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SCMT4
Las Vegas, USA, August 7-11, 2016
Salient Parameters Influencing the Strength Properties of Cement-
Less Wastepaper Based Lightweight Block
Oriyomi M Okeyinka1a, David A Oloke1b, and Jamal M Khatib1c
1School of Architecture and the Built Environment, Faculty of Science and Engineering, University of
Wolverhampton, City Campus, Wolverhampton, West Midlands WV1 1LY, United Kingdom.
1aEmail: <O.M.Okeyinka@wlv.ac.uk>, 1b Email:<D.A.Oloke@wlv.ac.uk>,
1cEmail:<j.m.khatib@wlv.ac.uk>.
ABSTRACT
The continuous suggestions of using environmental friendly construction materials as a means of achieving
sustainability in the construction industry has led to various investigation exploring the recycled use of
wastes for the production of building materials. Considering the level of research efforts to date, this
investigation was conducted to study the effect of salient parameters, which includes; particle size of
wastepaper aggregate (WA), curing methods/temperature, and crushing orientation on the compressive
strength of cement-less wastepaper lightweight block (CWLB). The laboratory experimentation involved
the systematic molding of 50mmx50mmx50mm CWLB specimens and testing their compressive strength
at 28 days of curing in ambient laboratory temperature (200C). The test results show that the compressive
strength of CWLB vary with particle size of WA, specimens molded from finer WA particles exhibit about
50% higher average compressive strength (for all the mixes tested) compared to those molded from the
coarser particle sizes. Curing at varying temperature has an insignificant effect on the compressive strength
of CWLB; at (200C) ambient laboratory temperature the specimen displayed 1.7% higher compressive
Strength at 28days curing age compared to those cured at (300C) oven temperature. Specimen crushed on
the as cast (top) face showed 101% higher compressive strength and ductile mode of failure compared to
the lower strength and brittle mode of failure observed on the as cast side. These findings indicates that;
CWLB is suitable for use at both hot and cold temperate regions, it exhibits varying strength at different
loading orientations, it displays properties different from wood in terms of loading orientation and the WA
particle size play a major role in the strength development of CWLB. Thus, to efficiently produce and make
specification for CWLB, adequate consideration should be given to the parameter studied. Future work will
study the effect of other parameters including; curing age, water content, binder content, and water/binder
ratio.
INTRODUCTION
The rapid growth of civil engineering construction has led to increasing demand for aggregates and other
natural resources required for the production of building material. One of the major notable environmental
impacts associated with the construction industry is the high consumption of natural resources. The raw
materials (e.g. aggregate and cement) utilized in the production of concrete are either obtained or produced
from naturally occurring minerals.
Fourth International Conference on Sustainable Construction Materials and Technologies
http://www.claisse.info/Proceedings.htm
According to literature, the production of every 1 ton of cement requires about 1.7 tons of non-fuel raw
materials out of which limestone account for 85%, while other raw materials (e.g. Clay and shale) accounts
for the remaining 15% (Oss and Padovani, 2003). The building industry requires about six to seven more
tonnes of sand and gravel, for each tonnes of cement used in construction, (United States Geological Survey
(USGS), 2013).Globally, sand and gravel accounts for 68 to 85% of about 59 billion tonnes of material
mined every year (Seinberger et al, 2010; Krausmann et al, 2009). The 25.9 to 29.6 billion estimated world
use of aggregate for concrete in year 2012 alone was estimated to represent enough concrete to build a 27
meter high by 27 meter wide wall around the equator (UNEP Global Environmental Alert Services (UNEP
GEAS), 2014). The world over 40 billion tonnes annual aggregate consumption was estimated to be about
100% more than the yearly aggregate renewal by all rivers of the world (UNEP GEAS, 2014).
The cummulative effect of these consumption is gradually making the creation of the built environment to
become a threat to the natural eco –system. As an evidence, the natural resources based of the world has
been reported to be in severe state of over-exploitation and depletion (Giljum et al, 2009). It is therefore
paramount to investigate means of achieving sustainability in the production of building materials in the
construction industry.
To effectively offset the impact, there has been a continuous suggestion of exploiting environmentally
friendly construction materials. Mehta (2002) recommended two sets of approaches viz; the practice of
industrial ecology in which the waste by product from one industry is utilized as a major raw material in
another industry, and secondly, the reduction in the impact of unwanted by-products through a minimization
of material consumption. Other suggestions includes: reducing the environmental impact of materials used
in construction and targeting responsible sourcing of construction products (Strategic for Sustainable
Construction, 2008), use of environmentally-friendly construction materials, innovative manufacturing
processes and design of innovative products using recycled material (European Union(EU) Commission,
2013).
Following these suggestions, several researches had been conducted to explore the potential of developing
building materials from various types of wastes including wastepaper. Building materials such as: fibre
cement board (Asorie et al, 2011), lightweight block (Okeyinka et al, 2015a; Modry, 2001, Fuller et al,
2006), low density board (Esmeradal, 2000), papercrete (Fuller et al, 2006), plastering mortar (Acui et al,
2014), have been produced from wastepaper. However, extensive literature review has shown that, building
material produced from waste paper suffers high water absorption (Akinwumi et al, (2014); Tizmany,
(2006), and Acui et al, (2014)), thickness swelling and low strength with increasing paper fibre content.
This drawback of strength reduction arise due to the corresponding water content increment that occurs in
the mix with increasing waste paper content (Abdul Ghani and Shukeri, 2008).This indicates the
contradiction that exists between the hygroscopic properties of paper fibre and the moderate water
requirement for cement hydration, which means that the high water cement ratio resulting from increasing
paper content lowers the strength of the building material concerned. The utilization of considerable
quantity of cement to improve the strength properties offset the environmental friendliness of building
materials made from wastepaper.
The development of cement-less wastepaper based lightweight block (CWLB) was another important step
towards the production of eco-friendly building materials. This block which was designed to be used for
non-load bearing/ non-structural application was developed without the use of hydraulic cement. It
constituents are majorly waste materials, which includes; postconsumer waste paper, waste additive
(obtained as industrial waste by-product), and lesser quantities of sand, water and admixture. The details of
the exploratory study involved in development of its mixture proportioning process was reported and
published (Okeyinka et al, 2015a; Okeyinka et al, 2015b).
Considering the level of recycled waste content in the CWLB, it development and production will not only
reduce the consumption of natural resources in building construction but will also offset the utilization of
cement whose production is associated with environmental impacts such as GHG emission, high raw
material consumption and high energy consumption. Being a relatively new material, many of the
characteristics of CWLB are yet to be studied and understood. For instance, unlike concrete and papercrete
which form paste in the fresh state due the inclusion of hydraulic cement in their constituents, CWLB
exhibits fibrous form in the fresh state (Okeyinka et al, 2015b) as it was made from majorly inert/unreactive
materials. Thus, adequate understandings of the salient parameters that affect its strength properties are
important for processing and product optimization. This study was therefore conducted to determine the
effect of parameters which includes; curing method, wastepaper aggregate (WA) particle sizes and crushing
orientation on the compressive strength of CWLB.
MATERIALS AND METHODS
The materials used in this experimentation includes wastepaper aggregate (WA), sand (fine aggregate),
waste additive (binder), clay (admixture) and water. The wastepaper aggregate (WA) was produced through
a systematically processing of post-consumer wastepaper (Okeyinka et al, 2015) specifically old Newsprint.
The WA used was divided into two different types (viz; type (A) and type (B)) in terms of their particle
granulation. The type (A) WA exhibited particle size/granulation ranging from 4mm-0.125mm (Fig 1).The
type (B) WA has particle sizes ranging from 1mm-0.063mm (Fig 1) and it was produced by subjecting the
type (A) WA (with 4mm-0.125mm particle size) to grinding in a ball milling machine at a rotating speed
of 360rpm for 15 minutes.
Mixture Proportioning and Batching of Constituent Materials
The choice of mixes selected for the production of test specimen in this experimentation was based on the
exploratory study conducted to develop the mixture proportioning process for the CWLB under study as
published in (Okeyinka et al, 2015a; Okeyinka et al, 2015b). Five (5) mixes containing varying sand
contents ranging from 36% (by weight of WA) to 52% (by weight of WA) but constant; binder quantity
(20% by weight of WA), admixture quantity (5% by weight of WA) and water/ binder ratio (3.75) were
found to possess desirable properties that satisfies the criterial for the selection of efficient mix composition
in terms of dimensional stability and density (Okeyinka et al, 2015b) as specified by the BS EN 772-2
(2013) and BS EN 2028-1, (1975) for masonry block to be used for wall construction. The compressive
strength of the selected mixes is expected to be improved upon based on the findings from the study of
salient parameters. In order to limit the number of runs and obtain only the factor effects, each of the
parameter studied were tested against the compressive strength separately. Also, other parameters of these
mixes which includes; water/binder ratio, optimum water content, curing, optimum amount of compacting
pressure etc., will be further optimized based on the outcome of future investigation of the effect of different
salient parameters on the compressive strength of the CWLB specimen.
Figure 1. Type (A) and Type (B) WA with varying particle size/granulation
Considering the disparity between the physical properties of the wastepaper aggregate (WA) and the fine
aggregate (sand) as shown in table (2). All constituent materials used in this experimentation were measured
by weight in order to ensure adequate proportioning. Materials which include; sand, binder, water and
admixture were measured relative to the quantity of WA in the mixture.
Table 2. Differences between the physical properties of wastepaper aggregate and sand
(fine aggregate) (Source: Okeyinka et al, (2015b))
Physical Properties
Materials
WA
Sand
Specific gravity
0.661
2.63
Loose Bulk density
0.096 kg/l
1.428 kg/l
Particle sizes
4mm-0.125mm
4mm-0.063mm
Manufacture of Test Specimen
After mixing the constituent materials in a portable mortar mixer, a predetermined quantity of the mixture
was weighed and filled into the 50mm x 50mm x 150mm cubic mould to produce the cube block specimen
(Fig 3). A 10 tonnes capacity manual hydraulic press with a pressure measuring gauge and piston (Fig 4)
was used to compress the mixture against the other end of the mould to form the 50mmx50mmx50mm cube
block specimen. The 50mm x 50mm x 150mm mould was initially utilised to accommodate the fibrous and
the voluminous nature of the mixture. The amount of compacting force employed in compressing the
mixture was 2.5metric tons which is equivalent to a compacting pressure of 9.807MPa.This process was
repeated for all specimens produced from each of the mixes.
Figure 3. 50mm X 50mm x 50 mm CWLB System
Figure 4. 10 tonnes capacity manual
hydraulic press with a pressure
measuring gauge and piston
Preparation of Specimen for the study of salient parameters
The details of the mixes and different additional preparation for the production of specimen use in testing
the salient parameters under study are explained in this section.
Details of Specimen for testing the effect of curing method/Temperature.
The specimen used for exploring the effect of two different curing methods on the compressive strength of
the CWLB specimen were made from mixes 1 and 5 as detailed in table 2. The two curing
methods/temperature investigated includes; ambient curing (200C) and oven curing(300C).The ambient
cured specimen were kept in room condition at 200C temperature till the 28 day testing age, while the oven
cured specimen were subjected to curing in the oven at 300C for 28days and were taken out to cool down
in room temperature before testing. The oven cured temperature of 300C was adopted to replicate the
average temperature condition that the specimen may be subjected to in a hot/warm temperate region.
Investigating this parameter is expected to help in determining the suitability of using the CWLB in
hot/warm environment.
Table 3. Mixture proportioning of specimen for testing the effect of curing method and
crushing orientation.
Mix no
Specimen
designation
Aggregates
Binder (g)
Added water (g)
Admixture (g)
Curing Method
Curing
Temperature (0C)
WA
(type A)
(g)
Sand
(g)
1
c
300
156
60
225
15
Ambient
20
d
300
156
60
225
15
Oven
30
5
c
300
108
60
225
15
Ambient
20
d
300
108
60
225
15
Oven
30
Details of Specimen for testing the Effect of particle size
The specimen used to study this parameter were produced from mixes 1-5 (table 3) using the different types
of the wastepaper aggregates viz:
The Type A:- The coarser WA with particle size range of 4mm-0.125mm (fig 1)
The type B: - The finer WA with particle size range of 1mm-0.063mm (fig 2).
Given the effect of WA particle size on water requirement of the CWLB specimen as reported in (Okeyinka
et al 2015b), the water to binder ratios adopted for the mixes made from type (A) WA and type (B) WA
were; 10 and 3.75 respectively. After moulding and demoulding, the specimens were cured in ambient
laboratory condition for 28days.
Table 4. Mixture proportioning of specimen for testing the effect of WA particle size
Mix no
Designation
Aggregates
Binder (g)
Admixture (g)
Wastepaper Aggregate(WA)
(g)
Sand
(g)
Type A
Type B
1
a
300
-
156
60
15
b
-
300
2
a
300
-
144
60
15
b
-
300
3
a
300
-
132
60
15
b
-
300
4
a
300
-
120
60
15
b
-
300
5
a
300
-
108
60
15
b
-
300
Details of Specimen for testing the Effect of Crushing Orientation. To determine the effect of crushing
orientation on the compressive strength of the CWLB , cube block specimen of sizes 50mmx50mmx50mm
were moulded from mixes 1 and 2 (table 3) and were subjected to curing in ambient laboratory condition
for 28 days prior to compressive strength test. Two different crushing orientation which includes the as
cast face (Top Face) and the as cast side (side face) were investigated for the specimen produced from each
of the mixes.
Testing of Specimen. Considering the intrinsic importance of compressive strength in the design of
structures (Neville, 1995) and its recommendation as an important property for consideration in the
development of mixture proportioning process (BS 5328-2:1997), the salient parameters under study were
tested against the compressive strength of the CWLB specimen. Other properties of the block which
includes; water absorption, fire resistance, dimensional check, density, shrinkage and flexural strength will
be investigated in (future experimentation) after the optimisation of the mixes.
Compressive Strength Test. At 28days curing age, the CWLB specimens were subjected to compressive
strength test in a 2500KN capacity compression testing machine at a loading rate of 2400 N/S. The 28days
curing age was adopted for all the salient parameters investigated, in order to simplify the process and to
minimize the material consumption.
RESULT AND DISCUSSIONS
Effect of Curing Method on the Compressive Strength of CWLB. As presented in table 5 below,
the difference between mixture 1c and 1d is the curing method/temperature at 200C and 300C respectively.
The specimen 1c cured at ambient laboratory condition displayed 1.7% higher compressive Strength at
28days curing age compared to specimen 1d. A similar trend was also observed for the specimen 2c and
2d. Considering the negligible difference between the compressive strength of the specimen subjected to
the two different curing methods, it is clear that curing at higher or lower temperature produces little or no
significant effect on the development of compressive strength of CWLB. This indicates the possibility of
utilizing the CWLB block at both hot and cold temperate regions.
Table 5. Effect of curing method/Temperature on compressive strength of CWLB
Mix no
Parameter
Designation
Temperature
(0C)
Curing method
Average
Compressive
Strength (MPa)
Standard
deviation
1
c
20
Ambient
0.69
0.07
d
30
Oven
0.67
0.05
5
c
20
Ambient
0.54
0.03
d
30
Oven
0.51
0.05
Effect of Crushing Orientation on the Compressive Strength of CWLB. The compressive
strength displayed by the specimen subjected to crushing on the as-cast side face (1CS) and the as cast top
face (1CT) are presented in table 6 below. The difference between specimen 1CS and 1CT is the crushing
orientation at the side-face and top-face respectively. The specimen 1CT crushed on the top-face displayed
approximately 101% higher compressive strength compared to specimen 1Cs that was crushed on the as
cast side. A ductile mode of failure was also observed in specimen crushed on the top-face while a brittle
mode of failure was observed in specimen crushed on side-face. The physical observation of the specimen
cross section shows that, similar to the mechanism of densification of biomass (Kaliyan and Morey 2009),
the wastepaper fibres rearranged themselves in a direction perpendicular to direction of the applied pressure
during the process of compaction under the hydraulic press. This indicates that the CWLB block specimen
are stronger in the direction perpendicular to their fibre orientation and are weaker in the direction parallel
to their fibre orientation. A comparison of this characteristics with wood indicate that the CWLB exhibit
properties different from wood in terms of loading orientation given the fact that wood are stronger in the
direction of orientation of its fibre and are weaker in the direction perpendicular to its fibre orientation
(Thelanderson and Larsen , 2003).
Table 6. Effect of crushing orientation on compressive strength of CWLB
Mix no
Parameter
Designation
Crushing Orientation
Average Compressive
Strength (MPa)
Standard
deviation
1
CS
Side face
0.69
0.07
CT
Top Face
1.39
0.04
5
CS
Side face
0.54
0.03
CT
Top Face
1.10
0.04
Effect of Particle Size on the Compressive Strength of CWLB
As shown in the fig (5), specimen moulded from type (B) WA (particle size range of 1mm-0.063mm)
displayed higher compressive strength compared to the specimen moulded from Type (A) WA (particle
size of 4mm-0.125mm). For all the mixes tested, the finely graded WA particle sizes produced CWLB with
49.68% higher average compressive strength compared to the CWLB specimen molded from coarsely
graded WA. This was observed to be due to higher degree of compaction (as indicated by the increased
density (Okeyinka et al 2015b) made possible by the finer particle size contained in the granulation of the
type (B) WA. This result and observation is in agreement with the report by Tumuluru et al (2010) that
medium or finely ground particles are more suitable to achieve adequately compacted specimen in the
densification of fibrous materials. It was therefore deduced that similar to densified biomass, WA particle
granulation plays a major role in the degree of compaction of CWLB.
Figure 5. Influence of WA particle size/granulation on the Compressive Strength of CWLB
CONCLUSION
This paper presents the research findings of CWLB designed for non-load bearing/ non-structural
application and produced from the mixture of majorly waste materials, which includes; postconsumer waste
paper, waste additive (obtained as industrial waste by-product), and lesser quantities of sand, water and
negligible quantity of clay as admixture. The one factor at time approach (OFAT) was adopted to investigate
the effect of parameters which includes: particle size of wastepaper aggregate (WA), curing
methods/temperature and crushing orientation, on the compressive strength of CWLB at 28days curing age.
The effect of curing method/temperature was examined by comparing the compressive strength of by
specimen subjected to 200C ambient curing temperature and 300C oven curing temperature for periods of
28days respectively. The effect of particle size of WA was investigated by comparing the compressive
strength of CWLB specimen molded from a coarsely grained(4mm-0.125mm) WA and a finely
grained(1mm-0.063mm)WA. Effect of crushing orientation was studied by comparing the compressive
strength of CWLB subjected to compression on the as-cast top face and on the as-cast side face respectively.
The experimental results reported in this paper led to the following conclusions:
There was an insignificant difference between the compressive strengths of CWLB specimens cured at
300C oven temperature and those cured at 200C ambient laboratory temperature. This indicates the
possibility of utilizing the CWLB block at both hot and cold temperate regions.
CWLB exhibit varying compressive strength and mode of failure at different loading orientation. The
CWLB specimen loaded and crushed on the top-face displayed approximately 101% higher compressive
strength compared to those loaded and crushed on the as cast side. This indicates that the CWLB block
specimen are stronger in the direction perpendicular to their fibre orientation and are weaker in the direction
parallel to their fibre orientation unlike wood which are stronger in the direction of orientation of its fibre
and are weaker in the direction perpendicular to its fibre orientation. A ductile mode of failure was also
observed in the specimens crushed on the top-face while a brittle mode of failure was observed in the
specimens crushed on side-face.
WA particle granulation plays a major role in the degree of compaction of CWLB. Finely graded (1mm-
0.063mm) WA produces CWLB with 49.68% higher average compressive strength compared to the
coarsely graded (4mm - 0.125mm) WA.
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