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Adobe masonry is one of the oldest construction systems still in use today, Mexico has an enormous cultural heritage with traditional adobe houses being very representative of the rural communities and their culture. The 2017 Puebla Earthquake on September 19th struck the country causing the loss, destruction, and damage of historic buildings in several Mexican states, with the traditional earthen dwellings being the most vulnerable structures to these events. The fast abandonment of the local materials and techniques entails further research regarding the characterization of these construction systems, therefore, reconstruction efforts first require the recovery of the construction technique. After the seismic events, adobe samples of the remaining adobe structures of Jojutla de Juarez were collected. This population was one of the most affected in all the country, and, because of the major losses suffered, the study was conducted to determine the material properties of the dwellings’ adobe shards and natural quarry clays of the region. The characterization included destructive and non-destructive tests, mineralogical and granulometry analyses, and composition of the adobe samples of the buildings, as well as the aggregates. As a novelty, the compressive strength of the pieces was tested by two methods: the traditional compression strength test and the point-load test, in order to obtain the indicative values and the correlation equations between both tests. From the formal analysis and the laboratory, it was observed that the adobes from Jojutla presented different compositions which combined with the building malpractices and alterations to the traditional systems caused unpredictable behavior during the earthquake. The conduction of point-load tests in situ, as a part of a complete characterization methodology, could be an alternative to study the mechanical properties of patrimonial or damaged building samples before its disappearance.
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heritage
Article
Characterization of Adobe Blocks: Point-Load Assessment as a
Complementary Study of Damaged Buildings and Samples
Adria Sanchez-Calvillo 1, * , Elia M. Alonso-Guzman 2, * , Wilfrido Martinez-Molina 2,
Marco A. Navarrete-Seras 2, Jose L. Ruvalcaba-Sil 3, Antonia Navarro-Ezquerra 4and Alejandro Mitrani 3


Citation: Sanchez-Calvillo, A.;
Alonso-Guzman, E.M.;
Martinez-Molina, W.;
Navarrete-Seras, M.A.; Ruvalcaba-Sil,
J.L.; Navarro-Ezquerra, A.; Mitrani, A.
Characterization of Adobe Blocks:
Point-Load Assessment as a
Complementary Study of Damaged
Buildings and Samples. Heritage 2021,
4, 864–888. https://doi.org/10.3390/
heritage4020047
Academic Editors: Nicola Masini,
Andrea Macchia and
Fernanda Prestileo
Received: 18 April 2021
Accepted: 17 May 2021
Published: 20 May 2021
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with regard to jurisdictional claims in
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iations.
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1Faculty of Architecture, Universidad Michoacana San Nicolas de Hidalgo, Morelia 58070, Mexico
2Faculty of Civil Engineering, Universidad Michoacana San Nicolas de Hidalgo, Morelia 58070, Mexico;
wilfrido.martinez@umich.mx (W.M.-M.); mnavarrete@umich.mx (M.A.N.-S.)
3
Laboratorio Nacional de Ciencias para la Investigacion y la Conservacion del Patrimonio Cultural, LANCIC,
Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Mexico City 04510, Mexico;
sil@fisica.unam.mx (J.L.R.-S.); mitrani@fisica.unam.mx (A.M.)
4Escola Politecnica Superior d’Edificacio, Universitat Politecnica de Catalunya, 08034 Barcelona, Spain;
antonia.navarro@upc.edu
*Correspondence: 1644104g@umich.mx (A.S.-C.); elia.alonso@umich.mx (E.M.A.-G.)
Abstract:
Adobe masonry is one of the oldest construction systems still in use today, Mexico has
an enormous cultural heritage with traditional adobe houses being very representative of the rural
communities and their culture. The 2017 Puebla Earthquake on September 19th struck the country
causing the loss, destruction, and damage of historic buildings in several Mexican states, with the
traditional earthen dwellings being the most vulnerable structures to these events. The fast abandon-
ment of the local materials and techniques entails further research regarding the characterization
of these construction systems, therefore, reconstruction efforts first require the recovery of the con-
struction technique. After the seismic events, adobe samples of the remaining adobe structures of
Jojutla de Juarez were collected. This population was one of the most affected in all the country, and,
because of the major losses suffered, the study was conducted to determine the material properties of
the dwellings’ adobe shards and natural quarry clays of the region. The characterization included
destructive and non-destructive tests, mineralogical and granulometry analyses, and composition of
the adobe samples of the buildings, as well as the aggregates. As a novelty, the compressive strength
of the pieces was tested by two methods: the traditional compression strength test and the point-load
test, in order to obtain the indicative values and the correlation equations between both tests. From
the formal analysis and the laboratory, it was observed that the adobes from Jojutla presented differ-
ent compositions which combined with the building malpractices and alterations to the traditional
systems caused unpredictable behavior during the earthquake. The conduction of point-load tests
in situ, as a part of a complete characterization methodology, could be an alternative to study the
mechanical properties of patrimonial or damaged building samples before its disappearance.
Keywords:
earthen architecture; adobe masonry; materials properties; materials characterization;
point-load test; mechanical properties; seismic affectation.
1. Introduction
In part due to their natural availability and great insulating properties, clays have
seen extended use as a construction material around the world. Even if this extensive use
includes several heritage structures, studies focusing on this building material are relatively
scarce. The present paper discloses a global review of the adobe material characterization,
specifically the case of Mexico, a country with a history of extended use of earth in its
cultural heritage.
The abandonment of the traditional use of clay materials for construction in recent
times, accompanied with the loss of the techniques employed in this type of construction,
Heritage 2021,4, 864–888. https://doi.org/10.3390/heritage4020047 https://www.mdpi.com/journal/heritage
Heritage 2021,4865
poses a great difficulty to any restoration work. The devastating 2017 Puebla earthquake
on September 19th caused the loss of many historical buildings in central Mexico, with
traditional earthen dwellings being the most vulnerable. The restoration process has made
evident the need to recover the traditional construction techniques employed. In the
present paper, adobe and soil samples were collected from Jojutla, Morelos, Mexico—one
of the hardest hit areas—and an in-depth study was performed to elucidate the materials
and techniques used in their manufacture.
These samples were tested with a complete methodology for material characteri-
zation using both destructive and non-destructive techniques, and including geotechni-
cal, particle size and mineralogical tests, as well as the inclusion of the point-load test
(PLT) as an innovation and alternative to calculate the mechanical resistance of earthen
construction materials.
The results presented provide interesting details of the traditional building materi-
als and systems used in the region studied, helping to understand the behavior of these
structures and the way they were built. Furthermore, the PLT displayed promising re-
sults as a means to characterize in situ the mechanical properties of earthen architecture,
providing a useful tool when working with cultural heritage and structures affected by
natural phenomena.
1.1. Earthen Architecture in Mexico
Earth is one of the oldest construction materials known; archaeological evidence
reports its use for over thousands of years, being a key factor in the development of ancient
civilizations [
1
]. Its continued use over several millennia resulted in a variety of local
constructive traditions and architectural earthen heritage in several regions of the world [
2
].
These construction systems can be found in all continents—except Antarctica—showing
relevant local variations, and being present in all types of structures, including both
residential and religious architecture [
3
,
4
]. There is evidence of vernacular and monumental
examples from Latin America, Africa, Central Europe, and the Middle East [5].
In the American continent the magnificent structures of Peru are known worldwide,
being earthen monuments very representative of the Incas [
6
]. The city of Chan Chan, devel-
oped from the Chimúculture, is the largest built entirely with adobe in the American conti-
nent, and the site of Caral, over 5000 years old presents a very interesting mixture of monu-
mental and residential architecture with earthen materials, including adobe and “quincha”,
a traditional construction system which combines earth and vegetative material [7].
Mexico, as well, has a wide and rich amount of earthen construction heritage, includ-
ing both archaeological and architectural structures. There is evidence of the use of earthen
systems in Pre-Hispanic cultures since their earliest periods, with several examples being
found in both small and large archaeological sites, as well as historical buildings [
8
]. Most
of the great pyramids, which today function as monumental touristic sites, were built with
earth and then covered with stone coatings [8].
Even after the arrival of the Spanish and the colonization, the adobe masonry and
rammed earth systems were still handed down from generation to generation, being
commonly used in the housing and monumental construction of the cities [
9
]. Additionally,
as the Iberian Peninsula had a widespread and old tradition of earthen architecture [
10
],
adobe was one of the main building materials used by the first builders that arrived in
the American continent, along with other techniques like rammed earth [
11
], but due
to its simplicity and availability, it was implemented in the planning of new cities and
urban centers.
Nevertheless, over the years, the earthen architecture has suffered a progressive
abandonment, being displaced by modern materials and techniques. Currently, in Mexico,
the traditional adobe buildings are closely associated with the lower social classes and are
even considered unsafe materials [
12
], partly because of the constant earthquakes which
the country suffers.
Heritage 2021,4866
1.2. Characterization of Earthen Materials and the Case of the Mexican Cultural Heritage
In recent years, the literature about earthen materials has been very productive,
with an increase in the number of articles, conference proceedings, guidelines, outreach,
and training documents, with several works regarding the material characterization of
these structures.
Furthermore, the celebration of scientific events, has helped to raise the awareness
about the importance of these traditional techniques and its current situation in modern
construction. Events like TERRA World Congresses, held since 1972 in different countries
under the aegis of ICOMOS, and the Ibero-American SIACOT congress, have spread the
results from scientific studies of earthen materials.
Additionally, the work of institutions and universities is extremely valuable, including
the dissemination of knowledge by means of guidelines, technical reports, and handbooks;
intended not for specialists but the users and craftsmen who are the real target. The Earthen
Architecture Initiative of the Getty Conservation Institute has published meaningful guide-
lines about specific topics [
13
,
14
]. At the government level, during the last decades many
countries have released technical codes for raw earth construction, such as Australia, New
Zealand, Spain, France, Chile, or Peru [15].
Considering the scientific literature, some authors and institutions have gathered im-
portant information and results about these construction materials, including reviews con-
cerning hygrothermal properties, natural fibers, or building codes and standards
[5,15,16]
.
Other works place an emphasis on the identification, documentation, and cataloguing of
cultural heritage and sites for their protection and preservation [
17
22
], while others focus
on the technological enhancement and development of these sustainable materials [
23
25
].
Regarding the material characterization, the main topic of the present paper, we can
find recent research works which have implemented various methodologies, including
techniques listed by the Getty Conservation Institute guidelines [
14
], and incorporate
innovative ones for the study of these materials. The Portuguese research contributions
are very interesting [
26
30
], with a very productive activity in the last years; moreover
we can find recent ones from North Africa [
31
,
32
], and in Latin America the works from
Peru [33,34], and Chile [23,24], are very relevant.
Additionally, the seismic vulnerability of these structures has been studied from many
perspectives, including the structural and technological aspects [
34
38
], as well as the
social and cultural importance to transmit the original retrofitting strategies [
39
,
40
]. In
Latin America, many countries are prone to seismic events,
On the other hand, most of the investigations have revised the earthen construction
from the perspective of the construction technology and the cultural significance of the
traditional architecture [
10
,
11
,
19
,
20
]. In Mexico, the research approach has been focused
on this last perspective, while the technical knowledge and the materials engineering has
been overlooked. We can find a vast knowledge and literature of earthen structures in the
country and its sundry regions [
41
], nevertheless the articles and resources about material
characterization are scarce.
Staying in Mexico, in the archaeology field, the construction systems of the Pre-
Hispanic Mexican architecture have been identified, listed, and explained in previous
research studies, creating a vast knowledge of the first earthen structures in the country.
Complex techniques like the micromorphology have been applied in the study of archaeo-
logical earthen heritage [
42
], while the different construction systems, like adobes, earth
mortars, and ‘bajareque’ from archaeological monuments have been characterized and the
construction techniques have been identified with advanced analytical techniques [8,43].
Nevertheless, the adobe housing has been overlooked from the material character-
ization, especially regarding mineralogical studies and non-destructive laboratory tests.
The majority of the research and academic works focused on the mechanical properties,
determined by means of destructive tests [
44
]. The present paper intends to display a
complete characterization of earthen materials in a Mexican case of study.
Heritage 2021,4867
1.3. The Seismic Affectation on Mexican Earthen Architecture
Mexico is a large country prone to suffer important earthquakes which cause the
destruction of its structures and cultural heritage. The country is located within five
tectonic plates: the Pacific Plate, the North American plate, the Rivera Plate, the Cocos
Plate, and the Caribbean Plate, causing a high seismic activity in the boundaries between
plates. Some regions are really prone to suffer big impacts from earthquakes and the
presence of the Trans-Mexican Volcanic Belt crossing a large territory contributes to this
high seismic activity.
In September 2017, two major earthquakes struck the country, having a big impact
on the regions and states affected. (Mexico is organized as a federal republic composed of
32 Federal Entities: 31 states and Mexico City as an autonomous entity.) The first event
occurred on 7 September with an epicenter in the zone known as Gulf of Tehuantepec in
the Pacific Ocean, 133 Km southeast of Pijijiapan in the state of Chiapas; and a magnitude
of 8.2 Richter scale [
45
]. The affectation was strong in the southwestern part of the country,
especially in the states of Oaxaca and Chiapas. The second event occurred on 19 September,
just 32 years after the impactful 1985 Mexico City earthquake, which devastated the
capital of the country. The epicenter was located 12 Km southeast of Axochiapan [
46
]
(
See Figure 1
), in the boundaries between the states of Morelos and Puebla, also causing
important harms in the states of Tlaxcala, Mexico State, Guerrero, and Mexico City.
Heritage 2021, 4 FOR PEER REVIEW 4
mortars, and ‘bajareque’ from archaeological monuments have been characterized and the
construction techniques have been identified with advanced analytical techniques [8,43].
Nevertheless, the adobe housing has been overlooked from the material characteri-
zation, especially regarding mineralogical studies and non-destructive laboratory tests.
The majority of the research and academic works focused on the mechanical properties,
determined by means of destructive tests [44]. The present paper intends to display a com-
plete characterization of earthen materials in a Mexican case of study.
1.3. The Seismic Affectation on Mexican Earthen Architecture
Mexico is a large country prone to suffer important earthquakes which cause the de-
struction of its structures and cultural heritage. The country is located within five tectonic
plates: the Pacific Plate, the North American plate, the Rivera Plate, the Cocos Plate, and
the Caribbean Plate, causing a high seismic activity in the boundaries between plates.
Some regions are really prone to suffer big impacts from earthquakes and the presence of
the Trans-Mexican Volcanic Belt crossing a large territory contributes to this high seismic
activity.
In September 2017, two major earthquakes struck the country, having a big impact
on the regions and states affected. (Mexico is organized as a federal republic composed of
32 Federal Entities: 31 states and Mexico City as an autonomous entity.) The first event
occurred on 7 September with an epicenter in the zone known as Gulf of Tehuantepec in
the Pacific Ocean, 133 Km southeast of Pijijiapan in the state of Chiapas; and a magnitude
of 8.2 Richter scale [45]. The affectation was strong in the southwestern part of the country,
especially in the states of Oaxaca and Chiapas. The second event occurred on 19 Septem-
ber, just 32 years after the impactful 1985 Mexico City earthquake, which devastated the
capital of the country. The epicenter was located 12 Km southeast of Axochiapan [46] (See
Figure 1), in the boundaries between the states of Morelos and Puebla, also causing im-
portant harms in the states of Tlaxcala, Mexico State, Guerrero, and Mexico City.
Figure 1. Seismic intensity map of the 2017 Puebla Earthquake. (Source: Atlas Nacional de Riesgos,
map generated by Earthquake Institute of the National Autonomous University of México).
Although the impact of earthquakes is immediate and the damages are easily visible,
the population tends to forget the events over time, causing unawareness of the seismic
danger and the oblivion of the traditional retrofitting strategies and techniques [35]. The
different strategies of adaptation to a rugged environment and natural phenomena gen-
erated the “seismic culture” concept [39].
1.4. Case Study: Jojutla and the Destruction of Its Earthen Architecture
The state of Morelos has an important seismic history, considering its central location
in the territory of Mexico. The infamous 1985 Mexico City earthquake had catastrophic
consequences not only in the country’s capital but also in the rest of the central part of the
country, including the destruction of many dwellings and displacing many people from
Figure 1.
Seismic intensity map of the 2017 Puebla Earthquake. (Source: Atlas Nacional de Riesgos,
map generated by Earthquake Institute of the National Autonomous University of México).
Although the impact of earthquakes is immediate and the damages are easily visible,
the population tends to forget the events over time, causing unawareness of the seismic
danger and the oblivion of the traditional retrofitting strategies and techniques [
35
]. The dif-
ferent strategies of adaptation to a rugged environment and natural phenomena generated
the “seismic culture” concept [39].
1.4. Case Study: Jojutla and the Destruction of Its Earthen Architecture
The state of Morelos has an important seismic history, considering its central location
in the territory of Mexico. The infamous 1985 Mexico City earthquake had catastrophic
consequences not only in the country’s capital but also in the rest of the central part of the
country, including the destruction of many dwellings and displacing many people from
their homes. Furthermore, the 1999 Tehuacan earthquake also had a big impact in the
region, causing important damages on the historical and cultural heritage, being known
for the collapse of religious buildings. Along with these major events, the state suffered
other slight tremors in 1957, 1980, 2007, and 2008; nevertheless, all remained distant in the
collective memory of the society, and the authorities did not develop any risk management
plan to anticipate future disasters.
The 2017 earthquake was particularly pernicious to the material cultural heritage,
causing the loss of several churches and many of the oldest buildings in historic centers.
Heritage 2021,4868
Regarding the state of Morelos, the National Institute of Anthropology and History (INAH)
quantified the damages suffered by heritage buildings, with a total of 259 constructions
presenting damages [
47
], and being the focus of the heritage institutions from the entire
country. Especially remarkable was the destruction of the 16th Century Mexican colo-
nial monasteries, which are listed as UNESCO World Heritage Sites. Research efforts
and resources were allocated to study and comprehend the failure modes and seismic
response of these structures [
48
]. Besides the relevance and notoriety of these structures,
religious monuments are an important part of the traditions, culture, and way of life of the
local communities
Regarding the residential architecture and traditional housing, the situation was totally
opposite (See Figure 2). The reconstruction of the dwellings was done with industrial
materials, mainly cement blocks provided by the authorities, for the walls; and metallic
sheets for the roof structures. The traditional materials, particularly adobes, were rejected
by the majority of the population, perceived as unsafe systems and the main cause of the
structural damages. Although the seismic affectation was provoked by many factors, the
organizations in charge did not protect and support the vernacular architecture and the
traditional techniques [
49
], with the immediate consequence of the disappearance of this
local culture.
Heritage 2021, 4 FOR PEER REVIEW 5
their homes. Furthermore, the 1999 Tehuacan earthquake also had a big impact in the re-
gion, causing important damages on the historical and cultural heritage, being known for
the collapse of religious buildings. Along with these major events, the state suffered other
slight tremors in 1957, 1980, 2007, and 2008; nevertheless, all remained distant in the col-
lective memory of the society, and the authorities did not develop any risk management
plan to anticipate future disasters.
The 2017 earthquake was particularly pernicious to the material cultural heritage,
causing the loss of several churches and many of the oldest buildings in historic centers.
Regarding the state of Morelos, the National Institute of Anthropology and History
(INAH) quantified the damages suffered by heritage buildings, with a total of 259 con-
structions presenting damages [47], and being the focus of the heritage institutions from
the entire country. Especially remarkable was the destruction of the 16th Century Mexican
colonial monasteries, which are listed as UNESCO World Heritage Sites. Research efforts
and resources were allocated to study and comprehend the failure modes and seismic
response of these structures [48]. Besides the relevance and notoriety of these structures,
religious monuments are an important part of the traditions, culture, and way of life of
the local communities
Regarding the residential architecture and traditional housing, the situation was to-
tally opposite (See Figure 2). The reconstruction of the dwellings was done with industrial
materials, mainly cement blocks provided by the authorities, for the walls; and metallic
sheets for the roof structures. The traditional materials, particularly adobes, were rejected
by the majority of the population, perceived as unsafe systems and the main cause of the
structural damages. Although the seismic affectation was provoked by many factors, the
organizations in charge did not protect and support the vernacular architecture and the
traditional techniques [49], with the immediate consequence of the disappearance of this
local culture.
Figure 2. Destruction of a building in Jojutla months after the 2017 Puebla Earthquake. (Image
source: A. Sanchez-Calvillo and E. G. Navarro-Mendoza).
Morelos is one of the 32 total states which comprise Mexico, being located in the cen-
tral part of the country, bordered by the states of Puebla, Guerrero, State of Mexico, and
Mexico City. Regarding the earthen architecture, Morelos has an important tradition of
adobe buildings [49], with well conserved examples in the south-eastern and north-east-
ern parts of the state. Several of the traditional dwellings have two or more centuries of
existence, and they have resisted all types of natural phenomenon including seismic
events. Adobe constructions present a set of earthquake-resistant strategies, like simple
geometric proportions and forms, an adequate slenderness and thickness of the walls, roof
flexible systems, compatibility between the materials, a good maintenance from the users,
among others. The most well-preserved houses from these regions responded rather well
Figure 2.
Destruction of a building in Jojutla months after the 2017 Puebla Earthquake. (Image source:
A. Sanchez-Calvillo and E. G. Navarro-Mendoza).
Morelos is one of the 32 total states which comprise Mexico, being located in the
central part of the country, bordered by the states of Puebla, Guerrero, State of Mexico,
and Mexico City. Regarding the earthen architecture, Morelos has an important tradition
of adobe buildings [
49
], with well conserved examples in the south-eastern and north-
eastern parts of the state. Several of the traditional dwellings have two or more centuries of
existence, and they have resisted all types of natural phenomenon including seismic events.
Adobe constructions present a set of earthquake-resistant strategies, like simple geometric
proportions and forms, an adequate slenderness and thickness of the walls, roof flexible
systems, compatibility between the materials, a good maintenance from the users, among
others. The most well-preserved houses from these regions responded rather well to the
2017 Puebla earthquake [
49
], an inherent feature of the vernacular architecture, which has
always responded to the local environment [
39
]. In Figure 3b, the choropleth map of the
state can be observed, showing the municipalities with a higher preservation of earthen
constructions, and the ones where modern materials and systems have substituted adobe.
The case study Jojutla is spotted in the south-western region of the state, an area where less
traditional architecture predominates.
Heritage 2021,4869
Heritage 2021, 4 FOR PEER REVIEW 6
to the 2017 Puebla earthquake [49], an inherent feature of the vernacular architecture,
which has always responded to the local environment [39]. In Figure 3b, the choropleth
map of the state can be observed, showing the municipalities with a higher preservation
of earthen constructions, and the ones where modern materials and systems have substi-
tuted adobe. The case study Jojutla is spotted in the south-western region of the state, an
area where less traditional architecture predominates.
(a)
(b)
Figure 3. Location of Morelos and Jojutla. (a) Location of the state of Morelos within Mexico (Image source: Commons);
(b) Choropleth map of earthen construction in Morelos, with the case of study Jojutla highlighted. The zones with more
preservation of earthen structures have darker color tones; and the lighter ones correspond to the municipalities where
modern materials and systems have substituted adobe. (Map source: ArcMap 10.3, map elaborated by A. Sanchez-Cal-
villo).
In contrast to other regions and localities of Morelos, Jojutla, showed drastic changes
to the traditional buildings of Morelos. The dwellings were fairly modified over the last
decades, integrating new interior spaces with modern industrial materials and facilities,
but the implementation was commonly suboptimal. The repercussions of these construc-
tive changes were also treated in a previous research from the authors, focusing on the
physical damages observed in the buildings after the earthquake [50]. The adobe build-
ings of Jojutla presented changes in the morphology, original uses, and architectural
plans, the addition of new floor levels and construction materials, lack of maintenance,
and abandonment.
The town of Jojutla showed a local seismic-regionalization, with greater damages in
some particular colonies or neighbourhoods, as seen in Figure 4, displaying areas with
high and medium risk to its buildings. The high risk includes the collapse of the structures,
since Jojutla experienced major material and human losses. Two colonies of the city were
specially affected: the historic center, where most of the adobe dwellings and monuments
were located; and the Emiliano Zapata colony, much more recently built with the majority
of its constructions consisting of concrete structures.
Figure 3.
Location of Morelos and Jojutla. (
a
) Location of the state of Morelos within Mexico (Image source: Commons);
(
b
) Choropleth map of earthen construction in Morelos, with the case of study Jojutla highlighted. The zones with more
preservation of earthen structures have darker color tones; and the lighter ones correspond to the municipalities where
modern materials and systems have substituted adobe. (Map source: ArcMap 10.3, map elaborated by A. Sanchez-Calvillo).
In contrast to other regions and localities of Morelos, Jojutla, showed drastic changes
to the traditional buildings of Morelos. The dwellings were fairly modified over the last
decades, integrating new interior spaces with modern industrial materials and facilities, but
the implementation was commonly suboptimal. The repercussions of these constructive
changes were also treated in a previous research from the authors, focusing on the physical
damages observed in the buildings after the earthquake [
50
]. The adobe buildings of Jojutla
presented changes in the morphology, original uses, and architectural plans, the addition
of new floor levels and construction materials, lack of maintenance, and abandonment.
The town of Jojutla showed a local seismic-regionalization, with greater damages in
some particular colonies or neighbourhoods, as seen in Figure 4, displaying areas with
high and medium risk to its buildings. The high risk includes the collapse of the structures,
since Jojutla experienced major material and human losses. Two colonies of the city were
specially affected: the historic center, where most of the adobe dwellings and monuments
were located; and the Emiliano Zapata colony, much more recently built with the majority
of its constructions consisting of concrete structures.
The geotechnical survey of the Emiliano Zapata colony provided some of the reasons
for the poor seismic performance of the buildings, including suboptimal resistance of the
structural systems, issues with the foundations and construction malpractices [
51
]. The
terrain presented a superposition of clay and silt layers and a travertine stratum formed by
disposal of calcium carbonate [51], which is not well suited for building purposes.
Additionally, the use of incompatible materials with different elasticities, the poor
connections between the structural elements, the changes in the morphology of the build-
ings, and the low mechanical properties have been reported as the main causes of the
seismic vulnerability in historic earthen constructions and historic centers around the
world [9,18,36,40,52].
Knowing the propensity of the region to seismic activity and with the experience of
past events like the 1985 Mexico City earthquake or the 1999 Puebla earthquake, it was
surprising that he municipal development plan of the city council of Jojutla, published on
May of 2016, months before the seismic events, did not include any mitigation strategies
against natural hazards like earthquakes, floods, or fires; and, more importantly, no risk
maps had been made, nor a reorganization of the city [53].
Heritage 2021,4870
Heritage 2021, 4 FOR PEER REVIEW 7
Figure 4. Mapping of the damaged buildings in Jojutla after the 2017 Puebla Earthquake by the emergency brigades (Map
source: ArcMap 10.3, map elaborated by A. Sanchez-Calvillo).
The geotechnical survey of the Emiliano Zapata colony provided some of the reasons
for the poor seismic performance of the buildings, including suboptimal resistance of the
structural systems, issues with the foundations and construction malpractices [51]. The
terrain presented a superposition of clay and silt layers and a travertine stratum formed
by disposal of calcium carbonate [51], which is not well suited for building purposes.
Additionally, the use of incompatible materials with different elasticities, the poor
connections between the structural elements, the changes in the morphology of the build-
ings, and the low mechanical properties have been reported as the main causes of the
seismic vulnerability in historic earthen constructions and historic centers around the
world [9,18,36,40,52].
Knowing the propensity of the region to seismic activity and with the experience of
past events like the 1985 Mexico City earthquake or the 1999 Puebla earthquake, it was
surprising that he municipal development plan of the city council of Jojutla, published on
May of 2016, months before the seismic events, did not include any mitigation strategies
against natural hazards like earthquakes, floods, or fires; and, more importantly, no risk
maps had been made, nor a reorganization of the city [53].
2. Materials and Methods
Thirteen samples of earthen architecture were collected from the remains of affected
buildings left in the region of Jojutla after the seismic disaster of 2017. Considering that
the structures were severely damaged and a whole study of the construction typologies
would not be feasible, all the samples were carried to the laboratory “Ing. Luis Silva
Ruelas” of the Faculty of Civil Engineering of the Universidad Michoacana San Nicolas
de Hidalgo, in Morelia, Mexico.
2.1. Sampling Adobe and Soils
There were 11 representative shards of adobe bricks collected from 11 different tra-
ditional houses in downtown Jojutla (See Figure 5). These samples were collected before
Figure 4.
Mapping of the damaged buildings in Jojutla after the 2017 Puebla Earthquake by the
emergency brigades (Map source: ArcMap 10.3, map elaborated by A. Sanchez-Calvillo).
2. Materials and Methods
Thirteen samples of earthen architecture were collected from the remains of affected
buildings left in the region of Jojutla after the seismic disaster of 2017. Considering that the
structures were severely damaged and a whole study of the construction typologies would
not be feasible, all the samples were carried to the laboratory “Ing. Luis Silva Ruelas” of
the Faculty of Civil Engineering of the Universidad Michoacana San Nicolas de Hidalgo,
in Morelia, Mexico.
2.1. Sampling Adobe and Soils
There were 11 representative shards of adobe bricks collected from 11 different tra-
ditional houses in downtown Jojutla (See Figure 5). These samples were collected before
the demolition of the buildings, which was shortly after the field trip in May 2018. There
also were two samples of quarry soils of the region taken, concretely in the extraction
area for the manufacture of adobe bricks and ceramic bricks, and an excavation in the city
(See Table 1). The region is recognized by their rice production, even the Morelos rice is a
trade mark, and of course they have plenty of water. The superficial stratum of the town
comprises fluvial and lacustrine deposits, which held large amounts of clays [
51
], very
susceptible to volumetric changes with the moisture.
Sample
Type
Collection Date
Provenance
M1
Soil
17/07/2018
Excavation in Emiliano Zapata colony
M2
Adobe
18/07/2018
Francisco Javier MinaSt., Jojutla downtown
M3
Adobe
18/07/2018
Zayas Enriquez St., Jojutla downtown
M4
Adobe
18/07/2018
Zayas Enriquez St., Jojutla downtown
M5
Adobe
18/07/2018
Carlos Cuaglia St., Jojutla downtown
M6
Adobe
18/07/2018
Zayas Enriquez St., Jojutla downtown
M7
Adobe
18/07/2018
M. Cepeda Medrano St., Jojutla downtown
M8
Adobe
18/07/2018
J. H. Preciado St., Jojutla downtown
M9
Adobe
18/07/2018
Francisco J. Bocanegra St., Jojutla downtown
M10
Adobe
18/07/2018
21 de Marzo St., Jojutla downtown
M11
Adobe
17/07/2018
Zayas Enriquez St., Jojutla downtown
M12
Adobe
17/07/2018
Ricardo Sanchez St., Jojutla downtown
M13
Soil
17/07/2018
Clay quarry near Jojutla
Figure 5. Location of the samples within the urban area. (Source: Google MyMaps).
Heritage 2021,4871
Table 1. List of collected samples, type, date, and provenance.
Sample Type Collection Date Provenance
M1 Soil 17/07/2018 Excavation in Emiliano Zapata colony
M2 Adobe 18/07/2018 Francisco Javier MinaSt., Jojutla downtown
M3 Adobe 18/07/2018 Zayas Enriquez St., Jojutla downtown
M4 Adobe 18/07/2018 Zayas Enriquez St., Jojutla downtown
M5 Adobe 18/07/2018 Carlos Cuaglia St., Jojutla downtown
M6 Adobe 18/07/2018 Zayas Enriquez St., Jojutla downtown
M7 Adobe 18/07/2018 M. Cepeda Medrano St., Jojutla downtown
M8 Adobe 18/07/2018 J. H. Preciado St., Jojutla downtown
M9 Adobe 18/07/2018
Francisco J. Bocanegra St., Jojutla downtown
M10 Adobe 18/07/2018 21 de Marzo St., Jojutla downtown
M11 Adobe 17/07/2018 Zayas Enriquez St., Jojutla downtown
M12 Adobe 17/07/2018 Ricardo Sanchez St., Jojutla downtown
M13 Soil 17/07/2018 Clay quarry near Jojutla
Previous research works involving historical and archaeological heritage followed
similar strategies for the sampling, collecting both adobe pieces or shards and local soils
from clay quarries. Fratini et al. [
54
], gathered information regarding the production and
manufacturing of the adobes following the artisans’ indications of the towns of Sambiasi
and Nicastro. Mellakhaifi et al. [
31
], decided to study the vernacular heritage in southeast
Morocco only from the samples of unaltered soils, extrapolating the results to the earthen
traditional techniques and its properties. Regarding archaeological heritage, Pérez et al. [
8
],
studied the Great Pyramid of Cholula, taking samples of complete adobe bricks of the
inner construction, besides 5 soil samples corresponding to some important Pre-Hispanic
development stages of the ancient city.
Taking into account the emergency state of Jojutla de Juarez and the situation between
the inhabitants and their damaged buildings, the sample collection responded to the criteria
of taking the maximum possible amount of material before the demolition of the remaining
houses (See Figure 6). Our group also had the opportunity to talk with the owners of the
buildings and families of the town; some of the owners from collapsed buildings said
they were taking good care of their properties, even if they had collapsed, by protecting
the remaining structures from inclement weather. They let the group take the samples
from broken adobes, a family from the town even gave the group adobe samples from two
buildings more than 200 years old.
Although some of the owners from the land plots and the damaged dwellings planned
on reusing the adobe bricks preserved in good condition, most of them thought that
earthen materials are unsafe and preferred to wait for the concrete blocks provided by the
authorities. One of the main advantages of earthen architecture is that the materials can be
reused perpetually since clays are sustainable resources [21,55].
The traditional mortar plasters from the samples collected were in poor condition.
The plasters operate as the skin of the adobes and passivate them from the environmental
attack, being really important to preserve cultural heritage [
8
,
56
,
57
]. Usually the plasters
and adobes from historic constructions come from the same quarry but are stabilized with
different additions [46].
Heritage 2021,4872
Heritage 2021, 4 FOR PEER REVIEW 9
owners of the buildings and families of the town; some of the owners from collapsed
buildings said they were taking good care of their properties, even if they had collapsed,
by protecting the remaining structures from inclement weather. They let the group take
the samples from broken adobes, a family from the town even gave the group adobe sam-
ples from two buildings more than 200 years old.
Although some of the owners from the land plots and the damaged dwellings
planned on reusing the adobe bricks preserved in good condition, most of them thought
that earthen materials are unsafe and preferred to wait for the concrete blocks provided
by the authorities. One of the main advantages of earthen architecture is that the materials
can be reused perpetually since clays are sustainable resources [21,55].
(a)
(b)
(c)
(d)
Figure 6. Sample collection. (a) Semi-complete adobe bricks from an old demolished building; (b) Collecting samples from
a building in the city centre; (c) Clay quarry for the production of adobes and ceramic bricks; (d) Excavation in the Emiliano
Zapata colony. (Image source: A. Sanchez-Calvillo and E. G. Navarro-Mendoza).
The traditional mortar plasters from the samples collected were in poor condition.
The plasters operate as the skin of the adobes and passivate them from the environmental
attack, being really important to preserve cultural heritage [8,56,57]. Usually the plasters
and adobes from historic constructions come from the same quarry but are stabilized with
different additions [46].
2.2. Preparation of the Samples
In order to perform the mechanical tests of the samples and some non-destructive
trials, these had to be prepared. First, all the material was dried for one to two weeks in
Figure 6.
Sample collection. (
a
) Semi-complete adobe bricks from an old demolished building;
(
b) Collecting
samples from a building in the city centre; (
c
) Clay quarry for the production of adobes
and ceramic bricks; (
d
) Excavation in the Emiliano Zapata colony. (Image source: A. Sanchez-Calvillo
and E. G. Navarro-Mendoza).
2.2. Preparation of the Samples
In order to perform the mechanical tests of the samples and some non-destructive trials,
these had to be prepared. First, all the material was dried for one to two weeks in the oven
at a maximum temperature of 50–60
C; a higher temperature could change composition
of the clay materials. The samples were weighed every day until they presented a constant
weight, then, they were left cooling for 24 h.
As most of the samples were collected from badly damaged building remains, they
were in a precarious state that did not allow all of the original samples to qualify for the
compression strength test nor the ultrasonic pulse velocity (UPV), as they didn
´
t have the
minimum dimensions or were extremely inconsistent. From the 11 patrimonial samples
only 6 could be eligible for the mechanical characterization trials, needing a previous
preparation, as can be seen in Figure 7. The samples were smothered and then covered with
liquid sulphur to achieve the regularity conditions to be tested with the
universal machine.
For the mineralogical studies each of the samples were selected, crushed and sieved
by the sieve n
º
200 ASTM till obtain a powder type material for X-ray diffraction and X-ray
fluorescence analyses. The specimens were tested in the LANCIC Laboratory [The speci-
mens were tested in the National Science Laboratory for the Research and Conservation
of Cultural Heritage, of the Physics Institute of the National Autonomous University of
Mexico (LANCIC-IFUNAM)].
Heritage 2021,4873
Heritage 2021, 4 FOR PEER REVIEW 10
the oven at a maximum temperature of 5060 ; a higher temperature could change com-
position of the clay materials. The samples were weighed every day until they presented
a constant weight, then, they were left cooling for 24 hours.
As most of the samples were collected from badly damaged building remains, they
were in a precarious state that did not allow all of the original samples to qualify for the
compression strength test nor the ultrasonic pulse velocity (UPV), as they didn´t have the
minimum dimensions or were extremely inconsistent. From the 11 patrimonial samples
only 6 could be eligible for the mechanical characterization trials, needing a previous
preparation, as can be seen in Figure 7. The samples were smothered and then covered
with liquid sulphur to achieve the regularity conditions to be tested with the universal
machine.
For the mineralogical studies each of the samples were selected, crushed and sieved
by the sieve nº200 ASTM till obtain a powder type material for X-ray diffraction and X-
ray fluorescence analyses. The specimens were tested in the LANCIC Laboratory [The
specimens were tested in the National Science Laboratory for the Research and Conserva-
tion of Cultural Heritage, of the Physics Institute of the National Autonomous University
of Mexico (LANCIC-IFUNAM)].
Figure 7. Preparation and capping of the adobe samples with sulphur for the compressive strength test. (Image source: A.
Sanchez-Calvillo).
2.3. Characterization Methodology
Four types of tests were undertaken with the adobe and soils samples: non-destruc-
tive tests, destructive tests, geotechnical, and mineralogical analysis. All the samples were
classified by the Unified Soil Classification System (USCS) to obtain the composition of
the adobe bricks and the type of soils used for construction materials in the region [58].
Figure 7.
Preparation and capping of the adobe samples with sulphur for the compressive strength
test. (Image source: A. Sanchez-Calvillo).
2.3. Characterization Methodology
Four types of tests were undertaken with the adobe and soils samples: non-destructive
tests, destructive tests, geotechnical, and mineralogical analysis. All the samples were
classified by the Unified Soil Classification System (USCS) to obtain the composition of
the adobe bricks and the type of soils used for construction materials in the region [
58
].
The fiber percentage was also obtained, actually straw in the case of study, for each one of
the adobes.
The moisture content of the samples was determined by two methods: first, with the
moisture meter equipment Delmhorst DH-BD2100, which provides the relative humidity
and can be taken in situ; secondly, calculating the percentage between the wet weight
and the dried weight of the samples after drying them in the oven for one to two weeks.
This step is very important before fulfilling the non-destructive tests and the physico
and micro-characterization.
For Color Spectroscopy, we followed the CIE system (Acronym of Commission Inter-
nationale de l’Eclairage) [
59
], and using the CLRM-200 colorimeter equipment, the adobe
samples were measured, obtaining three parameters: the coordinates a* and b* (red to
green and yellow to blue axis), and the luminosity L*.
With the carved samples of the adobes it was also possible to effectuate non-destructive
tests, such as the ultrasonic pulse velocity (UPV), calculating and correlating it with the
bulk density of the adobes. For this purpose V-Meter MK IV from James Instruments Non
Destructive Test Equipment was used; with a frequency range from 24 to 500 kHz, based
on transducers selected, and receiver sensitivity between 30 and 100 kHz.
X-ray diffraction analysis (XRD) was carried out to measure the mineralogical compo-
sition of the natural soils and the adobes; clay minerals are most easily identified using
this technique rather than other physical tests. The measurements were performed using a
bench-top Thermo Scientific
ARL
Equinox 100 Diffractometer using a 50 W microfocus
Cu X-ray tube and a curved position sensitive detector (CPS) that measures all diffraction
peaks simultaneously (0–1002θrange).
Heritage 2021,4874
Elemental analysis was performed using X-ray Fluorescence (XRF) spectrometry with
an X-ray spectrometer developed at LANCIC [
60
]. This system has a SDD X-ray Amptek
detector and a 75 W Mo X-ray tube. Measurements were undertaken at 45
X-ray detection
for 180 s with 35 kV and 0.2 mA, the spot at the surface has 1 mm diameter.
The use of scanning electron microscope (SEM) images coupled with EDS, a technique
with widespread use in cultural heritage [
61
], allowed us to confirm the chemical com-
position of the mineralogical phases in those soils [
62
]. The microphotographs and EDS
microanalyses were performed in a benchtop SEM Hitachi 3030+ to quantify their presence
in soils under low vacuum using a 18 kV electron beam. The samples were not covered
with any metallic or carbon thin film.
The mechanical strength is the most important index test in construction materials.
Adobes are patrimonial and historical masonry pieces designed to protect human beings
from the elements, and it is, therefore, essential for them to possess the mechanical behavior
required to withstand different loads. Recovering the building technology of adobes
improves the conservation and restoration of the original bricks, as well as allowing the
production of new ones that will better adhere to the original structure, preserving it
against environmental and acute attacks [37].
It was decided to apply compressive strength and PLT in order to obtain the indica-
tive values of mechanical resistance, which could be compared to other patrimonial and
vernacular study cases. For being able to perform the analysis the samples were carved till
appropriate dimensions were obtained, and later capped with melted sulphur, due to the
irregularities presented in their surface. Once prepared, they were introduced in the Tinius
Olsen Universal Test Machine to obtain their ultimate resistance to compressive strength,
(See Figure 8).
Heritage 2021, 4 FOR PEER REVIEW 12
Figure 8. Compressive strength testing of one adobe sample. (Image source: A. Sanchez-Calvillo).
2.4. Point Load Test
PLT allows determining mechanical resistance of non-carved samples of several
types of masonries and rocks, both: natural or artificial, being especially designed for the
study of rocks [63]. The first research works which utilised the test achieved to associate
the uniaxial compressive resistance with the PLT index (Is), creating the basis to apply the
analysis to rock fragments [64], and geotechnical applications [65].
Recent studies have concluded that the relation between uniaxial compressive
strength (UCS) and IS is not linear for other materials like soft rocks [66], granites in dif-
ferent weathering conditions [67], or basalt aggregates [68]. Research works in Bukit Ti-
mah, Singapur, have sampled from residual soils to non-weathered rocks, concluding that
the conversation ratio should vary from the original one. Nevertheless, the materials re-
searched in this work are adobe bricks, being a first approximation to the characterization
of solid clay fragments with this technique.
The equipment used during the trial was digital rock strength apparatus 100 KN cap
by the Controls Group (See Figure 9). The best asset of this equipment is the possibility to
use it in situ due to its portability; having the choice to perform the analysis both in the
field or in the laboratory.
The guidelines followed for the fulfilment of the test were the ASTM standards, and
the previous experience with the PLT procedure in the materials laboratory [6971]. The
samples of fragments of adobes were measured and listed before the trial was performed,
recording the values of each piece. Later, all the samples were compressed with the Point
Load apparatus till cracking and reaching the failure. The new fragments obtained by
rupture could be tested again, only if they meet the requirements of dimension and pro-
portion. The result of the analysis is a rupture load value, which needs to be transformed
by an equation system explained later in this manuscript, that leads to the ultimate un-
confined uniaxial compression resistance.
The PLT index (Is) without correction factor is calculated with the following equation:

(1)
where:
Is = Point-load index, MPa;
P = Maximum load, kN;
De = Equivalent core diameter, mm.
The resistance index value (is a non-corrected value which varies depending on
the thickness of the fragments tested. To obtain the corrected resistance index ( it is
necessary to multiply the first index by the correction factor:

(2)
Depending on the size of the fragments, there will be two different correction factors.
The election between one or the other will be the proximity of each sample to the standard
Figure 8. Compressive strength testing of one adobe sample. (Image source: A. Sanchez-Calvillo).
2.4. Point Load Test
PLT allows determining mechanical resistance of non-carved samples of several types
of masonries and rocks, both: natural or artificial, being especially designed for the study
of rocks [
63
]. The first research works which utilised the test achieved to associate the
uniaxial compressive resistance with the PLT index (Is), creating the basis to apply the
analysis to rock fragments [64], and geotechnical applications [65].
Recent studies have concluded that the relation between uniaxial compressive strength
(UCS) and I
S
is not linear for other materials like soft rocks [
66
], granites in different
weathering conditions [
67
], or basalt aggregates [
68
]. Research works in Bukit Timah,
Singapur, have sampled from residual soils to non-weathered rocks, concluding that the
conversation ratio should vary from the original one. Nevertheless, the materials researched
in this work are adobe bricks, being a first approximation to the characterization of solid
clay fragments with this technique.
The equipment used during the trial was digital rock strength apparatus 100 KN cap
by the Controls Group (See Figure 9). The best asset of this equipment is the possibility to
Heritage 2021,4875
use it in situ due to its portability; having the choice to perform the analysis both in the
field or in the laboratory.
Heritage 2021, 4 FOR PEER REVIEW 13
value of 50 mm [12]. For the specimens near to this 50 mm thickness (D), the correction
factor is calculated with the following equation:

(3)
Figure 9. Adobe sample in the point-load equipment. (Image source: A. Sanchez-Calvillo).
Instead, when calculating fragments with thickness distant of 50 mm, the following
formula will be used:

(4)
The estimation of the compressive strength or UCS (Uniaxial Compressive
Strength) is obtained with the following equation:

(5)
The value is the main purpose which the PLT follows and it is going to be com-
pared with other values of mechanical resistance obtained by other tests. Another inter-
esting aspect of the test is to observe the rupture mode of the fragments, finding relations
between the composition of adobes, their morphology, size, fibers and aggregates distri-
bution (See Figure 10).
Figure 10. Fracture in adobe fragments with point-load equipment. (Image source: A. Sanchez-Calvillo).
Figure 9. Adobe sample in the point-load equipment. (Image source: A. Sanchez-Calvillo).
The guidelines followed for the fulfilment of the test were the ASTM standards, and
the previous experience with the PLT procedure in the materials laboratory
[6971]
. The
samples of fragments of adobes were measured and listed before the trial was performed,
recording the values of each piece. Later, all the samples were compressed with the Point
Load apparatus till cracking and reaching the failure. The new fragments obtained by rup-
ture could be tested again, only if they meet the requirements of dimension and proportion.
The result of the analysis is a rupture load value, which needs to be transformed by an
equation system explained later in this manuscript, that leads to the ultimate unconfined
uniaxial compression resistance.
The PLT index (I
s
) without correction factor is calculated with the following equation:
Is=P1000
D2
e
(1)
where:
Is= Point-load index, MPa;
P = Maximum load, kN;
De = Equivalent core diameter, mm.
The resistance index value (
Is)
is a non-corrected value which varies depending on
the thickness of the fragments tested. To obtain the corrected resistance index (
Is(50))
it is
necessary to multiply the first index by the correction factor:
Is(50)=FIs(2)
Depending on the size of the fragments, there will be two different correction factors.
The election between one or the other will be the proximity of each sample to the standard
value of 50 mm [
12
]. For the specimens near to this 50 mm thickness (D), the correction
factor is calculated with the following equation:
F=sDe
50 (3)
Instead, when calculating fragments with thickness distant of 50 mm, the following
formula will be used:
F=De
50 0.45
(4)
Heritage 2021,4876
The estimation of the compressive strength
σ
or UCS (Uniaxial Compressive Strength)
is obtained with the following equation:
σ=(C)Is(50)=24 Is(50)(5)
The value
σ
is the main purpose which the PLT follows and it is going to be compared
with other values of mechanical resistance obtained by other tests. Another interesting
aspect of the test is to observe the rupture mode of the fragments, finding relations between
the composition of adobes, their morphology, size, fibers and aggregates distribution
(See Figure 10).
Heritage 2021, 4 FOR PEER REVIEW 13
value of 50 mm [12]. For the specimens near to this 50 mm thickness (D), the correction
factor is calculated with the following equation:

(3)
Figure 9. Adobe sample in the point-load equipment. (Image source: A. Sanchez-Calvillo).
Instead, when calculating fragments with thickness distant of 50 mm, the following
formula will be used:

(4)
The estimation of the compressive strength or UCS (Uniaxial Compressive
Strength) is obtained with the following equation:

(5)
The value is the main purpose which the PLT follows and it is going to be com-
pared with other values of mechanical resistance obtained by other tests. Another inter-
esting aspect of the test is to observe the rupture mode of the fragments, finding relations
between the composition of adobes, their morphology, size, fibers and aggregates distri-
bution (See Figure 10).
Figure 10. Fracture in adobe fragments with point-load equipment. (Image source: A. Sanchez-Calvillo).
Figure 10.
Fracture in adobe fragments with point-load equipment. (Image source: A. Sanchez-Calvillo).
3. Results and Discussion
3.1. Non-Destructive Tests
Regarding the colorimetry test, the adobe samples had a significant increase in their
luminosity in relation to the natural clays, showing the transformation process of adding
stabilisers to the construction materials. Table 2shows the values of a* (red to green axis),
b* (yellow to green axis), and L* (luminosity); we can also see the representation of the true
color of adobes and soils. Previous research works done in Jojutla confirmed the use of
lime and lithic material, correlating the colorimetric values with the particle size and USCS
classification and microscopic techniques like XRD [62].
Table 2. Colorimetric values according to the CIE coordinates system.
Specimens a* b* L* Color
Adobes 4.92 11.45 42.15
Heritage 2021, 4 FOR PEER REVIEW 14
3. Results and Discussion
3.1. Non-Destructive Tests
Regarding the colorimetry test, the adobe samples had a significant increase in their
luminosity in relation to the natural clays, showing the transformation process of adding
stabilisers to the construction materials. Table 2 shows the values of a* (red to green axis),
b* (yellow to green axis), and L* (luminosity); we can also see the representation of the
true color of adobes and soils. Previous research works done in Jojutla confirmed the use
of lime and lithic material, correlating the colorimetric values with the particle size and
USCS classification and microscopic techniques like XRD [62].
The different additives and the addition percentage have a big influence in the aes-
thetic perception of the constructions made of adobe masonry [72]. The stabilizers with a
more similar color to the selected original clays have a lesser impact on the final variation.
Table 2. Colorimetric values according to the CIE coordinates system.
Specimens
a*
b*
L*
Color
Adobes
4.92
11.45
42.15
Soils
3.94
5.76
30.30
The average ultrasonic pulse velocity (UPV) for the adobes was 634.58 m/s. UPV al-
lows us to estimate the dynamic properties of the material, as well as internal composition
and porosity of the blocks, and if they have irregularities or construction flaws. Other
research works with patrimonial earthen heritage showed larger values of UPV [73], the
lower values obtained in Jojutla could be directly related to the effects of the 2017 Puebla
Earthquake on the constructions and building systems, decreasing most of the properties
and causing material fatigue and propagating microcracks which exfoliate pieces.
3.2. Mineralogical Analyses
XRD results (see Table 3) show the percentage of various minerals detected in the
samples, including calcite contents in almost every sample. As indicated in the methodol-
ogy section, M1 and M13 came from a local excavation and the clay quarry of the region;
while the rest came from damaged adobes of the historic centre of Jojutla. M1 was from a
zone where buildings collapsed, a clay stratum, and the soil was improved with lime for
foundations, because the community was building a new structure at the moment the
sample was taken; therefore, the material appeared in the XRD analysis. Instead, M13 did
not contain lime considering it was taken from a clay quarry surrounding Jojutla, before
the stabilization of the raw material for handmade ceramic bricks. M212, except M9 and
M11, contain lime, used to stabilize the adobes, being the most common material in all
Mexico for these purposes in earthen structures [74,75].
Tthe presence of kaolinite con also be observed in significant proportions for six of
the samples. Kaolinites have low shrink-swell capacity, which makes them better for
building purposes, being a great choice for the production of adobes.
Soils 3.94 5.76 30.30
Heritage 2021, 4 FOR PEER REVIEW 14
3. Results and Discussion
3.1. Non-Destructive Tests
Regarding the colorimetry test, the adobe samples had a significant increase in their
luminosity in relation to the natural clays, showing the transformation process of adding
stabilisers to the construction materials. Table 2 shows the values of a* (red to green axis),
b* (yellow to green axis), and L* (luminosity); we can also see the representation of the
true color of adobes and soils. Previous research works done in Jojutla confirmed the use
of lime and lithic material, correlating the colorimetric values with the particle size and
USCS classification and microscopic techniques like XRD [62].
The different additives and the addition percentage have a big influence in the aes-
thetic perception of the constructions made of adobe masonry [72]. The stabilizers with a
more similar color to the selected original clays have a lesser impact on the final variation.
Table 2. Colorimetric values according to the CIE coordinates system.
Specimens
a*
b*
L*
Color
Adobes
4.92
11.45
42.15
Soils
3.94
5.76
30.30
The average ultrasonic pulse velocity (UPV) for the adobes was 634.58 m/s. UPV al-
lows us to estimate the dynamic properties of the material, as well as internal composition
and porosity of the blocks, and if they have irregularities or construction flaws. Other
research works with patrimonial earthen heritage showed larger values of UPV [73], the
lower values obtained in Jojutla could be directly related to the effects of the 2017 Puebla
Earthquake on the constructions and building systems, decreasing most of the properties
and causing material fatigue and propagating microcracks which exfoliate pieces.
3.2. Mineralogical Analyses
XRD results (see Table 3) show the percentage of various minerals detected in the
samples, including calcite contents in almost every sample. As indicated in the methodol-
ogy section, M1 and M13 came from a local excavation and the clay quarry of the region;
while the rest came from damaged adobes of the historic centre of Jojutla. M1 was from a
zone where buildings collapsed, a clay stratum, and the soil was improved with lime for
foundations, because the community was building a new structure at the moment the
sample was taken; therefore, the material appeared in the XRD analysis. Instead, M13 did
not contain lime considering it was taken from a clay quarry surrounding Jojutla, before
the stabilization of the raw material for handmade ceramic bricks. M212, except M9 and
M11, contain lime, used to stabilize the adobes, being the most common material in all
Mexico for these purposes in earthen structures [74,75].
Tthe presence of kaolinite con also be observed in significant proportions for six of
the samples. Kaolinites have low shrink-swell capacity, which makes them better for
building purposes, being a great choice for the production of adobes.
The different additives and the addition percentage have a big influence in the aesthetic
perception of the constructions made of adobe masonry [
72
]. The stabilizers with a more
similar color to the selected original clays have a lesser impact on the final variation.
The average ultrasonic pulse velocity (UPV) for the adobes was 634.58 m/s. UPV
allows us to estimate the dynamic properties of the material, as well as internal composition
and porosity of the blocks, and if they have irregularities or construction flaws. Other
research works with patrimonial earthen heritage showed larger values of UPV [
73
], the
lower values obtained in Jojutla could be directly related to the effects of the 2017 Puebla
Earthquake on the constructions and building systems, decreasing most of the properties
and causing material fatigue and propagating microcracks which exfoliate pieces.
Heritage 2021,4877
3.2. Mineralogical Analyses
XRD results (see Table 3) show the percentage of various minerals detected in the
samples, including calcite contents in almost every sample. As indicated in the methodol-
ogy section, M1 and M13 came from a local excavation and the clay quarry of the region;
while the rest came from damaged adobes of the historic centre of Jojutla. M1 was from
a zone where buildings collapsed, a clay stratum, and the soil was improved with lime
for foundations, because the community was building a new structure at the moment the
sample was taken; therefore, the material appeared in the XRD analysis. Instead, M13 did
not contain lime considering it was taken from a clay quarry surrounding Jojutla, before
the stabilization of the raw material for handmade ceramic bricks. M2–12, except M9 and
M11, contain lime, used to stabilize the adobes, being the most common material in all
Mexico for these purposes in earthen structures [74,75].
Table 3. XRD results on the analyzed samples.
Mineral M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13
Albite 6.90 38.00 32.80 - - 33.30 9.90 2.20 72.80 - - - 8.50
Anothite 14.50 - - 53.00 44.00 16.90 48.10 77.10 - 68.60 53.20 79.60 49.50
Calcite 25.40 10.80 8.00 1.20 5.20 1.00 16.10 3.20 - 7.90 - 2.60 -
Cordierite
- - - - - 1.60 - 4.20 - 1.00 - 2.00 -
Cristobalite
- - 2.60 - - - - - - 4.50 - - -
Hematite
- - - 1.60 - - - - - - - - -
Illite 47.40 - - - 16.10 - 25.80 - - - 5.60 - 27.70
Kaolinite - 29.60 28.10 - 28.70 46.00 - 10.50 - - 36.70 - -
Magnetite
- 1.00 2.10 1.00 - - - - - - - - -
Muscovite
- 13.40 17.20 - - - - - - 9.80 - - -
Nacrite - - 5.10 40.70 - - - - 17.30 - - - -
Pargasite - - - - - - - - 0.20 - - 13.40 10.80
Pyrophyllite
- - - - - - - - 5.60 - - - -
Quartz 5.80 7.10 4.00 2.50 6.00 1.20 - 2.80 4.10 8.20 4.50 2.40 3.50
The presence of kaolinite con also be observed in significant proportions for six of the
samples. Kaolinites have low shrink-swell capacity, which makes them better for building
purposes, being a great choice for the production of adobes.
3.3. Elemental Analyses
XRF results average 5 measurements. The region of Jojutla is located on an agricultural
place, mainly producing sugar cane, rice, corn, and sorghum, then the XRF could detect
some aggregates which are imperative for farming purposes. The soils contained the
elements indicated in Figure 11a,b, to have a better display according to the intensity. The
vertical axis of the graphic refers to intensity and in the horizontal axis we find the different
elements. Sometimes the intensity of certain elements is very low and it is difficult to
identify the element, but anyway they were present in the samples.
Heritage 2021,4878
Heritage 2021, 4 FOR PEER REVIEW 15
Table 3. XRD results on the analyzed samples.
Mineral
M1
M2
M3
M4
M5
M6
M7
M8
M9
M10
M11
M12
M13
Albite
6.90
38.00
32.80
-
-
33.30
9.90
2.20
72.80
-
-
-
8.50
Anothite
14.50
-
-
53.00
44.00
16.90
48.10
77.10
-
68.60
53.20
79.60
49.50
Calcite
25.40
10.80
8.00
1.20
5.20
1.00
16.10
3.20
-
7.90
-
2.60
-
Cordierite
-
-
-
-
-
1.60
-
4.20
-
1.00
-
2.00
-
Cristobalite
-
-
2.60
-
-
-
-
-
-
4.50
-
-
-
Hematite
-
-
-
1.60
-
-
-
-
-
-
-
-
-
Illite
47.40
-
-
-
16.10
-
25.80
-
-
-
5.60
-
27.70
Kaolinite
-
29.60
28.10
-
28.70
46.00
-
10.50
-
-
36.70
-
-
Magnetite
-
1.00
2.10
1.00
-
-
-
-
-
-
-
-
-
Muscovite
-
13.40
17.20
-
-
-
-
-
-
9.80
-
-
-
Nacrite
-
-
5.10
40.70
-
-
-
-
17.30
-
-
-
-
Pargasite
-
-
-
-
-
-
-
-
0.20
-
-
13.40
10.80
Pyrophyllite
-
-
-
-
-
-
-
-
5.60
-
-
-
-
Quartz
5.80
7.10
4.00
2.50
6.00
1.20
-
2.80
4.10
8.20
4.50
2.40
3.50
3.3. Elemental Analyses
XRF results average 5 measurements. The region of Jojutla is located on an agricul-
tural place, mainly producing sugar cane, rice, corn, and sorghum, then the XRF could
detect some aggregates which are imperative for farming purposes. The soils contained
the elements indicated in Figure 11a,b, to have a better display according to the intensity.
The vertical axis of the graphic refers to intensity and in the horizontal axis we find the
different elements. Sometimes the intensity of certain elements is very low and it is diffi-
cult to identify the element, but anyway they were present in the samples.
(a)
Heritage 2021, 4 FOR PEER REVIEW 16
(b)
Figure 11. XRF results of the analyzed samples, in intensity by element. (a) Higher concentration elements; (b) lower
concentration elements.
3.4. SEM-EDS
The microphotographs and EDS microanalyses were performed in an Environmental
SEM to quantify their presence in soils. The samples were analysed under low vacuum
and were not covered with a metallic thin film. We also got mapping of some elements to
qualify their distribution and compare between them. Figure 12 shows the BSE (Backscat-
tered electron) high quality images, which also confirm the presence of lithic materials in
the adobes.
(a)
(b)
Figure 11.
XRF results of the analyzed samples, in intensity by element. (
a
) Higher concentration elements; (
b
) lower
concentration elements.
3.4. SEM-EDS
The microphotographs and EDS microanalyses were performed in an Environmental
SEM to quantify their presence in soils. The samples were analysed under low vacuum
and were not covered with a metallic thin film. We also got mapping of some elements to
qualify their distribution and compare between them. Figure 12 shows the BSE (Backscat-
tered electron) high quality images, which also confirm the presence of lithic materials
in the adobes.
Heritage 2021,4879
Heritage 2021, 4 FOR PEER REVIEW 16
(b)
Figure 11. XRF results of the analyzed samples, in intensity by element. (a) Higher concentration elements; (b) lower
concentration elements.
3.4. SEM-EDS
The microphotographs and EDS microanalyses were performed in an Environmental
SEM to quantify their presence in soils. The samples were analysed under low vacuum
and were not covered with a metallic thin film. We also got mapping of some elements to
qualify their distribution and compare between them. Figure 12 shows the BSE (Backscat-
tered electron) high quality images, which also confirm the presence of lithic materials in
the adobes.
(a)
(b)
Heritage 2021, 4 FOR PEER REVIEW 17
(c)
(d)
Figure 12. BSE images of selected samples. (a) M1; (b) M4; (c) M9; (d) M12.
3.5. Sieve Analysis and USCS Classification
The adobes had an average bulk density of 1279.06 kg/m3. Table 4 presents the meas-
ured moisture content percentage for the samples while Table 5 indicates the classification
of all the samples tested, including the adobes and the soils of the region, by the Unified
Soil Classification System (USCS); while Figure 13 shows the results of the plasticity index
and liquid limit and the position of each one of the specimens which were subdued to the
mechanical analysis; Figure 14 also shows the granulometric curves of all the samples,
differentiating the soils and the adobes by their graphical representation. M1 and M13,
the two soil samples from the clay material quarry were classified as high plasticity clays,
while the adobes vary from clays of low plasticity to mods. The low plasticity was proba-
bly due to the stabilization with other materials, for example, lime was found by XRD in
some specimens.
Table 4. Moisture content percentage.
Sample
Wet Weight (g)
Dried Weight (g)
Moisture (%)
M1
2652.10
2206.51
20.19
M2
1913.34
1859.93
2.87
M3
1523.20
1471.36
3.52
M4
1281.86
1261.25
1.63
M5
1397.40
1309.49
6.71
M6
1481.30
1443.48
2.62
M7
683.00
664.31
2.81
M8
972.92
959.78
1.37
M9
1389.50
1361.08
2.09
M10
195.55
192.54
1.56
M11
1106.30
1052.42
5.12
M12
2194.30
2054.93
6.78
M13
1713.20
1402.10
22.19
Adobes average
-
-
3.37
Soils average
-
-
21.19
Figure 12. BSE images of selected samples. (a) M1; (b) M4; (c) M9; (d) M12.
3.5. Sieve Analysis and USCS Classification
The adobes had an average bulk density of 1279.06 kg/m3. Table 4presents the mea-
sured moisture content percentage for the samples while Table 5indicates the classification
of all the samples tested, including the adobes and the soils of the region, by the Unified
Soil Classification System (USCS); while Figure 13 shows the results of the plasticity index
and liquid limit and the position of each one of the specimens which were subdued to
the mechanical analysis; Figure 14 also shows the granulometric curves of all the samples,
differentiating the soils and the adobes by their graphical representation. M1 and M13,
the two soil samples from the clay material quarry were classified as high plasticity clays,
while the adobes vary from clays of low plasticity to mods. The low plasticity was probably
due to the stabilization with other materials, for example, lime was found by XRD in
some specimens.
Heritage 2021, 4 FOR PEER REVIEW 18
Table 5. USCS classification of the specimens.
Sample
LL %
PL %
IP %
USCS Classification
M1
79.13
25.89
53.25
CH
Clay of high plasticity
M2
35.05
22.96
12.09
CL
Clay of low plasticity
M3
27.07
17.78
9.27
CL
Clay of low plasticity
M4
32.36
16.12
16.24
CL
Clay of low plasticity
M5
33.62
26.09
7.53
ML
Silt
M6
38.70
26.26
12.45
OL
Organic silt/Organic clay
M7
36.65
23.88
12.76
CL
Clay of low plasticity
M8
21.65
19.01
2.64
ML
Silt
M9
22.12
19.91
2.21
ML
Silt
M11
31.95
24.14
7.81
OL
Organic silt/Organic clay
M12
25.25
22.17
3.08
ML
Silt
M13
70.21
25.65
44.56
CH
Clay of high plasticity
Figure 13. Plasticity graphic and position of the adobes and soil samples.
The percentage of fine grained soils (clays and silts) of the adobes was in a range
between 15% and 40%, coinciding with the indicative values of adobe production foud in
the literature [76]. The graphic matches perfectly with the granulometric curves found in
historical adobe bricks in Peru; where the samples were extracted from colonial buildings
with two or three stories in the cities of Lima, Cusco, and Ica [33].
The soil and grain size classification of the adobes showed insufficient or absent
amounts of fibers, however there were no significant proportions of gravel or lithic mate-
rial in the pieces. Figure 13 shows how the healthy clays of the soil samples are in a very
different zone of the graphic than the adobe samples. To diminish the plasticity of the
adobes from high to low there could have been some type of stabilization with local ma-
terials, for the age of the adobes it could be lime, as it was confirmed with the XRD anal-
yses.
The Sieve analyses also permitted to separate and classify the mineral grains and
vegetal fibers in the adobes. It calculated the percentage of straw, the only fiber used in
this case, from the weight (See Table 6). Some of the adobes did not have any straw (sam-
ples M3 and M5) or an insignificant percentage (sample M9) or other fibers as reinforce-
ment or as a strategy to diminish shrinkage and improve the mechanical performance [77],
a situation which contributes to the lower mechanical values obtained. Because of rice
Figure 13. Plasticity graphic and position of the adobes and soil samples.
Heritage 2021,4880
Table 4. Moisture content percentage.
Sample Wet Weight (g) Dried Weight (g) Moisture (%)
M1 2652.10 2206.51 20.19
M2 1913.34 1859.93 2.87
M3 1523.20 1471.36 3.52
M4 1281.86 1261.25 1.63
M5 1397.40 1309.49 6.71
M6 1481.30 1443.48 2.62
M7 683.00 664.31 2.81
M8 972.92 959.78 1.37
M9 1389.50 1361.08 2.09
M10 195.55 192.54 1.56
M11 1106.30 1052.42 5.12
M12 2194.30 2054.93 6.78
M13 1713.20 1402.10 22.19
Adobes average - - 3.37
Soils average - - 21.19
Table 5. USCS classification of the specimens.
Sample LL % PL % IP % USCS Classification
M1 79.13 25.89 53.25 CH Clay of high plasticity
M2 35.05 22.96 12.09 CL Clay of low plasticity
M3 27.07 17.78 9.27 CL Clay of low plasticity
M4 32.36 16.12 16.24 CL Clay of low plasticity
M5 33.62 26.09 7.53 ML Silt
M6 38.70 26.26 12.45 OL Organic silt/Organic clay
M7 36.65 23.88 12.76 CL Clay of low plasticity
M8 21.65 19.01 2.64 ML Silt
M9 22.12 19.91 2.21 ML Silt
M11 31.95 24.14 7.81 OL Organic silt/Organic clay
M12 25.25 22.17 3.08 ML Silt
M13 70.21 25.65 44.56 CH Clay of high plasticity
The percentage of fine grained soils (clays and silts) of the adobes was in a range
between 15% and 40%, coinciding with the indicative values of adobe production foud in
the literature [
76
]. The graphic matches perfectly with the granulometric curves found in
historical adobe bricks in Peru; where the samples were extracted from colonial buildings
with two or three stories in the cities of Lima, Cusco, and Ica [33].
The soil and grain size classification of the adobes showed insufficient or absent
amounts of fibers, however there were no significant proportions of gravel or lithic material
in the pieces. Figure 13 shows how the healthy clays of the soil samples are in a very differ-
ent zone of the graphic than the adobe samples. To diminish the plasticity of the adobes
from high to low there could have been some type of stabilization with local materials, for
the age of the adobes it could be lime, as it was confirmed with the XRD analyses.
Heritage 2021,4881
Heritage 2021, 4 FOR PEER REVIEW 19
farming in the region there were plenty of different straws. Soils are Vertisol and Kastano-
zem at almost 70%. In Jojutla, the medium precipitation is around 1000 mm/year, and soils
are mainly clay/silt packed rocks, strata, varying from 15 m.
Figure 14. Granulometric curves of the adobes and soils.
Table 6. Fibre percentage results (only adobe samples).
Sample
Fibre Percentage (% Weight)
M2
0.38
M3
0.00
M4
0.68
M5
0.00
M6
1.33
M7
1.84
M8
1.00
M9
0.06
M10
0.77
M11
0.27
M12
0.23
3.6. Mechanical Properties
From the destructive tests, specifically the compressive strength, the mechanical re-
sistance varies between 5 and 13 kg/cm2, with 7.26 kg/cm2 being the average of the adobe
bricks. These values obtained with the UCS and the PLT are lower than values from other
researches which have similar characteristic cases in México [44,49]. The adobe blocks of
Jojutla presented low performance, probably due to the inefficient manufacture and the
absence of fiber material or other stabilizers or previous micro-cracking. Nevertheless, the
proportion of the fibers does not seem to have a direct relation with the compressive me-
chanical resistance, as samples M5 and M9 that had the lowest amount of straw reached
some of the highest values during the test.
The PLT allowed quantifying the strength in some of the samples after the compres-
sive strength test. Because those fragments of lower dimensions can be tested again with
Figure 14. Granulometric curves of the adobes and soils.
The Sieve analyses also permitted to separate and classify the mineral grains and
vegetal fibers in the adobes. It calculated the percentage of straw, the only fiber used in this
case, from the weight (See Table 6). Some of the adobes did not have any straw (samples M3
and M5) or an insignificant percentage (sample M9) or other fibers as reinforcement or as a
strategy to diminish shrinkage and improve the mechanical performance [
77
], a situation
which contributes to the lower mechanical values obtained. Because of rice farming in the
region there were plenty of different straws. Soils are Vertisol and Kastanozem at almost
70%. In Jojutla, the medium precipitation is around 1000 mm/year, and soils are mainly
clay/silt packed rocks, strata, varying from 1–5 m.
Table 6. Fibre percentage results (only adobe samples).
Sample Fibre Percentage (% Weight)
M2 0.38
M3 0.00
M4 0.68
M5 0.00
M6 1.33
M7 1.84
M8 1.00
M9 0.06
M10 0.77
M11 0.27
M12 0.23
3.6. Mechanical Properties
From the destructive tests, specifically the compressive strength, the mechanical
resistance varies between 5 and 13 kg/cm
2
, with 7.26 kg/cm
2
being the average of the
adobe bricks. These values obtained with the UCS and the PLT are lower than values from
other researches which have similar characteristic cases in México [
44
,
49
]. The adobe blocks
of Jojutla presented low performance, probably due to the inefficient manufacture and
the absence of fiber material or other stabilizers or previous micro-cracking. Nevertheless,
Heritage 2021,4882
the proportion of the fibers does not seem to have a direct relation with the compressive
mechanical resistance, as samples M5 and M9 that had the lowest amount of straw reached
some of the highest values during the test.
The PLT allowed quantifying the strength in some of the samples after the compressive
strength test. Because those fragments of lower dimensions can be tested again with the
equipment, it resulted in more specimens to study. The values obtained were more variable,
with 4.52 kg/cm
2
being the average of all the adobes, lower than the compression strength
results. The ratio between compressive strength and PLT values was 1.72:1 (See Table 7),
something comprehensible considering that the PLT is designed for the analysis of different
types of rocks.
Table 7. Comparative of compressive strength and point-load values results.
Sample UCS (Kg/cm2) PLT σ(Kg/cm2)UCS/PLT
M2 5.97 3.66 1.63
M4 9.35 3.64 2.57
M5 12.33 5.78 2.13
M9 5.08 4.69 1.08
M11 9.13 3.91 2.34
M12 7.09 2.52 2.81
Average 7.26 4.52 1.72
The compressive strength and PLT values were compared (see Figure 15) in a graphic
to observe the correlation between the two tests. Considering the compressive strength
values are slightly higher, most of the samples showed a lineal reciprocity, while some
showed deviation, near the 1.72:1 ratio calculated for both tests interrelation.
Heritage 2021, 4 FOR PEER REVIEW 20
the equipment, it resulted in more specimens to study. The values obtained were more
variable, with 4.52 kg/cm2 being the average of all the adobes, lower than the compression
strength results. The ratio between compressive strength and PLT values was 1.72:1 (See
Table 7), something comprehensible considering that the PLT is designed for the analysis
of different types of rocks.
Table 7. Comparative of compressive strength and point-load values results.
Sample
UCS (Kg/cm2)
PLT σ (Kg/cm2)
UCS/PLT
M2
5.97
3.66
1.63
M4
9.35
3.64
2.57
M5
12.33
5.78
2.13
M9
5.08
4.69
1.08
M11
9.13
3.91
2.34
M12
7.09
2.52
2.81
Average
7.26
4.52
1.72
The compressive strength and PLT values were compared (see Figure 15) in a graphic
to observe the correlation between the two tests. Considering the compressive strength
values are slightly higher, most of the samples showed a lineal reciprocity, while some
showed deviation, near the 1.72:1 ratio calculated for both tests interrelation.
In Figure 16, it is possible to find the coefficient of determination and the second-
degree polynomial which correlates the two variables. The coefficient of determination or
R2 has a value of 0.8723 and represents the proportion of the variance between the two
variables (PLT and compressive strength). Additionally, all the samples are inserted into
the confidence limits for a confidence level of 95%
The coefficient of determination R2 indicates how well a model can predict the data.
The higher the value of R2, the better the model will be at predicting [78]. This value of R2
will always be in a range between 0 and 1, then the results of PLT test had acceptable and
reliable values of mechanical resistance.
Figure 15. Correlation between the compressive strength and the point-load tests.
Figure 15. Correlation between the compressive strength and the point-load tests.
In Figure 16, it is possible to find the coefficient of determination and the second-
degree polynomial which correlates the two variables. The coefficient of determination or
R
2
has a value of 0.8723 and represents the proportion of the variance between the two
variables (PLT and compressive strength). Additionally, all the samples are inserted into
the confidence limits for a confidence level of 95%
Heritage 2021,4883
Heritage 2021, 4 FOR PEER REVIEW 21
Figure 16. Correlation equation and its variability using: (Image source: Elaborated by Marco A. Navarrete-Seras with
MATLAB R2017b).
4. Conclusions
When seismic affectations occur on adobe vernacular housing, the owners and in-
habitants cannot wait until they are re-built, as earthquakes have a big impact on the so-
ciety because of the great destruction they cause. To preserve mental health, the demoli-
tion processes begin as soon as possible, to allow the immediate reconstruction of the
housing and infrastructures. Before the total loss of the heritage it is necessary to design a
way to test the shards of pieces before they will be carried out of the places or before they
will be reused to protect the buildings. The study of traditional Mexican adobe buildings
from the perspective of material characterization needs to be improved with more com-
plete evaluations and a more extensive use of non-destructive tests which could be con-
ducted in situ.
These in situ tests could contain the PLT, the UPV, and spatial evaluation with
drones. The PLT could feed mathematical models and equations to predict and calculate
the performance under loads, hazards, and promotes the design of conservation and res-
toration works without the necessity of carrying out plenty of samples, which could break
down during the travel to laboratories, choosing the complete samples to research the
materials and techniques employed in the buildings. If PLT studies are accompanied with
densities it could be possible to get a lot of information to plan a way to characterize clay
materials.
Various researchers have studied the relationship between UCS and PLT for different
types of rocks, but there is no study applied in adobes. Therefore, in this research work,
the PLT was used to obtain the relationship with UCS and point load index by means of
a correlation equation. ASTM D5731-16 specifies that specimens in the form of rock cores,
blocks, or irregular shards with a test diameter of 30 to 85 mm can be tested [63]. Conse-
quently, irregular shards were used, which allows a non-cost and fast test to estimate the
UCS compared to sampling, transportation and preparation of regular cubes in the labor-
atory. In addition, this test can be performed in the field or the laboratory.
Even though the PLT was not designed for adobes but for sandstone rocks [63], the
ratio we found was 1.72:1, near to ratios found for local stones in Michoacan, Mexico (ratio
= 2:1) [71]. The ratio found is the first approximation of a ratio between mechanical tests
for compressive strength in adobes, similar to other comparisons in research works of
earthen materials [32]. Because of the convenient in situ of the test capability, further ex-
perimentation will be required with other study cases in future research.
Figure 16.
Correlation equation and its variability using: (Image source: Elaborated by Marco A. Navarrete-Seras with
MATLAB R2017b).
The coefficient of determination R
2
indicates how well a model can predict the data.
The higher the value of R
2
, the better the model will be at predicting [
78
]. This value of R
2
will always be in a range between 0 and 1, then the results of PLT test had acceptable and
reliable values of mechanical resistance.
4. Conclusions
When seismic affectations occur on adobe vernacular housing, the owners and inhab-
itants cannot wait until they are re-built, as earthquakes have a big impact on the society
because of the great destruction they cause. To preserve mental health, the demolition pro-
cesses begin as soon as possible, to allow the immediate reconstruction of the housing and
infrastructures. Before the total loss of the heritage it is necessary to design a way to test the
shards of pieces before they will be carried out of the places or before they will be reused to
protect the buildings. The study of traditional Mexican adobe buildings from the perspective
of material characterization needs to be improved with more complete evaluations and a
more extensive use of non-destructive tests which could be conducted in situ.
These in situ tests could contain the PLT, the UPV, and spatial evaluation with drones.
The PLT could feed mathematical models and equations to predict and calculate the
performance under loads, hazards, and promotes the design of conservation and restoration
works without the necessity of carrying out plenty of samples, which could break down
during the travel to laboratories, choosing the complete samples to research the materials
and techniques employed in the buildings. If PLT studies are accompanied with densities
it could be possible to get a lot of information to plan a way to characterize clay materials.
Various researchers have studied the relationship between UCS and PLT for different
types of rocks, but there is no study applied in adobes. Therefore, in this research work,
the PLT was used to obtain the relationship with UCS and point load index by means
of a correlation equation. ASTM D5731-16 specifies that specimens in the form of rock
cores, blocks, or irregular shards with a test diameter of 30 to 85 mm can be tested [
63
].
Consequently, irregular shards were used, which allows a non-cost and fast test to estimate
the UCS compared to sampling, transportation and preparation of regular cubes in the
laboratory. In addition, this test can be performed in the field or the laboratory.
Even though the PLT was not designed for adobes but for sandstone rocks [
63
], the
ratio we found was 1.72:1, near to ratios found for local stones in Michoacan, Mexico
(ratio = 2:1) [
71
]. The ratio found is the first approximation of a ratio between mechanical
tests for compressive strength in adobes, similar to other comparisons in research works
of earthen materials [
32
]. Because of the convenient in situ of the test capability, further
experimentation will be required with other study cases in future research.
Heritage 2021,4884
The point load test is justified since an acceptable coefficient of determination R2
of 0.8723 was obtained, and a correlation equation is proposed to estimate the uniaxial
compressive strength for the adobe bricks under study. Therefore, this test could be used
in other study cases and monuments where adobe bricks could be tested in situ.
Regarding the results obtained, both compressive strength and PLT showed low values
of mechanical resistance, particularly comparing them to the previous studies in traditional
buildings of the state of Morelos. Nevertheless, these low values did not justify the bad
seismic behavior of the dwellings, which were very vulnerable due to multiple factors,
like the lack of reinforcements and confinement of the structures, the incompatibility
between the construction materials or the poor maintenance of the buildings, among others.
Additionally, the social-economic necessity of dividing the land into minor spaces due to
the growth of the families and the necessity to inherit the properties to the descendants
caused alteration to the houses and the impossibility to continue using the traditional
thickness of adobe. In the case study, all these conditions converged, resulting into the
loss of most of its architectural heritage and infrastructure. The adobe walls did not
present any reinforcement, being this method unknown by the local population, who
preferred to substitute the traditional materials for modern ones representing for them a
better social status.
In addition to the mechanical tests, the rest of the methodology to study patrimonial
adobes has proven to be effective and it is possible to correlate the mineralogical studies
with the non-destructive analysis and the sieve analysis. The results of the granulometric
curves could be correlated to the standard values for soils in adobes and the guidelines
published by earthen architecture organizations [
76
]. Nevertheless, some of the adobes
did not have any fibers, which could be a clear sign of the oblivion and abandonment of
the traditional techniques. This loss of the traditional earthen construction techniques has
provoked a poor manufacture of the adobe houses, creating new scenarios where people
do not trust in the material and substitutes the earthen architecture with modern materials.
Although each country has different architectural typologies, the adobe houses in
Latin America show the same type of alterations and modifications over the original
systems. The abandonment and substitution of vernacular architecture is a global concern,
and when an earthquake occurs the consequences are very similar for these buildings, as
we have seen in the recent major events. The manufacturing of adobe is almost identical,
as well as the building process and structural performance of the pieces.
The primary focus of future research works will be to compare the results obtained
from the material characterization of the Jojutla samples with other study cases from
traditional Mexican adobe buildings, verify the results obtained with the PLT with other
historic constructions and upgrade the correlation equations.
By replicating the methodology and improving it, incorporating water vapor and
erosion resistance tests, it will be possible to generate a more precise knowledge about
earthen materials and necessary data for the conservation of this cultural heritage.
Author Contributions:
Conceptualization A.S.-C., E.M.A.-G., and A.N.-E.; methodology A.S.-C.,
E.M.A.-G., W.M.-M., M.A.N.-S., J.L.R.-S., A.N.-E., and A.M.; software, A.S.-C., M.A.N.-S., and
A.M.; investigation, A.S.-C. and E.M.A.-G.; writing – original draft preparation, review and editing,
A.S.-C
., E.M.A.-G.; A.M., and J.L.R.-S. supervision, E.M.A.-G., W.M.-M., J.L.R.-S., and A.N.-E., project
administration A.S.-C., E.M.A.-G., and W.M.-M.; funding acquisition, A.S.-C., E.M.A.-G., W.M.-M.,
and J.L.R.-S. All authors have read and agreed to the published version of the manuscript.
Funding:
This research was funded by Consejo Nacional de Ciencia y Tecnología (CONACYT), and
CIC-UMSNH, and partially funded by CONACYT grants: LN299076, LN314846, LN31585 and by
PAPIIT UNAM contract IN108521.
Acknowledgments:
The authors acknowledge the Materials Laboratory “Ing. Luis Silva Ruelas” of
the Faculty of Civil Engineering of the UMSNH for the equipment support, the Postgraduate Program
PIDA of the Faculty of Architecture of the UMSNH, the economic support given by CONACYT and
CIC-UMSNH and CIMNE, in Barcelona, Spain. The mechanical test support of D. Preciado-Villicaña
Heritage 2021,4885
and M. Ruiz-Mendoza; the field work support of E. G. Navarro-Mendoza and J. C. Bernabé-Reyes;
and the Technical support of the LANCIC, Instituto de Fisica, UNAM, J. Cañetas-Ortega for her
support during SEM and EDS analyses. The authors also acknowledge O. de la Paz Soto-Talavera
and C. Bustos-Mejía from the ITZ (Intituto Tecnológico de Zacatepec) for their support during the
field work and recollection of the samples in Jojutla.
Conflicts of Interest:
The authors declare no conflict of interest. The funders had no role in the design
of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or
in the decision to publish the results.
References
1. Heathcote, K. Durability of earthwall buildings. Constr. Build. Mater. 1995,9, 185–189. [CrossRef]
2.
Illampas, R.; Ioannou, I.; Charmpis, D.C. Overview of the Pathology, Repair and Strengthening of Adobe Structures. Int. J. Arch. Herit.
2013,7, 165–188. [CrossRef]
3. Minke, G. Building with Earth. Design and Technology of a Sustainable Architecture, 1st ed.; Birkhäuser: Basel, Switzerland, 2006.
4.
Rais, J.; Barakat, A.; Louz, E.; Barka, A.A. Geological heritage in the M’Goun geopark: A proposal of geo-itineraries around the
Bine El Ouidane dam (Central High Atlas, Morocco). Int. J. Geoherit. Parks 2021. [CrossRef]
5.
Giada, G.; Caponetto, R.; Nocera, F. Hygrothermal Properties of Raw Earth Materials: A Literature Review. Sustainability
2019
,11, 5342.
[CrossRef]
6. Moseley, M.L. The Incas and Their Ancestors: The Archaeology of Peru, 1st ed.; Thames and Hudson: London, UK, 1992.
7.
Solis, R.S.; Haas, J.; Creamer, W. Dating Caral, a Preceramic Site in the Supe Valley on the Central Coast of Peru. Science
2001
,292,
723–726. [CrossRef] [PubMed]
8.
Pérez, N.A.; Bucio, L.; Bokhimi, X.; Lima, E.; Soto, E. Quantification of amorphous phases in the silt fraction of Mexican
pre-Hispanic adobe earth bricks. J. Appl. Crystallogr. 2016,49, 561–568. [CrossRef]
9.
Yamín Lacouture, L.E.; Phillips Bernal, C.; Reyes Ortiz, J.C.; Ruiz Valencia, D. Estudios de vulnerabilidad sísmica, rehabilita-ción
y refuerzo de casas en adobe y tapia pisada. Apunt. Rev. Estud. Sobre Patrim. Cult. J. Cult. Herit. Stud. 2007,20, 286–303.
10.
Correia, M.; Merten, J.; Vegas, F.; Mileto, C.; Cristini, V. Earthen architecture in Southwestern Europe: Portugal, Spain and
Southern France. In Terra Europae. Earthen Architecture in the European Union, 1st ed.; Correia, M., Dipasquale, L., Mecca, S., Eds.;
Edizioni ETS: Pisa, Italy, 2011; pp. 71–76.
11.
Gómez-Patrocinio, F.J.; López-Manzanares, F.V.; Mileto, C.; García-Soriano, L. Techniques and Characteristics of Traditional
Earthen Masonry Walls: The Case of Spain. Int. J. Arch. Herit. 2019,14, 694–710. [CrossRef]
12.
Guerrero Baca, L.F. The loss of adobe architecture in Mexico. In ICOMOS World Report 2006–2007 on Monuments and Sites in
Danger, 1st ed.; Machat, C., Petzet, M., Ziesemer, J., Eds.; Hendrik Bäßler Verlag: Berlin, Germany, 2008; pp. 112–114.
13.
The Earthen Architecture Initiative. Guidelines for Teaching Earthen Conservation. Material Analysis—Earthen Construction Techniques;
The Getty Conservation Institute: Los Angeles, CA, USA, 2011.
14.
The Earthen Architecture Initiative. Guidelines for Teaching Earthen Conservation. Material Analysis—In Situ and Laboratory Material
Characterization; The Getty Conservation Institute: Los Angeles, CA, USA, 2011.
15.
Ramakrishnan, S.; Loganayagan, S.; Kowshika, G.; Ramprakash, C.; Aruneshwaran, M. Adobe blocks reinforced with natural
fibres: A review. Mater. Today Proc. 2021. [CrossRef]
16.
Schroeder, H. Modern earth building codes, standards and normative development. In Modern Earth Buildings. Materials,
Engineering, Constructions and Applications, 1st ed.; Hall, M.R., Lindsay, R., Krayenhoff, M., Eds.; Woodhead Publishing: Sawston,
UK, 2012; pp. 72–109. [CrossRef]
17.
Hanzalová, K.; Pavelka, K. Documentation and virtual reconstruction of historical objects in Peru damaged by an earthquake and
climatic events. Adv. Geosci. 2013,35, 67–71. [CrossRef]
18. Miccoli, L.; Gerrard, C.; Perrone, C.; Gardei, A.; Ziegert, C. A Collaborative Engineering and Archaeology Project to Investigate
Decay in Historic Rammed Earth Structures: The Case of the Medieval Preceptory in Ambel. Int. J. Arch. Herit.
2017
, 1–20.
[CrossRef]
19.
Schauppenlehner, T.; Eder, R.; Ressar, K.; Feiglstorfer, H.; Meingast, R.; Ottner, F. A Citizen Science Approach to Build a
Knowledge Base and Cadastre on Earth Buildings in the Weinviertel Region, Austria. Heritage 2021,4, 125–139. [CrossRef]
20.
Mousourakis, A.; Arakadaki, M.; Kotsopoulos, S.; Sinamidis, I.; Mikrou, T.; Frangedaki, E.; Lagaros, N.D. Earthen Architecture in
Greece: Traditional Techniques and Revaluation. Heritage 2020,3, 1237–1268. [CrossRef]
21.
Philokyprou, M.; Michael, A. Environmental Sustainability in the Conservation of Vernacular Architecture. The Case of Rural
and Urban Traditional Settlements in Cyprus. Int. J. Arch. Herit. 2020, 1–23. [CrossRef]
22.
Matoušková, E.; Pavelka, K.; Smolík, T.; Pavelka, K., Jr. Earthen Jewish Architecture of Southern Morocco: Documentation of
Unfired Brick Synagogues and Mellahs in the Drâa-Tafilalet Region. Appl. Sci. 2021,11, 1712. [CrossRef]
23.
Araya-Letelier, G.; Antico, F.; Burbano-Garcia, C.; Concha-Riedel, J.; Norambuena-Contreras, J.; Concha, J.; Flores, E.S. Experi-
mental evaluation of adobe mixtures reinforced with jute fibers. Constr. Build. Mater. 2021,276, 122127. [CrossRef]
Heritage 2021,4886
24.
Araya-Letelier, G.; Gonzalez-Calderon, H.; Kunze, S.; Burbano-Garcia, C.; Reidel, U.; Sandoval, C.; Bas, F. Waste-based natural
fiber reinforcement of adobe mixtures: Physical, mechanical, damage and durability performance assessment. J. Clean. Prod.
2020
,
273, 122806. [CrossRef]
25.
Ben Mansour, M.; Jelidi, A.; Cherif, A.S.; Ben Jabrallah, S. Optimizing thermal and mechanical performance of compressed earth
blocks (CEB). Constr. Build. Mater. 2016,104, 44–51. [CrossRef]
26.
Silva, A.; Oliveira, I.; Silva, V.; Mirão, J.; Faria, P. Vernacular Caramel
´
s Adobe Masonry Dwellings—Material Characterization.
Int. J. Arch. Herit. 2020, 1–18. [CrossRef]
27.
Parracha, J.L.; Lima, J.; Freire, M.T.; Ferreira, M.; Faria, P. Vernacular Earthen Buildings from Leiria, Portugal—Material
Characterization. Int. J. Arch. Herit. 2019, 1–16. [CrossRef]
28.
Costa, C.; Arduin, D.; Rocha, F.; Velosa, A. Adobe Blocks in the Center of Portugal: Main Characteristics. Int. J. Arch. Herit.
2019
,
1–12. [CrossRef]
29.
Coroado, J.; Paiva, H.; Velosa, A.; Ferreira, V.M. Characterization of Renders, Joint Mortars, and Adobes from Traditional
Constructions in Aveiro (Portugal). Int. J. Arch. Herit. 2010,4, 102–114. [CrossRef]
30.
Silveira, D.; Varum, H.; Costa, A.; Martins, T.; Pereira, H.; Almeida, J. Mechanical properties of adobe bricks in ancient
constructions. Constr. Build. Mater. 2012,28, 36–44. [CrossRef]
31.
Mellaikhafi, A.; Tilioua, A.; Souli, H.; Garoum, M.; Hamdi, M.A.A. Characterization of different earthen construction materials in
oasis of south-eastern Morocco (Errachidia Province). Case Stud. Constr. Mater. 2021,14, e00496. [CrossRef]
32. Baglioni, E.; Fratini, F.; Rovero, L. The characteristics of the earthen materials of the Drâa valley’s architecture. J. Mater. Environ.
Sci. 2016,7, 3538–3547.
33.
Vicente, E.; Torrealva, D. Mechanical properties of historical adobe in Perú. In Proceedings of the Terra Lyon 2016: Articles
Sélec-Tionnés Pour Publication en Ligne/Articles Selected for On-Line Publication/Artículos Seleccionados Para Publicación en
Línea, Lyon, France, 10–14 July 2016; Joffroy, T., Guillaud, H., Sadozaï, C., Eds.; CRAterre: Villefontaine, France, 2018; pp. 1–11.
34.
Brando, G.; Cocco, G.; Mazzanti, C.; Peruch, M.; Spacone, E.; Alfaro, C.; Sovero, K.; Tarque, N. Structural Survey and Empirical
Seismic Vulnerability Assessment of Dwellings in the Historical Centre of Cusco, Peru. Int. J. Arch. Herit.
2019
, 1–29. [CrossRef]
35.
Blondet, M. Mitigation of Seismic Risk on Earthen Buildings. In Survival and Sustainability. Environmental Concerns in the 21st
Century, 1st Ed.; Gökçekus, H., Türker, U., LaMoreaux, J.W., Eds.; Springer: Berlin/Heidelberg, Germany, 2011; pp. 391–400.
[CrossRef]
36.
Salazar, L.G.F.; Ferreira, T.M. Residential Building Models for Seismic Risk Assessment at the Historic Downtown of Mexico City.
Int. J. Arch. Herit. 2020, 1–18. [CrossRef]
37.
Tassios, T.P. Seismic Protection of Monuments. In Earthquakes and Tsunamis. Civil Engineering Disaster Mitigation Activities
Implementing Millennium Development Goals, 1st ed.; Tugrul Tankut, A., Ed.; Springer: Ankara, Turkey, 2009; Volume 11. [CrossRef]
38.
Ortega, J.; Vasconcelos, G.; Rodrigues, H.; Correia, M.; Miranda, T.F.D.S. Development of a Numerical Tool for the Seismic
Vulnerability Assessment of Vernacular Architecture. J. Earthq. Eng. 2019, 1–29. [CrossRef]
39.
Ortega, J.; Vasconcelos, G.; Correia, M.R. Seismic-resistant building practices resulting from Local Seismic Culture. In Seismic
Retrofitting: Learning from Vernacular Architecture, 1st Ed.; Correia, M.R., Lourenço, P.B., Varum, H., Eds.; Taylor & Francis Group:
London, UK, 2018; pp. 17–22.
40.
Lourenço, P.B.; Ciocci, M.P.; Greco, F.; Karanikoloudis, G.; Cancino, C.; Torrealva, D.; Wong, K. Traditional techniques for the
rehabilitation and protection of historic earthen structures: The seismic retrofitting project. Int. J. Arch. Herit.
2019
,13, 15–32.
[CrossRef]
41. Guerrero Baca, L.F. Arquitectura en tierra. Hacia la recuperación de una cultura constructiva. Apuntes 2007,20, 182–201.
42.
Mateu Sagues, M.; Daneels, A. La micromorfología aplicada al estudio del patrimonio construido con tierra. Rev. Grem.
2021
,7,
10–23.
43.
Daneels, A.; de Vivar, A.R.; Chávez, L.; Reyes, M.; Tapia, E.; León, M.; Cienfuegos, E.; Otero, F.J. Bitumen-stabilized earthen
architecture: The case of the archaeological site of La Joya, on the Mexican Gulf Coast. J. Archaeol. Sci. Rep.
2020
,34, 102619.
[CrossRef]
44.
Quiroz, P.C.; Moreno-Martínez, J.Y.; Galván, A.; Matus, R.A. Obtención de las propiedades mecánicas de la mampostería de
adobe mediante ensayes de laboratorio. Acta Univ. 2019,29, 1–13. [CrossRef]
45.
Reporte Especial. Sismo de Tehuantepec (2017-09-07 23:49 Mw 8.2); Servicio Sismológico Nacional; Universidad Nacional Autónoma
de México: Mexico City, Mexico, 2017.
46.
Reporte Especial. Sismo del día 19 de Septiembre de 2017, Puebla-Morelos (M 7.1); Servicio Sismológico Nacional; Universidad Nacional
Autónoma de México: Mexico City, Mexico, 2017.
47.
Meli Piralla, R. La ingeniería civil ante los efectos de los sismos de 2017 en los edificios patrimoniales (el equilibrio entre la
autenticidad y la seguridad). In Sismos y Patrimonio Cultural. Testimonios, Enseñanza y Desafios, 2017 y 2018, 1st Ed.; Goldberg
Mayo, D., Ed.; Secretaría de Cultura; Dirección General de Publicaciones: Mexico City, Mexico, 2018; pp. 62–81.
48.
Fuentes, D.D.; Julià, P.A.B.; D’Amato, M.; Laterza, M. Preliminary Seismic Damage Assessment of Mexican Churches after
September 2017 Earthquakes. Int. J. Arch. Herit. 2021,15, 505–525. [CrossRef]
49.
Guerrero Baca, L.F. Comportamiento sísmico de viviendas tradicionales de adobe, situadas en las faldas del volcán Popoca-tépetl,
México. Rev. Grem. 2019,6, 105–118.
Heritage 2021,4887
50.
Sanchez-Calvillo, A.; Preciado-Villicaña, D.; Navarro-Mendoza, E.G.; Alonso-Guzman, E.M.; Nuñez-Guzman, E.A.; Chavez-
Garcia, H.L.; Ruiz-Mendoza, M.; Martinez-Molina, W. Analysis and characterisation of adobe blocks in jojutla de juárez, méxico.
Seismic vulnerability and loss of the earthen architecture after the 2017 puebla earthquake. ISPRS Int. Arch. Photogramm. Remote
Sens. Spat. Inf. Sci. 2020,44, 1133–1140. [CrossRef]
51.
del Campo Alatorre, R.M.; Ochoa González, G.H.; Álvarez Partida, F. Estudio Geotécnico de la Colonia Emiliano Zapata, Jojutla,
Morelos, Tras los Daños de los Sismos del 19 de Septiembre de 2017; ITESO, Departamento de Hábitat y Desarrollo Ur-bano: Guadalajara,
Mexico, 2018.
52.
Morais, E.C.; Vigh, L.G.; Krähling, J. Cyclic Behaviour, Dynamic Analysis and Seismic Vulnerability of Historical Building
Archetypes in Hungary. Int. J. Arch. Herit. 2019, 1–21. [CrossRef]
53.
Consejería Jurídica del Poder Ejecutivo del Estado de Morelos. Plan Municipal de Desarrollo 2016–2018, del Ayuntamiento de Jojutla,
Morelos; Dirección General de Legislación, Subdirección de Jurismática; Ayuntamiento Constitucional de Jojutla, Morelos: Jojutla
de Juárez, México, 2016.
54.
Fratini, F.; Pecchioni, E.; Rovero, L.; Tonietti, U. The earth in the architecture of the historical centre of Lamezia Terme (Italy):
Characterization for restoration. Appl. Clay Sci. 2011,53, 509–516. [CrossRef]
55.
Costa, C.; Cerqueira, Â.; Rocha, F.; Velosa, A. The sustainability of adobe construction: Past to future. Int. J. Arch. Herit.
2018
,13,
639–647. [CrossRef]
56.
Lima, J.; Faria, P.; Silva, A.S. Earth Plasters: The Influence of Clay Mineralogy in the Plasters’ Properties. Int. J. Arch. Herit.
2020
,
14, 948–963. [CrossRef]
57.
Navarro-Mendoza, E.G.; Alonso-Guzmán, E.M.; Ruvalcaba-Sil, J.L.; Sánchez-Calvillo, A.; Martínez-Molina, W.; Chavez-Garcia,
H.L.; Bedolla-Arroyo, J.A.; Becerra-Santacruz, H.; Borrego-Perez, J.A. Compressive Strength and Ultrasonic Pulse Velocity of Mor-
tars and Pastes, Elaborated with Slaked Lime and High Purity Hydrated Lime, for Restoration Works in México.
Key Eng. Mater.
2020,862, 51–55. [CrossRef]
58.
ASTM International. ASTM D2487—17e1, Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification
System); ASTM International: West Conshohocken, PA, USA, 2017. [CrossRef]
59.
Johnston-Feller, R. Color Science in the Examination of Museum Objects. Non-destructive Procedures; The Getty Conservation Institute:
Los Angeles, CA, USA, 2011.
60.
Ruvalcaba-Sil, J.L.; Miranda, D.R.; Melo, V.A.; Picazo, F. SANDRA: A portable XRF system for the study of Mexican cultural
heritage. X-ray Spectrom. 2010,39, 338–345. [CrossRef]
61.
Ion, R.; Iancu, L.; David, M.; Grigorescu, R.; Trica, B.; Somoghi, R.; Vasile, S.; Dulama, I.; Gheboianu, A.; Tincu, S. Multi-Analytical
Characterization of Corvins’ Castle—Deserted Tower. Construction Materials and Conservation Tests. Heritage
2020
,3, 941–964.
[CrossRef]
62.
Sánchez-Calvillo, A.; Alonso-Guzmán, E.M.; Ruvalcaba-Sil, J.L.; Martínez-Molina, W.; Chavez-Garcia, H.L.; Bedolla-Arroyo, J.A.;
Navarro-Mendoza, E.G.; Blancas-Herrera, V.H.; Perez, J.A.V. Colorimetry of Clays as a Tool to Identify Soil Materials for Earthen
Buildings Restoration. Key Eng. Mater. 2020,862, 56–60. [CrossRef]
63.
ASTM International. ASTM D5731-16, Standard Test Method for Determination of the Point Load Strength Index of Rock and Application
to Rock Strength Classifications; ASTM International: West Conshohocken, PA. USA, 2016. [CrossRef]
64. Broch, E.; Franklin, J.A. The point-load strenght test. Int. J. Rock Mech. Min. Sci. Geomech. Abst. 1972,9, 669–676. [CrossRef]
65. Bieniawski, Z. The point-load test in geotechnical practice. Eng. Geol. 1975,9, 1–11. [CrossRef]
66.
Kahraman, S. The determination of uniaxial compressive strength from point load strength for pyroclastic rocks. Eng. Geol.
2014
,
170, 33–42. [CrossRef]
67.
Wengang, Z.; Liang, H.; Zixu, Z.; Yanmei, Z. Digitalization of mechanical and physical properties of Singapore Bukit Timah
granite rocks based on borehole data from four sites. Undergr. Space 2020. [CrossRef]
68.
Koohmishi, M. Assessment of strength of individual ballast aggregate by conducting point load test and establishment of
classification method. Int. J. Rock Mech. Min. Sci. 2021,141, 104711. [CrossRef]
69.
Navarrete Seras, M.; Mártinez Molina, W.; Alonso Guzmán, E.M.; Arteaga Arcos, J.; Chávez García, H.L.; Lara Gómez, C.;
Díaz González, N. Mathematical models applied to the physicalmechanical mechanical characterization of stone materials bank
Huiramba, México. In Proceedings of the X Congreso Internacional de Ingeniería. Engineering and Its Applications, Queretaro,
Mexico, 12–15 May 2014; Esquivel Escalante, K., Elizalde Peña, E., Rodríguez Morales, J.A., Eds.; Universidad Au-tónoma de
Querétaro: Queretaro, Mexico, 2014; Volume 1, pp. 252–256.
70.
Seras, M.A.N.; García, H.L.C.; Molina, W.M.; Guzmán, E.M.A.; Sánchez, M.A. Bank Material Study for the Restoration of
Historical Monuments in Michoacán, Mexico. Mater. Sci. Forum 2017,902, 47–51. [CrossRef]
71.
Navarrete, M.; Molina, W.M.; Alonso-Guzmán, E.M.; Lara-Gómez, C.; Bedolla-Arroyo, J.A.; Chavez, H.; Delgado, D.; Arteaga-
Arcos, J.C. Caracterización de propiedades físico-mecánicas de rocas ígneas utilizadas en obras de infraestructura. Rev. Alconpat
2013,3, 129–139. [CrossRef]
72.
Martínez, W.; Torres-Acosta, A.A.; Alonso-Guzmán, E.M.; Chávez, H.L.; Lara, C.; Bedolla, A.; Ruvalcaba, J.L. Colorimetry of clays
modified with mineral and organic additives. Rev. Alconpat 2018,8, 163–177.
Heritage 2021,4888
73.
Aguilar, R.; Saucedo, C.; Montesinos, M.; Ramírez, E.; Morales, R.; Uceda, S. Caracterización mecánica de las unidades de
adobe del complejo arqueológico Huaca de la Luna mediante ensayos de ultrasonido. In Proceedings of the Tierra, Sociedad,
Comunidad: 15
Seminario Iberoamericano de Arquitectura y Construcción con Tierra, Cuenca, Ecuador, 9–13 November 2015;
Universidad de Cuenca: Cuenca, Ecuador, 2015; pp. 28–39.
74.
Navarro Mendoza, E.G.; Sánchez Calvillo, A.; Alonso Guzmán, E.M. Estabilización de suelos arcillosos con cal para firmes
y blocks. In Proceedings of the 19
Seminario Iberoamericano de Arquitectura y Construcción con Tierra, Oaxaca, Mexico,
15–18 October 2019
; Neves, C., Salcedo Gutiérrez, Z., Borges Faria, O., Eds.; FUNDASAL/PROTERRA: San Salvador, El Salvador,
2019; pp. 284–291.
75.
Guerrero, L. Lime and construction systems. In Lime: History, properties and use, 1st ed.; Barba Pingarrón, L., Villaseñor Alonso, I.,
Eds.; UNAM, LANCIC-IFUNAM: Mexico City, Mexico, 2013; pp. 49–72.
76.
Martins Neves, C.M.; Borges Faria, O.; Rotondaro, R.; Cevallos Salas, P.; Hoffmann, M.V. Selección de Suelos y Métodos de Control en
la Construcción con Tierra—Prácticas de Campo; Rede Ibero-Americana Proterra: Lisboa, Portugal, 2009.
77.
Yetgin, ¸S.; Çavdar, Ö.; Çavdar, A. The effects of the fiber contents on the mechanic properties of the adobes. Constr. Build. Mater.
2008,22, 222–227. [CrossRef]
78.
Garza-Ulloa, J. Methods to develop mathematical models: Traditional statistical analysis. In Applied Biomechatronics Using
Mathematical Models, 1st ed.; Garza-Ulloa, J., Ed.; Elsevier: Amsterdam, The Netherlands, 2018; pp. 239–371. [CrossRef]
... Clays are by definition mineral sediments constituted mainly by hydrous aluminium phyllosilicates with a fine and divided particle size. Additionally, clays have excellent binding properties, so they have been used historically as cementitious materials (Sanchez-Calvillo, et al., 2021). In Mexico, we can find different types of clays, and they have been used for construction purposes over time; particularly, in the State of Michoacan, we can find the presence of clays in construction components like adobes, ceramic bricks, union mortars and earthen refurbishments, among many others. ...
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