 There is no significant difference in the perception of Nigerian respondents on strategies
that can improve the adoption of AAC blocks on building projects.…...…………………....76-77
4.5.13 There is no significant difference in the perception of South African respondents on
strategies that can improve the adoption of AAC blocks on building projects……………….78-79
4.5.14 There is no significant difference in the perception of Nigerian and South African
professionals on strategies to improve AAC block adoption.………………….……………...79-81
4.6 Discussion of Findings....………………………………………...……………….......81-85
CHAPTER FIVE
5.0 CONCLUSION AND RECOMMENDATIONS……. ..................................... ………..86
5.1 Introduction……………………………………..…………………………………..……86
5.2 Summary of Findings……………………..…………………………………..……...86-90
5.3 Conclusions…………………………………..………………………………….…...90-91
5.4 Recommendations…………………….....……..………………………………….…91-92
5.5 Contributions to knowledge……….….....……..………………………………….…92-93
5.6 Suggestions for further studies………………………………………………………...…94
REFERENCES………………………………………………………………….....95-101
APPENDICES…………………………………………………………………….102-107
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LIST OF TABLES
2.1 Past and present innovations of 20 variants of AAC 19-21
2.2 Past and present innovations of 20 variants of AAC adopted on building projects 21-23
4.1 Response rates from respondents 40
4.21 Demographic profile of Nigerian respondents 41-42
4.22 Demographic profile of Nigerian respondents 44
4.3 Awareness of AAC block variants in Nigeria and South Africa 46
4.4 Prospect for adoption of AAC block in the Nigerian Construction industry 48
4.5 Adoption of AAC block variants in South Africa 49
4.6 Important drivers for the adoption of AAC on building
projects……………………………………………………………………….....….…50-51
4.7 Significant barriers impeding AAC block adoption for building projects ……………52-54
4.8 Important strategies that can improve the adoption of AAC for building
projects………………………………………………………………………………..54-56
4.9 ANOVA on the level of awareness of AAC block variants among ownership of
organisations 57-58
4.10 ANOVA on the level of adoption of AAC block among organisations 59-60
4.11 Mann-Whitney U test results for comparing perception of Nigerian professionals and South
African Professionals on the level of Awareness of AAC block variants…………….61-62
xi
4.12 ANOVA on the prospect for adoption of AAC block among organisations…………..…63
4.13 Kendall’s Coefficient of concordance test of agreement on the ranking of AAC variants on
10 building projects 64
4.14 ANOVA on the drivers of AAC block among the ownership organisations 64-66
4.15 ANOVA on the drivers of AAC block among the ownership of organisations 66-67
4.16 Mann-Whitney U test results for comparing perception of Nigerian professionals and
referred South African Professionals on drivers to AAC block adoption 68-69
4.17 ANOVA on the drivers of AAC block among the ownership of organisations…...… 70-71
4.18 ANOVA on the barriers impeding AAC block adoption among the ownership of
organizations……………………………………………………………………....… 72-73
4.19 Mann-Whitney U test results for comparing perception of Nigerian and South African
professionals on barriers impeding AAC block adoption 74-75
4.20 ANOVA on enhanced strategies to AAC block adoption among the ownership of
organizations………………………………………………………………………… 76-77
4.21 ANOVA on enhanced strategies to AAC block adoption among the ownership of
organisations ..…………………………………………………………………....… 78-79
4.22 Mann-Whitney U test results for comparing perception of Nigerian South African
Professionals on enhanced strategies of AAC block adoption………………….....… 79-80
xii
LIST OF FIGURES
2.1 Process flow of aerated concrete between the foamed concrete (NAAC) and AAC 13
2.2 Manufacturing process of AAC 18
xiii
LIST OF ABBREVIATIONS
AAC = Autoclaved Aerated Concrete
AC = Aerated Concrete
ACC = Autoclaved Cellular Concrete
ALC = Autoclaved Lightweight Concrete
ANOVA = Analysis of Variance
AP = Aluminium Powder
AS = Air-cooled Slag
ASTM = American Society for Testing and Materials
BIA = Building Industry Association
BFS = Blast Furnace Slag
BLA = Bamboo Leaf Ash
CBA = Coal Bottom Ash
CG = Coal Gangue
CSB = Concrete Sandwich Block
CT = Copper Tailings
DS = Dune Sand
ES = Efflorescence Sand
FA = Fly Ash
GDP = Gross Domestic Product
HP = Halloysite Powder
IOT = Iron Ore Tailings
ISSA = Incinerated Sewage Sludge Ash
LWC= Light Weight Concrete
NACC = Non-Autoclaved Aerated Concrete
NIS = Nigerian Industrial Standard
xiv
NZ = Natural Zeolite
OPC = Ordinary Portland Cement
OQS= Online Questionnaire Survey
PF = Polypropylene Fibre
PFA = Pulverized Fuel Ash
POFA = Palm Oil Fuel Ash
PS = Phosphorous Sand
PW = Perlite Waste
RHA = Rice Husk Ash
SAQ = Self- Administered Questionnaire
SCG = Self-ignition Coal Gangue
SF = Silica Fume
SMEs = Small and Meduim Enterprises
SPSS = Statistical Package for the Social Sciences
WG = Waste Glass
xv
ABSTRACT
The rationale for this study stems from reports that while Autoclaved Aerated Concrete (AAC) has
been in existence for over a century and has been adopted in Europe and other parts of the world,
its awareness and adoption on building projects in Nigeria and Africa at large is still very low or
non-existent. The study aims to explore the awareness and usage of AAC block variants with a
view to providing walling materials that are sustainable. The objectives of the study are to compare
the level of awareness of AAC block variants in Nigeria and South Africa; to determine the
prospect for adoption of AAC blocks in Nigeria; to evaluate the adoption level of AAC block
variants on South African building projects; to identify drivers to the adoption of AAC blocks on
building project; to evaluate barriers impeding the adoption of AAC blocks on building projects
and to propose strategies that would improve the adoption of AAC blocks on building projects.
Following a review of existing literature, the study mainly adopted quantitative research where
questionnaire surveys were administered to the targeted respondents. The population of the study
was made up of two groups comprising Nigerian and South African professionals. Structured Self-
administered Questionnaires were designed to elicit information from the Nigerian professionals
in the Lagos metropolis while Online Questionnaire Survey (through Google Forms) was designed
to collect data from the referred South African professionals. The study utilized a multi-sampling
method where both convenience and snowball sampling techniques were deployed to gather the
viewpoints of the Nigerian and South African professionals acquainted with the knowledge and
have been involved in its use on building projects. The response data obtained from the
administration of the questionnaires were coded, processed and analyzed with the aid of Statistical
Package for the Social Sciences (SPSS) version 23.0, Data were analyzed using the following
descriptive statistical tools such as frequency, percentages, mean score and ranking, while One-
way ANOVA, Mann-Whitney U test and Kendall’s coefficient of concordance (W) were used as
tools of analysis for the inferential statistics, respectively. Results revealed that the Nigerian
professionals are slightly aware of 19 out of the 20 AAC variants while the South African
respondents are moderately aware of 13 out of 20 AAC variants. Also, there is a moderate
disposition for adoption of AAC block by the Nigerian Respondents. Also, AAC with 52.5 grade
ordinary Portland cement is the most used AAC variants in South Africa. It was also revealed that
the barriers impeding the adoption of AAC block on construction projects in Nigeria were mired
by various issues which included inadequate government policies and supports, market potentials
and low level of awareness and knowledge on the concept of sustainability while huge capital to
set up AAC plant, lack of readily available accessible information and availability of conventional
materials were the barriers to its adoption in the South African building industry. Also, the result
revealed strategies to improve the adoption of AAC block in Nigeria, these include government
encouragement and focusing research on specific green building materials while in South Africa,
growth in the infrastructural sector and growth preferences for low cost houses are the strategies
to improve its adoption. The study concludes that the level of awareness of AAC block variants is
higher in South Africa than in Nigeria. This implies that AAC block producers would not thrive at
present in Nigeria because there would be low patronage. If awareness is increased, patronage will
be increased. The study hereby recommends that professionals should update their knowledge of AAC
block. This can be achieved via continuous development training, seminars and workshops on AAC block
in the building industry. The study also recommends that government should provide more support and
develop AAC production technology based on the studies of existing foreign technologies which will not
only place the nation into the limelight in the use of the material but also enhance the country’s GDP.
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CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the study
The global trend towards searching for substitutes to conventional building materials, along with
the drive for sustainability in local materials and construction technologies, has spurred studies on
the viability and application of locally accessible raw materials for construction purposes. One
such materials in view is autoclaved aerated concrete (AAC), which according to Rathi and
Khandve (2015) has been identified as a potential substitute for bricks in walls to provide eco-
friendly solutions to greener environment.
AAC was invented in the early 1920s by a Swedish Architect named Eriksson whose purpose for
designing AAC was to reduce consumption of timber and provide a cheaper and sustainable
building material. This innovation focuses on eco friendliness and directs a path to sustainable
development as it satisfies the rule of 3R’s: Reduce, Recycle and Reuse (Cheran, Shanthi &
Krithigaa, 2017).
According to Jerman, Keppert, Vyborny and Cerny (2013) AAC is a structural material which is
commonly used in Europe and other parts of the world, particularly as it combines ease of
construction with excellent combination of mechanical and thermal properties. In addition, Desani,
Soni, Gandhi and Mishra (2016) opine that this light weight concrete (LWC) has no coarse
aggregates in its mixture and stated that lightweight concrete is either aerated using mortar injected
by gas bubbles or air entraining agents.
Keyvani (2014) noted that aerated concrete is relatively homogenous when compared to normal
concrete yet, shows vast variation in its properties. The properties of aerated concrete are
dependent on its composition and microstructure (void paste system) which is influenced by the
curing method; binder used and method of pore-formation (Narayanan & Ramamurthy, 2000).
2
Aerating concrete by using air entraining agents is more practical in production of LWC. Air
entraining agents are expanding agent that increases the volume of the mixture while reducing the
dead weight and is generally lighter than conventional concrete.
AAC is manufactured by a process that involves slurry preparation, foaming/rising, cutting and
steam curing (autoclaving) process during which the main ingredients react together chemically
(Cheran et al. 2017). Curing is an important factor affecting the mechanical and physical properties
of concretes in different categories and considering the methods of curing, aerated concrete can be
categorized into two main groups which are AAC and non-autoclaved aerated concrete (NAAC)
(Desani et al. 2016).
Advancement in modern technology and new building systems has brought to fore a wide range
in choice of walling materials with bricks, sandcrete blocks, timber and glass taking the centre
stage (Olawuyi & Babafemi, 2013). Sandcrete blocks are however, the most widely used walling
units in Nigeria accounting for 90% of houses according to (Baiden & Tuuli, 2004).
According to Oo and Hlaing (2018), the first bricks were sun-dried mud bricks, fired bricks were
later found to be more resistant to harsher weather conditions which made them a much more
reliable brick for use in buildings where mud bricks would not have been sufficient. Fired clay
bricks absorb heat during the day and then release it at night. In addition, it possesses certain
inherent sustainable properties such as durability and high thermal mass; however, the kilning
process has raised some sustainable concerns because of energy consumption and greenhouse gas
emissions (Chusid, Miller & Rapport, 2009).
Similarly, the kilning process of fired clay brick releases large amount of carbon dioxide and other
harmful gasses leading to the menace of global warming and climate change (Gautam & Sexena,
2013). Sustainability is defined as meeting the needs of the present without compromising the
3
ability of future generations to meet their own needs (Building Industry Association [BIA], 2009;
American Society for Testing and Materials [ASTM], 2006).
The Nigerian Industrial Standard (NIS 87: 2000) provides the range of minimum compressive
strength of sandcrete blocks between 2.5N/mm2 and 3.45N/mm2. The objective of the Nigerian
Industrial Standard (NIS 87:2000) is that all blocks manufacturer meets the minimum standard
(Wilson, Raji & Alomaja, 2016). Relatedly, Aiyewalehinmi and Akande (2015) posit that the
present sandcrete blocks available in building and construction material market in Nigeria are
below the Nigerian Industrial Standard (NIS 87:2000) of 2.5N/mm2. There are no known studies
on AAC in Nigeria. This study, therefore, investigates the application of AAC blocks on
construction projects in Nigeria.
1.2 Statement of Research problem
Tropical climates like Nigeria are attributed with high temperature during the day. The outer high
temperature heats up the building walls and heat is absorbed within the hollow sections of the
sandcrete block from dawn till twilight. Jannat, Hussein, Abdullah and Cotgrave (2020) revealed
that sandcrete block walls have high heat absorption, heat diffusivity and heat emissivity capacity
compared to other material such as bricks. Similarly, Kadir and Mohajerani (2011) reported that
bricks have better thermal properties compared with other materials in the construction industry
but still absorbs and emits a level of heat invariably. The heat stored within the mass of the walling
systems, radiate or move inwards into the building space; causing a rise in the inside temperature
of the rooms/spaces. This rise in the inside temperature directly increase the cost of cooling for
thermal indoor comfort of the occupants (Al-Homoud, 2005). Significantly, walls and roof systems
are the major culprits of this thermal action in building. Thus, if the wall composition is made of
AAC, the thermal comfort demand in the building indoor spaces will be reduced. Singh, Pandey
and Srivastava (2017) studied smart and eco-friendly construction materials and revealed that
4
conventional brick material produces large amount of CO2 and other greenhouse gases which are
hazardous/toxic in nature which cause environmental and health related problems.
Relatedly, Kashim (2014) gave a situation report on cement developments in cement
manufacturing and distribution in Nigeria and posits that three grades of cement are available
globally which are: 32.5 grades, 42.5 grades and 52.5 grades. Kashim (2014) recommended that
stakeholders and the general public should be enlightened about the application of these different
grades of cement available in the markets for easy identification and application. Similarly,
Hudson (2014) stated that the 32.5 grade Ordinary Portland Cement (OPC) is the best multi-
purpose cement for Nigeria based on some number of factors as Nigeria is in a very hot tropical
environment, with a low heat of hydration. The 32.5 grade becomes very suitable as it does not
cause cracking, well grinded, good for workability and has very good environmental impact
because with a little bit of extra limestone or other additives put into it, carbon dioxide (CO2)
emissions are reduced.
However, Saiyed, Makwana, Pitroda, and Vyas (2015) explained what is not green about Portland
cement as it contains about 60% limestone, or calcium carbonate and must be burned at high
temperatures in kilns using lots of energy and creating carbon dioxide (CO2), a greenhouse gas
linked to global warming. The newer magnesia-based cement can be burned at lower temperatures
using less energy and creating less CO2. Moreover, Umoh and Odesola (2016) discovered that up
to 15% replacement of cement with bamboo leaf ash (BLA) in concrete produced satisfactory
results. There has been no such study of BLA as partial replacement with cement in AAC. These
may as well produce satisfactory results, leading to various options of AAC blocks. Additionally,
there could be variants of AAC blocks made with several grades of cement, such as 32.5, 42.5 and
52.5 grades. However, the sustainability of each of these variants is yet to be known. Therefore,
the problem that this study seeks to solve is the use of unsustainable construction materials on
building projects.
5
1.3 Research questions
The research questions for the study are as follows:
1. What is the level of awareness of AAC block variants in Nigeria and South Africa?
2. What is the prospect for adoption of AAC block in Nigeria?
3. To what extent is the adoption level of AAC block variants in South Africa?
4. What are the drivers to the adoption of AAC on building projects in Nigeria and South
Africa?
5. What are the barriers impeding the adoption of AAC on building projects in Nigeria and
South Africa?
6. What are the strategies that can improve the adoption of AAC on building projects in Nigeria
and South Africa?
1.4 Aim and objectives of the study
The research is aimed at exploring the awareness and usage of AAC block options with a view to
providing walling materials that are sustainable.
The specific objectives to be achieved in this study are:
1. to compare the level of awareness of AAC block variants in Nigeria and South Africa.
2. to determine the prospect for adoption of AAC blocks in Nigeria.
3. to evaluate the adoption level of AAC block variants on building projects in South Africa.
4. to identify drivers to the adoption of AAC blocks on building projects in Nigeria and South
Africa.
5. to evaluate barriers impeding the adoption of AAC blocks on building projects.
6. to propose strategies that can improve the adoption of AAC blocks on building projects.
6
1.5 Research hypotheses
The following hypotheses were postulated in line with the objectives of this study:
H 01a: There is no significant difference among the ownership of organizations on the awareness
of AAC block variants in the Nigerian building industry.
H 01b: There is no significant difference on the level of awareness of AAC block variants among
the ownership of the organisations in South African building industry.
H 01c: There is no significant difference in the perception of Nigerian and South African
professionals on the level of awareness of AAC block variants.
H 02: There is no significant difference on the prospect for adoption of AAC among the
ownership of organisations in the Nigerian building industry.
H 03: There is no significant agreement among South African professionals on the adoption of
AAC variants on building projects.
H 04a: There is no significant difference among the respondents on the drivers of AAC in the
Nigerian Construction industry.
H 04b: There is no significant difference in the perception of South African respondents on
drivers of AAC blocks among the ownership of the organisations.
H 04c: There is no significant difference between Nigerian and South African respondents on
drivers of AAC blocks.
H 05a: There is no significant difference in the perception of the Nigerian respondents on
barriers impeding adoption of AAC blocks on building.
H 05b: There is no significant difference in the perception of the South African professionals on
barriers impeding adoption of AAC blocks on building.
7
H 05c: There is no significant difference in the perception of Nigerian and African respondents’
professionals on barriers impeding the adoption of AAC blocks.
H 06a: There is no significant difference in the perception of Nigerian respondents on the
strategies that can improve the adoption of AAC blocks on building projects.
H 06b: There is no significant difference in the perception of South African respondents on
strategies that can improve the adoption of AAC blocks on building projects.
H 06c: There is no significant difference in the perception of Nigerian and South African
professionals on the strategies to improve AAC block adoption.
1.6 Significance of the study
The study on the level of awareness of AAC block variants would be of great benefit to consultants,
developers/clients and contractors as it would add to the body of literature on sustainable
construction materials and shed more light on the various AAC block options available which
materials specifiers can recommend for building projects.
Also, the prospect for adoption of AAC blocks would benefit the Nigerian professionals as it would
reveal the possibilities of adopting the block on building projects in the nearest future.
Also, the adoption level of AAC block variants would be of great benefit to developers/clients and
Architects as the study would reveal the percentages of usage of each of the AAC block variants
available of which professionals can work with the information available on each variant and
choose from the options presented.
Being a sustainable construction material, the identified drivers would be beneficial to building
owners, developers and occupants as there would be great savings in cost of construction as a result
8
of the blocks being lightweight, energy costs would be reduced due to the block being energy
efficient and optimum indoor comfort level for the occupants as a result of the micro-climate
characteristics the block offers.
Furthermore, barriers impeding the adoption of AAC blocks on building projects would be
identified and findings from the study would be beneficial to building owners, the government,
developers, consultants and contractors to put measures in place to guard against the challenges.
Finally, the strategies to achieve AAC block adoption on building projects if implemented would
attract patronage from stakeholders, serves as employment generation and increase the country’s
Gross Domestic Product (GDP).
1.7 Scope and delimitation of the study
The scope of this study is delimited to building projects in Lagos metropolis and building projects
in South Africa where AAC blocks are being used. The research is focused on Lagos state, not
only because of easy access to information but also due to its large material usage as a result of
the massive construction activities ongoing in the state and its high number construction
practitioners, stakeholders and policy makers plying their trades in the state.
1.8 Operational definition of terms
Autoclaved Aerated Concrete (AAC): is a lightweight concrete which offers excellent thermal
insulation performance resulting from low volume weight and porous structure with sufficient
mechanical strength. It is an ecofriendly and certified green building materials.
Sustainability: Sustainability is defined as meeting the needs of the present without compromising
the ability of future generations to meet their own needs
9
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 INTRODUCTION
This chapter presents the literature review. The literature review will examine the following
headings: definition of Autoclaved Aerated Concrete (AAC) and sustainable construction
materials, awareness of AAC block variants, prospect for adoption of AAC blocks in the Nigerian
construction industry, adoption of AAC block variants in the South African construction industry,
drivers to AAC block adoption, barriers impeding the usage of AAC and strategies that can
improve the usage of AAC blocks on construction projects.
2.2 Definition of AAC and sustainable construction materials
According to Wikipedia (2021) Autoclaved Aerated Concrete (AAC) is otherwise known as
Autoclaved Cellular Concrete (ACC), Autoclaved Lightweight Concrete (ALC), Autoclaved
Concrete, Cellular concrete, Porous Concrete, and Aircrete. Narayanan and Ramamurthy (2000)
define AAC as a load bearing building material with a low density due to its higher porosity
compared to other load bearing building materials. AAC is manufactured by varying production
parameters as regards densities in the range of 93–1800 kg/m3 whereas its constituent particle
density is around 2600 kg/m3. This implies 30–90% of its volume consists of pores (Kadashevich,
Schneider & Stoyan, 2005).
Relatedly, Pandey, Kirar, Singh and Rajak (2018) posit that AAC is one of the eco-friendly and
certified green building materials that is porous, non-toxic, reusable, renewable and recyclable and
10
added that AAC is a lightweight, load-bearing, high insulating, durable building product, which is
produced in a wide range of sizes and strengths. Saiyed, Makwana, Pitroda and Vyas (2015)
explain that AAC is quite different from dense concrete (i.e. “normal concrete”) in both the way it
is produced and in the composition of the final product. AAC does not contain any aggregate as
all the main mix components are reactive, even milled sand where it is used. The sand, inert when
used in dense concrete, behaves as a pozzolana in the autoclave due to the high temperature and
pressure. Different researchers have provided different definitions to AAC. Therefore, different
definitions can be found in different references. Basically, AAC is a green building material that
offers excellent thermal insulation property and directs a path to sustainability.
On the other hand, Sustainable construction materials can be defined as materials with overall
superior performance in terms of specified criteria. For Selection of Sustainable construction
materials the following criteria are commonly used: locally produced and sourced materials;
transport costs and environmental impact; thermal efficiency; occupant needs and health
considerations; financial viability; recyclability of building materials and the demolished building;
waste and pollution generated in the manufacturing process; energy required in the manufacturing
process; use of renewable resources; toxic emissions generated by the product and maintenance
costs (Patil & Patil, 2017).
Sustainability in construction is all about following suitable practices in terms of choosing
materials, their sources and construction methodologies as well as design philosophy, so as to be
able to improve performance, decrease the environmental burden of the project, minimize waste
and be ecologically friendlier, taking into consideration environmental, socio-economic and
cultural values. All materials are ultimately derived from the bio-geo-sphere. They are everything
11
between the take and waste and are the key to sustainability. The choice of materials for
construction controls whole of life cycle impacts such as emissions, gross take, properties of
wastes returned to the bio-geosphere, use of recycled wastes and their own recyclability. Materials
also strongly influence lifetime energies, user comfort and durability (Kibert, 1994).
Similarly, Sustainable building materials are those which are produced or sourced locally. These
materials are containing recycled & industrial waste materials and byproducts. Sustainable
materials have a lower impact on environment & are thermally efficient. The production of these
building materials requires considerably less amount of energy in production when compared to
the modern or traditional construction materials.
The advantages in selection of sustainable building material lies in the fact that they are not only
economically viable but also reduce toxic emissions thereby reduce overall environment impact.
Sustainable building material & technology should be utilized appropriately & contextually in each
neighborhood development. The use of sustainable material & technology not only reduces
transport & production cost, carbon emissions but also provides avenues for employment & skill
development for community members (Patil & Patil, 2017).
2.2.1 Classification of Aerated concrete
According to Narayanan and Ramamurthy (2000) Aerated concrete is classified based on three
methods. They comprise:
i. Based on the method of pore formation
a. Air-entraining method (also known as gas forming): this method results in a mass of
increased volume when injected into lime/cement mortar mixture during the liquid or plastic stage.
12
A porous structure is formed when the gas escapes. Examples of aerating agents are: Aluminum
powder; hydrogen peroxide/bleaching powder; calcium carbide; liberated hydrogen; oxygen and
acetylene respectively. However, Aluminium powder is the most commonly used aerating agent.
b. Foaming method (foamed concrete): there are no chemical reactions involved in this
method and it is regarded as the most economical and controllable pore-forming process. Pores are
introduced through chemical means either by pre-formed foaming (foaming agent mixed with a
part of mixing water) or mix foaming (foaming agent mixed with mortar). The various foaming
agents used comprise: detergents; resin soap; glue resin; saponin; hydrolyzed proteins such as
keratin, etc., (Valore, 1954).
c. Combined pore-forming method: production of cellular concrete by combining foaming
and air-entraining methods using Aluminium powder and glue resin.
ii. Based on the type of binder
Aerated concrete is classified into cement or lime based depending on the binder used. Attempts
have been made to use pozzolanic materials such as pulverized fuel ash (PFA) or slate waste as
partial replacement to the binder or sand. Vu and Nguyen (2017) investigated the influence of
admixtures on properties of AAC using Dune sand as the fine aggregate. Similarly, Naik et al.
(2018) carried out studies and experiments on AAC by using flu Ash. In addition, Rahman,
Fazlizan, Asim and Thongtha (2020) conducted a review on the utilization of waste material for
AAC production.
13
iii. Based on the method of curing
Based on the method of curing, Aerated concrete can be non-autoclaved (NACC) or Autoclaved
(AAC). The compressive strength, absorption properties, dry shrinkage etc., directly depends on
the method and duration of curing. The strength development is rather slow for moist-cured
products. The variables of significance are the age and condition of the mix at the start of the curing
cycle and rates of change of temperature and pressure (Narayanan & Ramamurthy, 2000;
Ikponmwosa, Falade & Fapohunda, 2014).
Figure 1. Process flow of aerated concrete between the foamed concrete (NAAC) and AAC (Hamad, 2014)
It should be noted however, that properties of aerated concretes are classified in terms of physical
(microstructure, density), chemical, mechanical (compressive & tensile strengths, modulus of
elasticity, drying shrinkage and functional (thermal insulation, moisture transport, durability, fire
resistance & acoustic insulation characteristics (Narayanan & Ramamurthy, 2000).
2.3 Constituent material and manufacture of AAC Block
The AAC production process differs slightly between individual production plants but the
principles are similar. The basic raw materials used in the production of AAC blocks include:
14
Portland cement, fine aggregate (sand), quicklime, gypsum, aluminum powder and water (Rathi
& Khandve, 2015; Naik et al. 2018; Manikandan, Gopalakrishnan & Cheran, 2018).
The batching ratio of AAC block before mixing according to Sahu and Singh (2017) comprises;
Fly ash 69%, Sand 20%, Lime: Cement 8%, Gypsum 3 %, Aluminum 0.08% of total dry materials
and Water ratio 0.60-0.65. Subash, Satyannarayana and Srinivas (2016) added that unlike most
other concrete applications, AAC is produced using no aggregate larger than sand. Quartz sand,
calcined gypsum, lime (mineral) and/or cement and water are used as a binding agent. Aluminum
powder is used at a rate of 0.05%–0.08% by volume (depending on the pre-specified density). In
some countries, fly ash generated from thermal power plants with silica of 50-65% are used as
aggregate. Additionally, Rathi and Khandve, (2015); Naik et al. (2018); Manikandan et al. (2018)
explained the materials used for the production of AAC block which include:
a. Fly Ash/Sand: Key ingredient for manufacturing AAC blocks is silica rich material like fly ash
or sand. Most of the AAC companies in India use fly ash to manufacture AAC blocks. Fly ash is
mixed with water to form fly ash slurry. The slurry thus formed is mixed with other ingredients
like lime powder, cement, gypsum and Aluminum powder in quantities consistent with the recipe.
Alternately, sand can also be used to manufacture AAC blocks or a combination of both materials.
A ‘wet’ ball mill finely grinds sand with water converting it into sand slurry. Sand slurry is mixed
with other ingredients just like fly ash slurry.
Sand is a naturally occurring granular material composed of finely divided rock and mineral
particles. It is defined by size, being finer than gravel and coarser than silt. Sand can also refer to
a textural class of soil or soil type. The composition of sand varies, depending on the local rock
sources and conditions, but the most common constituent of sand in inland continental settings and
15
non-tropical coastal settings is silica, usually in the form of quartz (Satish, Sukumar, Srinath, Tamil
& Bharathidason, 2017).
Fly ash is one of the naturally occurring products from the coal combustion process and is a
material that is nearly the same as volcanic ash. When coal is burned in today’s modern electric
generating plants, combustion temperatures reach approximately 2800°F. The noncombustible
minerals that naturally occur from burning coal form bottom ash and fly ash. Fly ash is the material
that is carried off with the flue gases, where it is collected and can be stored in silos for testing and
beneficial use.
Fly ash can be classified into classes. Class F fly ash is normally produced by burning anthracite
or bituminous coal. Usually it has less than 5% of CaO. Class C fly ash normally produced by
burning lignite or sub-bituminous coal. Usually it has CaO content in excess of 10% (Satish,
Sukumar, Srinath, Tamil & Bharathidason, 2017).
Recently, bamboo leaf ash (BLA), which was obtained by the burning of bamboo leaf at a
controlled temperature has been found to possess high reactive silica, which makes it suitable for
use as a supplementary cementitious material (Villar-Cociña, Santos, Savastano & Frías, 2011;
Dwivedi, Singh, Das, & Singh, 2006; Arum, Ikumapayi & Aralepo, 2013). The use of bamboo leaf
ash in concrete exposed to a sulfate environment has been reported (Ademola & Buari, 2012; Asha,
Salman & Kumar, 2014) to enhance the resistance of concrete to sulfate attack.
Similarly, Adewuyi, Olusola and Oladokun (2013) reported its use as a supplementary
cementitious material in the production of sandcrete blocks produced satisfactory results.
Therefore, the availability of bamboo leaf and the low technology required to process it into ash
necessitates its usage as a material for the production of some building elements for affordable
housing provision, especially in developing countries.
16
b. Lime Powder: Lime powder required for AAC production is obtained either by crushing
limestone to fine powder at AAC factory or by directly purchasing it in powder form. Although
purchasing lime powder might be little costly, many manufacturers opt for it rather than investing
in lime crushing equipment like ball mill, jaw crusher, bucket elevators, etc. Lime powder is stored
in silos fabricated from mild steel (MS) or built using brick and mortar depending of individual
preferences.
c. Cement:
Ordinary Portland Cement (OPC) is the most common cement used in general concrete
construction when there is no exposure to sulphates in the soil or groundwater. Cement can be
defined as the bonding material having cohesive & adhesive properties which makes it capable to
unite the different construction materials and form the compacted assembly. The OPC was
classified into three grades namely, 32.5 grade, 42.5 grade and 52.5 grade depending upon the
strength of the cement at 28 days when tested (Satish et al., 2017). Cement is usually stored in
silos. However, in Nigeria, cement is stored in 50kg sacs.
d. Gypsum: Gypsum is easily available in the market and is used in powder form. It is stored in
silos.
e. Aluminium Powder/Paste: Aluminium powder/paste is easily available from various
manufacturers. As very small quantity of Aluminium powder/paste is required to be added to the
mixture, it is usually weighed manually and added to the mixing unit. Aluminium powder is
usually used to obtain AAC by a chemical reaction generating a gas in fresh mortar; it contains a
large number of gas bubbles. When Aluminium is added to the mixing ingredients by 0.2%-0.5%
to the dry density of cement. The Aluminium powder can be classified into three types: atomized,
flake and granules. In case of an atomized particle, its length, width and thickness are all of
17
approximately the same order where the length or width of a flake particle maybe several hundred
times in thickness. Aluminium powder in the AAC industry is often made from foil scrap and
exists of microscopic flake-shaped aluminium particles (Satish et al., 2017).
2.3.1 Mixing of raw materials
Raw materials containing silica sand or quartz sand, fly ash, cement and water are placed in a huge
container and mixed together. The hydration of cement occur forming bond between the fine
aggregates and cement paste.
2.3.2 Addition of expansion agent
After the mixing process, an expansion agent such as aluminum powder is added to the mixture to
increase its volume which could be up to 2 or 5 times more than the original volume of the paste.
Calcium hydroxide is the product of reaction between cement and water. The reaction between
aluminum powder and calcium hydroxide causes forming of microscopic air bubbles which results
in increasing of pastes volume. These microscopic air bubbles will increase the insulation capacity
of AAC.
2Al + 3Ca (OH) 2 + 6H2O = 3CaO.Al2O3 + 3H2
Aluminum powder + Hydrated lime (Tricalcium hydrate) + Hydrogen
2.3.3 Pre-curing and cutting
Pre curing process starts after concrete mix is poured into metal moulds with dimensions of 6000
mm × 1200 mm × 600 mm. In these moulds, concrete will be pre cured after it is poured into mould
to reach its shape and after this pre curing process cutting will take place below. Cutting will be
done with wire cutter to avoid deformation of concrete during process. Aerated concrete blocks
are available in different dimensions and various thicknesses. Dimensions for these blocks which
are commonly used are: 600×250×100 mm, 600×250×150mm, and 600×250×200.
18
2.3.4 Curing process
Steam curing is a heat treatment which has been used for many years to accelerate the strength
development of concrete products. Because the hydration rate of cement increases with the
increase in strength can be speeded up by curing concrete in steam. For compressive strength
development of concrete, duration of steam curing is also an important parameter as well as
temperature (Tu¨rkel & Alabas, 2005).
The curing process is achieved by an autoclave. Autoclave is defined as a strong, pressurized and
steam-heated vessel. Concrete mix that is categorized as autoclaved has its ultimate mechanical
properties conditions. Curing with autoclaving method requires three main factors which are
moisture, temperature and pressure. These three factors should be applied on material all at the
same time. The temperature inside the autoclave should be 1900C and essential pressure should
be about 10 to 12 atmospheres. Moisture will be controlled by autoclave and this process should
be continued up to 12 hours to provide proper condition for hydration.
2.3.5 Packing and transporting
After completion of mentioned processes, AAC is ready for packing and transportation, but the
important factor that shall be carefully considered for this process is that; material should be
cooled, the cut blocks are then loaded into the autoclave. It takes a couple of hours for the autoclave
to reach maximum temperature and pressure, which is held for perhaps 8-10 hours, or longer for
high density/high strength aircrete.
19
Figure 2. Manufacturing process of AAC (Hamad, 2014)
2.4 Awareness of Autoclaved Aerated Concrete (AAC) block variants
Table 2.1 shows past and present innovations of 20 variants of AAC available in literature. These
innovations have been done by replacing its based materials using waste materials (industrial by-
products). These innovations are either to improve AAC characteristics, properties, and
performance or the manufacturing cost while maintaining its properties at the acceptable ranges.
Besides waste materials, additions or replacement, additives such as fibers, micro-particles,
hydrophonic agents and superplasticizers are also being applied in AAC preparation (Deng, Zhang,
& Wang, 2020). These additives could also enhance the properties of AAC, such as an addition of
amorphous SiO2 increased the compressive and flexural strength.
20
Table 2.1: Past and present innovations of 20 variants of AAC
S/N
AAC
Variant/Parameter
studied
Replacement
method/salient feature
of the study
Improvement/Enhancement
Sources
1
AAC with 32.5 grade
Ordinary Portland Cement
(OPC)
Cement is partially being
replaced with BLA
Still Under laboratory
investigation
Simeon and
Oladiran, (2021)
2
AAC with 42.5 grade
Ordinary Portland Cement
(OPC)
42.5 grade OPC is replaced
with ZSM-5 waste. 51% of
ZSM-5 waste, 12% cement,
34% quicklime, 3% gypsum,
0.14% Aluminium powder,
0.78 Ca/Si and 0.8 W/C
Compressive strength is
enhanced (4.2MPa) which far
exceeded the specification of
A2.5, B05 grade
Hu, Qian, Wang,
Ma, & Wang
(2021).
3
AAC with 52.5 grade
Ordinary Portland Cement
(OPC)
Cement is partially replaced
by lime
Lime had no effect on the
strength of the mixture.
Khan, (2020)
4
AAC with Coal Bottom
Ash (CBA)
CBA was used to replace
sand. Optimum replacement
of CBA is 50%
Thermal conductivity value is
decreased up to 39% and
increased strength up to 16%
higher than reference AAC.
Kurama, Topcu
and Karakurt
(2009).
5
AAC with Natural Zeolite
Additive (NZ)
Sand was replaced by up to
50% NZ
Decreases the unit weight of
aerated concrete specimens
hence, decreases density
Karakurt, Karuma
and Topcu (2010).
6
AAC with Self-ignition
Coal Gangue (SCG)
Optimum mix proportion is
SCG to lime to cement to
gypsum is 54:23:20:3 with
1.3% aluminum powder
The products consisted of CSH
gel and tobermorite phase.
Cong, Lu, Yao &
Wang (2016).
7
AAC with Incinerated
Sewage Sludge Ash
(ISSA)
ISSA for the production of
AAC block
Should only be considered for
use if alternatives (PFA or
Natural Sand) are not available
or uneconomic
Dunster (2007).
8
AAC with Bamboo Leaf
Ash (BLA)
Up to 15% of BLA is being
partially replaced with
cement
Still Under laboratory
investigation
Simeon and
Oladiran, (2021)
9
AAC with Silica Fume (SF)
/ Fly Ash (FA)
52.5 grade OPC is being
replaced with various
percentages up to 25% of
SF.
Compressive strength increases
up to 80% when cement is
replaced by 15% of SF.
Rathod and
Akbari (2017).
10
AAC with Dune Sand (DS)
Normal sand was being
replaced by up to 30% Dune
sand
A drastic reduction in strength
was observed when higher than
30%
Vu and Nguyen
(2017).
11
AAC with Rice Husk Ash
(RHA) / Aluminum Powder
(AP)
RHA and Aluminium
containing waste as a partial
aggregate and expansive
replacement agent
Delicate particle size has a
positive effect on the CSH to
tobermorite conversion.
Kunchariyakun,
Asavapist and
Sombatsompop
(2015).
21
12
AAC with Concrete
Sandwich Block (CSB) /
Waste Glass (WG)
Sand was being replaced by
various types of WG
AAC with cathode ray tube glass
has similar characteristics to
reference sample.
Walczak,
Malolepszy,
Reben, Szymanski
and Rzepa (2015).
13
AAC with Halloysite
Powder (HP)
Clay mineral was used as a
cement replacement
Application of halloysite as a
cement replacement in the
amount of 5.5% increases the
strength by 5.8% at the
same bulk density of the
autoclaved aerated concrete.
Owsiak, Soltys,
Sztaboroski and
Mazur (2015).
14
AAC with Air-cooled Slag
(AS)
AS was used to replace lime
and sand (optimum at 50%
low-lime mixes and 30% for
high-lime mix)
Improvement in compressive
strength and shorter curing
duration
Mostafa (2005).
15
AAC with Efflorescence
Sand (ES)
Normal sand was being
replaced by up to 25% ES
Compressive strength is
enhanced.
Haung et al.
(2012).
16
AAC with Phosphorus Sand
(PS)
Normal sand was being
replaced by up to 30% PS
Control heat of hydration
Demir, & Güçlüer,
(2017).
17
AAC with Coal Gangue
(CG) / Iron Ore Tailings
(IOT)
Optimum composition at:
20% CGC, 40% IOT, 25%
lime, 10% cement, 5%
0.06% Aluminium powder
Completely replaced sand to
achieve bulk density and
compressive strength of
609kg/m3and 3.68MPa,
respectively.
Wang, Ni, Zhang,
Wang, and Gai
(2016).
18
AAC with Pulverized Fuel
Ash (PFA) / Palm Oil Fuel
Ash (POFA)
Cement was completely
replaced by PFA and POFA
Control heat of hydration
Mehmannavaz et
al. (2014).
19
AAC with Copper Tailings
(CT) / Blast Furnace Slag
(BFS)
Optimum composition SCT
to BFS to Sand to Cement to
Gypsum is 30:35:20:10:5
The compressive strength was
4.0 MPa, and the dry density was
610.2kg/m3
Huang, Ni, Cui,
Wang and Zhu
(2012).
20
AAC with Perlite Waste
(PW) / Polypropylene Fiber
(PF)
Sand was replaced by PW
PW at 10% reduced the thermal
conductivity about 15% without
significant reduction of
compressive strength.
Rozycka and
Pichor (2016).
Simeon (2021).
2.5 Adoption of Autoclaved Aerated Concrete Block Variants
Unlike in Africa, AAC is most used building material in Europe and is rapidly growing in many
other countries around the world. According to Pandey, Singh, Kirar and Rajak (2018), AAC has
become one of the most adopted building materials in Europe and is rapidly growing in other
22
countries around the world. Due to its excellent properties, AAC is adopted in many building
construction projects such as in residential, commercial, schools, hotels, hospitals and many other
application. It therefore replaces clay bricks which are environmentally unsustainable. Table 2.2
shows 20 variants that have been adopted on building projects.
Table 2.2: Past and present innovations of 20 variants of AAC adopted on building projects.
S/N
AAC
Variant/Parameter
studied
Replacement
method/salient feature
of the study
Improvement/Enhancement
Sources
1
AAC with 32.5 grade
Ordinary Portland Cement
(OPC)
Cement is partially being
replaced with BLA
Still Under laboratory
investigation
Simeon and
Oladiran, (2021)
2
AAC with 42.5 grade
Ordinary Portland Cement
(OPC)
42.5 grade OPC is
replaced with ZSM-5
waste. 51% of ZSM-5
waste, 12% cement, 34%
quicklime, 3% gypsum,
0.14% Aluminium
powder, 0.78 Ca/Si and
0.8 W/C
Compressive strength is
enhanced (4.2MPa) which far
exceeded the specification of
A2.5, B05 grade
Hu, Qian, Wang,
Ma, & Wang
(2021).
3
AAC with 52.5 grade
Ordinary Portland Cement
(OPC)
Cement is partially
replaced by lime
Lime had no effect on the
strength of the mixture.
Khan, (2020)
4
AAC with Coal Bottom
Ash (CBA)
CBA was used to replace
sand. Optimum
replacement of CBA is
50%
Thermal conductivity value is
decreased up to 39% and
increased strength up to 16%
higher than reference AAC.
Kurama, Topcu
and Karakurt
(2009).
5
AAC with Natural Zeolite
Additive (NZ)
Sand was replaced by up
to 50% NZ
Decreases the unit weight of
aerated concrete specimens
hence, decreases density
Karakurt, Karuma
and Topcu (2010).
6
AAC with Self-ignition
Coal Gangue (SCG)
Optimum mix proportion
is SCG to lime to cement
to gypsum is 54:23:20:3
with 1.3% aluminum
powder
The products consisted of CSH
gel and tobermorite phase.
Cong, Lu, Yao &
Wang (2016).
7
AAC with Incinerated
Sewage Sludge Ash
(ISSA)
ISSA for the production of
AAC block
Should only be considered for
use if alternatives (PFA or
Natural Sand) are not available
or uneconomic
Dunster (2007).
8
AAC with Bamboo Leaf
Ash (BLA)
Up to 15% of BLA is
being partially replaced
with cement
Still Under laboratory
investigation
Simeon and
Oladiran, (2021)
23
9
AAC with Silica Fume
(SF) / Fly Ash (FA)
52.5 grade OPC is being
replaced with various
percentages up to 25% of
SF.
Compressive strength increases
up to 80% when cement is
replaced by 15% of SF.
Rathod and
Akbari (2017).
10
AAC with Dune Sand
(DS)
Normal sand was being
replaced by up to 30%
Dune sand
A drastic reduction in strength
was observed when higher than
30%
Vu and Nguyen
(2017).
11
AAC with Rice Husk Ash
(RHA) / Aluminum
Powder (AP)
RHA and Aluminium
containing waste as a
partial aggregate and
expansive replacement
agent
Delicate particle size has a
positive effect on the CSH to
tobermorite conversion.
Kunchariyakun,
Asavapist and
Sombatsompop
(2015).
12
AAC with Concrete
Sandwich Block (CSB) /
Waste Glass (WG)
Sand was being replaced
by various types of WG
AAC with cathode ray tube glass
has similar characteristics to
reference sample.
Walczak,
Malolepszy,
Reben, Szymanski
and Rzepa (2015).
13
AAC with Halloysite
Powder (HP)
Clay mineral was used as
a cement replacement
Application of halloysite as a
cement replacement in the
amount of 5.5% increases the
strength by 5.8% at the
same bulk density of the
autoclaved aerated concrete.
Owsiak, Soltys,
Sztaboroski and
Mazur (2015).
14
AAC with Air-cooled Slag
(AS)
AS was used to replace
lime and sand (optimum at
50% low-lime mixes and
30% for high-lime mix)
Improvement in compressive
strength and shorter curing
duration
Mostafa (2005).
15
AAC with Efflorescence
Sand (ES)
Normal sand was being
replaced by up to 25% ES
Compressive strength is
enhanced.
Haung et al.
(2012).
16
AAC with Phosphorus
Sand (PS)
Normal sand was being
replaced by up to 30% PS
Control heat of hydration
Demir, &
Güçlüer, (2017).
17
AAC with Coal Gangue
(CG) / Iron Ore Tailings
(IOT)
Optimum composition at:
20% CGC, 40% IOT, 25%
lime, 10% cement, 5%
0.06% Aluminium powder
Completely replaced sand to
achieve bulk density and
compressive strength of
609kg/m3and 3.68MPa,
respectively.
Wang, Ni, Zhang,
Wang, and Gai
(2016).
18
AAC with Pulverized Fuel
Ash (PFA) / Palm Oil Fuel
Ash (POFA)
Cement was completely
replaced by PFA and
POFA
Control heat of hydration
Mehmannavaz et
al. (2014).
19
AAC with Copper
Tailings (CT) / Blast
Furnace Slag (BFS)
Optimum composition
SCT to BFS to Sand to
The compressive strength was
4.0 MPa, and the dry density was
610.2kg/m3
Huang, Ni, Cui,
Wang and Zhu
(2012).
24
Cement to Gypsum is
30:35:20:10:5
20
AAC with Perlite Waste
(PW) / Polypropylene
Fiber (PF)
Sand was replaced by PW
PW at 10% reduced the thermal
conductivity about 15% without
significant reduction of
compressive strength.
Rozycka and
Pichor (2016).
Simeon (2021).
2.6 Drivers to the adoption of AAC block
Rathi and Khandve (2015) replaced red bricks with eco-friendly AAC blocks and it was revealed
that as AAC block usage reduces the cost of construction by up to 20%. The reduction of dead
load of the wall on the beams makes comparatively lighter members, the use of AAC blocks also
reduces the requirements of materials such as cement and sand by up to 50%.
Similarly, in studies conducted by Oo and Hlaing (2018) on the beneficial usage of AAC block, it
was revealed that the cost of AAC block for building a wall that has 100ft2 is lesser than the cost
of conventional brick. In the same vein, the weight of AAC block to build a wall that has 100ft2 is
lesser than the weight of conventional brick.
Furthermore, the compressive strength of AAC block is higher than that of conventional brick. So
also, the quality. Relatedly, Pandey et al. (2018) reported that AAC is one of the eco-friendly and
certified green building materials that is porous, non-toxic, reusable, renewable and recyclable.
Pandey et al. (2018) asserted that AAC is lightweight, load bearing, high insulating, durable and
is produced in a wide range of sizes and strength. Being aerated, it contains 50-60% of air, leading
to its lightweight and low thermal conductivity.
25
AAC is manufactured from common and abundant natural raw materials, it is therefore extremely
resource-efficient and eco-friendly. The energy consumed in the production process emits no
pollutants and creates no by-products or toxic waste products. The workability of AAC helps to
eliminate waste on the job and its compressive strength is comparatively more than traditional clay
brick. The density of AAC block is one-third that of traditional clay brick and there is no change
in wet condition. It helps in reducing a dead load of the structure thereby reducing cost of
construction by up to 20% (Rathi & Khandve, 2015).
Furthermore, Nahhas (2013) reported that AAC block has its obvious advantages of higher
strength to weight ratio, better tensile strain capacity, lower coefficient of thermal expansion, and
enhanced heat and sound insulation characteristics due to air voids in the concrete.
Research and Market (2020) gives an account of drivers to adoption of AAC on building projects
in various regions of the world, these are stated as follows. In China, there is high demand for eco-
friendly construction material to drive the AAC market. While in Japan, AAC is widely used due
to its lightweight nature in earthquake-prone. In India however, newly-adopted green building
AAC material is used to substitute conventional red clay bricks.
Similarly, in South Korea, AAC blocks are widely used to minimize cooling and heating loads in
buildings. While in Australia, there is improved investment scenario in commercial construction
will drive the demand for AAC. Furthermore, in Europe, Germany aims to have an almost climate-
neutral building stock by 2050. While in the UK, changes to building regulations and solutions to
improve thermal and acoustic performance drives the market.
26
AAC which was first developed in Scandinavia is now widely used in buildings. In Russia, demand
for AAC is high despite the overall decline in construction activities. In Poland however, growing
residential construction increases the demand for AAC construction material. In North America,
in the US, demand for AAC is growing and frequently being used in flooded areas owing to its
moisture absorbing feature. In Canada, AAC has how been widely accepted in Canada due to its
heat resistant property. In Mexico, rapidly growing infrastructure is attracting leading AAC
manufacturers in the country.
In the Middle East and Africa, in Turkey, blocks are most widely used AAC materials. In the UAE
however, AAC is accepted and approved across UAE for use in many prestigious projects. In Saudi
Arabia, several ongoing and upcoming infrastructural projects are in place to boost the demand for
AAC materials while in South Africa, surge in private investment in the construction sector is
expected to drive the AAC market. In South America, Brazil is witnessing growing demand for
AAC materials in infrastructural development. In Argentina, favorable building & construction
industry outlook is facilitating Growth of AAC Market.
The major drivers to the use of AAC block for masonry construction comprise: Excellent thermal
absorption property; Superior fire insulation; Pest and mold resistant; Lightweight; Better thermal
conductivity; Reduced dead weight on structure; Reduction of building costs as a result of decrease
structural element; Eco-friendly (lower environmental impact); Adaptability of AAC blocks to
tropical climates; Recyclable; Quick and easy installation; Excellent acoustic performance;
Breathable wall system; Monetarily and ecologically better than other conventional walling
materials; Attractive appearance; Readily adaptable to any style of architecture; Reduced transfer
of load on the foundation; Manufactured from common and abundant raw material; Versatile as
27
components can be used for walls, floors and ceiling, Energy efficient; Use of reduced labour in
manufacture and its installation; Reduced cost of maintenance; AAC production process does not
develop toxic gases; Durability; Used in the construction of dwellings in low-cost housing units
on the mass scale and Moisture resistant.
2.7 Barriers impeding AAC block adoption
Research and Market (2020) posit that AAC is one of the world most produced building materials
after concrete and is mostly manufactured as blocks and panels. Unlike concrete masonry units,
AAC blocks are solid with no moulded core holes. 4 inches of AAC has a 4-hour rating making it
ideal in commercial buildings for encasing steel columns, surrounding elevator shafts and for other
fire stopping requirements.
Despite the immense benefits of AAC block for construction of sustainable buildings, its level of
adoption is still very low when compared to conventional sandcrete blocks and bricks. This
according to Falade and Ikponmwosa (2008) is that stakeholders are being addicted to the use of
conventional construction materials like sandcrete blocks, concrete and the likes.
Similarly, cost associated with AAC, lack of awareness of AAC blocks, low market penetration
and brittle nature of the material are barriers of AAC block adoption (Research & Market, 2020).
The use of sustainable building materials in the construction industry still faces a lot of challenges
for its implementation.
28
Based on the studies of Landman (1999), Anderson, Bennett and Collopy (2000), Rao and
Brownhill, (2001) factors impeding the use of sustainable building materials as follows: The real
or perceived financial cost and risks which include the problem of the upfront cost and the ongoing
costs usually coming from separate budgets, if not separate organization, lack of information and
training of designers, contractors, and clients, lack of demand from the clients, lack of support
from subcontractors and regulation.
In the same vein, Anderson et al. (2000) and Davis (2001) stated that barriers to using sustainable
building materials and products are: Construction practitioners that are not aware of how important
it is to prevent the environment from being polluted by the waste generated from construction
industry, the absence of well-known sustainable building products to be used in construction, the
lack of sufficient environmental information about structural materials to make adequate
comparison between alternatives and the absence of regulations and codes that encourage the use
of green building.
Djokoto, Dadzie and Ohemeng-Ababio (2014) identified 20 barriers to sustainable construction in
Ghana which comprises lack of building codes and regulation, lack of incentives, higher
investment cost, risk of investment, higher final cost, lack of public awareness, lack of demand,
lack of strategy to promote sustainable construction, lack of design and construction team, lack of
expertise, lack of professional knowledge, lack of database and information, lack of technology,
lack of government support, lack of a measurement tool, increased documentation, extensive pre-
contract planning, change resistance, lack of training, lack of cooperation.
29
The major barriers impeding AAC block adoption for building projects are simplified and listed
below: Unfavorable perception of home buyers to AAC in the short term; Lack of interest in new
products by buyers and house owners; Little interest in new products by Architects and
Developers; Costs of the “learning curve” while working with a new product; Startup costs
associated with promoting and teaching the industry to build with AAC; Market potentials;
Inadequate building codes and regulations; Low demand for sustainable housing; Lack of easy
rating systems for eco-buildings; Absence of design standards for AAC products; Inadequate
government policies and supports; Existing structure of the construction industry; Lack of readily
available accessible information; Low level of awareness and knowledge on the concept of
sustainability; Low level of demand and knowledge of AAC products; Inadequate exemplar
demonstration project to infuse confidence for using AAC; Non-awareness of people towards the
advantageous use of AAC, Huge capital to set up AAC plant; Lack of readily available accessible
information; Inadequate technical know-how and manpower to manufacture AAC products; Use
of unsustainable construction materials; Availability of conventional material and Affordability.
2.8 Strategies that can improve the usage of AAC blocks
Pandey et al. (2018) recommended that in order to improve the application of AAC product in
various fields, an approach requires investment in high quality and automated equipment that uses
the latest manufacturing technology. Producing a complete AAC solution is a next step towards
the market expansion and increasing market share of AAC as a building material. Investment in
innovative plant upgrades and new plants with modern AAC technology are essential to staying
ahead of the ever-changing construction market.
30
Furthermore, Research and Markets (2020) posit that strategies that can improve AAC block usage
are growth in the infrastructural sector, rising demand for light weight construction materials,
growth preferences for low-cost houses and an ever-increasing focus on green and soundproof
buildings. Other strategies that can improve AAC block adoption are explained below:
a. Proper awareness of sustainable construction
There is no doubt that sustainable design is an imperative part of design education today. Tertiary
Institutions in Nigeria both for Undergraduate and Post graduate level need to optimize sustainable
design in their semester curriculum. It could include sustainable development, sustainable design
processes, principles, policies and building regulations (Davies & Davies, 2017). Davies and
Davies (2017) further stated that the mentality of the younger designers will be built to be more
conscious of sustainable development and construction and added that the lack of exposure to
sustainable design in Tertiary Institution requires that this education needs to be obtained. To
bridge the education gap, practitioners could utilise the services of a consultant or local resource
centres. Davies and Davies (2017) revealed that other designers, unlike architects, are not familiar
with building regulations that promote energy efficiency and environmental sustainability.
b. Support of government policies
Davies and Davies (2017) recommended that government policies should be made in favour of
sustainable construction and energy saving. Regulations should be developed in Nigeria, which
should assist the built environment in becoming more sustainable and added that presently, there
are no policies, regulations or bodies to sustainable development and promote environmental
sustainability and energy savings. And none have been implemented.
31
Complete overhaul of planning and implementation policies such as building codes, that regulate
performance standards for design and construction works based on sustainable principles be
facilitated. Ofori (2006) Posit that the National Building Code of the Federal Republic of Nigeria
was not developed based on sustainable development but rather on persistence collapse of
buildings; the paucity of reference design standards for professionals; and the use of unskilled
professionals.
However, total overhaul of the National Building Code that will incorporate sustainable
construction is pertinent most especially for residential buildings. The development of bye-laws
for major cities in Nigeria should be advocated and encouraged because of their strategic level of
development. Governments (federal, state and local), through respective regulatory agencies,
should play significant roles in reversing the trend of building failures and collapse.
c. Products suppliers and manufacturers
It is essential that product and material suppliers and manufacturers continue developing
environmentally responsible products and broadening their product ranges, as with greater
selection, designers and clients are more likely to choose this alternative. In addition to this, and
despite its difficulty, designers need to continually ask product suppliers and manufacturers about
their raw materials, processes and the origin of products. With persistence, this would yield
positive results (Eley, 2011; El-Gohary & El-Diraby, 2010; Du-Plessis, 2007; Thorpe & Ryan,
2007; Haselbach, 2008).
d. Client education
Barriers preventing clients from committing to a sustainable design approach are presently surplus
cost, a selective use of materials, as well as education into the pressing need for sustainability. This
32
results in clients not willing to consider the environmental responsibility, and lack of enthusiasm
from designers to advocate sustainable design (Eley, 2011; El-Gohary & El-Diraby, 2010; Du
Plessis, 2007; Thorpe & Ryan, 2007; Haselbach, 2008; Hakkinen & Belloni, 2011).
The higher educational background will enable clients to becoming better informed on the benefits
of sustainable development/ design alternatives. This will consequently boost the client’s
awareness and thereby enhance level of acceptance. It will be eventually increase in demand for
sustainable construction and cause a reduction in price of the sustainable construction materials
and techniques (Yudelson, 2007).
e. Introduction of sustainable construction in the educational institutions
It is pertinent to introduce sustainable and green construction education into the curriculum based
on the fact that every year, many people graduate from different educational institutions with
degrees in construction and construction related fields. These fields of study also include various
renewable resources and building sciences, technology, and design degree programmes. This will
facilitate real-world practical experience into classrooms by the professionals and academicians to
the students (Davies & Davies, 2017).
g. Accessibility of information and intricacy of analysis
Azapagic and Perdan (2000); Singh et al. (2013) and Yudelson (2009) emphasised on the
significant of accessibility of information and intricacy of analysis on the sustainable construction.
It is a measure of qualitative, quantitative and progress of sustainable activities for the whole
system. It provides a framework and a systematic approach to assess sustainability in construction.
33
Information and intricacy of analysis guide the decision makers to appraise the selection process
of construction equipment on the triple bottom line of sustainability.
An extensive review of the literature of the sub-themes of the project title has been carried out.
The following have been extensively reviewed: definition of Autoclaved Aerated Concrete (AAC)
and sustainable construction materials, awareness of AAC block variants, adoption level of AAC
on building projects, barriers impeding AAC block adoption and strategies that can improve the
usage of AAC blocks on building projects.
34
CHAPTER THREE
3.0 RESEARCH METHOD
3.1 Introduction
This chapter presents the general outline or procedure for conducting the study. It discusses the
research design, population of the study, area of the study, sampling technique and procedures,
method of data collection, instrument of data collection, types of data used, reliability and validity
of the research instrument, method of data analysis and constraints to the study.
3.2 Area of the study
The first study area was delimited to Lagos state which is located in the south-western region of
Nigeria. It is the largest metropolitan area in Nigeria (Ayeni, 1979). The choice of Lagos state was
because it is the economic nerve center of Nigeria. As the economic and commercial nerve-center
of the country, Lagos has a high number of construction practitioners as well as a large
concentration of construction related organizations of various categories and sizes. There is a high
demand of building materials for residential, commercial and institutional buildings, civil and
heavy engineering works in Lagos due to the large population of the state.
It is the second most populous state in Nigeria with over 9 million human populations (National
Population Commission, 2009). This ranks the state among the fastest growing cities in Nigeria
with a significant level of construction activities which enhanced the collection of data for this
study. The second study area was delimited to five provinces from South Africa and the
respondents were obtained through referral.
35
3.3 Research design
Research design provides an outline that serves the purpose of guiding a researcher on how to
generate data on a particular study (Asika, 2012). A survey research design was adopted in the
study to achieve the outlined research questions, hypothesis testing to meet the study’s objectives.
Specifically, a cross-sectional research design was used where samples were drawn from the
population of study at one point in time. The term survey is used for the techniques of investigation
by a direct observation of a phenomenon or a systematic gathering of data from population by
applying personal contact and interviews when adequate information about certain problem is not
available in records, files and other sources (Pandey & Pandey, 2015).
3.4 Population of the study
Umeh (2018) defines the study population as the totality of all elements, subjects, or members that
possess one common or a set of common characteristics. The targeted population for this study
were made up of two groups comprising Nigerian and South African professionals acquainted with
the knowledge and have been involved in the use of AAC on building projects.
3.5 Sample size and sampling techniques
Asika (2012) defines a sample as precisely a part of the population. A sample is a subset of a
population drawn specifically to make inference about the population.
The study adopted multi-sampling method, with convenience sampling method being the first.
Convenience sampling is a non-probabilistic sampling technique and one in which selection of
sampling units by a researcher is based on the members of the frame that: easily volunteered; are
available; or are easy to assess (Umeh, 2018). It was adopted due to the researcher’s inability to
36
obtain a current and comprehensive list of built environment professionals in the construction
industry operating or based in Lagos as at the time of carrying then study.
Secondly, the study also utilized snowball sampling method to obtain responses from the referred
South African respondents. Snowball sampling is especially useful when a researcher is trying to
identify samples of a population that are difficult to locate (Umeh, 2018). Absence of list
comprising registration of AAC contractors/firms (sample frame) afforded the researcher to rely
on participant referrals to recruit new participant and this prompted the use of snowball sampling
technique as AAC block is not one of the conventional walling materials adopted in the provinces.
Few respondents who met the criteria and have been involved in AAC projects were first identified.
The identified respondent then made referrals to others that have used the block until the last
respondent is attained. Snowball sampling could be used for qualitative and quantitative studies,
and the use of a questionnaire for collecting data could be appropriate (Gaal, 2016; Showkat &
Parveen, 2017).
3.6 Instrument for data collection
Two field research instruments were developed to collect data namely: “Structured Self-
administered Questionnaires was designed for the Nigerian professionals in the Lagos metropolis”
and “Online Questionnaire Survey (through Google Forms) was designed to collect data from the
referred South African respondents”.
The structured questionnaire contained close-ended questions for eliciting information relating to
the research objectives from the targeted respondents. The variables were being identified through
a comprehensive literature review which were summarized and simplified for the study.
37
Copies of the structured questionnaires were used in obtaining responses from the Nigerian
professionals as regards their demographic profile; level of awareness of AAC block variants;
prospect for adoption of AAC block in the Nigerian building industry; drivers of AAC blocks;
barriers impeding AAC block adoption and strategies to enhance AAC block adoption. While
Online survey questionnaire through Google forms were used to gather responses from the
viewpoints of referred South African respondents as regards their demographic profile; level of
awareness of AAC block variants; adoption level of AAC block on building projects in South
Africa provinces; drivers of AAC blocks; barriers impeding AAC block adoption and strategies to
enhance AAC block adoption.
The survey instrument consists of six sections for each categories of respondents. Section ‘A’
sought to obtain information on the demographic profile of the respondents. The information in
section A was required to moderate the core parts of sections B, C, D, E, & F. In section B, the
respondents were required to indicate their level of awareness of the 20 different variants of AAC
available in literature (Source: Almajeed & Turki (2019); Khan (2020); Naik et al. (2018); Wahane
(2017); Abed et al. (2017); Owsiak et al. (2015); Rathod & Akbari (2017); Dunster (2007); Huang
(2012); Mostafa (2004); Rathod & Akbari (2017); Demir & Güçlüer (2017); Vu & Nguyen (2017);
Kuram et al. (2008); Demir, & Güçlüer, (2017); Haung et al. (2012); Owsiak et al. (2015); Naik et
al. (2018); & Hauser et al. (1999)) by ticking the appropriate scale that indicates their level of
awareness of AAC block options: 5 represents fully aware, 4 represents highly aware, 3 represents
somewhat aware, 2 represents slightly aware and 1 represents not at all aware.
38
Section C1 of the research instrument sought to evaluate prospect for AAC block adoption in the
Nigerian building industry by ticking: 1 represents very poor, 2 represents poor, 3 represents
moderate, 4 represents good and 5 represents very good.
Section C2 of the research instrument sought to evaluate the adoption level of AAC by ticking the
AAC variants that were used in the last ten (10) projects: Note: 0 represents Nil, 1 represents
project 1, 2 represents project 2, 3 represents project 3, 4 represents project 4, 5 represents project
5, 6 represents project 6, 7 represents project 7, 8 represents project 8, 9 represents project 9 while
10 represents project 10.
Section D of the research instrument sought to assess 26 drivers of AAC on building projects
(Source: Talati et al. (2018); Walczok et al. (2015); Habib et al. (2015); Aasif & Shrivastava
(2018); Nagavenkatasaikumar & Satihish (2017); Domingo (2008);
www.researchandmarkets.com; Manikandan et al. (2018); Sachin et al. (2018); Rathi & Khandve
(2015); Asha et al. (2014); Oo & Hlaing (2018); Pulliattu & John (2017); & Güçlüer et al. (2015))
by ticking the appropriate scale that indicates drivers of AAC by ticking one of the options for
each driver: 5 represents most important, 4 represents more important, 3 represent moderately
important, 2 represents slightly important and 1 represents not important.
Section E of the research instrument sought to assess significant barriers impeding the adoption of
AAC (Source: Abidin, (2010); Muazu, & Alibaba, (2017); Tey et al. (2013);
www.researchandmarkets.com; Djokoto et al. (2014); Williams & Dair (2017); Ametepey et al.
(2015); Sutton (1999); Landman (1999); Anderson et al. (2000); Rao & Brownhill, (2001); Kissi
et al. (2018); Dahle & Neumayer (2001), Griffin et al. (2010), Shafii et al. (2006); Muazu &
Alibaba (2017); & Tey et al. (2013 )) by ticking one of the options for each factor: 5 represents
39
most Significant, 4 represents more Significant, 3 represents moderately significant, 2 represents
slightly significant and 1 represents not significant.
While section F evaluates important strategies that can improve the adoption of AAC on
construction sites in Lagos state (Source: www.marketsandmarkets.com;
www.researchandmarkets.com & Davies & Davies (2017)) by ticking one of the options for each
effect: 5 represents most important, 4 represents more important, 3 represent moderately important,
2 represents slightly important and 1 represents not important.
3.7 Data distribution and collection procedure
Primary data was collected via Structured Self-administered Questionnaires to the Nigerian
professionals, while Online Questionnaire Survey (through Google Forms) were administered to
gather the viewpoints of 17 referred South African Professionals who have been involved in the
use AAC blocks in five South African provinces. Personal phone calls and site visits were made
to the respondents to retrieve the questionnaires in Lagos metropolis. While, Google form links
and reminders were sent to the mails of the referred respondents to obtain their responses.
3.8 Types of data used in the study
Two types of data were used: primary data and secondary data. The primary data was obtained
from the field with the aid of structured questionnaire while the secondary data were obtained from
the review of relevant literature from published sources such as journals, seminar papers,
conference proceedings and textbooks.
40
3.9 Validity of Research Instrument
According to Ogolo (1996) Validity testing entails content rating by a group of judges. An
instrument is said to be valid if it covers the entire subject. The content validity of the instrument
was assessed by my project Supervisor, a Lecturer in Civil Engineering department, an AAC block
manufacturer and a staff PhD candidate in Cape Town University, South Africa. The corrections
identified by these experts were rectified in the questionnaire before it was administered.
3.10 Procedure for data processing and analysis
The response data from the study were coded, processed and analyzed with the aid of Statistical
Package for Social Sciences (SPSS) version 23.0, Data were analyzed using the following
descriptive statistical tools such as frequency, percentages, mean score and ranking, while One-
way ANOVA, Mann Whitney U test and Kendall’s coefficient of concordance were used as the
tools of analysis for the inferential statistics, respectively.
3.11 Constraints to study
The research faced some constraints which are listed below:
There was reluctance of some respondents to participate in the survey. Whereas, some respondents
were most interested in the research project but unwilling to participate because they felt the
questionnaire was geared towards eliciting confidential information pertinent toward their own
41
market and technical research which they believe is not relevant to my evaluation of the Nigerian
market.
Also, there was time constraint due to the short time this dissertation was conducted however, if
there had been more time all the questionnaires would have been retrieved and there would have
been a more robust analysis of data. Lastly, the fund required to aid the retrieval of the
questionnaire was on the high side which made it impossible for all the questionnaires to be
retrieved.
42
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION OF FINDINGS
4.1 Introduction
This chapter deals with the presentation of results of the analysis of data. The discussions of the
results are also presented in this chapter.
4.2 The response rates
The response rate is depicted in Table 4.1
Table 4.1: Response rates from respondents
Questionnaires
Number
Total numbers of questionnaire administered
145
Total numbers of questionnaire returned
99
Response rate
68.3%
Table 4.1 shows that 145 copies of questionnaire were distributed to the respondents. At the end
of the survey period, a total of 99 questionnaires were duly completed and retrieved. A total of 99
questionnaires were then analyzed for the study representing a 68.3% response rate. This is a good
response rate considering the difficulties in getting responses to questionnaires in Lagos state.
Moreover, 17 numbers of questionnaires were obtained from referred South African construction
professionals acquainted with the material and have been involved in the use of AAC block for
building projects in 5 South African provinces.
43
4.3 Demographic profile of the respondents
The demographic data of the respondents are presented in Tables 4.21 and 4.22
Table 4.21: Demographic profile of the Nigerian respondents
Profile
Nigerian Professionals
Frequency Percentage
Professional Background
Architecture
7
7.1
Building
38
38.4
Civil Engineering
45
45.5
Quantity Surveying
9
9.1
Total
99
100.0
Professional Body
NIA
7
7.1
NIOB
38
38.4
NSE
45
45.6
NIQS
9
9.1
Total
99
100.0
Grade of membership
Graduate
48
48.5
Corporate
47
47.5
Fellow
4
4
Total
99
100.0
Highest Academic Qualification
OND
0
0
HND
10
10.1
BSc/BTech
55
55.6
MSc/MBA
31
31.3
PhD
3
3
Total
99
100.0
Years of Experience
1-5 Years
25
25.3
6-10 Years
29
29.3
11-15 Years
26
26.3
16-20 Years
12
12.1
21 Years and above
7
7.1
Total
99
100.0
Organisation Type
Consulting
31
31.3
Contracting
45
45.5
Client Organisation
5
5.1
Design & Build
18
18.2
Total
99
100.0
44
Organisation Size
Small sized with 1-50
43
43.4
Medium sized with 51-250
47
47.5
Large size with 250 or more
9
9.1
Total
99
100.0
Ownership and Management
Fully Indigenous
60
60.6
Fully Expatriate
5
5.1
Partly Indigenous & partly expatriate
34.3
34.3
Total
100
100.0
Nature of work undertaken
New construction
27
27.3
Renovation
5
5.1
General contracting
67
67.7
Total
99
100.0
Table 4.21 shows the demographic information of the Nigerian respondents as it captured the
professional background of respondents that participated in the study. From the first category of
respondents; 7.1% were Architects, 38.4% were Builders, 45.5% were Civil Engineers while 9.1%
were Quantity Surveyors. This result revealed that most of the respondents had Civil Engineering
academic background. Also, for professional affiliation, 7.1% are registered with Nigerian Institute
of Architects (NIA), 38.4% are registered with Nigerian Institute of Building (NIOB), 45.5% are
registered with Nigerian Society of Engineers (NSE) while 9.1% are registered with Nigerian
Institute of Quantity Surveyors (NIQS). This result indicates that most of the respondents are
registered with the Nigerian Society of Engineers.
Table 4.21 also indicates the highest academic qualification of the Nigerian respondents. 10.1% of
the respondents have higher National Diploma, 55.6% of the respondents have University’s
Bachelor degree, 31.3% and 3.0% of the respondents possesses Master’s and Doctorate Degrees
respectively. This inference that can be drawn from this result is that the respondents have acquired
45
a significant level of formal education and were able to understand the questions and were able to
provide quality responses to the various research questions.
Experience is key and could depict the level of knowledge of a respondent with reference to a
study. 25.3% of the Nigerian respondents had years of experience ranging from 1 to 5 years, 29.3%
of the respondents had years of experience ranging from 6 to 10 years, 26.3% of the Nigerian
respondents had years of experience ranging from 11 to 15 years, 12.1% of the Nigerian
respondents had years of experience from 16-20 years while 7.1% of the Nigerian respondents had
years of experience from 21 and above years.
Table 4.21 further shows the participating proportion of each organisation type. 31.3% of the
Nigerian respondents were from Consulting organisation, 45.5% were from Contracting
organisation, 5.1% were from Client organisation while 18.2% were from Design & Build
organisation.
Table 4.21 further reveal that the study sample consisted of mainly medium-sized organisations
with 47.5%, followed by small-sized organisation with 43.4% and large-sized organisations with
9.1%. The table further indicates the type of ownership and management of the organisations that
participated in the survey and reveals that 60.6% are indigenously owned, 5.1% are fully expatriate
while 34.3% are partly indigenous and partly expatriate.
Table 4.21 further showed the nature of construction works undertaken by the organizations.
27.3% respondents undertake new construction works, 5.1% respondents undertake
renovation/refurbishment works while 67.7% respondents undertake general contracting works.
This result indicates that a larger number of the Nigerian respondents undertakes general
contracting works.
46
Table 4.22: Demographic profile of the South African respondents
Profile
South African Professionals
Frequency Percentage
Years of Experience
1-5 Years
1
5.9
6-10 Years
3
17.6
11-15 Years
8
47.1
16-20 Years
3
17.6
21 Years and above
2
11.8
Total
17
100.0
Organisation Size
Small sized with 1-50
6
35.3
Medium sized with 51-250
7
41.2
Large size with 250 or more
4
23.5
Total
17
100.0
Ownership and Management
Fully indigenous
8
47.1
Fully expatriate
3
17.6
Partly indigenous & partly expatriate
6
35.3
Total
17
100.0
Nature of work undertaken
New construction
4
23.5
Renovation
1
5.9
General contracting
12
70.6
Total
17
100.0
Province
Western Cape
9
52.9
Gauteng
2
11.8
Eastern Cape
2
11.8
Free State
2
11.8
KwaZulu-Natal
2
11.8
Total
17
100.0
Experience is key and could depict the level of knowledge of a respondent with reference to a
study. 5.9% of the South African respondents had years of experience ranging from 1 to 5 years,
17.6% of the South African respondents had years of experience ranging from 6 to 10 years, 47.1%
47
of the South African respondents had years of experience ranging from 11 to 15 years, 17.6% of
the South African respondents had years of experience from 16-20 years while 11.8% of the South
African respondents had years of experience from 21 and above years.
Table 4.22 further reveals that the study sample consisted of mainly medium-sized organisations
with 35.3%, followed by small-sized organisation with 41.2% while large-sized organisations with
23.5%.
Table 4.22 further indicates the type of ownership and management of the organisation and reveals
that 47.1% of the organisation in South Africa that participated in the survey are indigenously
owned, 17.6% of the organisation are fully expatriate while 5.3% of the organisation are partly
indigenous and partly expatriate respectively.
Table 4.22 further showed the nature of construction works undertaken by the participating
organizations. 23.5% of the respondents undertake new construction works, 5.9% of the
respondents undertake renovation/refurbishment works while 70.6% of the respondents undertake
general contracting works. This result indicates that a larger number of the respondents undertake
general contracting works.
The latter part of Table 4.22 revealed the provinces of the referred professionals from South Africa.
59% plies their trade in Western Cape, 11.8% plies their trades in Gauteng, Eastern Cape, Free
State, KwaZulu-Natal respectively. This shows that majority of the participating professionals are
from Western Cape.
48
4.4 Results of the stated objectives of the study
4.4.1 Awareness of AAC block variants
The awareness of 20 AAC block variants extracted from literature in Nigeria and South Africa are
presented in Table 4.3
Table 4.3: Awareness of AAC block variants in Nigeria and South Africa
Nigerian Professionals South African Professionals
AAC Variants
N
MS
Rank
N
MS
Rank
AAC with 52.5 grade Ordinary
Portland Cement (OPC)
94
2.11
1
17
4.94
1
AAC with 42.5 grade Ordinary
Portland Cement (OPC)
95
2.07
2
17
4.24
2
AAC with Aluminum Powder (AP)/
Rice Husk Ash (RHA)
93
2.01
3
16
4.00
3
AAC with Self-ignition Coal Gangue
(SCG)
95
1.98
4
17
2.47
17
AAC with Coal Bottom Ash (CBA)
94
1.95
5
17
2.94
6
AAC with Concrete Sandwich Block
(CSB)/ Waste Glass (WG)
95
1.94
6
17
2.88
7
AAC with Natural Zeolite Additive
(NZ)
95
1.94
6
17
2.76
9
AAC with Pulverized Fuel Ash
(PFA)/ Palm Oil Fuel ash (POFA)
95
1.89
8
17
3.35
4
AAC with Copper Tailings (CT)/
Blast Furnace Slag (BFS)
94
1.85
9
17
2.76
9
AAC with Efflorescence Sand (ES)
95
1.77
10
17
2.65
12
AAC with Silica Fume (SF)/ Fly Ash
(FA)
94
1.76
11
17
3.06
5
AAC with Air-cooled Slag (AS)
94
1.76
11
17
2.59
13
AAC with Perlite Waste (PW)/
Polypropylene Fibre (PF)
95
1.71
13
17
2.35
18
AAC with Phosphorus Slag (PS)
92
1.70
14
17
2.59
13
AAC with Dune Sand (DS)
93
1.68
15
17
2.82
8
AAC with Halloysite Powder (HP)
93
1.68
15
17
2.59
13
AAC with Coal Gangue (CG)/ Iron
Ore Tailings (IOT)
95
1.67
17
16
2.69
11
AAC with Incinerated Sewage Sludge
Ash (ISSA)
93
1.66
18
17
2.59
13
AAC with 32.5 Grade Ordinary
Portland Cement (OPC)
97
1.63
19
17
1.94
19
AAC with Bamboo Leaf Ash (BLA)
95
1.36
20
17
1.41
20
Note: 1 represents not at all aware, 2 represents slightly aware, 3 represents moderately aware, 4 represents highly
aware, 5 represents fully aware. N represents the number of Respondents; MS represents the Mean Score.
49
Table 4.3 shows the responses of respondents on the level of awareness of AAC block variants.
To quantify the respondents’ awareness level of the variants, a graduated scale of 1.00 to 5.00 was
adopted and the mean scores were calculated. The mean values were interpreted using the
following scale 1.00 ≤ MS < 1.49 ‘'means not at all aware’, 1.50 ≤ MS < 2.49 means ‘slightly
aware’, 2.50 ≤ MS < 3.49 means ‘moderately aware’, 3.50 ≤ MS < 4.49 means ‘highly aware’ and
4.50 ≤ MS ≤ 5.00 means ‘fully aware’.
The study revealed that the Nigerian respondents are slightly aware of 19 out of the 20 listed AAC
variants, with mean score ranging from 1.63 to 2.11. The top ranked AAC variants that were
slightly aware by the professionals comprises AAC with 52.5 grade OPC (MS=2.11), closely
followed by AAC with 42.5 grade OPC (MS= 2.07) and AAC with RHA/AP (MS=2.01). On the
other hand, as evidenced, AAC with Bamboo Leaf Ash (MS= 1.36) ranked the least of the AAC
variants and the professionals are not at all aware of the variant. On the other hand, from table 4.3,
the mean scores of AAC block options as perceived by the South African respondents range from
1.41 to 4.94. The South African professionals are Fully aware of AAC made with 52.5 grade OPC.
Relatedly, the professionals are highly aware of AAC made with 42.5 grade OPC and AAC with
RHA/AP.
The professionals are moderately aware of 13 of the 20 AAC variants. Also, the professionals are
slightly aware of three AAC variants include; AAC made with SCG with a mean score of 2.47,
AAC made with PW/PF with a mean score of 2.35 and AAC made with 32.5 grade OPC with a
mean score of 1.94. The professionals are not at all aware of AAC made with BLA (MS=3.07).
50
4.4.2 Prospect for adoption of AAC block in the Nigerian Construction industry
Table 4.4: Prospect for adoption of AAC block in the Nigerian Construction industry
Type
Response rate
MS
SD
1
2
3
4
5
Prospect
5 (5.2%)
25(25.8%)
36(37.1%)
26(26.8%)
5(5.2%)
3.01
.794
Note: 1 represents very poor, 2 represents poor, 3 represents moderate, 4 represents good and 5
represents very good. MS represents Mean Score while SD represents Standard Deviation.
Table 4.4 shows the responses of Nigerian professionals on the prospect for adoption of AAC
blocks in the Nigerian construction industry. The response rates for the prospect for adoption of
AAC block variants are: 5.2% of the respondents are indicated “very poor”, 25.8% of the
respondents indicated “poor”, 37.1% of the respondents indicated “moderate”, 26.8% of the
respondents indicated “good” while 5.2% of the respondents indicated “very good”. Based on these
results, majority of the Nigerian professionals have a moderate disposition about AAC block being
adopted in the future.
Also, the mean value for the prospect for adoption of AAC block in the Nigerian construction
industry was interpreted using the following scale 1.00 ≤ MS < 1.49 represents ‘Very poor’, 1.50
≤ MS < 2.49 represents ‘Poor’, 2.50 ≤ MS < 3.49 represents ‘Moderate’, 3.50 ≤ MS < 4.49
represents ‘Good’ and 4.50 ≤ MS ≤ 5.00 represents ‘Very good’. The table indicated a moderate
prospect for adoption of AAC block by the Nigerian Respondents. This implies that there is a
likelihood of the block being adopted in the future.
51
4.4.3 Adoption level of AAC block variants on building projects in the South African Construction
Industry
Table 4.5: Adoption of AAC block variants in South Africa
AAC variant
Freq.
% MU
Rank
AAC with 52.5 grade Ordinary Portland Cement (OPC)
85
31.5
1
AAC with 42.5 grade Ordinary Portland Cement (OPC)
74
27.4
2
AAC with Rice Husk Ash (RHA) / Aluminum Powder (AP)
43
15.9
3
AAC with Pulverized Fuel Ash (PFA) / Palm Oil Fuel Ash (POFA)
43
15.9
3
AAC with Silica Fume (SF) / Fly Ash (FA)
11
4.1
5
AAC with 32.5 grade Ordinary Portland Cement (OPC)
9
3.3
6
AAC with Dune Sand (DS)
3
1.1
7
AAC with Efflorescence Sand (ES)
2
0.7
8
AAC with Coal Bottom Ash (CBA)
0
0
9
AAC with Natural Zeolite Additive (NZ)
0
0
9
AAC with Self-ignition Coal Gangue (SCG)
0
0
9
AAC with Incinerated Sewage Sludge Ash (ISSA)
0
0
9
AAC with Bamboo Leaf Ash (BLA)
0
0
9
AAC with Concrete Sandwich Block (CSB) / Waste Glass (WG)
0
0
9
AAC with Halloysite Powder (HP)
0
0
9
AAC with Air-cooled Slag (AS)
0
0
9
AAC with Phosphorus Sand (PS)
0
0
9
AAC with Coal Gangue (CG) / Iron Ore Tailings (IOT)
0
0
9
AAC with Copper Tailings (CT) / Blast Furnace Slag (BFS)
0
0
9
AAC with Perlite Waste (PW) / Polypropylene Fiber (PF)
0
0
9
Total uses of variants
270
100
Note: Freq. represents frequency of usage on the project, % MU represent percentage mean usage
Table 4.5 shows the descriptive analysis result of the adoption level of AAC block variants in the
South African building construction industry. Respondents were asked to indicate the AAC block
variants that they used in their last 10 recent projects. Results show that the major AAC block variants
used on building projects are AAC with 52.5 grade OPC with (% MU=31.5%), AAC with 42.5 grade
OPC with (% MU=27.4%), AAC with Aluminum Powder/RHA with (% MU=15.9%) and AAC with
52
PFA/POFA with (% MU=15.9%) as they are the top most four used AAC variants on building
projects. However, AAC with 52.5 grade OPC is mostly adopted AAC block variants in South Africa.
4.4.4 Important drivers for the adoption of AAC on building projects
Table 4.6: Important drivers for the adoption of AAC on building projects
Drivers
Nigerian Professionals
South African Professionals
N
MS
Rank
N
MS
Rank
Lightweight
95
4.17
1
17
4.71
2
Energy efficient
96
4.16
2
17
4.71
2
Ecologically better than other
conventional walling
materials
93
3.98
3
17
4.41
14
Adaptability of AAC to
tropical climates
95
3.95
4
17
4.35
16
Superior thermal absorption
property
96
3.84
5
17
4.71
2
Excellent fire insulation
96
3.84
5
17
4.76
1
Readily adaptable to any
style of architecture
94
3.84
5
17
4.59
5
Use of reduced labor in
manufacture and installation
96
3.81
8
17
4.35
16
Made from abundant raw
materials
96
3.80
9
17
4.18
21
Reduction in construction
cost
96
3.80
9
17
4.35
16
Eco-friendly
97
3.78
11
17
4.59
5
53
Optimum thermal
conductivity
94
3.73
12
17
4.59
5
Low maintenance cost
94
3.72
13
17
4.12
23
Fast and easy installation
96
3.70
14
17
4.53
8
Reduced dead load on
structure
95
3.69
15
17
4.41
14
Good acoustic performance
93
3.68
16
17
4.18
21
Highly durable
96
3.68
16
17
4.47
10
Versatile as components can
be used for walls, floors and
ceilings
96
3.68
16
17
4.24
20
Recyclable
96
3.65
19
17
4.35
16
Reduced transfer of load on
the foundation
96
3.64
20
17
4.47
10
Reduced transfer of load on
foundation
96
3.64
20
17
4.47
10
Breathable wall system
95
3.62
21
17
4.47
10
Its production process does
not emit toxic gasses
96
3.61
22
17
4.53
8
Used for construction of low
housing units
96
3.53
23
17
4.47
10
Moisture resistant
95
3.52
24
17
4.12
23
Resistance to pest and mold
96
3.33
25
17
3.94
26
Aesthetically appealing
96
3.07
26
17
4.06
25
Note: 1 represents not important, 2 represents slightly important, 3 represents moderately important, 4 represents
more important, 5 represents most important. While, N represents the number of Respondents; MS represents the
Mean Score
54
Table 4.6 shows the responses of Nigerian and referred South African professionals to important
drivers to AAC block adoption on building projects. To quantify the drivers of AAC adoption, a
graduated scale of 1.00 to 5.00 was adopted and the mean scores were calculated. The mean values
were interpreted using the following scale 1.00 ≤ MS < 1.49 ‘'means not important’, 1.50 ≤ MS <
2.49 means ‘slightly important’, 2.50 ≤ MS < 3.49 means ‘moderately important’, 3.50 ≤ MS <
4.49 means ‘more important’ and 4.50 ≤ MS ≤ 5.00 means ‘most important’. The survey
instrument used was a 26-item questionnaire. Frequency counts and mean scores of the drivers to
the adoption of AAC blocks on building projects ranged from 3.07 to 4.17 and 4.06 to 4.71 for the
Nigerian and South African respectively. Results confirmed 24 drivers were more important to the
professionals in the Nigerian construction industry while 2 drivers (resistance to pest and mold
MS=3.33 and aesthetically appealing MS=3.07) were moderately important to the Nigerian
construction professionals. Moreover, results confirmed 9 out of the 26 drivers were most
important to the South African Professionals, while the remaining 17 drivers were more important
to the respondents.
4.4.5 Barriers impeding the adoption of AAC block for building projects
Table 4.7: Significant barriers impeding AAC block adoption for building projects
Barriers
Nigerian Professionals
South African Professionals
N
MS
Rank
N
MS
Rank
Inadequate government
policies and supports
94
3.88
1
17
3.35
15
Market potentials
95
3.81
2
17
3.53
5
Low level of awareness and
knowledge on the concept of
sustainability
96
3.80
3
17
3.18
21
55
Non-awareness of people
towards the advantageous use
of AAC products
96
3.79
4
17
3.35
14
Lack of interest in new products
by buyers and house owners
96
3.78
5
17
3.47
8
Lack of readily available
accessible information
95
3.78
5
17
3.59
2
Huge capital to set up AAC
plant
95
3.76
7
17
4.00
1
Existing structure of the
construction industry
95
3.76
7
17
3.47
8
Little interest in new products
by Architects and Developers
95
3.76
7
17
3.53
5
Absence of design standards for
AAC products
96
3.75
10
17
3.41
12
Availability of conventional
materials
95
3.75
10
17
3.59
2
Startup costs associated with
promoting and teaching the
industry to build with AAC
products
95
3.75
10
17
3.47
12
Inadequate exemplar
demonstration project to infuse
confidence for using AAC
products
96
3.74
13
17
3.47
12
Low level of demand and
knowledge of AAC products
96
3.74
13
17
3.12
23
Little demand for energy
efficient buildings
93
3.72
15
17
3.59
2
Use of unstainable construction
materials
95
3.72
15
17
3.35
14
Affordability
95
3.71
17
17
3.35
14
56
Unfavorable perception of
home buyers to AAC block in
the short term
95
3.71
17
17
3.47
8
Inadequate technical know-
how and manpower to
manufacture AAC products
93
3.69
19
17
3.53
5
Inadequate building codes and
regulations
96
3.69
19
17
3.29
19
Costs of the 'learning curve'
while working with a new
product
96
3.68
21
17
3.18
21
Low demand for sustainable
housing
96
3.66
22
17
3.35
22
Lack of easy rating systems
for eco-friendly
97
3.65
23
17
3.29
23
Note: 1 represents not significant, 2 represents slightly significant, 3 represents moderately significant, 4 represents
more significant, 5 represents most significant. While, N represents the number of Respondents; MS represents the
Mean Score
Table 4.7 shows the responses of Nigerian and referred South African professionals to significant
barriers impeding AAC block adoption on building projects. To quantify the barriers impeding
AAC adoption, a graduated scale of 1.00 to 5.00 was adopted and the mean scores were calculated.
The mean values were interpreted using the following scale 1.00 ≤ MS < 1.49 ‘'means not
significant’, 1.50 ≤ MS < 2.49 means ‘slightly significant’, 2.50 ≤ MS < 3.49 means ‘moderately
significant’, 3.50 ≤ MS < 4.49 means ‘more significant’ and 4.50 ≤ MS ≤ 5.00 means ‘most
significant’. The survey instrument used was a 23-item questionnaire. Frequency counts and mean
scores of the barriers to the adoption of AAC blocks on building projects ranged from 3.65 to 3.88
and 3.29 to 4.00 for the Nigerian and South African respectively. Results confirmed all the 23
57
barriers were more significant to the professionals in the Nigerian construction industry. Moreover,
results confirmed 7 out of the 23 barriers were more significant to the referred South African
Professionals, while the remaining 16 barriers were moderately significant to the respondents.
4.4.6 Important strategies that can improve the adoption of AAC for building projects
Table 4.8: Important strategies that can improve the adoption of AAC for building projects
Strategies
Nigerian Professionals
South African Professionals
N
MS
Rank
N
MS
Rank
Government encouragement
94
3.88
1
17
4.41
11
Focusing research on specific
green building materials
95
3.81
2
17
4.59
4
Development of new
construction materials and
processes
96
3.80
3
17
4.35
13
Public private partnerships on
energy efficiency and
sustainable materials
96
3.79
4
17
4.18
17
Industrialization
96
3.78
5
17
4.82
2
Growth preferences for low
cost houses
95
3.78
5
17
4.59
4
Growth in the infrastructural
sector
95
3.76
7
17
4.94
1
Education and training to built
environment professionals
about AAC products
95
3.76
7
17
4.47
9
The readiness of construction
practitioners such as
developers and contractors in
adopting sustainable materials
95
3.76
7
17
4.29
15
Increasing funding for
sustainable building materials
96
3.75
10
17
4.47
9
Government financial
supports and subsidy
95
3.75
10
17
4.24
16
58
Demand for lightweight
construction materials
95
3.75
10
17
4.65
3
Marketing strategy
development
96
3.74
13
17
4.53
6
Integrating sustainability into
formal curricula
96
3.74
13
17
4.35
13
Increasing focus in green and
sound proof buildings
93
3.72
15
17
4.53
6
Creating demonstration and
training centers
95
3.72
15
17
4.41
11
Government promotion of
product
95
3.71
17
17
4.53
6
Use of tool ratings
95
3.71
17
17
4.12
18
Note: 1 represents not important, 2 represents slightly important, 3 represents moderately important, 4 represents more
important, 5 represents most important. While, N represents the number of Respondents; MS represents the Mean
Score
Table 4.8 shows the responses of Nigerian and referred South African professionals to important
strategies to AAC block adoption on building projects. To quantify the strategies of AAC adoption,
a graduated scale of 1.00 to 5.00 was adopted and the mean scores were calculated. The mean
values were interpreted using the following scale 1.00 ≤ MS < 1.49 ‘'means not important’, 1.50
≤ MS < 2.49 means ‘slightly important’, 2.50 ≤ MS < 3.49 means ‘moderately important’, 3.50 ≤
MS < 4.49 means ‘more important’ and 4.50 ≤ MS ≤ 5.00 means ‘most important’.
The survey instrument used was an 18-item questionnaire. Frequency counts and mean scores of
the enhanced strategies of AAC blocks adoption on building projects ranged from 3.71 to 3.88 and
4.12 to 4.94 for the Nigerian and referred South African professionals respectively. Results
confirmed 18 strategies were more important to the professionals in the Nigerian construction
59
industry. Besides, the results confirmed 8 out of the 18 important strategies were most important
to the referred South African Professionals, while the remaining 10 strategies were more important
to the respondents.
4.5 Test of Hypothesis
4.5.1: There is no significant difference among ownership of organisations on the awareness
of AAC block variants in the Nigerian construction industry.
One-way Analysis of Variance (F test) was used to test for significant difference in the level of
awareness of AAC block variants among organisations. The inferential results are presented in
Table 4.9
Table 4.9: ANOVA on the level of awareness of AAC block variants among ownership of
organisations
AAC Block Variants
DFb
DFw
DFt
F
P-value
Decision
AAC with 32.5 grade Ordinary
Portland Cement (OPC)
2
94
96
.047
.954
NS
AAC with 42.5 grade Ordinary
Portland Cement (OPC)
2
92
94
.401
.671
NS
AAC with 52.5 grade Ordinary
Portland Cement (OPC)
2
91
93
.424
.656
NS
AAC with Coal Bottom Ash (CBA)
2
91
93
.621
.540
NS
AAC with Natural Zeolite Additive
(NZ)
2
92
94
.556
.576
NS
AAC with Self-ignition Coal Gangue
(SCG)
2
92
94
.510
.602
NS
AAC with Incinerated Sewage
Sludge Ash (ISSA)
2
90
92
.112
.894
NS
AAC with Bamboo Leaf Ash (BLA)
2
92
94
.015
.985
NS
60
AAC with Silica Fume (SF) / Fly Ash
(FA)
2
91
93
.702
.498
NS
AAC with Dune Sand (DS)
2
90
92
.043
.958
NS
AAC with Rice Husk Ash (RHA) /
Aluminum Powder (AP)
2
90
92
1.378
.257
NS
AAC with Concrete Sandwich Block
(CSB) / Waste Glass (WG)
2
92
94
.522
.595
NS
AAC with Halloysite Powder (HP)
2
90
92
.541
.584
NS
AAC with Air-cooled Slag (AS)
2
91
93
.908
.407
NS
AAC with Efflorescence Sand (ES)
2
92
94
1.062
.350
NS
AAC with Phosphorus Sand (PS)
2
89
91
1.163
.317
NS
AAC with Coal Gangue (CG) / Iron
Ore Tailings (IOT)
2
92
94
.769
.466
NS
AAC with Pulverized Fuel Ash
(PFA) / Palm Oil Fuel Ash (POFA)
2
92
94
.448
.640
NS
AAC with Copper Tailings (CT) /
Blast Furnace Slag (BFS)
2
91
93
.733
.483
NS
AAC with Perlite Waste (PW) /
Polypropylene Fiber (PF)
2
92
94
.609
.546
NS
DFb represents degree of Freedom between groups, DFw represents degree of Freedom within
groups, DFt represents degree of Freedom total, NS represents no significant difference, S
represents Significant difference. Note: P is significant at P ≤ 0.05.
From the results of the one-way ANOVA presented in table 4.9, there are no significant differences
(P ≤ 0.05) on the level of awareness of AAC block variants among the ownership and management
of the organisations on twenty (20) out of the twenty (20) hypothesized AAC block variants. The
overall result indicated no significant difference among organisations as regards the level of
awareness of AAC variants. The results of the hypotheses imply that the level of awareness of
AAC variants is similarly perceived among the ownership of the organisations in the Nigerian
construction industry.
61
4.5.2 There is no significant difference on the awareness of AAC block variants among
the ownership of the organisations in South Africa building industry.
The inferential results are presented in Table 4.10
Table 4.10: ANOVA on the awareness of AAC block variants among organisations
AAC Block Variants
DFb
DFw
DFt
F
P-value
Decision
AAC with 32.5 grade Ordinary
Portland Cement (OPC)
2
14
16
.905
.910
NS
AAC with 42.5 grade Ordinary
Portland Cement (OPC)
2
14
16
1.083
.365
NS
AAC with 52.5 grade Ordinary
Portland Cement (OPC)
2
14
16
.529
.600
NS
AAC with Coal Bottom Ash (CBA)
2
14
16
.705
.511
NS
AAC with Natural Zeolite Additive
(NZ)
2
14
16
3.157
.074
NS
AAC with Self-ignition Coal Gangue
(SCG)
2
14
16
1.390
.281
NS
AAC with Incinerated Sewage
Sludge Ash (ISSA)
2
14
16
2.117
1.57
NS
AAC with Bamboo Leaf Ash (BLA)
2
14
16
.786
.475
NS
AAC with Silica Fume (SF) / Fly Ash
(FA)
2
14
16
.622
.551
NS
AAC with Dune Sand (DS)
2
14
16
.824
.459
NS
AAC with Rice Husk Ash (RHA) /
Aluminum Powder (AP)
2
13
15
1.690
.223
NS
AAC with Concrete Sandwich Block
(CSB) / Waste Glass (WG)
2
14
16
.487
.625
NS
AAC with Halloysite Powder (HP)
2
14
16
1.343
.293
NS
AAC with Air-cooled Slag (AS)
2
14
16
.967
.404
NS
62
Table 4.10 Cont’d
AAC with Efflorescence Sand (ES)
2
14
16
2.242
.143
NS
AAC with Phosphorus Sand (PS)
2
14
16
1.499
.257
NS
AAC with Coal Gangue (CG) / Iron
Ore Tailings (IOT)
2
13
15
.129
.880
NS
AAC with Pulverized Fuel Ash
(PFA) / Palm Oil Fuel Ash (POFA)
2
14
16
.451
.646
NS
AAC with Copper Tailings (CT) /
Blast Furnace Slag (BFS)
2
14
16
1.984
.174
NS
AAC with Perlite Waste (PW) /
Polypropylene Fiber (PF)
2
14
16
.487
.625
NS
DFb represents degree of Freedom between groups, DFw represents degree of Freedom within groups, DFt represents
degree of Freedom total, NS represents no significant difference, S represents Significant difference. Note: ρ is
significant at ρ ≤ 0.05.
From the results of the one-way ANOVA presented in table 4.10, there are no significant
differences (P ≤ 0.05) on the level of awareness of AAC block variants among the ownership and
management of the owners of the South African construction organisations on twenty (20) out of
the twenty (20) hypothesized AAC block variants. The overall result indicated no significant
difference among organisations as regards the level of awareness of AAC variants.
The AAC variants for which there are no significant differences and for which the null hypothesis
was accepted comprise (AAC with 32.5 grade Ordinary Portland Cement (OPC), AAC with 42.5
grade Ordinary Portland Cement (OPC), AAC with 52.5 grade Ordinary Portland Cement (OPC),
AAC with Coal Bottom Ash (CBA), AAC with Natural Zeolite Additive (NZ), AAC with Self-
ignition Coal Gangue (SCG), AAC with Incinerated Sewage Sludge Ash (ISSA), AAC with
Bamboo Leaf Ash (BLA), AAC with Silica Fume (SF) / Fly Ash (FA), AAC with Dune Sand
(DS), AAC with Rice Husk Ash (RHA) / Aluminum Powder (AP), AAC with Concrete Sandwich
63
Block (CSB) / Waste Glass (WG), AAC with Halloysite Powder (HP), AAC with Air-cooled Slag
(AS), AAC with Efflorescence Sand (ES), AAC with Phosphorus Sand (PS), AAC with Coal
Gangue (CG) / Iron Ore Tailings (IOT), AAC with Pulverized Fuel Ash (PFA) / Palm Oil Fuel
Ash (POFA), AAC with Copper Tailings (CT) / Blast Furnace Slag (BFS) and AAC with Perlite
Waste (PW) / Polypropylene Fiber (PF)). The results of the hypotheses imply that the level of
awareness of AAC variants is similarly perceived among the ownership of the organisations in the
South African construction industry.
4.5.3: There is no significant difference in the perception of Nigerian and South African
professionals on the level of awareness of AAC block variants.
The inferential results are presented in Table 4.11
Table 4.11: Mann-Whitney U test results for comparing perception of Nigerian professionals
and South African Professionals on the level of Awareness of AAC block variants
AAC Variants
Nigerian
Professionals
South African
Professionals
U
P-value
Decision
N
MS
N
MS
AAC with 32.5 grade Ordinary
Portland Cement (OPC)
97
54.85
17
72.62
567.500
.024
S
AAC with 42.5 grade Ordinary
Portland Cement (OPC)
95
49.78
17
94.03
160.500
.000
S
AAC with 52.5 grade Ordinary
Portland Cement (OPC)
94
48.06
17
99.91
52.500
.000
S
AAC with Coal Bottom Ash (CBA)
94
51.68
17
79.88
393.000
.000
S
AAC with Natural Zeolite Additive
(NZ)
95
52.54
17
78.65
431.000
.001
S
AAC with Self-ignition Coal
Gangue (SCG)
95
53.71
17
72.12
542.000
.023
S
64
AAC with Incinerated Sewage
Sludge Ash (ISSA)
93
51.17
17
79.18
388.000
.000
S
AAC with Bamboo Leaf Ash
(BLA)
95
55.75
17
60.68
736.500
.457
NS
AAC with Silica Fume (SF) / Fly
Ash (FA)
94
50.03
17
89.03
237.500
.000
S
AAC with Dune Sand (DS)
93
49.42
17
88.76
225.000
.000
S
AAC with Rice Husk Ash (RHA) /
Aluminum Powder (AP)
93
48.99
16
89.91
185.500
.000
S
AAC with Concrete Sandwich
Block (CSB) / Waste Glass (WG)
95
52.15
17
80.79
394.500
.000
S
AAC with Halloysite Powder (HP)
93
50.88
17
80.79
360.500
.000
S
AAC with Air-cooled Slag (AS)
94
51.36
17
81.68
362.500
.000
S
AAC with Efflorescence Sand (ES)
95
52.14
17
80.85
393.500
.000
S
AAC with Phosphorus Sand (PS)
92
50.36
17
80.12
355.000
.000
S
AAC with Coal Gangue (CG) / Iron
Ore Tailings (IOT)
95
51.33
16
83.72
316.500
.000
S
AAC with Pulverized Fuel Ash
(PFA) / Palm Oil Fuel Ash (POFA)
95
51.10
17
86.68
294.500
.000
S
AAC with Copper Tailings (CT) /
Blast Furnace Slag (BFS)
94
51.41
17
81.35
368.000
.000
S
AAC with Perlite Waste (PW) /
Polypropylene Fiber (PF)
95
52.43
17
79.26
420.500
.001
S
Note: P represents significant at P ≤ 0.05, U is Mann-Whitney, S represents significant difference,
NS represents not significant
The hypothesis states that there is no significant difference in the perception of Nigerian
professionals and South African professionals on the awareness of AAC block variants as
illustrated in Table 4.11. In Table 4.11 indicated that there are significant differences in the
perception of respondents on 19 out of the 20 hypothesized AAC block variants. AAC block
65
options for which there are significant differences and for which the null hypothesis were rejected
are: (AAC with 32.5 grade Ordinary Portland Cement (OPC), AAC with 42.5 grade Ordinary
Portland Cement (OPC), AAC with 52.5 grade Ordinary Portland Cement (OPC), AAC with Coal
Bottom Ash (CBA), AAC with Natural Zeolite Additive (NZ), AAC with Self-ignition Coal
Gangue (SCG), AAC with Incinerated Sewage Sludge Ash (ISSA), AAC with Silica Fume (SF) /
Fly Ash (FA), AAC with Dune Sand (DS), AAC with Rice Husk Ash (RHA) / Aluminum Powder
(AP), AAC with Concrete Sandwich Block (CSB) / Waste Glass (WG), AAC with Halloysite
Powder (HP), AAC with Air-cooled Slag (AS), AAC with Efflorescence Sand (ES), AAC with
Phosphorus Sand (PS), AAC with Coal Gangue (CG) / Iron Ore Tailings (IOT), AAC with
Pulverized Fuel Ash (PFA) / Palm Oil Fuel Ash (POFA), AAC with Copper Tailings (CT) / Blast
Furnace Slag (BFS) and AAC with Perlite Waste (PW) / Polypropylene Fiber (PF). Whereas, AAC
variant which there are no significant difference between the perception of Nigerian and South
African professionals and for which the null hypothesis is accepted include AAC made with
Bamboo leaf Ash (BLA) as obtained in table 4.11.
4.5.4 There is no significant difference on the prospect for adoption of AAC block among
the ownership of the organisations.
The inferential results are presented in Table 4.12
Table 4.12: ANOVA on the prospect for adoption of AAC block among organisations
Sum of Squares
df
Mean Square
F
Ρ-value
Between Groups
3.103
2
1.552
1.659
.196
Within Groups
87.887
94
.935
Total
90.990
96
Note: ρ is significant at P ≤ 0.05.
66
The result in table 4.12 indicated there is no significant difference among the groups of ownership
of the organisations as regards agreement with prospect for adoption of AAC in the Nigerian
construction industry.
4.5.5 There is no significant agreement among South African professionals on the adoption
of AAC block variants on building projects.
The inferential results are presented in Table 4.13
Table 4.13: Kendall’s Coefficient of Concordance test of agreement on the ranking of AAC
variants on 10 building projects
N
Kendall’s W
Chi-square
Df
P-Value
17
.743
240.065
19
.000
Note: P represents significant at P ≤ 0.05, W represents Kendall’s Coefficient of concordance test,
N is the number of Respondents.
Table 4.13 shows Kendall’s coefficient of concordance test used to test agreement among
respondents in their ranking of 20 variants of AAC. It is used to find out if there is an agreement
between respondents or raters. The result indicated a significant agreement at P ≤ 0.05 level; hence
the null hypothesis was rejected.
4.5.6 There is no significant difference among the respondents on the drivers of AAC
blocks in the Nigerian construction industry.
The inferential results are presented in Table 4.14
Table 4.14: ANOVA on the drivers of AAC block among the ownership organisations
Drivers
DFb
DFw
DFt
F
P-value
Decision
Superior thermal absorption
property
2
93
95
.908
.407
NS
Excellent fire insulation
2
93
95
1.339
.267
NS
Resistance to pest and mold
2
93
95
1.218
.301
NS
67
Lightweight
2
92
94
1.161
.318
NS
Optimum thermal conductivity
2
91
93
1.565
.215
NS
Reduced dead load on structure
2
92
94
3.192
.406
NS
Reduction in construction cost
2
93
95
.398
.673
NS
Eco-friendly
2
94
96
2.241
.112
NS
Adaptability of AAC to tropical
climates
2
92
94
.155
.856
NS
Recyclable
2
93
95
1.309
.275
NS
Fast and easy installation
2
93
95
1.646
.198
NS
Good acoustic performance
2
90
92
.836
.437
NS
Breathable wall system
2
92
94
1.503
.228
NS
Ecologically better than other
conventional walling materials
2
90
92
1.429
.245
NS
Aesthetically appealing
2
93
95
.585
.559
NS
Readily adaptable to any style
of architecture
2
91
93
1.910
.154
NS
Reduced transfer of load on the
foundation
2
93
95
.616
.542
NS
Made from abundant raw
material
2
93
95
2.258
.110
NS
Versatile as components can be
used for walls, floors and