I componenti della malta di calce storica risalente al periodo coloniale spagnolo nelle Filippine
10.6092/issn.1973-9494/7164
Raramente una ricerca scientifica dettagliata applicata al settore dei beni culturali viene praticata nelle Filippine. Questo studio intende presentare un approccio sistema- tico nella corretta caratterizzazione chimica di un campione di antica malta di calce proveniente dalle rovine di una chiesa dell’era spagnola. Le tecniche analitiche impiegate sono state: assorbimento atomico spettroscopia (AAS), spettroscopia infrarossa (IR), microscopia elettronica a scansione a raggi X e spettroscopia a dispersione di energia (SEM-EDX), analisi termogravimetrica. I risultati hanno mostrato che si tratta di una calce aerea, perlopiù calcitica e non dolomitica. È stato osservato un leggero carattere idraulico a causa di possibili impurità di argilla. Oltre alla miscela di sabbia tipica nelle malte, come aggregati sono stati anche utilizzati frammenti di conchiglie. Sono stati inoltre individuati dei possibili composti organici. I dati ottenuti da questo studio sono molto importanti per comprendere le tecniche di costruzione tradizionali che possono migliorare il lavoro di conservazione del patrimonio nelle Filippine.
application/pdf
1973-9494
7164
en
Aniano N. Jr. Asor
Conservation Science in Cultural Heritage
Philippines
Characterization of Historica Lime Mortar from the Spanish Colonial Period in the Philippines
Text.Serial.Journal
https://conservation-science.unibo.it/
16
Articles
2017-07-24
2017-07-17
2017-07-24
2017-09-04
33-57
CSCH
Aniano N. Jr. Asor
2016
10.6092/issn.1973-9494/7164
33
De La Salle University, Manila
1973-9494
Philippines
en
57
Villalon, A. (2013) Pride of Place: Guiuan Church, a National Cultural Treasure in Samar, Heavily Damagedby ‘Yolanda’, Available at: http://lifestyle.inquirer.net/137505/guiuan-church-a-national-cultural-treasure-in-samar-heavily-dam-aged-by-yolanda [Accessed 10/20/2016].
Characterization of Historica Lime Mortar from the Spanish Colonial Period in the Philippines
https://conservation-science.unibo.it/article/download/7164/6887
16
C    HARACTERIZATION OF HISTORICAL LIME MORTAR
     FROM THE SPANISH COLONIAL PERIOD IN THE
     PHILIPPINES

   Jan-Michael C. Cayme*1, Aniano N. Asor, Jr.
   Chemistry Department, College of Science
   De La Salle University, Manila, Philippines


   Keywords: lime mortar, binder, analytical chemistry techniques, cultural heritage
   preservation, Philippines


  1. Introduction

    One of the enduring legacies of the Spanish Colonial Period (1521-1898) in the
Philippines, is the grand Roman Catholic Church structures that still stand today and
are strategically located in the central plaza of most towns throughout the country.
The Philippines was governed by the Spanish empire for almost 380 years. It began
with the arrival of Ferdinand Magellan in 1521, when he claimed possession of the
entire island, and remained under the King of Spain until the outbreak of the Spanish-
American War when the country was later turned over to American rule in 1898. During
the early years of the Spanish Conquest, different religious orders i.e. Augustinians
(1565), Franciscans (1578), Jesuits (1581), Dominicans (1587) and Recollects (1606),
arrived with the Spanish contingent and initiated missionary work in different parts of
the country. These missionaries were not only pastors and evangelizers, they were
also church builders. In Europe, they had been eye witnesses to the magnificent Eu-




                                                                                                  CONSERVATION SCIENCE IN CULTURAL HERITAGE
ropean medieval and baroque cathedrals and desired to duplicate this architectural
and artistic style as well as impart their knowledge to the locals [1]. However, Filipino
masons, being more familiar with local environmental conditions, also contributed to
enriching this church building process by integrating native elements, designs and lo-
cal ingenuity. The product is an architectural style which is uniquely Filipino and quite
different from what was seen in Europe or other Spanish Colonies at that time [2].
Hundreds of colonial churches were built during this period. Some have recently been
destroyed by natural calamities, like earthquakes [3] and typhoons [4], others are in a
state of neglect or decay, but most are now being preserved, albeit the conservation
method applied may not be compatible with the original materials.
    Studies on historical lime mortars in the Philippines are very limited. Eusebio tested
the presence of egg whites on mortar samples using a simple qualitative Biuret test
but yielded negative results [5]. Jose, Jr. presents an old parish account of records
(Libros de Cargo y Data) that mentions the purchase of duck eggs for renovation work
on the churches of Bacoor and Imus in Cavite, which was presumed to be one of the
ingredients in making mortar [6]. In another study, Jose, Jr. also mentions the use of
molasses, honey and chopped leaves from local trees, which were added to the mortar
mixture for their supposedly binding and water proofing characteristics [7]. There was

* Corresponding author: jm_cayme@yahoo.com


                                                                                             33
                                                                                                                   no detailed information on the exact amount or ratio of these organic additives included
                                                                                                                   in the mortar mixture. Moreover, the absence of a specific set of standards, partly due
                                                                                                                   to variations in the actual natural building materials available on-site and also in the
                                                                                                                   local building skills, probably gave rise to different mineral and chemical compositions
Jan-M. C. Cayme - Characterization of historical lime mortar from the Spanish colonial period in the Philippines




                                                                                                                   which affected the properties of the mortar. Studies done by Cayme et al. concluded
                                                                                                                   that historical brick samples from various locations in the Philippines indeed have dif-
                                                                                                                   ferent chemical compositions [8, 9]. This lack of proper documentation on the exact
                                                                                                                   methodology in making old building materials has resulted in the inappropriate use of
                                                                                                                   modern day materials in preservation work. For historical lime mortars, cement is com-
                                                                                                                   monly added to facilitate the hardening of the mixture.
                                                                                                                       Mortars (argamasa) are used to hold the brick and stone together in old church
                                                                                                                   constructions. They are made by kneading a mixture of lime, sand, water and organic
                                                                                                                   additives. Since the Philippines is composed of many islands, the common source
                                                                                                                   of lime would be crushed and powdered seashells (oysters) or corals. This would be
                                                                                                                   burned constantly in a lime kiln by putting it between layers of firewood. The clump-like
                                                                                                                   product was then moistened into a paste and stored until usage. It would eventually be
                                                                                                                   mixed with the other ingredients of the mortar [10].
                                                                                                                       This study describes the composition of a lime mortar sample attached to a loose
                                                                                                                   brick fragment from the ruins of an old church from the Spanish Colonial period in Ma-
                                                                                                                   nila, Philippines. The absence of a systematic and detailed baseline data on historical
                                                                                                                   lime mortar composition in the Philippines makes this study innovative and very impor-
                                                                                                                   tant in future conservation work, as it will ensure that mortar replacements are more
                                                                                                                   compatible with the original material. The sample in this study was sieved in order to
                                                                                                                   determine the distribution of aggregate (stones, rocks or shell fragments) and binder
                                                                                                                   (lime). The amount of calcium, magnesium and iron were quantified using atomic ab-
                                                                                                                   sorption spectroscopy (AAS). These elements are very important in determining the
                                                                                                                   durability of the mortar sample. The total elemental composition and morphology were
                                                                                                                   obtained from scanning electron microscopy with energy-dispersive X-ray spectros-
                                                                                                                   copy (SEM-EDX) techniques. Infrared spectroscopy (FTIR) was used to determine the
                                                                                                                   bulk composition, while thermogravimetric analysis (TGA) provided information on the
                                                                                                                   nature of the calcium carbonate binder in the mortar sample.


                                                                                                                     2. Materials and methods

                                                                                                                     2.1. Lime mortar sample

                                                                                                                      The mortar sample collected in October 2013 was attached to a loose brick frag-
                                                                                                                   ment found within the ruins of an old 19th century Roman Catholic Church in Manila,
                                                                                                                   Philippines (Figure 1). Upon careful examination, the mortar contains small shell frag-
                                                                                                                   ments and stones of various sizes and irregular shapes. Based on its physical charac-
                                                                                                                   teristics, the sample was made entirely of lime and not of modern-day cement which
                                                                                                                   has a more massive texture. The inner portion of the mortar was gently scraped-off at
                                                                                                                   an approximate depth of 0.5-1.5 cm from the surface, without being contaminated by
                                                                                                                   the brick fragment. A total of 28.3 g of mortar sample was obtained and the remaining
                                                                                                                   fragments were returned to the site. Sampling was accomplished ensuring that enough
                                                                                                                   minimal sample amounts were taken from the collection site to perform the detailed
                                                                                                                   analysis in this study.


                                                                                                              34
Figure 1. Historical lime mortar samples from the ruins of a 19th century church.

   2.2. Sieve analysis

    About 16.0 g of mortar sample were crushed very lightly into small pieces and care-
fully disaggregated in a ceramic mortar with a wooden pestle. Since shell fragments
mixed in the mortar are generally quite hard, they will not be pulverized during this
process. The resulting material was sieved through a USA Standard Testing Sieve
ASTME-11 Specification, with sizes of 4.75, 2.36, 1.18, 0.600, 0.425, 0.250, 0.150 and
0.075 mm. Sieves were shaken using a mechanical shaker (US Tyler brand) for about
5 min to provide complete separation of the crushed samples. Each fraction was la-
belled according to the size of the respective sieve where it was retained. The fraction
retained on the “pan”, <0.075 mm, was also included in the analysis.




                                                                                                CONSERVATION SCIENCE IN CULTURAL HERITAGE
   2.3. Digestion with hydrochloric acid solution

   The various sieved fractions were heated for 24 hrs in an oven at 110°C and weighed
separately. Each fraction was then placed in separate 100mL Erlenmeyer flasks with
4mL distilled water and 30 mL 2M hydrochloric acid solution. Each mixture was stirred
at room temperature (29°C) for 5 min, followed by heating in a boiling water bath for
another 15 min and was filtered immediately [11]. The filtrate was transferred to a 100
mL volumetric flask and diluted to the mark with distilled water. These digested sam-
ples were subjected to atomic absorption spectroscopy (AAS) measurements.

   2.4. Analysis by atomic absorption spectroscopy (AAS)

   2.4.1. Preparation of standard solutions

   Calibration curves were constructed from a series of standard solutions of known
concentrations of calcium (ranging from 0.30 to 1.3 ppm), magnesium (ranging from
0.05 to 1.0 ppm) and iron (ranging from 0.10 to 8 ppm), prepared from 1000 ppm stock
solutions (Fluka brand, analytical standard grade). The concentration ranges were se-
lected based on the ideal straight line plot in agreement with Beer’s Law. Since calcium
and magnesium atoms are prone to chemical interferences, a 5.0% w/v Sr(NO3)2 was


                                                                                           35
                                                                                                                   added to each standard solution as a chemical suppressant. The blank solution used
                                                                                                                   throughout the experiment is distilled water. AAS absorbance measurements were
                                                                                                                   performed in triplicate [8, 9]. The detection wavelength for the target elements are: 423
                                                                                                                   nm for calcium, 285 nm for magnesium and 248 nm for iron, respectively. The absorb-
Jan-M. C. Cayme - Characterization of historical lime mortar from the Spanish colonial period in the Philippines




                                                                                                                   ance was recorded in a Shimadzu AA-6300 Atomic Absorption Spectrophotometer in
                                                                                                                   an air-acetylene gas mixture.

                                                                                                                     2.4.2. Preparation of unknown mortar fraction solutions

                                                                                                                      The amount of calcium in the mortar sample was determined initially by mixing to-
                                                                                                                   gether a 0.20 mL aliquot of the digested stock solution of each sieved fraction with 0.50
                                                                                                                   mL of 5.0% Sr(NO3)2 in different 100 mL volumetric flasks. Since the concentration did
                                                                                                                   not fit within the standard curve range, the solutions were further diluted by pipetting
                                                                                                                   20 mL aliquot portions into another 100mL volumetric flask. The absorbance reading
                                                                                                                   was measured in triplicate at 423 nm. To determine the amount of magnesium in the
                                                                                                                   sample, a 1.5 mL aliquot portion of each sieved mortar fraction was added with 3.5
                                                                                                                   mL 5.0% Sr(NO3)2 and diluted to 100 mL in volumetric flasks with distilled water. The
                                                                                                                   absorbance reading was again measured in triplicate at 285 nm. Lastly, the amount of
                                                                                                                   iron was determined by getting a 1.0 mL aliquot portion from each sieved mortar sam-
                                                                                                                   ple solution which was then diluted with distilled water in individual 100 mL volumetric
                                                                                                                   flasks. The absorbance was measured at 248 nm and was done in triplicate.

                                                                                                                     2.5. Analysis by infrared spectroscopy (FTIR)

                                                                                                                      An unsieved portion of the mortar sample of about 1 to 2%, relative to the KBr
                                                                                                                   amount, was mixed and ground together with the KBr powder. Precautions were taken
                                                                                                                   to ensure that the KBr powder would absorb minimum moisture from the surroundings.
                                                                                                                   The spectrum was recorded on a Thermo Scientific Nicolet 6700 FT-IR Spectropho-
                                                                                                                   tometer and acquired over the frequency range of 4000-400 cm-1 using a resolution of
                                                                                                                   4 cm-1 with 32 scans per spectrum.

                                                                                                                     2.6. Analysis by scanning electron microscopy with energy-dispersive x-ray
                                                                                                                     spectroscopy (SEM-EDX)

                                                                                                                       The sample was prepared by grinding an unsieved dry portion of mortar and dis-
                                                                                                                   persed on double-sided conductive tape attached to an aluminium stub. The sample
                                                                                                                   was coated with gold to make it more conductive. The SEM profile was recorded with a
                                                                                                                   SEM/EDX JEOL JSM-5310 scanning microscope combined with an Oxford Link Isis in
                                                                                                                   the spot profile mode. Observations were made in the back-scattered electron mode.
                                                                                                                   The elemental composition of the SEM sampling region was provided by the EDX pro-
                                                                                                                   file which was taken at 62 eV system resolution.

                                                                                                                     2.7. Analysis by thermogravimetric analyzer (TGA)

                                                                                                                      A 6.50 mg mass of an unsieved mortar sample was heated from a temperature
                                                                                                                   range of 25 to 900°C, at a ramping heating rate of 10°C/minute in dynamic air. The
                                                                                                                   percentage by weight loss of the sample was plotted relative to the change in tempera-
                                                                                                                   ture. The thermograph was recorded in a Mettler Toledo TGA.

                                                                                                              36
   3. Results and discussion

   3.1. Distribution of particles in the mortar

   Sieve analysis was employed to obtain the particle-size distribution present in the
historical mortar sample. The size of the soil particles in the mortar can influence its
adhesion to bricks and other masonry characteristics, such as compressibility, shear
strength and hydraulic conductivity [12]. Figure 2 shows the percentage by weight of
each retained fraction in the sieve. Shell fragments are apparent from the sieve sizes
of 4.750 mm and 2.360 mm as shown in Figure 3. Most of the weight retained from the
4.750 mm sieve is composed of shell fragments rather than gravel, hence digesting
the entire mortar with acid to obtain the binder / aggregate ratio was not feasible [13].
The distribution of weight is highest at around 0.600 mm followed by 1.180 mm sieved
sizes, which means that the sample is mainly composed of coarse to medium sand
aggregates. The fraction retained in the pan (<0.075 mm) is associated with the binder
and is mainly CaCO3 [14].




                                                                                                            CONSERVATION SCIENCE IN CULTURAL HERITAGE
Figure 2. Weight distribution in percentage of the various sieved fractions in the historical mortar
sample.




Figure 3. (A) Shell fragments retained from the 4.750 mm sieve; (B) shell fragments with other
minerals retained from the 2.360 mm sieve.



                                                                                                       37
                                                                                                                      The graph in Figure 4 is a logarithmic plot showing the cumulative percentage of
                                                                                                                   sample passing through a certain mesh size. This percentage is called percent finer
                                                                                                                   (% finer). The value for D10 is 0.17 mm, D30 is 0.43 mm, and D60 is 0.90 mm, respec-
                                                                                                                   tively, and were obtained by extrapolation from the plot. These are the values for the
Jan-M. C. Cayme - Characterization of historical lime mortar from the Spanish colonial period in the Philippines




                                                                                                                   grain size diameters (D) that correspond to 10%, 30% and 60% of the sample passing
                                                                                                                   through the sieve by weight, respectively. From these parameters, the coefficient of
                                                                                                                   uniformity (Cu) was computed to be 5.29 and the coefficient of curvature (Cc) was equal
                                                                                                                   to 1.21. Since the value for Cu is greater than 4 and Cc has a value between 1 and 3,
                                                                                                                   the mortar sample is considered to be well-graded. This means that the particle sizes
                                                                                                                   are well represented over a wide range [15].




                                                                                                                                    Figure 4. Grading curve distribution of the mortar sample.

                                                                                                                     3.2. Acid digestion and atomic absorption spectroscopy (AAS) analysis

                                                                                                                       The sieved fractions were digested separately with hydrochloric acid to find the
                                                                                                                   distribution of calcium, magnesium and iron in the mortar sample. Since mortars are
                                                                                                                   mainly composed of a mixture of lime and sand, the acid soluble fractions are consid-
                                                                                                                   ered part of the binder, while the acid insoluble residues are generally the aggregates.
                                                                                                                   Table 1 shows that the amount of calcium is higher compared to magnesium and iron.
                                                                                                                   This is expected since the binder is made of lime and would contain high amounts of
                                                                                                                   calcium carbonate. The fractions at 4.750 mm and 2.360 mm have about 10 to 15%
                                                                                                                   calcium which is due to the shell fragments observed during the sieving analysis. The
                                                                                                                   sieved sizes at 0.075 mm and the fraction retained on the pan (<0.075 mm), respec-
                                                                                                                   tively, have the highest percentage of calcium (about 18 to 26%), thus inferring that
                                                                                                                   CaCO3 is more concentrated in the smaller sized fractions. The presence of about
                                                                                                                   4 - 9% calcium in the sieve sizes ranging from 0.150 mm to 1.180 mm, respectively,
                                                                                                                   implies that the lime is uniformly distributed within the different sieved fractions.
                                                                                                                       Results also show that magnesium is only present in trace amounts (< 0.480%),
                                                                                                                   thus the lime content in the mortar is considered as being non-dolomitic [16]. The
                                                                                                                   amount of iron is attributed to clay mineral impurities that are present in the aggre-
                                                                                                                   gates. This explains why a higher percentage of iron (about 1.20 to 2.25%) was ob-
                                                                                                                   served in the sieve fractions containing the sand aggregates (0.075 mm to 1.180 mm).
                                                                                                                   It is also possible that small pieces of broken bricks may have been used as additives
                                                                                                                   and contributed to the increased amount of iron. Moreover, another possible source


                                                                                                              38
of iron impurities may have originated from the brick kilns, or “horno”, doubling as lime
kilns in burning seashells to produce lime [17].

Table 1. Summary of the Atomic Absorption Spectroscopy (AAS) data for calcium, magnesium
and iron content.

                       Mass of Mortar                Average % Composition
 Sieve Size (mm)
                        Sample (g)              Ca              Mg              Fe
       4.750               0.6174             10.852           0.056           1.059
       2.360               1.0718             15.080           0.146           0.065
       1.180               2.5012             5.646            0.258           1.270
       0.600               4.2310             4.390            0.223           1.348
       0.425               1.8975             5.584            0.475           2.106
       0.250               2.1765             5.380            0.440           2.235
       0.150               0.8467             8.790            0.471           1.373
       0.075               0.6475             18.944           0.211           1.606
   < 0.075 (pan)           0.6268             26.082           0.144           0.818

  3.3. Infrared (IR) spectroscopy characterization

    IR absorption peaks (Figure 5) corresponding to inorganic minerals and possible
protein content in the mortar sample are evident from the spectrum. Characteristic
absorption peaks for the binder components, mainly containing the mineral calcite
which is composed of CaCO3, are seen from the intense peaks for the C-O in-plane




                                                                                                  CONSERVATION SCIENCE IN CULTURAL HERITAGE
bending (ʋ4) at 712 cm-1 and C-O out-of-plane bending (ʋ2) at 877 cm-1. Since only
few organic compounds absorb strongly at these wavenumbers, the sharp peaks con-
firm the identification of carbonates in the sample spectrum. Furthermore, the broad
peaks for the C-O asymmetric stretching (ʋ3) at 1425 cm-1, 1797 cm-1, and 2514 cm-1,
respectively, are also attributed to CaCO3. Since sand is a major component of mor-
tars, absorption peaks for the mineral quartz should be present. These were identified
from the spectrum, based on the Si-O stretching peaks at 652 cm-1,786 cm-1 and 1060
cm-1, respectively. Moreover, the AAS data for the different sieved fractions showed
significant amounts of iron in the mortar sample, which was complemented by the
presence of the Fe-O bending peak for the mineral hematite at 536 cm-1 [8, 9]. Overlap-
ping absorption peaks cause difficulty in identifying the other mineral groups, which is
expected because the raw materials used in making mortars contain different inorganic
minerals [18].
    The possible presence of proteins in the mortar sample was established by the
characteristic peaks for the amide group which includes the broad bands centered
at 3439 cm-1, assigned to the N-H stretching vibration, and at 1627 cm-1 for the C=O
stretching vibration, respectively [19]. Since proteins, usually in the form of eggs, are
added in low concentrations, it is likely that peaks from inorganic components of the
sample may interfere with its detection [5]. Further qualitative tests for proteins should
be performed to confirm these assumptions.



                                                                                             39
Jan-M. C. Cayme - Characterization of historical lime mortar from the Spanish colonial period in the Philippines




                                                                                                                         Figure 5. Spectrum of the mid-infrared region (4000-400 cm-1) of the mortar sample.

                                                                                                                      3.4. Microstructure of mortar using scanning electron microscopy and ener-
                                                                                                                      gy-dispersive x-ray spectroscopy (SEM-EDX)

                                                                                                                      SEM provides information on the size, texture and distribution of aggregates and
                                                                                                                   binder components in the mortar sample. Analysis of magnified images in Figures
                                                                                                                   6A and 6B shows that the mortar has a compact microstructure with no major pores.
                                                                                                                   Aggregates, mainly in the form of quartz, were observed to be well-embedded in the
                                                                                                                   sample matrix (Figure 6A). The presence of quartz was also confirmed by the EDX




                                                                                                                   Figure 6. SEM image of the mortar sample magnified (a) 3,500x, and (b) 1,500x. The resulting
                                                                                                                   EDX spectrum of these images is shown in (c).


                                                                                                              40
spectrum (Figure 6C) which provided an atomic percentage for Si at 2.95% and the
fourth most abundant element relative to the SEM image. The crystal structure mag-
nified at 1,500x (Figure 6B), gives details on the mineral calcite which forms part of
the binder [20, 21]. This was supported by the EDX spectrum in Figure 6C as having
a high atomic percentage for Ca at 14.82%. Hence, the mortar sample is essentially
composed of lime and is calcium-rich. The EDX data supports the results of the AAS
in that magnesium is indeed present in low amounts (0.16%) implying that the lime is
non-dolomitic. Table 2 summarizes the percentage composition of different elements
from the EDX spectrum.

Table 2. Summary of elemental composition using EDX.
                            ELEMENT               ATOMIC %
                                O                      58.72
                                C                      21.81
                                Ca                     14.82
                                Si                      2.95
                                Al                      0.89
                                Fe                      0.37
                                K                       0.21
                               Mg                       0.16
                                Ti                     0.04*
                               Mn                      0.04*
                               Total                   100.00
                                              *trace amounts




                                                                                                CONSERVATION SCIENCE IN CULTURAL HERITAGE
  3.5. Thermal analysis

   Information on the binder composition was determined by measuring the weight loss
of the mortar sample as the temperature was increased to 900°C. A continous weight
loss was observed from the thermograph (Figure 7) which became significant between
790°C and about 850°C. This non-linear drop in the sample’s mass is a characteristic
peak for the decompostion of calcium carbonate by the release of CO2. Weight loss
between 200°C and 600°C is due to the evaporation of water chemically bound to hy-
draulic compounds, while the decrease in weight above 600°C is attibuted to the loss
of CO2 [22, 23]. Futhermore, the binder composition was classified based on the ratio
of CO2/H2O from the thermograph. The 1st derivative plot shows that the weight loss of
the sample was highest at 2.73% for the hydraulic H2O temperature range (200-600
°C) and the maximum weight lost for the CO2 temperature range (790-850 °C) was at
24.97%. Thus, the CO2/H2O ratio is equal to 9.15. This implies that the mortar sample
shows binder characteristics for a typical air-lime with a slightly hydraulic character.
The hydraulic nature of the sample was supported by the significant amount of iron
found on the sand aggregates as recorded by the AAS. Air-lime mortar slowly hardens
in air by reacting with CO2 in the atmosphere through time. The hydraulic character
may be attributed to clay impurities (i.e. iron) during the lime burning process, effec-
tively making the binder carbonate faster [24].


                                                                                           41
                                                                                                                      Moreover, the TGA data gives consistent results with the AAS and EDX in which no
                                                                                                                   significant amount of magnesite or dolomite decomposition was detected in the binder.
                                                                                                                   This is due to the absence of major weight loss between 400°C and 650°C [25].
Jan-M. C. Cayme - Characterization of historical lime mortar from the Spanish colonial period in the Philippines




                                                                                                                   Figure 7. Thermograph of the mortar sample showing loss of weight as temperature
                                                                                                                   is increased.


                                                                                                                      4. Conclusion

                                                                                                                       This paper presents different analytical techniques that effectively characterize the
                                                                                                                   chemical composition of historical lime mortars in the Philippines and will serve as use-
                                                                                                                   ful baseline information for renovation work to be employed for structures built within
                                                                                                                   the Spanish-Colonial Period. The mortar material is calcitic and well-graded, with shell
                                                                                                                   fragments used as aggregates. This implies that the source of the raw material may
                                                                                                                   have come from the vicinity of the seashore, since the sampling site is near Manila
                                                                                                                   Bay. Sand with silicates, quartz and hematite minerals were observed from the IR
                                                                                                                   and SEM-EDX analysis and provided a basic mineralogical description of the sample.
                                                                                                                   Organic protein compounds may have also been added to the mortar mixture. This will
                                                                                                                   be explored further using protein extraction techniques. Furthermore, the binder has a
                                                                                                                   typical air-lime characteristic with a slightly hydraulic property which allowed for effec-
                                                                                                                   tive carbonation. Signs of Portland cement were not observed on the sample; hence it
                                                                                                                   is regarded as original and not affected by any modern restoration.


                                                                                                                      Acknowledgements

                                                                                                                       The authors would like to express their deepest gratitude for the generous support
                                                                                                                   given by the Chemistry Department of the De La Salle University, Manila, Philippines.
                                                                                                                   The helpful insights and valuable assistance of the following persons from the Chem-
                                                                                                                   istry Department are greatly appreciated: Dr. Glenn Alea, Mr. Michael Ajero, Mr. Irving
                                                                                                                   Chiong and Dr. Maria Carmen Tan.



                                                                                                              42
      References

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                                                                                                                      Biographical notes

                                                                                                                      Jan-Michael C. Cayme, M.Sc. is an assistant professorial lecturer at the Chemistry
                                                                                                                   Department of the De La Salle University, Manila and a licensed chemist in the Philip-
                                                                                                                   pines. He also holds a Masters’ degree in chemistry. Currently, he is completing his
                                                                                                                   PhD in Chemistry at the University of the Philippines, Diliman. He used to be part of
                                                                                                                   the Institute of Philippine Culture of the Ateneo de Manila University that documents
                                                                                                                   the architectural styles and history of pre-World War 2 houses and structures in Metro
                                                                                                                   Manila. His other research interests include the use of chemical techniques in analys-
                                                                                                                   ing the composition of cultural heritage materials from historical churches and fortifica-
                                                                                                                   tions.

                                                                                                                      Aniano N. Asor, Jr., M.Ed. (chemistry) is a chemical laboratory assistant at the De
                                                                                                                   La Salle University, Manila and a licensed teacher in the Philippines. He holds BS/BA
                                                                                                                   and BSE degrees in chemistry, mathematics and math/science. He obtained his Mas-
                                                                                                                   ters’ degree in chemistry education at the De La Salle University, Manila. His research
                                                                                                                   interests focus on the analytical techniques of chemical analysis.


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