SPECIAL ISSUE
Natural building stones of Mexico–Tenochtitla´n: their use,
weathering and rock properties at the Templo Mayor,
Palace Heras Soto and the Metropolitan Cathedral
Wanja Wedekind • Joerg Ruedrich •
Siegfried Siegesmund
Received: 8 March 2011 / Accepted: 22 April 2011 / Published online: 26 May 2011
 The Author(s) 2011. This article is published with open access at Springerlink.com
Abstract In the Aztec period and in colonial times dif-
ferent natural stones originating in the Valley of Mexico
were used for building construction. Stone weathering was
investigated onsite at various historical buildings within the
old quarter of Mexico City. In this study, different aspects
of weathering and deterioration at three significant histor-
ical buildings will be presented, the Aztec excavation site
Templo Mayor, the Metropolitan Cathedral, and the colo-
nial palace of the dukes of Heras Soto. Petrophysical
properties of the main building stones of these structures
were investigated like density, porosity, pore radii distri-
bution, water uptake rate and coefficient, thermal and
hygric expansion, and the mechanical properties of uniaxial
compressive strength. A relationship between single criti-
cal property values, according to anisotropy fabric char-
acteristics, and specific weathering forms could be
deduced.
Keywords Stone weathering  Mexico-DF 
Petrophysical properties  Isotropy–anisotropy  Critical
values
Introduction
Because of its geological setting, volcanic rocks are the
most prevalent rock types in the Valley of Mexico. Mexico
City, formerly called Mexico–Tenochtitla´n by the Aztecs,
is located in the Valley of Mexico in the center of the
Trans-Mexican Volcanic Belt. Located in the high plateaus
of south-central Mexico, it has a minimum altitude of
2,200 m above sea level. Mountains and volcanoes that
attain elevations of over 5,000 m surround the once char-
acteristic Lakeland area of the valley. Today only small
remnants of the historical Lake Texaco are left, which once
had dimensions of 72 km by 35 km.
Human settlements in the Valley of Mexico have a very
long history; initial traces of agriculture around the lake
began about 7,000 years BCE (Niederberger 1979) and the
first evidence of villages occur between 1,700 and 1,250
BCE, which developed the first identifiable cultures (Nei-
derberger 1996). Around 2,000 years later, the founding of
the Aztec capital Tenochtitla´n took place in 1325. The city
of Tenochtitla´n was destroyed under the command of
Hernan Cortes (1485–1557) in the summer of 1521. The
once largest city (Sanders 2008) of the Americas had been
razed to the ground and an estimated 240,000 Aztecs died
(Hassig 1994) during the fall of their capital. The Aztec
culture and the Spanish Conquistadors left behind a large
stone building legacy. Within the 9 km2 area of the his-
torical city center, around 1,500 historical buildings and
200 monuments are preserved and 80 museums are located.
In 1987, the UNESCO declared the historical center of
Mexico City a World Heritage Site. Today many cam-
paigns for restoration and the rehabilitation of the historical
center were done or are still in the planning stage.
Weathering and stone deterioration in this region is
affected by four main factors: the extreme pollution of the
metropolitan area, the semi-arid to subtropical climate, the
specific hydrological situation, and the frequent seismic
activity. In general, weathering and deterioration of
building stones in Mexico City have been poorly
investigated.
Different publications exist concerning the restoration of
the Metropolitan Cathedral, but they mostly focus on
W. Wedekind (&)  J. Ruedrich  S. Siegesmund
Geoscience Centre of the University Go¨ttingen,
Goldschmidtstr.3, 37077 Go¨ttingen, Germany
e-mail: wwedekind@gmx.de
123
Environ Earth Sci (2011) 63:1787–1798
DOI 10.1007/s12665-011-1075-z
structural surveys (Ortiz Lajous 1980; Tamez et al. 1997).
Publications dealing with petrophysical investigations on
the building materials are rare. For example, geotechnical
investigations by Pirella and Ramı´rez (2001) were done on
just one column of the cathedral.
Other investigations studied just one type of volcanic
tuff variety, which is used on many historical facades in the
city (Sua´rez Pareyo´n Aveleyra 2002). The influences of
urban and industrial pollution on stone were discussed by
Martı´nez and Martı´nez (1991) for three types of stone also
investigated in this paper.
Five different types of the main building stones from the
Valley of Mexico were investigated for mineralogical and
petrophysical characterization. Altogether six large-scaled
samples of the original historical and already weathered
material from the Cathedral and the Templo Mayor as well
as fresh building material from different local quarries
were selected. The sample of the Cathedral was from the
roof covering of the left tower and the samples of the
Templo Mayor were fragments of historical floor plates.
Methods
The petrophysical properties analyzed in this investigation
are density, porosity, pore radii distribution, water uptake
rate and coefficient, thermal and hygric expansion as well
as the mechanical properties of uniaxial compressive
strength. For the last three parameters, the investigations
were carried out in three different fabric directions, parallel
(Y) and perpendicular (Z) to the foliation and as far as
possible parallel to the lineation (X).
The laboratory tests are complemented with field
observations consisting of mapping and diagnostic mea-
surements on the objects such as surface temperature,
electrical conductivity and shore-hardness tests on the
stone surfaces.
In order to acquire the matrix and bulk density as well as
the porosity, hydrostatic weighing was carried out. Water
uptake was determined by capillary suction in a closed
cabinet while weighing. The water uptake coefficient
(w value) describes how much water can be absorbed in a
definite time according to the area of suction. The pore
radii distribution was analyzed by using the mercury
injection porosimetry (e.g., Brakel et al. 1981).
The hygric expansion is a property of some materials
(e.g., clay minerals), which causes them to swell in contact
with water. The present explanation is that this behavior is
controlled by the amount of swelling clay minerals and the
proportion of micropores present in the rock (see discus-
sion in Weiss et al. 2004 or Ruedrich et al. 2005 and
Ruedrich and Siegesmund in this issue). The hygric
expansion of the stones was determined on cylindrical
samples (diameter 40 mm, length 50 mm), which were pre-
conditioned at 30% relative humidity and room tempera-
ture. Afterwards, the samples were completely immersed in
distilled water. Thermal expansion was measured on
cylindrical samples (diameter 15 mm, length 50 mm) by
heating up to 90C and cooling down to 20C during five
cycles to determine an eventually residual (irreversible)
strain.
For the compressive strength tests, standard cylindrical
specimens of 25.4 mm in diameter and 50 mm in length
with co-planar end-faces were used. After grinding, all
specimens were dried at 50C until weight constancy was
achieved. This weight is defined as the dry status of the
specimens.
In the next step, one charge of the specimens was
evacuated and saturated with water up to weight constancy,
which defines the fully saturated sample condition (100%
water saturation). The compressive load was applied by a
servo-hydraulic testing machine with a very stiff testing
frame (3,000 kN/mm2) and a class 1 load range up to
300 kN. The load was applied to the end-faces of the
specimen with a strain rate of 10–5 s-1 until failure. The
maximum load is defined as the uniaxial compressive
strength.
Mapping and in situ investigations of the buildings
The Templo Mayor
The Templo Mayor was one of the main temples of the
Aztecs in their capital city of Tenochtitla´n, which repre-
sents Mexico City today. The temple is located in the
center of the historical town and was once the central part
of the ceremonial center of Tenochtitla´n. The Templo
Mayor was originally a towering pyramid topped by two
sanctuaries (Fig. 1a). The outline of the temple measuring
approximately 100–80 m at its base dominated a sacred
precinct. The construction was based on hundreds or even
thousands of fence-post-sized supporting piles within the
porous marshy terrain to stabilize the building (Sanders
2008). Construction of the first temple started around 1324.
The sixth and last rebuild took place in 1487 (Parker 1995)
(Fig. 1a). In 1521, the Spanish systematically destroyed the
temple.
The first fragments of the temple were recovered at the
end of the nineteenth century and the first half of the
twentieth century. Systematic excavations took place from
1978 to 1982 by the demolition of 13 younger buildings. In
1980, the site was restored and treated with impregnation
materials using silanes and hydrophobizantes (Franco
1987; Wacker and Meyer 1997). Since 1987, the site has
been added to the UNESCO World Heritage List.
1788 Environ Earth Sci (2011) 63:1787–1798
123
Stone, adobe, wood, and lime mortar were the main
building materials used in Aztec architecture (Lo´pez Luja´n
et al. 2003). In the Templo Mayor, the main building stone
is called ‘‘tezontle’’ (I), which in the Aztec language, Nu-
atle, is the appellation for an extrusive volcanic basaltic
andesite scoria. These dominant building materials are
followed by different other types of andesite, and rarely by
basalts popularly known as ‘‘recinto’’ as well as limestones.
Weathering is mostly visible in the tezontle and a red-
dish basaltic hornblende andesite, in Nuatle known as
tenayoca´tetl (II). This material was used as floor or facing
plates or for platform structures.
While the most recognizable deterioration in the te-
zontle consists of fractures and cracks (Fig. 2a), the
weathering feature observable in the tenayoca´tetl is a
scaling parallel to the surface with a thickness of 2–5 mm
(Fig. 2b). Both weathering forms are specific for each
single type of stone. Especially in the case of the tena-
yoca´tetl, the damages are observable on plenty of plates in
the platform. In this study, tezontle from a quarry in the
state of Mexico, which is used for plenty of restoration
works today and the tenayoca´tetl from the Templo Mayor
has been investigated.
Palace of the dukes of Heras Soto
The Palace of the dukes of Heras Soto was built during the
period, 1753–1760, and was the representative domicile of
Adria´n Xime´nes de Alendral, a rich tradesman for silver
(Fig. 1b). The name given to the palace-like residence was
because of its aristocratic inhabitant in the nineteenth
century (Demm 1991). The building in style and con-
struction is a typical exponent of the baroque colonial
palace in Mexico City. The residence is nearly 40 by 40 m
in size and is a two-storied building with a center court and
arcaded sidewalk. The domicile is located at a distance of
two blocks northwest from the cathedral. A first compre-
hensive restoration took place in 1978. In 1931, the
building was declared a historic monument and is part of
the UNESCO World Heritage List of Mexico-DF. The bare
brickwork of the typical palaces and houses is made of
bricks and adobe, while different building stones cover the
fac¸ades. The same construction is found in the case of the
palace, Heras Soto.
Beside tezontle, recinto, and tenayoca´tetl, the most
dominant building stone is ‘‘cantera’’ Gris de los Remedios
(III). The ornamental sculpture of the facade is made from
these devitrified tuffs (Fig. 1b).
Weathering can be recognized in the basement area of
the building, especially where the sunlit fac¸ades are
affected by deterioration (Fig. 3a). In the case of this
colonial building, the material of the tenayoca´tetl variety is
used as building blocks, mostly horizontal to the flowing
structure, which means the bedding or flow structure is
observable.
The tenayoca´tetl variety shows extreme back-weath-
ering of layers and partial detachment by fragmentation.
Ashlars are used like plates, which means perpendicular to
the flow structure and also scaling is observable. Conse-
quently, the outline single ashlars show rounding (Fig. 3a,
d). Weathering also takes place on the tuff stone connected
to the basement area. Two weathering forms can be dis-
tinguished: scaling with a thickness up to 1 cm parallel to
the surface and rounding by splitting and sanding (Fig. 3c).
In general, the Gris de los Remedios shows a high resis-
tance to weathering. Only in building parts exposed to wet–
dry conditions, like the foundations or balconies, is back-
weathering able to be detected.
Fig. 1 The investigated
buildings within the historical
center: a location and model of
the Templo Mayor, b the palace
of the dukes of Heras Soto and
c the Metropolitan Cathedral
with the left tower under
restoration
Environ Earth Sci (2011) 63:1787–1798 1789
123
The Metropolitan Cathedral
The Metropolitan Cathedral of Mexico City was con-
structed from 1573 to 1813 on the former Aztec ceremonial
center. The cathedral is the largest and oldest in the
Americas (Fig. 1c). The cathedral facades are oriented to
the south and are approximately 54.5 m wide and 110 m
long. The two bell towers were constructed in the latter half
of the eighteenth century. The building combined different
architectural styles like the Baroque, Neo-Renaissance, and
Neo-Classic.
Seismic activity and ground subsidence in the area has
affected the cathedral’s construction. Besides the structural
problems, weathering takes place especially on building
parts exposed to wet–dry conditions. Restorations have
been carried out throughout the entire history of this large
building. After the restoration of the cupola in the last
several years, the bell towers are now currently undergoing
restoration.
Because the cathedral was constructed over a period of
more than two centuries, not only is its design a mixture of
different architectural styles, but also all the various
building stones used originating from the Valley of Mexico
can be seen on different parts of the building. The main
building stones used consist of tezontle, tuff stone, and
andesite (Pirella and Ramı´rez 2001).
The main building stone used for the main facade and
the two towers is a gray to green colored pyroxene
andesitic tuff (IV). Present-day restoration work uses a
similar variety originating from the Chiluca quarries (V). In
Fig. 2 a Structural cracks observable in the tezontle (arrows) and b scaling of tenayoca´tetl plates parallel to the surface
Fig. 3 a Weathered and
replaced building stones at the
ground level, b Mapping area,
c lithographic mapping,
d Mapping of damages
1790 Environ Earth Sci (2011) 63:1787–1798
123
this study, we focus on these building materials because of
their significant weathering features and because of their
importance as historical building material. The pyroxene
andesite of the Metropolitan Cathedral shows a typical
weathering form starting with crust formation, and then
scaling due to flaking and rounding (Fig. 4).
During the process of weathering, the first centimeter of
the stone material is especially affected. Thus, the pore
radii distribution, porosity, capillary water uptake, and
hardness change. Tests conducted in the laboratory with
this weathered material clearly demonstrated this process.
After the moistening of a truncated stone sample, the water
penetrates and remains in the weathered zone only
(Fig. 5a). Here the pore size contribution changes for the
benefit of a higher amount of capillary active pores from 27
to 76% in comparison to the unweathered material
(Fig. 5I–III). Capillary active pores are defined as those
having a cross-sectional dimension ranging from 0.1 to
[100 lm (Klopfer 1985). Porosity increases from 10 to
13% (Fig. 5I–III), whereas the surface hardness measured
with a durometer DO (ASTM D 2240), decreases down to
70% in comparison to the intact material.
Today the outlines and sharp edges of cut stones often
are back-weathered. These weathering processes take place
especially in the pedestal area (Fig. 5b) or in building parts,
which are exposed to rain and down flowing water.
Rock fabrics and petrophysical properties
Tezontle basalt
Of the vesicular Tezontle basalt (I) fresh material of a
quarry nearby Mexico City was investigated. Macro-
scopically it shows a typical cellular fabric. The voids
are predominantly 8 mm in diameter. Locally, partially
melted rock fragments from older volcanic rocks are
incorporated. These fragments show irregular shapes with
a red colored rim, which can be traced back to iron
oxide minerals.
Microscopically the cell walls of the cellular rock fabric
show a cryptocrystalline fabric with acicular plagioclase
crystals. Only isolated small pyroxene and amphibole
crystals as well as hematite impregnations occur (Fig. 6I).
X-ray fluorescence analyses after Acevedo-Da´vila et al.
2007. The Tezontle basalt geochemically contains
approximately 60% SiO2, 12% Al203, 8% MgO, 5%
Fe2O3, 4% CaO and 3% Na2O.
The material is permeated by fractures and small cracks.
Its porosity in non-weathered conditions ranges from 35 to
66% with an average value of 52 vol.%. This strong vari-
ation of the porosity can be traced back to its heteroge-
neous cellular structure. Due to the high porosity the bulk
density with a value of 1.4 g/cm3 is very low. The particle
or matrix density reaches a value of about 2.71 g/cm3.
Possibly mafic minerals like pyroxene and amphibole
possibly cause this relatively high value. The average
w value only reaches 0.40 kg m-2 h-1/2. Active capillary
pores amount to 76.2% of the pore radii distribution by a
considerable outbalance of larger capillary pores
([10 lm = 43.7%) and macro pores (Table 1). Further-
more, the basalt exhibits no measurable hygric swelling but
with 7.0 10-6 K-1 a relatively high thermal dilatation
coefficient (Table 3). A residual strain after five cycles
could not be detected.
Under dry conditions, the compressive strength ranges
from 12 to 32 N/mm2. The highest values are reached in
Z direction averaged with 27 N/mm2. The lowest values
were measured in Y direction averaged with around 21 N/
mm2. The anisotropy amounts nearly 21% (Table 4). The
modulus of elasticity ranges from 3.57 to 8.34 kN/mm2
with an anisotropic behavior of around 13%. The uniaxial
compressive strength is with 23.8 N/mm2 very low. Under
dry sample conditions, the strength varies between 21.33
and 26.90 N/mm2. In contrast, the uniaxial compressive
strength values of the water-saturated specimens are 3%
higher and range between 27.76 and 22.31 (Table 4). This
is caused by the rock heterogeneity, and thus the rock
strength does not depend on the water content. The
Young’s modulus of the Tezontle rock is around 5.7 kN/
mm2 (Table 4).
Fig. 4 Crust formation, scaling and rounding of a sculpture at the
Metropolitan Cathedral
Environ Earth Sci (2011) 63:1787–1798 1791
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Tenayoca´tetl rhyolitic ignimbrite
The volcanic rock from tenayoca´tetl (II) is grayish to red in
color and is characterized by a porhyritic fabric. By min-
eralogical classification, the rock exhibits a rhyolitic
composition and represents a welded ash tuff with a small
portion of lapilli fragments. This rock shows the charac-
teristic foliation, which is caused by flow structures.
Microscopically the fine-grained ash matrix cannot be
further detected. The lapilli fragments mainly show roun-
ded quartz.
Altered crystals of plagioclase, hornblende, andesine,
oligoclase, labradorite and augite are observable. Within
the fine matrix, small acicular crystals define the flow
direction (Fig. 6, third row). This matrix is colored in
layers from light red to dark red because of kaolinite and
hematite.
Because of the limited amount of original historical
material available, compressive strength tests could only be
done in the fabric directions parallel (Y) and perpendicular
(Z) to the flow direction under dry conditions.
Tenayoca´tetl has a porosity of 7.3% and a density of
2.45 g/cm3 (Table 1) The w value shows extreme aniso-
tropic behavior of nearly 99%. While the w values in the
Z and X direction only reach 0.10–0.11 kg m-2h-1/2, the
Y direction with a value of 9.16 kg m-2h-1/2 is nearly ten
times higher. (Table 2). The pore radii distribution shows
an amount of nearly 53% as sum of all fractions of capil-
lary active pores (0.1 to[10 lm) as well as a proportionate
dominance of micropores (0.01–0.1 lm) of nearly 38%
(Table 1). Thermal dilatation reaches 9.71 mm/m with a
very low anisotropy of 2.2% (Table 3). Also for the rhy-
olitic Ignimbrite a residual strain after five heating-cycles
could not be detected.
Hygric swelling shows an extreme anisotropic behavior
of 51.4%: hygric swelling in the Z direction with 5.68 mm/
m reaches a value nearly two times higher than in the other
fabric directions (Table 3).
Compressive strength attains a value of 50.83 N/mm2 by
isotropic behavior (Table 4). The e-module ranges from
12.13 to 14.81 kN/mm2 with a moderate anisotropic
behavior of almost 17%.
Fig. 5 a Truncated stone sample of pyroxene andesite from the Metropolitan Cathedral. I, II and III depict changing pore radii distributions
according to the different zones of weathering. b Rounding in the Chiluca variety
1792 Environ Earth Sci (2011) 63:1787–1798
123
While the stone shows nearly the same values
according to its mechanical properties, the water uptake
capacity and the hygric dilatation show extreme aniso-
tropic values (Tables 2, 3). Water suction only seems to
be possible through the direction of lineation (Y). Hygric
expansion shows an anisotropic value of 51.4%. The
expansion perpendicular to the flow direction is almost
two times higher than parallel to the direction of foliation
or lineation.
The thermal expansion shows height values and isotro-
pic behavior (Table 3). Thermal expansion is reaching
5.6 mm/m at 60C and 9.8 mm/m at 90C.
Fig. 6 First row the different building stones. Second row thin sections. Third row remarks (a matrix of the Remedios tuff and its pore size
distribution, b inclusion of the Remedios tuff and its pore size distribution)
Table 1 Pore space and density properties of the investigated rocks
Rock type Porosity
(Vol.%)
Bulk density
(g cm-3)
Particle density
(g cm-3)
Average pore
radius (lm)
Pore radii distribution (%)
0.001–0.01 (lm) 0.01–0.1 (lm) 0.1–1 (lm) 1–10 (lm) [10 (lm)
Tezontle 51.8 1.40 2.71 1.870 8.3 15 10 22.5 43.7
Cathedral 10.6 2.40 2.68 0.114 5.9 56.3 23.8 2.9 10.9
Chiluca 8 2.37 2.58 0.358 4 22.8 40 30 3.2
Tenayoca´tetl 7.3 2.27 2.45 0.303 9.2 37.8 15.8 19.6 17.5
Remedios 28.2 1.82 2.55 1.285 0 15.3 18.8 55 10.9
Table 2 Moisture transport properties of the investigated rocks in
non-weathered condition (anisotropy calculated with A = nmax -
nmin/nmax 9 100)
Rock type w value (kg m-2 h-1/2) A (%)
X Y Z
Tezontle 0.39 0.45 0.38 15.5
Tenayoca´tetl 0.11 9.16 0.10 98.9
Remedios 8.30 9.08 6.21 30.8
Cathedral 0.30 0.37 0.32 18.9
Chiluca 0.39 0.34 0.38 12.8
Environ Earth Sci (2011) 63:1787–1798 1793
123
Remedios tuff (Gris de los Remedios)
The volcanic rock of Remedios represents a lapilli tuff
(III), supported by an ash matrix. The color of this tuff is
gray to light gray. Two types of lapilli fragments are dis-
tinguished, one is white in color, and the other is dark. The
ash matrix is more or less gray. Within the matrix, dark
spots occur that can be traced back to mafic minerals. The
mafic minerals often show prismatic crystal shapes and
represent mostly idiomorphic developed hornblende crys-
tals. The white lapilli fragments are dominated by pumice.
Microscopic examinations revealed the presence of
minerals and compounds like cristobalite, clays, sodium
plagioclase, hornblende, and sparitic particles. While the
crystals within the inclusions are unaltered, the crystals
within the matrix show alteration. Both the matrix and the
inclusions are closely connected. Between these two
components, no pore space is observable (Fig. 6III). The
porosity and density of the matrix and the inclusions differ
at around 45%. The pore radii distribution also differs in
the same dimension (Fig. 6, third row). The matrix
(a) shows a distinct concentration of capillary active pores
(1–10 lm), while the inclusions (b) show nearly the same
volume of capillary active macropores and micropores
(0.001–0.1 lm). The inclusions define a flow orientation,
whereas an orientation of the single crystals within the
matrix cannot be discerned.
Secondary precipitated calcite is located in small cracks
and in the pore space. Chemical analyses indicate that the
calcite comprises 0.8 wt%.
The porosity of Gris de los Remedios ranges from 24.5
to 31.5%, whereas their bulk density is around 1.78–1.92 g/
cm3. The average w value reaches 7.8 kg m-2 h-1/2 with
an anisotropy value of 30.8% (Table 2). The amount of
capillary active pores comprises 84.7%. From the capillary
active pores, a 55% fraction ranges between 1 and 10 lm
(Table 1). Thermal dilatation averaged reaches 6.14 mm/m
with a moderate anisotropy of nearly 15% (Table 3). A low
Table 3 Thermal expansion coefficients (a) and the residual strain of one heating cycle (20 -90 -20 C) as well as the hygric expansion of the
investigated rocks in non-weathered condition
Rock type Thermal dilatation Hygric expansion
X (mm m-1) Y (mm m-1) Z (mm m-1) A (%) X (mm m-1) Y (mm m-1) Z (mm m-1) A (%)
Tezontle 7.01 6.97 7.52 7.3 n.d. n.d. n.d. –
Cathedral 7.91 7.78 7.50 5.1 3.05 2.98 3.05 2.3
Chiluca 7.80 8.42 6.85 18.6 2.82 2.81 3.02 6.9
Tenayoca´tetl 9.71 9.60 9.82 2.2 2.76 3.14 5.68 51,4
Remedios 6.7 5.7 6.03 14.9 4.94 5.88 6.21 20,4
Anisotropy calculated with A = nmax - nmin/nmax 9 100
n.d. not detectable
Table 4 Compressive strength
in dry and water-saturated
conditions as well as the elastic
modulus
Rock type Direction/
anisotropy
Tezontle Cathedral Chiluca Tenayoca´tetl Remedios
Compressive strength dry
(N/mm2)
X 23.40 105.02 91.94 50.82 17.25
Y 21.33 97.78 83.2 50.86 16.58
Z 26.90 91.88 90.58 50.82 18.08
A (%) 20.7 12.5 20.7 0.07 8.29
Compressive strength water
saturated (N/mm2)
X 23.67 – 76.45 – 10.03
Y 22.31 – 68.73 – 9.67
Z 27.76 – 71.29 – 10.82
A (%) 19.6 – 10.0 – 10.62
Compressive strength
reduction (%)
?3.01 – -19.6 – -41.2
Young’s modulus
(kN/mm2)
X 5.8 9.8 12.70 14.81 3.14
Y 6.1 8.45 14.26 13.42 2.85
Z 5.3 10.2 14.12 12.13 3.85
A (%) 13.1 17.1 10.9 16.8 26
1794 Environ Earth Sci (2011) 63:1787–1798
123
residual (irreversible) strain during the five cycles of
measurement could be detected.
Hygric swelling averages show a value of 5.67 mm/m
with an anisotropy of 20.4% (Table 3).
Under dry conditions, the compressive strength of single
samples ranges from 15.8 to 19.3 N/mm2. The anisotropy
amounts to 8.29% (Table 4). The elastic modulus ranges
from 3 to 5 kN/mm2 with an anisotropic behavior of
around 26%. The Remedios variety has an average com-
pressive strength of 17.3 N/mm2 and an e-module of
8.29 kN/mm2.
At water saturation, the compressive strength decreases
down to 10.17 N/mm2 by a moderate anisotropy of 10.6%
(Table 4). Compressive strength decreases to 41.2%
according to the measurements under dry conditions
(Table 4).
The stone has a high w value (7.8 kg/m2) and a high
hygric dilatation by reaching an average value of 5.6 mm/
m. Both values clearly show anisotropy. The w-value is
nearly 31% and the hygric dilatation 20% (Tables 2, 3).
Average compressive strength values only reach 17.3 N/
mm2 at dry conditions and decreases to 10.1 N/mm2 in the
water-saturated state, a reduction of 41% according to the
measurements under dry conditions (Table 4).
The thermal dilatation also reaches critical values of
around 4 mm/m at 60C and around 6 mm/m at 90C. The
curve does not follow a linear gradient. When heating up to
60C, a small depression is recognized. This reduction is
probably caused by the dehydration of crystal water within
the material. After five cycles, a residual strain could not be
detected.
The investigated material was coming from the quarries
of Los Remedios located in the mountains northwest of
Mexico City.
Chiluca: fresh and altered (Cathedral)
Two varieties of the pyroxene andesite tuff Chiluca have
been investigated, an altered sample from the cathedral
(described as Cathedral, IV), and a fresh sample from a
quarry (described as Chiluca, V). The altered Chiluca tuff
sample was removed from the cathedral during the current
restoration campaign. The properties of the Chiluca type of
the Cathedral differ from the fresh sample.
The Chiluca tuff represents an ash tuff with a high
proportion of fragmented feldspar single crystals, giving
the rock a porphyritic appearance. The tuff is gray in color
with dark inclusions of mafic minerals, which is probably
amphibole. Feldspar single crystals occur in a fine-grained
matrix. Microscopic examinations show that both stone
varieties have a vesicular phenoporphyritic texture and
microcrystalline matrix consisting of andesite constituents
(around 85%). In both varieties, hornblende crystals are
present (around 15%) (Martı´nez and Martı´nez 1991).
Some crystals show alteration (Fig. 6, second line) in
the sample from the cathedral, whereas the crystals within
the matrix of the new stone from the chiluca quarry mostly
are still intact (Fig. 6, second line). The Chiluca variety
also shows isolated augite crystals and plagioclase. An
orientation within the fine matrix cannot be discerned by
standard microscopic techniques. Macroscopic observa-
tions detected an orientation in the elongated hornblende
crystals.
The porosity measured in the altered cathedral variety
is 10.6% with the density being 2.68 g/cm3 (Table 1). The
Chiluca variety comes with a porosity of 8% and a density
of 2.58 g/cm3 (Table 1). Both varieties differ in porosity
and density by only 2%. The w value of the cathedral
variety averaged 0.33 kg m-2 h-1/2 with an anisotropy of
nearly 19%, whereas the Chiluca variety shows a w value
of 0.37 kg m-2 h-1/2 with a moderate anisotropy of
around 13% (Table 2). Active capillary pores in the case
of the altered cathedral variety reach 37.6% and in the
sample from Chiluca 73.2% (Table 1). The highest
amount of pore fractions (56.3%) within the pore radii
distribution in the cathedral variety can be found for mi-
cropores with a pore radii size of 0.01–0.1 lm, whereas
the Chiluca variety has a concentration of 40% for the
pore radii fraction ranging from 0.1 to 1 lm (Table 1).
Thermal dilatation of the altered variety averaged around
7.73 mm/m with a low anisotropy of 7.3% (Table 3). Only
for the samples from the cathedral, a low residual strain
could be detected.
Hygric swelling shows a value of 3.02 mm/m with a
very low anisotropy of only 2.3% (Table 3). In the quarry
fresh Chiluca, the value of thermal dilatation averaged
7.69 mm/m and is comparable to the altered stone, but it
has a clear anisotropy of around 19% (Table 3). Hygric
swelling reaches an average of 3.1 mm/m and is slightly
higher than the sample from the cathedral as well as
showing an anisotropy of nearly 7% (Table 3).
Both varieties have a high compressive strength. The
altered variety averaged 98.2 N/mm2 with an anisotropy of
12.5%, whereas the Chiluca variety shows a value of
88.6 N/mm2 with an anisotropy of 21% (Table 4).
The modulus of elasticity of the cathedral variety ranges
from 8.45 to 10.2 kN/mm2 with an anisotropic behavior of
around 17%, whereas the Chiluca only shows an anisotropy
of 11% and a averaged e-module of 13.7 kN/mm2. Because
of the limited amount of the original historical material,
compressive strength by water saturation could only be
measured for the fresh Chiluca variety. By compressive
strength tests at water saturation, a decrease of nearly 20%
took place in the this variety (Table 4).
Environ Earth Sci (2011) 63:1787–1798 1795
123
Discussion
All five building stones show different petrophysical
properties and specific weathering and deterioration forms
under the same environmental conditions. Whereas tezon-
tle and Gris de los Remedios in historical buildings show a
significant resistance towards weathering, the andesite
varieties are more vulnerable for different weathering
phenomenon. In field studies the building structure and
position of the different building stones within the con-
struction was also regarded:
Sample I
I. The main building material in Aztec times, Tezontle,
could be easily mined by fracturing because of the mod-
erate hardness with a compressive strength average of
23.8 N/mm2. The scoria mainly is out of glass making the
material highly fragile. The low specific density also
allowed the stone to be transported by boats (Table 1). The
material was mostly used as rubblestone. Big building
blocks were an exception. Therefore, tezontle could not be
used for larger self-supporting structures. The moderate
hardness and its premature fracture formation during the
lava cooling process seems to be the reason why the
material is so susceptible to crack formation. Tezontle
nearly shows no hygric swelling and a low w value
(Table 2) by a moderate compressive strength and a low
Young’s modulus (Table 4). These properties, on the other
hand, are ideal for compact structures on muddy ground.
The specific material properties seem to be the one con-
tributing factor for the formation of the typical compact
outline discernible in Aztec architecture.
Water uptake only takes place in the compact mostly
reddish colored areas of the material. Only these areas
come with a capillary active porosity. These linked pore
space areas are sporadic within the material. Therefore,
tezontle does not show any susceptibility neither for rising
damp nor capillary action. Tezontle nearly shows no hygric
swelling but a high thermal dilatation (Table 3).
In tezontle, crack formation is also detectable because of
the improper masonry mortar (Fig. 2a, Sagarra Lagunes
1993), where the Young’s modulus is potentially to high
according to the moderate values for tezontle of 5.73 kN/
mm2 (Table 4).
Natural building stones were selected in colonial times
not only because of their use for decoration but also for
building construction purposes. This systematic construc-
tion also exemplifies the mapping of the pedestal area as
well as the first floor of the palace of Heras Soto (Fig. 3c,
d).
Basalts like recinto with a low capacity for water uptake
and a high resistance towards hygric swelling, were mostly
used for the basement area followed by an array of an
andesitic variety (Figs. 3c, 5b). To this day the different
basaltic varieties show almost no weathering.
Sample II
While the tenayoca´tetl variety shows nearly the same values
according to its mechanical properties, the water uptake
capacity and the hygric dilatation show extreme anisotropic
values (Tables 2, 3). Water suction seems to be possible only
more or less through the fluidal direction of the material (Z).
Hygric expansion also shows extreme anisotropic values:
The expansion perpendicular to the flow direction is almost
two times higher than parallel to the direction of foliation or
lineation. Thermal expansion shows high values but nearly
isotropic behavior (Table 3) by reaching a value of 5.6 mm/
m at 60C and 9.8 mm/m at 90C.
The anisotropic properties in the tenayoca´tetl variety with
respect to the w value and the hygric expansion are respon-
sible for the described weathering forms. Water transport,
swelling and shrinking pressure and salt seems to be
responsible for the deterioration. Scaling of the platform
plates of the Templo Mayor can also be increased because of
the hydrophobizing in the 1980s (Wacker and Meyer 1997).
Sample III
In the tuff variety Gris de los Remedios, one reason for its
general resistance could be found in the bond of the matrix
and the inclusions. The both component are closely con-
nected. This bonding seems to be one reason, why we find
no back-weathering of clastic material. Normally the
clastic material weathers out. This is an often recognized
phenomenon of many rhyolitic tuffs (To¨ro¨k et al. 2005) and
is also found in different tuff varieties of Me´xico like for
example in Guadalajara (Ja´uregui and Wedekind 2009).
Compositionally the stone is classified as an andesitic or
trachytic-andesitic tuff (Ordo´nez and Ezequiel 1996). The
tuff is showing a low residual strain, but hair cracks or
craquele, which are often found in sun-exposed surfaces of
different Mexican tuff varieties, could not be observed.
The field observations and the results of the investiga-
tions lead to the conclusion that hygric expansion probably
in combination with the action of salt weathering is the
main factor for the weathering of the tuff variety Gris de
los Remedios. Salt efflorescences can be often recognized
in combination with weathering phenomena and are an
indicator for wet–dry conditions. This hypothesis is con-
firmed by the use of the tuff variety as a part of the
architectural structure: The Remedios tuff was mainly used
for architectural sculptures in areas that are not directly
affected by water. In the tuff that was used in the palace
Heras Soto for the ground floor weathering can be
1796 Environ Earth Sci (2011) 63:1787–1798
123
recognized. This part of the building is affected by wet–dry
conditions (Fig. 3c).
Sample IV, V
New mining methods at the beginning of industrialization
(late eighteenth century) created means for excavating
large amounts of the phenoporphyritic andesite for the
cathedrals main facade and bell towers. Before this tine
these types of andesites were normally used for the con-
struction of the ground floor and pedestal areas. Both
building parts, the bell towers as well the foundation zones
are affected by wet–dry conditions. In the phenoporphyritic
andesite the limited depth of weathering seems to be con-
nected to the low w-value measured in both varieties
(Table 2). Chiluca contains a low porosity; the w-value is a
littler higher than the original material of the cathedral
(Table 2). This is due to the different pore radii distribu-
tions in both varieties. The active capillary pore space of
Chiluca accounts for 73.2%, whereas the original material
of the cathedral only attains a value of 37.6% (Table 1).
During a water uptake of 4 h, suction of only 0.5 cm could
be determined. This correlates with the depth profile of
weathering and crust formation (Fig. 5).
The concentration of weathering in the outline of the
stone can be traced back to the high hygric dilatation of the
material and associated shear forces. During this process,
insulation weathering also seems to play a role because of
the thermal dilatation.
The pyroxene andesitic tuff of the cathedral shows a
critical thermal expansion of around 4 mm/m by heating up
to 60C and reaching nearly 8 mm/m at 90C. The Chiluca
stone shows similar values. A tendency of anisotropy to the
fabric direction of foliation (Z) can be detected. By heating
up to 68C a dint can be recognized during the linear
gradient. This reduction is probably caused by the dehy-
dration of crystal water within the material. Thermal
expansion by heating up to 60C is reached at around
4.2 mm/m in the fabric directions Z and X and 5.3 mm/m
in the Y direction. A similar anisotropic behavior occurs
when the material is heated up to 90C (Table 3).
These two critical property values, the high thermal
dilatation and the high hygric swelling associated with
shear and tension stress can give an explanation for
weathering forms like scaling and rounding. For the variety
of the Cathedral a low residual strain could be detected.
Today Chiluca is used as a restoration material for the
replacement of ashlars affected by weathering at the
cathedral and other historical buildings. In comparison with
the original stone of the cathedral, the investigated Chiluca
samples show adverse properties towards weathering,
especially when considering its higher water uptake
capacity and lower compressive strength.
Conclusion and prospects
The results show that typical weathering forms can be
deduced because of specific petrophysical properties on
different rock materials. Significant anisotropic behavior or
single critical values can influence the sensitivity to dif-
ferent weathering forms. With regard to the investigated
rocks in this study, a factor that influences the creation of
material immanent weathering starts with an anisotropy up
to 20%. Cementation can also play a key role in the rock’s
resistance to weathering.
The results help in the understanding of the different
weathering processes, and contribute to the evaluation of
the relevant different deterioration factors. In Mexico
today, deteriorated stone material is usually replaced with a
new one. The present investigation has shown that weath-
ering is mostly limited to the surface area of the different
materials. Conservation and preservation of the original
historical material seems to be possible and more cost-
effective. Long-term studies and cost calculations have
shown that conservation can be up to four times more cost-
effective than changing the stone material (Gra¨f 2009).
Studies on consolidation were already done for three of the
samples presented in this paper. These studies have shown
best results for vinyl acetate, type Mowolith 50 and a silica
acid ester, type Wacker OH (Martı´nez 1992).
Considering all available data for the rock types and
conservation status of the described monuments, first steps
in the development of a sustainable conservation procedure
are already done. Future tasks have to be focused on the
development of adequate methods and materials, like
mortars for restoration.
Acknowledgments We would like to thank Dr. Axel Vollbrecht of
the Geoscience Center of Go¨ttingen, Ma´ria Barajas Roche, Depart-
ment Chairperson of Restoration at the Museo Templo Mayor, the
architects and conservators of the Cathedral Metropolitan, INHA
(Instituto Nacional de Antropologia e Historia), CONACULTA
(Consejo Nacional para la Cultura y las Artes), Ing. Ricardo Luna
Alvarado and the restorer conservator Karla Ja´uregui Arreola. Our
work was kindly supported by the Hans-Bo¨ckler-Fundation.
Open Access This article is distributed under the terms of the
Creative Commons Attribution Noncommercial License which per-
mits any noncommercial use, distribution, and reproduction in any
medium, provided the original author(s) and source are credited.
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