ChapterPDF Available

Contribution to the study of Ançã limestone

Authors:

Abstract and Figures

In this paper we are presenting an inventory of the existing types of limestone in the Ançã area, analysis of their properties, determination of their main utilization, actual and possible, both for construction and industry. The Ançã limestone is located in the Ançã region, about 15 km NW of Coimbra in central Portugal. The field work was done to identify and characterize the geology, the existing quarries, active or abandoned, and to select the most representative ones for a deeper study. The analysis of the geological and structural data, allowed the identification of five structural zones. With the results obtained in the field and of the laboratory, five types of limestone with well-defined characteristics could be identified. One of the limestone types, the “Ançã stone” is well known because of the monuments which were built with this particular stone and of the beautiful artistic works that have been carved in it. The environmental aspects of the quarry exploration were also analyzed.
Content may be subject to copyright.
10/2/2015 WebofScience[v.5.19]AllDatabasesFullRecord
http://apps.webofknowledge.com/full_record.do?product=UA&search_mode=GeneralSearch&qid=2&SID=S27qCowYjCXEeNPIDpi&page=1&doc=1 1/2
ContributiontothestudyofAncalimestone
By: Trindade,MF(Trindade,MF);Ferreira,MOQ(Ferreira,MOQ);Oliveira,R(Oliveira,R)
Editedby: Moore,D;Hungr,O
EIGHTHINTERNATIONALCONGRESSINTERNATIONALASSOCIATIONFORENGINEERING
GEOLOGYANDTHEENVIRONMENT,PROCEEDINGS, VOLS15
Pages: 29452952
Published: 1998
Conference
Conference: 8thInternationalCongressoftheInternationalAssociationforEngineeringGeologyand
theEnvironment
Location: VANCOUVER,CANADA
Date: SEP2125,1998
Sponsor(s): IntAss ocEngnGeol&Environm
Abstract
Inthis paperwearepresentinganinventoryoftheexistingt ypesof limestoneintheAncaarea,
analysisoftheirproperties,determinationoftheirmainutilization,act ualandpossible,bothfor
constructionandindustry.TheAncalimestoneis locatedintheA ncaregion,about15kmNWof
CoimbraincentralPortugal.
Thefieldworkwasdonetoidentify andcharacterizethegeology,t heexistingquarries,ac tiveor
abandoned,andtoselect themost representativeonesforadeeperstudy. Theanalysis ofthe
geologicalandstructuraldata,allowedtheidentificationoffiv estruct uralzones.Witht heresults
obtainedinthefieldandofthelaboratory,f ivety pesoflimestonewithwelldefinedcharacteristics
couldbeidentified.Oneoft helimestonety pes,the"Ancastone"iswellknownbecauseofthe
monumentswhichwerebuiltwiththisparticularstoneandofthebeautifulartisticworksthat havebeen
carvedinit. Theenvironmentalaspects ofthequarryexplorationwerealsoanalyzed.
AuthorInformation
ReprintAddress:Trindade,MF(reprintauthor)
UnivCoimbra,DeptCienciasTerra,P3000Coimbra,Portugal.
Addresses:
[1] UnivCoimbra,DeptCienciasTerra,P3000Coimbra,Portugal
Publisher
AABALKEMAPUBLISHERS,SCHIPHOLWEG107C,POBOX447,2316XCLEIDEN,
NETHERLANDS
Categories/Classification
ResearchAreas: Engineering;EnvironmentalSciences&Ecology
WebofScienceCategories: Engineering,Geological;EnvironmentalSc iences
DocumentInformation
DocumentType: ProceedingsPaper
Language: English
AccessionNumber: WOS: 000078260900410
ISBN: 9054109904
OtherInformation
CitationNetwork
0TimesCited
18CitedReferences
ViewRelatedRecords
ViewCitationMap
CreateCitationAlert
(datafromWebof ScienceTMCoreCollection)
AllTimesCitedCoun ts
0inAllDatabases
0inWebofScienceCoreCollection
0inBIOSI SCitationI ndex
0inChineseScienceCitation
Database
0inDataCitationIndex
0inSciELOCitationIndex
UsageCount
Last180Days: 0
Since2013:0
Learnmore
Thisrecordisfrom:
WebofScience TMCoreCollection
Suggestacorrectio n
Ify ouwouldliketoimprovethequality
ofthedataint hisrecord,please
suggestacorrection.
WebofScience TM InCites TM JournalCit ationReports ®EssentialScienceIndicators SM EndNote TM Sign In Help English
MyTools SearchHistory MarkedList
 AddtoMarkedList
SavetoEndNoteonline
1of1
Search ReturntoSearchResults
10/2/2015 WebofScience[v.5.19]AllDatabasesFullRecord
http://apps.webofknowledge.com/full_record.do?product=UA&search_mode=GeneralSearch&qid=2&SID=S27qCowYjCXEeNPIDpi&page=1&doc=1 2/2
IDSNumber: BM28K
CitedReferencesinWebofScienceCoreCollection: 18
TimesCitedin WebofScienceCoreCollection: 0
1of1
©2015THOMSONREUTERS TERMSOFUSE PRIVACYPOLICY FEEDBACK
M.F. Trindade, M.O. Quinta Ferreira & R. Oliveira: Contribution to the study of Ançã limestone (2nd version) 1
Contribution to the study of Ançã limestone
M.F. Trindade
Dep. Ciências da Terra. University of Coimbra. 3049 Coimbra. Portugal.
M.O. Quinta Ferreira
Dep. Ciências da Terra. University of Coimbra. 3049 Coimbra. Portugal.
R. Oliveira
COBA S.A. and Faculty of Sciences and Technology. New University of Lisbon. Portugal.
ABSTRACT: In this paper we are presenting an inventory of the existing types of limestone in the Ançã area,
analysis of their properties, determination of their main utilization, actual and possible, both for construction
and industry. The Ançã limestone is located in the Ançã region, about 15 km NW of Coimbra in central
Portugal.
The field work was done to identify and characterize the geology, the existing quarries, active or
abandoned, and to select the most representative ones for a deeper study. The analysis of the geological and
structural data, allowed the identification of five structural zones. With the results obtained in the field and of
the laboratory, five types of limestone with well-defined characteristics could be identified. One of the
limestone types, the “Ançã stone” is well known because of the monuments which were built with this
particular stone and of the beautiful artistic works that have been carved in it. The environmental aspects of the
quarry exploration were also analyzed.
RÉSUMÉ: Dans cette comunication nous voulons faire l’inventoire des diffèrent types de calcaires qui
existent dans la région de Ançã, de l’étude de leurs propriétés et de leurs principaux utilisations, au présent et
au future, pour la construction et pour l’industrie. Ce calcaire ce trouve dans la région de Ançã, environ la
Ville de Coimbra au centre du Portugal.
Le travail a possibilité de identifier et de caractériser la géologie, les carrières, actives et abandonnées, et de
sélectionner les plus représentatives pour un étude plus détaillée. L’analyse des éléments géologiques et
structuraux ont permis l’identification de cinq zones structurales. Avec les résultats obtenus sur le terrain et au
laboratoire, cinq types de calcaires ont été définis. L’un des types de calcaires, la “pierre de Ançã”, et bien
connue à cause dés monuments qu’ont été construits avec ce type particulier de calcaire et à cause des beau
travaux artistiques. Les aspects de l’environnement liés à l’exploitation des carrières ont été aussi analysés.
1 INTRODUCTION
In this paper we identify and characterize the main
limestone types present in the “Ançã limestone”
outcrop. It is an area of about 8 km by 10 km, and it
is located about 15 km NW of Coimbra, between
Cordinhã, Ançã and Zambujeiro, in central Portugal.
Over many centuries the Ançã limestone has been
used in the construction of monuments, statues and
buildings. Despite the wide utilization, time has
showed that this rock sometimes does not have the
adequate properties for the utilization intended, the
most serious problem being the lack of durability.
A peculiar rock type, the “Ançã stone”, a white
and very porous limestone, is very famous and has
been used for sculpture and architecture since the
XIV century. It can be found in the most important
monuments in Portugal like the National Palace of
Queluz, the Old Cathedral and the Saint Cross
Church in Coimbra, but also in Brazil, in the former
Portuguese colonies (Goa, Guinea Bissau, Angola,
Macao, etc.) and in sanctuaries like Santiago of
Compostela (Spain), Jerusalem and Rome as refered
to by Tavares (1989).
Frequently the designation “Ançã limestone” is
confused with the “Ançã stone” leading to believe
that the whole outcrop is constituted of “Ançã
stone”. To clarify this situation an inventory of the
main limestone types was made, starting with a
bibliographic research, photo-interpretation and field
work in the area. In the field we concentrated the
work on the numerous quarries in the area that
provided better conditions of observation and study.
In each observation site a file was used to record data
related to the geology, quarrying conditions,
geotechnical characteristics of the limestone and the
environment impact (Trindade, 1994).
2 GEOLOGY
The “Ançã limestone” dates from Middle Jurassic
(Dogger) and has a thickness between 250m and
300m (Barbosa et al., 1988). It forms a large syncline
with the axis plunging to SW.
M.F. Trindade, M.O. Quinta Ferreira & R. Oliveira: Contribution to the study of Ançã limestone (2nd version) 2
The geomorphology of the area is flat, with the
higher surface attributed to the Plio-Pleistocene, at
an elevation of about 100m. This plateau tilts gently
to south, and in the northern edge shows a
topographic step in the transition of the marly
limestone of Póvoa da Lomba to the marls of S.
Gião. Over the limestone of Póvoa da Lomba, Ançã
and Andorinha an incisive main drainage network is
observed of the subsequent type. This limestone is
superficially karstified, penetrating to a depth of
about 10 m, as seen in the “D´El Rei” caves and it is
associated with the exsurgence of Portunhos
(Barbosa et al., 1988).
For the study of the discontinuities in outcrops,
photo-interpretation was mainly used, together with
geologic mapping at scale 1/50,000. According to
Neiva (1989) the orogenic movements, probably
from the Laramic phase, folded the limestone layers
into large cylindrical structures, with the axes
oriented NE-SW, plunging 2° to 8° SSW. The main
faults at Pocariça-Ferraria are oriented NW-SE and
are related to the tectonics at the end of the Pliocene.
From the fracture map of Figure 1 some conclu-
sions were drawn. The outcrops are essentially af-
fected by three sets of discontinuities. The most
important has a trend NW-SE, while the two other
sets have trends NNE-SSW and ENE-WSW. The
least fractured zone is at SW between Andorinha,
Zambujeiro and Vila Nova. The most fractured zone
is at East of Portunhos and Pena with fractures
oriented NW-SE and NE-SW and less frequently
oriented ENE-WSW and N-S. In the central zone
between Portunhos, Vila Nova and Outil the
fractures are intermediate and essentially oriented
NW-SE, and less frequently NNE-SSW and ENE-
WSW.
3 DATA COLLECTION
The field work started with the inventory of the
existing twenty five quarries in the outcrop. Data was
collected on the site about the activity, past and
present, utilization of the limestone, macroscopic
description of the rocks, environmental impact and
natural hazards in the quarries.
After the analysis of the data it was decided that
the detailed geological and geotechnical study should
be restricted to only ten representative quarries,
because most of them presented very similar
characteristics.
For the ten selected quarries a careful study of the
discontinuities using the methodology proposed
by
Figure 1. Map of fractures and location of quarries studied.
M.F. Trindade, M.O. Quinta Ferreira & R. Oliveira: Contribution to the study of Ançã limestone 3
the ISRM (1981) was also done. Mainly the orienta-
tion, spacing, continuity of discontinuities, statistical
analysis of the data, definition of the main jointing
systems and the shape of the unit block was
analyzed. A stratigraphic section for each quarry was
also executed. All the information was recorded in a
data file.
4 ZONING OF THE OUTCROP
The analysis of the information obtained allowed the
division of the outcrops into the following five
zones.
4.1 Zone between Ançã and Portunhos.
The limestone is mainly yellow, fine grained, with
low clay content, high porosity and hard. A milky
white, fine grained, very homogeneous, highly
porous and of low hardness limestone is also found
and corresponds to the “Ançã stone”. Thin layers of
marls, around 0.1 m to 0.15 m, are found interbedded
with the limestone.
The number of discontinuity sets in the area is of
type VI (ISRM, 1981) with one subhorizontal set
associated with the bedding, and two more
subvertical joint sets. The subhorizontal
discontinuities related to the bedding, are moderate
to widely spaced (0.4 m to 0.8 m) and have very high
persistence (> 20 m). The discontinuities in the
subvertical joint sets have a moderate to wide
spacing (0.3 m to 1.0 m), have high persistence and
are tight. The rock blocks obtained in the quarries of
this zone are mainly tabular, with average
dimensions essentially between 0.2 m to 1.5 m.
The main environmental impact caused by the
quarries is visual because they are located at the
sides of the road EN.234-1. The noise caused by the
use of explosives and the dust is also evident. The
increase in the road traffic is low because these
quarries have reduced production.
4.2 Zone between Portunhos, Pena and Cordinhã.
In this area the main limestone extracted is gray, fine
grained, dense, hard, fossiliferous and interbedded
with fine layers of marls. The yellow Ançã
limestone, refered to in the previous section is
overlying the gray limestone of Pena. It is close to
the village of Pena that the gray limestone becomes
dominant.
The number of discontinuity sets of the rock mass
is of type VII, with the subhorizontal set of disconti-
nuities associated with the bedding, widely spaced
(0.5 m to 2.0 m), and with very high persistence (>20
m) and two subvertical sets widely spaced (0.5 m to
1.5 m), with medium to high persistence and tight.
There are also several random discontinuities.
The limestone extracted in the quarry nº 10 was
used in the construction of the harbour breakwater of
Costa Nova (Aveiro). The blocks extracted were of
tabular shape and of large to very large size.
Due to the intense fracturing of the rock mass and
the random orientation of the discontinuities, the
blocks obtained in the other quarries have a wide
range of shapes and sizes.
In this area there is only one quarry (nº 14) still
active, producing aggregates, limestone used in
Portland cement industry and blocks for masonry and
rockfill.
The main impact of the inactive quarries is in the
landscape because they are located alongside the
EN.234-1 and they have not been reclaimed. For
quarry nº 14 we can refer the impacts in the
landscape, the noise, dust and traffic because it has a
high production.
4.3 Zone between Portunhos and Andorinha
The limestone extracted in this zone is yellow, com-
pact, dense, hard, durable and with low porosity. It is
a micritic limestone, but can also be a
biomicrosparite, having microfissures randomly
oriented and cemented with calcite. It is extracted
close to the road EN.584 at W of Portunhos.
Concerning the discontinuities, the rock mass is
of type VIII, with three subvertical joint sets, one
horizontal joint set and some random joints. The
subhorizontal joint set has very high persistence and
is widely spaced (0.6 m to 2.0 m). The joints of the
subvertical sets have medium persistence, moderate
spacing (0.2 m to 0.6 m) and are tight. The blocks
extracted in quarries nº 15 and nº 16 are of irregular
shape and with sizes from small to large.
The environmental impact caused by these
quarries is mainly to the fauna and flora due to the
noise and dust. The intense traffic of trucks inside
Portunhos is another very important impact because
these two quarries are of significant production.
4.4 Zone between Andorinha and Vila Nova
In this area the limestone is compact, hard, with
colours from yellow to gray, rarely has microfissures
and it is of good durability and strength.
In the quarries nº 19 and nº 20 the number of dis-
continuity sets in the rock mass is of type VI, with
one subhorizontal set of discontinuities showing
moderate spacing (0.6 m), related to the bedding, and
with two subvertical joint sets. In the quarry nº 24
the rock mass is of type VIII with three sets of
subvertical joints and some random discontinuities.
In the quarries nº 19 and nº 20 the subvertical joints
have very high persistence, wide spacing, and are
intensely karstified and filled with residual soils 0.2
m to 1.0 m thick. In quarry nº 24 the subvertical
discontinuities have medium persistence, moderate
spacing and are closed. In these two quarries large
blocks with tabular shape are obtained. In the quarry
M.F. Trindade, M.O. Quinta Ferreira & R. Oliveira: Contribution to the study of Ançã limestone 4
nº 24 the blocks obtained are irregular and with a
wide range of dimensions.
The quarries nº 19 and nº 20 are far from
populated areas and the production is artisanal and
sporadic without the production of significant noise
and dust. The environmental impact is mainly in the
landscape. In the quarry nº 24 the use of explosives
and the dust during the extraction process cause
impacts mainly in the fauna. Some slope instability
characterized by rockfalls was also observed.
4.5 Zone between Fornos and Zambujeiro
The limestone of this zone is well observed along
road EN.586 at north of the village of Fornos. It is
completely different from the other four limestones,
because they have granular texture and are usually
medium grained but sometimes coarse grained. In
this area it was possible to separate two kinds of
limestone. One is white, homogeneous and porous
(e.g. sample F1 in Table 1) and the other is yellow,
very heterogeneous and with different zones in the
same sample that can be compact or friable (e.g.
sample F2).
The number of discontinuity sets in the rock mass
in this zone is of type VII. All the discontinuity sets
have very high persistence. The subhorizontal set is
widely spaced (1.0 m to 2.0 m) corresponding to the
bedding surfaces. The subvertical joint sets have very
wide spacing (2.0 m to 4.0 m), and the joints are
karstified and filled with residual soil 0.2 m to 0.5 m
thick. The blocks that can be obtained are essentially
equidimensional.
In this area only one quarry was founded and it
was inactive having some negative impact on the
landscape.
5 LABORATORY STUDY
After the field study of the rockmass a detailed
laboratory characterization was carried out in order
to improve the knowledge of the several types of the
Ançã limestone. For each type it was studied the
mineralogy, the petrography, the chemistry, the void
system, the hydric properties, the hardness, the
mechanical properties and the weatherability.
5.1 Sampling
The samples were obtained from the quarries and all
types of limestone were collected. Each sample was
initially identified by one or two letters followed by a
number. The larger numbers represent the number at-
tributed to the quarry (Figure 1), while the smaller
figures in the index, are the number of the sample in
that quarry. After the laboratory characterization of
the samples, labeled in the field, they were grouped
according to their properties as presented in Table 1
and described in section 7.
5.2 Mineralogy, petrography and chemistry
For each sample the macroscopic description and
microscopic study was made. The clay minerals were
identified using X-Ray. A solution with hydrochloric
acid was made to determine the insoluble residue.
The chemical composition was obtained by
spectrophotometry by EDTA.
5.3 Evaluation of the void system
The porosity was determined by vacuum saturation
and hydrostatic weighing following the procedure nº
3 of the ISRM (1981).
To evaluate the pores and the fissures indirectly,
the sonic wave velocity (VL) was measured
following the recommendations of the ISRM (1981)
and VL was used to compute the Index of Quality:
IQ= (VLdry / VLcomputed) x 100% (1)
as proposed by Tourenq et al. (1971).
5.4 Hydraulic properties
Under this designation were grouped the tests
performed to evaluate the behaviour and the
properties of the limestone in the presence of water.
The tests executed were: water absorption under
vacuum (W); free water absorption by total
immersion (Ia) and index of rapid absorption (IAr)
both proposed by Hamrol (1961); coefficient of
saturation according to test nº II.1 of RILEM (1980);
water absorption by capillarity; water absorption in
controlled relative moisture atmosphere; and linear
expansion by water immersion.
5.5 Hardness evaluation
For assessing the scratch hardness a sclerometer was
used following the procedure LNEC/LERO PE-11
(1993).
5.6 Mechanical properties
The strength of the rock materials was evaluated
using the uniaxial compression test and the point
load test. The uniaxial compression test was
performed following the specification E-236 of the
LNEC (1970). The point load test was performed
according to the procedures of the ISRM (1985) to
obtain Is(50), but another parameter, the PLS (point
load strength) as defined by Guifu & Hong (1986)
was also determined.
5.7 Weatherability, durability and behaviour
prevision
In this group we included the following tests: the Los
Angeles test carried out according to the
specification LNEC, E 237 (1970) using grading B
and F; the slake-durability index (ISRM, 1981); the
M.F. Trindade, M.O. Quinta Ferreira & R. Oliveira: Contribution to the study of Ançã limestone 5
salt crystallization in a salt spray chamber, according
to the procedure PE-19 of LNEC/LERO (1993); the
magnesium sulfate test using the specification E 238
of LNEC (1970) using the sizes 9.51/4.76 mm.
The index of rock durability (IRD) proposed by
Delgado Rodrigues & Jeremias (1990) was used to
evaluate the durability. The IRD has the formula:
IRD = (R/Rt) / (n+2a) (2)
where R - uniaxial compressive strength UCS), Rt - a
dimensional parameter (1 MPa), n - porosity, 2a -
mantissa of the swelling expansion expressed as 10-
4. According to these authors a micritic limestone
with IRD over 5 is a suitable material for
construction, and with an IRD over 10 has a good to
excellent durability.
6 GEOTECHNICAL CLASSIFICATION
The table proposed by Delgado Rodrigues (1986)
was used to classify the limestone as presented in
Figure 2. Excluding the sample PE14, all the
limestones are included in group “A” meaning that
their behaviour is essentially controlled by the
porosity. From Class I to V (Figure 2) the strength
decreases, but the wear possibility, weatherability
and the ease to be polished all increase. The
behaviour of the sample PE14 is the most influenced
by the presence of water because it has a higher
content of clay minerals.
7 LIMESTONE TYPES
The results obtained allowed to verify that the Ançã
outcrop has five limestone types with different
chemical and physical properties causing different
mechanical behaviour and weatherability.
A summary of the properties of the five limestone
types is presented in Table 1.
7.1 Ançã limestone (s.s.)
The Ançã limestone (s.s.) is essentially micritic,
compact, of yellow colour, medium hard, with a
percentage of clay and dolomite very low. Samples
A5, A6, A81, PE102 and PE143 are included in this
group. The content of CaCO3 is over 95%, the
porosity is medium to high (8-12%) with coefficients
of water absorption medium to low and very low
expansion. Its mechanical behaviour is essentially
dependent on the porosity, and is not significantly
affected by the presence of water. The uniaxial
compressive strength is high (80 to 140 MPa) and
the ultrasonic wave velocity (VL) is high to very
high (4600 to 5300 m/s). The results of the Los
Angeles abrasion test are between 25% for grading B
and 33% for grading F. The loss on the slake-
durability index is between 0.8% and 1.7%, the IRD
(index of rock durability) is medium (5 to 8) and the
IQ (Index of Quality) is between 70 and 85%.
In this group it is worth to mention the presence,
between Ançã and Portunhos, of a quite different
limestone. It is a white limestone, homogeneous,
very fine grained, porous and with very low
hardness, known as the famous “Ançã stone”. It is a
quite pure limestone, with an extremely low content
of clay and dolomite, having sometimes a few quartz
grains. Samples A2, A62, A83 and A9 are of “Ançã
stone”. Due to a very low content of clay minerals,
the porosity is very high (18% to 28%) and the water
absorption is also very high, mainly the capillary
coefficient. The swelling is very low allowing the
behaviour to be essentially controlled by the
porosity. The strength is medium to low and the wear
is high when analyzing the results of the Los Angeles
abrasion test and of the slake-durability index. The
“Ançã stone” is very prone to weather by salt
crystallization, having very low indexes of quality
(IQ=54,9%) and of durability (IRD=2,2).
7.2 Pena limestone
The Pena limestone is micritic, fossiliferous,
compact and medium hard. The content of CaCO3
ranges between 79% and 94%, and is lower than the
Ançã limestone. The porosity has values around
12%. The content of clay minerals is sufficient to
influence the behaviour of the rock when the water is
present. In dry samples the uniaxial compressive
strength is high (UCS = 80 to 140 MPa), but it is
Samples:
Classes: I, II, III, IV and V
Groups: A, B, C, D
Figure 2. Geotechnical classification of limestone
using the table by Delgado Rodrigues (1986).
M.F. Trindade, M.O. Quinta Ferreira & R. Oliveira: Contribution to the study of Ançã limestone 6
reduced to about 50% when the samples are
saturated.
The result of the Los Angeles abrasion test is
higher than 30%, and the loss in the slake-durability
index is of 1% or 2%. This limestone is very
sensitive to the weathering by salt crystallization,
having a medium to low IRD (4 to 8) and a IQ
around 70%.
A few layers of laminated micritic and
fossiliferous marly limestone are also found (e.g.
sample PE142), and they have a significant content
of dolomite and clay (over 10%). They are very
expansive and their properties are sharply influenced
by the presence of water.
7.3 Portunhos limestone
It has low porosity, around 2,7%, very low
coefficients of water absorption and swelling,
implying that the mechanical behaviour of the rock is
little affected by the presence of water. The UCS is
high, over 100 MPa. The presence of microfissures
filled by calcite, acting as discontinuities prevent the
rock of having higher strength.
The IQ around 90% and the IRD around 20 are
both high.
The Los Angeles abrasion test is 23% for grading
B and 29% for grading F, and the loss in the slake-
durability index of 0.3% shows that this limestone
has low wearing characteristics.
7.4 Outil limestone
This limestone can be found southwest of Outil
lagoon, and is oomicrosparite, very compact, hard,
and with yellow to gray colour. It is very pure, with
medium to high porosity, low coefficients of water
absorption and low expansibility.
Some strength anisotropy was observed, with the
samples cut perpendicular to the bedding showing a
reduction in strength between 20% and 40%. The
reduction in strength due to saturation was about
30%. The wear is low in the slake-durability index
with less than 1% loss. The Los Angeles abrasion
test ranges between 23% for grading B and 31% for
grading F. This limestone has an IQ about 70%, and
the IRD between 8 and 10.
7.5 Fornos limestone
In this area it was possible to separate two kinds of
limestone biosparite, as reported in section 4 for
zone 5. One is white, homogeneous and porous (e.g.
sample F1) and the other is yellow, very
heterogeneous and with different zones in the same
sample that can be compact or friable (e.g. sample
F2). They are both very pure limestone. Generally
the sample F2 has better properties than sample F1.
Their porosity is medium (6,5% to 9%), the
strength is medium (50 to 60 MPa), but showing a
reduction of 50% when saturated. They have low
water absorption coefficients and low swelling
properties.
The loss in the slake-durability index is very
reduced, with 0.5% to 0.7% loss. The results of the
Los Angeles abrasion test are very high (44% for
grade B). The IQ is very good (86% to 90%) but the
durability is low, with an IRD around 5.
8 POSSIBLE UTILIZATION
It was possible to verify that under the designation of
“Ançã limestone” there are five different types of
limestone with some local variations.
Based on the results obtained and in the
specifications for utilization it was possible to
discuss the application of each limestone type. For
most of the applications the specifications published
in the work of Manupella et al. (1982) were used for
comparison.
8.1 Construction materials
According to the specification of the Portuguese
Road Authority (JAE), the crushed limestone of
Ançã, Outil and Portunhos can be used for flexible
road pavements.
For the production of concrete, only the Portunhos
limestone fulfills the required properties of the
Portuguese regulations.
The utilization of limestone for railways ballast is
very exigent, and only the Portunhos limestone
would be possible to be used but with some
restrictions. At present, as far as we know, the
limestone is not being used as granular material in
railway construction in Portugal because it suffers
high degradation essentially due to the dynamic
action of the trains. The limestones used in the past
have been replaced mainly by igneous rocks.
Due to the fact that the rock mass is very fractured
there is no quarry where it would be possible to
obtain a sufficient number of large blocks that would
justify the production and the cut of blocks and
plates for ornamental use.
For the production of dimensional stone, the
limestone of Ançã and Outil are being extracted to
produce plates for exterior facing of walls. The
results obtained point out that the Outil limestone
has better physical and mechanical properties, and
higher durability.
At present the production of small blocks for
paving is only done in the quarries of Ançã and
Outil. The Fornos limestone can not be used for
paving because it is very heterogeneous. For the
Pena limestone the laminated layers must be avoided
because they slake easily.
Concerning the use of the limestone for masonry,
the only that should not be used is the Pena
limestone because it has a considerable swelling,
M.F. Trindade, M.O. Quinta Ferreira & R. Oliveira: Contribution to the study of Ançã limestone 7
particularly the laminated samples. The Portunhos
limestone is the most durable, the Ançã limestone
has high water absorption capacity and low strength.
For sculpture and also for ashlar masonry some
very important properties are the workability, the
colour, the homogeneity of the grain size and texture,
and a durable and unweathered rock. For this
purpose the white Ançã limestone has certainly been
the most used for several centuries, despite its high
porosity, high water absorption capacity and low
durability. The utilization of the white Ançã
limestone in artwork in several ancient monuments
showed very significant degradation with time. Some
examples in Coimbra can be found in the Old
Cathedral (Sé Velha), the Santa Cruz Church and the
old University buildings.
The white Ançã limestone is suitable for use
inside buildings, where the direct contact of water is
absent. When used outside buildings some
waterproof treatments would be recommended. The
Outil limestone is also used in ashlar masonry being
more durable than the white Ançã limestone.
The use of the limestone for rockfills has to be
analyzed according to the rockfill structure to be
built and the limestone that will be used in the
construction. The rockfills for shore protection
require blocks of large size and low weatherability.
The only case known of the use of limestone for
shore protection is the Pena limestone of quarry nº
10 that was used in the construction of the harbour
breakwater of Costa Nova (Aveiro). Recently it was
verified that this limestone is very prone to weather
as a result of wetting and drying cycles and with the
salt crystallization. Our results, as quoted in section
7.2 are in accordance with the observed behaviour.
According to the classification of Wilson &
Marsal (1979) the use of the limestones to construct
very high rockfill structures is restricted to the
Portunhos limestone that is the one with a Los
Angeles result lower than 25%. The Portunhos
limestone has also good durability and high strength.
8.2 Industry and agriculture
For the production of Portland cement, and using the
specifications of CIMPOR, the biggest Portuguese
cement company, only sample PE142 has MgO
higher than the acceptable limits. All the other
limestones have percentages of CaCO3 over 43%,
requiring their composition to be corrected adding
SiO2, Al2O3, and Fe2O3. At present there is only one
quarry (nº 14) that is producing limestone to
CIMPOR, mainly used to correct the composition of
the marly limestone extracted in the CIMPOR quarry
of Souzelas.
For the production of lime, for siderurgy and for
the chemical industry, only the Pena limestone must
be excluded because it has higher MgO content than
allowed. For filler in porcelain and faience the
limestone form quarry nº 24 can be used and also the
white Fornos limestone. For filler in paper only the
limestone of quarry nº 24 is pure enough to be used.
For the production of soil amendment quarries nº 15
and nº 24 are being used.
8.3 Present activity
At present only quarries nº 14, 15, 16 and 24 are
producing crushed rock for civil engineering
construction.
The only quarry producing rock used in the
Portland cement industry is quarry 14.
The Outil quarries only produce rock for facing
wall, paving, masonry and ashlar masonry.
All the quarries of Fornos are abandoned.
Concerning the landscape impact of the numerous
quarries in the Ançã outcrop, it can be stressed that
due to the long term extraction of rock in the area,
for more than five centuries, the residents in the area
accept very well the fact that the quarries are not
reclaimed because they consider the quarries as a
valuable resource belonging to their life style. This
situation is changing very slowly, but the Portuguese
legislation can do very little concerning to the old
abandoned quarries. For the active quarries, it can be
generally stated that the environmental protection
procedures are progressively being followed, needing
stronger effort to improve the quarries reclamation.
9 FINAL REMARKS
The Ançã limestone continues to be an extremely
valuable natural resource in the region.
In our research it was possible to identify five
limestone types with some local variations, having
different composition, properties and utilization.
The most important task for the future is the
environmental reclamation of the existing quarries,
and the preservation of the reserves still available for
a balanced development of the region.
REFERENCES
Barbosa B.P., Soares, A.F., Rocha, R.B., Manuppella, G.
& Henriques, M.H. 1988. Carta geológica de
Portugal na escala de 1:50 000. Notícia explicativa
da Folha 19 A - Cantanhede. Serv. Geol. Portugal,
Lisboa, 46p (In Portuguese).
Delgado Rodrigues, J. & Jeremias, F.T. 1990.
Assessment of rock durability through index prop-
erties. Proc. 6th Int. Cong. IAEG, Vol.4, pp.3055-
3060, Amsterdam.
Delgado Rodrigues, J. 1986. Contribuição para o estudo
das rochas carbonatadas e para a sua classificação
geotécnica. Internal report of LNEC, Lisboa (In
Portuguese).
Guifu, X. & Hong, L. 1986. On the statistical analysis of
data and strengh expression in the rock point load test.
Proc. 5th Int. Cong. IAEG. Buenos Aires.
Hamrol, A. 1961. A quantitative classification of the
weathering and weatherability of rocks. Proc. 5th Int.
Cong. Soil Mec. Found. Eng., 7/3.
M.F. Trindade, M.O. Quinta Ferreira & R. Oliveira: Contribution to the study of Ançã limestone 8
ISMR 1981. Basic geotechnical description of rock
masses. Document Nº 1. Int. J. Rock Mech. Min. Sci.
& Geomech. Abstr., Vol.18, pp.85-100.
ISRM 1985. Suggest method for determining point load
strenght. Int. J. Rock Mech. Min. Sci. & Geomech.
Abstr., Vol.22, nº2, pp.51-60.
LNEC, E236 1970. Uniaxial compressive strength test.
LNEC, Lisbon (In Portuguese).
LNEC, E237 1970. Los Angeles Abrasion test. LNEC,
Lisbon (In Portuguese).
LNEC, E238 1970. Magnesium Sulfate test. LNEC,
Lisbon (In Portuguese).
LNEC/LERO, PE-11. 1993. Test for assessing the scratch
hardness. LNEC, Lisbon (In Portuguese).
LNEC/LERO, PE-19 1993. Salt Cristalization in a Salt
Spray Chamber. LNEC, Lisbon (In Portuguese).
Manuppela, G., Moreira, J. & Romão, M. 1982. Calcários
portugueses, sua utilização industrial. Bol. Minas,
Publ. DGGM., Sep. Vol.18, nº4, Lisboa (In
Portuguese).
Neiva, J.M.C. 1989. Geologia da região de entre
Cordinhã, Ançã e Zambujeiro (Cantanhede) e os
Calcários de Ançã. 1ª jornada do G.A.A.C.
Cantanhede (In Portuguese).
RILEM 1980. Recommended test to measure the
deterioration of stone and to assess the effectiveness
of treatment methods - Tentative Recommendations.
Matériaux et Constructions, Vol.13, nº75.
Tavares, 1989. Pedra de Ançã: O Meio - O Homem - A
Arte. 1ª jornada do G.A.A.C. Cantanhede-Portugal (In
Portuguese).
Tourenq, C., Fourmaintraux, D. & Denis, A. 1971.
Propagation des ondes et descontinuités des roches.
Symp. Soc. Int. Mec. Roches, Nancy.
Trindade, F. 1994. Calcário de Ançã. Caracterização
geológica e geotécnica visando a sua utilização
industrial. MsC Thesis. Universidade Nova de Lisboa
(In Portuguese).
Wilson, S.D. & Marsal, R.J. 1979. Current trends is de-
sign and construction of embankment dams. ASCE.
Table 1. Summary of the properties of the five limestone types identified.
Sample
Ca
CO3
MgCO
3
Insol.
Res.
VL UCS
E
x10
4
υ n γd Ιar S48h C
W
equi
ε
x10
-4
H
ard.
(%) (%) (%) (m/s) (MPa)
(MPa)
(%) (kN/m3)
(%)
(g/(cm2
x
min
0.5
)
(%) (mm)
ANÇÃ
A5
94.92
1.21
3.43
4952
124
5.2
0.23
10.7
24.31
2.9
0.75
5.4
0.23
2.1
0.33
A6
95.92
1.36
2.13
5295
101
5.8
0.25
8.2
24.93
2.5
0.77
3.2
0.20
1.6
0.43
A81
96.56
1.27
2.66
5430
10.4
24.20
4.1
PE102
97.12
1.36
1.10
4624
135
4.5
0.20
12.7
23.68
4.6
0.85
6.6
0.30
1.4
PE143
95.12
1.42
3.10
4665
82
5.2
0.19
11.4
24.04
3.8
0.72
3.3
0.28
3.1
A2
94.12
1.00
4.11
3595
58
2.5
0.17
23.3
20.80
9.7
0.85
36.4
0.18
1.7
0.74
A62
98.12
1.23
1.43
18.0
23.50
6.3
A83
94.68
2.09
3.26
4207
17.7
22.30
6.0
A9
95.40
0.92
1.70
3240
37
1.9
0.21
27.0
19.90
0.90
15.9
0.10
2.0
1.09
PENA
PE101
92.12
1.44
5.3
4367
95
4.1
0.19
12.8
23.58
4.7
0.88
6.9
0.30
2.4
0.50
PE11
4.4
12.4
24.00
4.3
0.28
PE13
94.42
1.40
4990
12.0
24.80
0.97
PE141
88.61
2.20
8.0
4020
101
3.6
0.17
13.2
23.53
4.3
0.84
4.3
0.65
4.9
0.51
PE142
79.09
14.01
11.1
3491
46
2.7
0.17
16.5
22.73
6.5
0.92
8.4
1.31
8.4
0.50
A7
89.61
5.92
3.7
5521
137
6.6
0.23
7.4
25.10
2.1
0.77
2.5
0.26
1.7
0.30
A82
6.7
5487
12.1
23.70
4.5
PORTUNHOS
PO151
93.12
0.50
4.1
5889
102
8.0
0.22
2.7
26.37
0.7
0.64
1.0
0.13
1.0
0.28
PO152
96.12
0.52
2.8
5989
106
8.2
0.23
2.9
26.39
0.9
0.79
1.0
0.15
1.2
0.28
PO16
96.12
0.65
2.3
5699
108
7.6
0.21
2.6
26.69
0.8
0.74
1.0
0.14
1.4
0.29
O24
98.12
0.21
0.9
6249
139
8.7
0.24
4.1
26.13
1.3
0.71
1.4
0.11
1.0
0.25
OUTIL
O191
96.62
0.41
2.1
5096
102
5.4
0.23
10.7
24.22
3.3
0.79
5.8
0.139
1.6
0.37
O192
96.62
0.40
2.0
5005
109
5.3
0.22
11.4
24.05
4.3
0.80
5.6
0.191
1.6
0.40
0201
97.62
0.46
1.5
4831
121
5.1
0.21
9.4
24.54
3.1
0.79
5.4
0.145
1.6
0.32
0202
1.0
5144
104
5.6
0.23
9.1
24.66
3.1
0.79
6.4
0.145
1.3
0.32
FORNOS
F1
98.62
0.94
0.97
5483
55
6.4
0.22
9.1
24.65
2.8
0.70
5.8
0.122
1.4
0.38
F2
98.12
0.79
0.99
5680
58
7.1
0.24
6.5
25.39
1.1
0.50
1.8
0.136
1.4
0.22
* bm - biomicrite; bp - biosparite; c - compact; ch - chalky; f - fossiliferous; g - gray; h - heterogeneous; l - laminated; m - micrite;
ma - marly; o - oolits; om - oomicrosparite; op - oosparite; p - porous; w - white; y - yellow.
... Ançã stone is a specific limestone type from Ançã limestones Formation (Bajocian) occurring in Cantanhede municipality (Coimbra, Portugal), Fig. 1 a). This Formation has a thickness of about 250 m and comprises fine-grained limestone beds with different characteristics, either in terms of fossil's content, clay amount or engineering properties [31][32][33]. Lower beds are of greywish limestone, slightly marly, changing to light gray and yellowish to white laterally [32,33]. ...
... Hard limestone types of low porosity and high strength are exploited on different quarries located in Ançã-Portunhos-Outil region ( Fig. 1 for lime production, paving, masonry and aggregates [31,32]. ...
... Ançã limestones Formation also comprises a softer and porous type, worldwide known as Ançã stone [34]. The designation Ançã stone can be confused with "Ançã limestone" leading to believe that the entire Formation is constituted of Ançã stone [31]. ...
Article
Soft limestones are widely present in noteworthy constructions, but they are prone to decay due to their specific characteristics. In this paper, soft Ançã stone possessing a wide range of properties are analyzed to explain the degradation patterns and degradation rates that can be found in monuments and to estimate decay susceptibility. Experimental results indicated good correlations between physical, hydric and mechanical properties, allowing to propose drilling resistance and shore hardness as the key to estimate several other properties of soft limestones in-situ. Integrity loss rate of soft limestones submitted to freeze-thaw cycles, was found to be closely related to the saturation coefficient. Analytic relation to estimate decay of soft limestones and number of freeze-thaw cycles required to reach a pre-collapse state are drawn.
... The selection of a "representative" sound stone for this step is considered of outmost importance as well. It is advisable to use homogeneous, soft and white stones, composed by calcium carbonate, as much as possible (as Anç ã stone [37,38]). ...
... Highly cracked xerogel (a) and film (b) obtained from the drying of a commercial consolidant Tegovakon v 100 (Evonik), TV100. Drilling resistance increment provided by TV100 to a porous carbonate stone (Anç ã stone[37,38]). ...
Article
The need of a thoughtful methodology to support the design and development of new consolidation products in built heritage is consequence of the demanding requirements that consolidation treatments in built heritage should fulfill; of physical and chemical specificities of porous carbonate stones and of sol–gel processes complexity. Absence of well-defined planning strategies and systematic studies poses serious difficulties in what concerns validation of new sols for consolidation purposes. This work aims at discussing and to propose a methodology to support the design, development, screening and tailoring of alkoxysilane-based sols to consolidate porous carbonate stones. This methodology addresses three important steps and propose criteria to validate or exclude sols, while the knowledge acquired during the process contribute to the improvement of initial sols. The first step concerns selection of most promising sols from a set of theoretically designed “mixtures”; sols with potential to act as consolidants are assessed in the second step and, in the third step, sols for consolidation of porous carbonate stones are finally proposed. The methodology herein presented contributes to a more systematic and critical design and development of alkoxysilane-based products. It reduces the probability of failure and avoids unnecessary and time-consuming testing plans, often based on trial and error approaches.
... The Ançã limestone was used to carve the sculptural groups and all the decorative elements namely statues, columns, friezes and niches. The Ançã limestone was exploited in a region close to Cantanhede in the surrounds of Coimbra, in Portugal, and corresponds to a carbonated formation of Bajocian-Bathonian (Middle Jurassic) (Trindade et al. 1998;Barbosa et al. 2008). It is almost composed by calcite, but the presence of silica in the form of quartz is also common (Ferreira . ...
... Due to its open porosity (20-27.2%), water absorption (10-14%), low mechanical strength and frost resistance (INETI n.d.;Trindade et al 1998;Ferreira Pinto and Delgado-Rodrigues 2008;Costa and Delgado-Rodrigues 2012;Delgado-Rodrigues and Ferreira Pinto 2015) it is very susceptible to deterioration by many degradation processes, including salt damage (Costa and Delgado-Rodrigues 2012). For the structural elements of the "Porta Férrea", was applied a different stone from the same region named Outil limestone, due to its higher compression breaking load, lower porosity and water absorption (INETI n.d.). ...
Article
Full-text available
The “Porta Férrea” (Iron Gate) is the main access to the “Paço das Escolas” (University Palace) at the University of Coimbra, Portugal. It has undergone several adaptations and reconstructions from an original castle gate until the present portal that was built in 1634. The inscription of “University of Coimbra, Alta and Sofia” in the UNESCO Word Heritage list increased the interest in developing conservation works and to do the characterization of the limestone materials of the “Porta Férrea” portal. To support the conservation works, a research project was developed. The intervention plan, the sampling and testing performed and the conservation developed are presented. The rock material in the portal is the Ançã limestone, showing very high porosity around 30%, creating quite important degradation and conservation problems. The deterioration pattern, analyses performed, and the conservative works are presented. In this study it can be confirmed that Ançã limestone of “Porta Férrea” do not decay according a theoretical predictable pattern in response to polluted environments, as the defined for Portland limestone, assuming erosion rates and forms controlled by a range of micro-environment conditions particularly related with architectural constraints.
Article
This work aims at investigating and comparing the ability of novel products to act as consolidants for carbonate stones and how the lithotype and testing conditions influence the perception of their initial efficacy. Novel consolidants based in alkoxysilanes and ammonium phosphate can penetrate deeply, and have initial efficacy on porous limestone in a pre-collapse condition and on marble in granular disintegration, when applied by brushing until their apparent saturation is reached. Nevertheless, unsatisfactory consolidation outcomes can be obtained in both lithotypes due to opposite reasons, namely, insufficient strengthening ability in fissured media (marble) and over-consolidation in pore-shape stone (soft limestone). Simple strategies dealing with the treatment procedures to optimize the application processes revealed useful to “scale-up” or “scale-down” the treatments in order to better met the requirements of each lithotype. The assessment of the potential initial efficacy of consolidants requires broader approaches, since its perception depends on diverse testing parameters, such as, the pore-shape and the lithotype aging conditions.
Book
Full-text available
Carta Geológica de Portugal na escala de 1:50 000. Notícia explicativa da folha 19A – Cantanhede
Article
Deals with the influence of size and shape factors of samples on the results of rock point load tests by means of statistical analysis. In order to find out the relationship of point load test results with all of the influencing factors to establish a more rational expression, the progressive regression analysis was undertaken by use of a microcomputer. On this basis, a new expression of point load strength including all of the main influencing factors is suggested as PLS=P/A f, where PLS is the point load strength, P is the failure load, A f is the area of the surface of fracture. The expression has a definite physical meaning, and it will not be necessary to make size correction and to limit the size and the shape of samples when it is used, so it will enable the test and data processing to be simplified. -from Authors
Article
The overall performance of rockfill structures is greatly influenced by the intrinsic properties of the individual rock fragments. This feature is highly characteristic of rockfills and, therefore, makes them different from soil structures. In some specific aspects, it may even be feasible to predict that behaviour by resorting to simple tests performed directly on individual rock pieces.
Calcário de Ançã. Caracterização geológica e geotécnica visando a sua utilização industrial
  • F Trindade
Trindade, F. 1994. Calcário de Ançã. Caracterização geológica e geotécnica visando a sua utilização industrial. MsC Thesis. Universidade Nova de Lisboa (In Portuguese).