neults are

he resultsparticularrties

Journal of Colloid and Interface Science 279 (2004) 228–234www.elsevier.com/locate/jcis

On the role of organic adlayers in the anomalous water sorptivityof Lépine limestone

Ioannis Ioannoua,∗,1, William D. Hoff a, Christopher Hallb

a School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, P.O. Box 88, Manchester M60 1QD, UKb Center for Materials Science & Engineering and School of Engineering &Electronics, The University of Edinburgh, The King’s Buildings,

Edinburgh EH9 3JL, UK

Received 31 December 2003; accepted 8 June 2004

Available online 19 August 2004

Abstract

Sorptivity data are reported for the capillary absorption of water, ethanol, propan-2-ol, andn-heptane by the calcitic limestone Lépi(Lavoux à grain). The data confirm that the water sorptivity is anomalously low, an indication of partial wetting by water. Resexpressed in terms of a wetting index. The water sorptivity increases after heat treatment and chemical oxidation byhydrogen peroxidebleaching, while the sorptivity with organic liquids is unchanged. These treatments, therefore, increase the water wetting index. Tprovide strong evidence that the presence of a natural organic adlayer is responsible for the anomalously low water sorptivity of thislimestone. This natural water repellency effect may be exploited in developing chemical treatments to modify the water transport propeof stone. 2004 Elsevier Inc. All rights reserved.

Keywords:Wettability; Capillary absorption; Sorptivity; Limestone; Calcite; Wetting index

andsmade-f thetrib-ial.nrytion

r re-lidsab-r to

ize

p-idst thehisn onde-andedatar-ility

olidore

1. Introduction

There are many processes in building constructionperformance that are mediated by water[1]. Such processeinclude the degradation and decay of porous masonryterials. In stonework, salt transport and crystallizationpend on water movement through the pore structure ostone. Frost damage is directly associated with the disution of water within the capillary structure of the materThe transport of organic liquids in stone (and brick) masois also of practical importance because many preservatreatments make use of organic solvents to carry watepellents and sealants into the pore structures of the soA thorough understanding of the processes of capillarysorption and transport is, therefore, essential in orde

* Corresponding author. Fax: +357-22-89-2254.E-mail address:ioannis@ucy.ac.cy(I. Ioannou).

1 Current address: School of Engineering, University of Cyprus, 75Kallipoleos Avenue, P.O. Box 20537, 1678 Nicosia, Cyprus.

0021-9797/$ – see front matter 2004 Elsevier Inc. All rights reserved.doi:10.1016/j.jcis.2004.06.099

-

.

understand the mechanisms of weathering and to minimdamage.

In a previous paper[2], we presented data on the caillary absorption of water and a number of organic liquby a range of limestones. The experiments showed thawater sorptivities of limestones were anomalously low. Twas explained as the effect of pore surface contaminatiothe water wettability of these materials. In this paper, wescribe an investigation of the effects of heat treatmentchemical modification of theinternal pore surfaces on thabsorption properties of Lépine limestone. These newprovide strong evidence thatsurface contamination by oganic adlayers is responsible for the partial water wettabof limestones.

2. Theoretical and experimental background

The Darcian flow of liquids in an unsaturated porous sresults from the capillary forces that arise from the p

I. Ioannou et al. / Journal of Colloid and Interface Science 279 (2004) 228–234 229

s of

thene-

ehas

heowecap

nofheeres, inr-eid

-

sis

-ickynesre-aly

lsri-lt of

ofd ceonesac-ndex-

nog-thetactface

ere-to

facever,sur-obic)

e

-dily

nts,teor-rface

ch-ar-eiffera-p toHange

nialidcar-nics,e in

reat-rialhersper-snowentsng-useor-ingulti-tion

erelso

structure of the solid. The process is analyzed in termunsaturated flow theory[3,4], which is valid for all frac-tional saturations. A central result of this analysis is thattotal volume of liquid absorbed by a porous solid during odimensional capillary absorption is given by

(1)i(t) = St1/2.

Herei(t) is the cumulative volume of liquid absorbed at timt per unit area of the absorbing surface and thereforedimension [L]. Equation(1) defines the sorptivityS (dimen-sion [L T−1/2]). This square-root-of-time dependence of tcapillary absorption of liquids by masonry materials is nwell established[1,5] and the sorptivity is recognized as thmost useful fundamental parameter to characterize theillary liquid absorption properties of porous materials.

The sorptivity depends on the liquid–air surface tensioσ

and the viscosityη of the liquid and on the microstructurethe solid. For a liquid which completely wets the solid, tliquid surface is tangential to the solid at all points whliquid, air, and solid phases meet. In these circumstancea pore of radiusr, the radius of curvature of the liquid suface is equal tor. However, for partially wetting liquids, thradius of curvature of the liquid surface for a given liqucontent is increased by a factor 1/β , where we defineβ asthe wetting index(0 � β � 1). The wetting index can be interpreted as(σSA−σSL)/σ , whereσSA, σSL are the solid–airand solid–liquid interfacial tensions. Following the analygiven in[2] we can define an intrinsic sorptivitySI , which isindependent of the properties of the liquid:

(2)S = SI

(β

σ

η

)1/2

.

For those liquids that are completely wetting,β = 1, and inthese circumstances the sorptivity scales simply as(σ/η)1/2.Gummerson et al.[6] have confirmed this result for absorption of water and a range of organic liquids into brceramic. Taylor[7] further investigated this relationship btesting whether the sorptivities of concretes and limestoalso scale in a similar way to that found for ceramics. Thesults of a range of experiments indicated a marked anomduring the transport of water inboth cement-based materia[8] and limestones[2]. In the case of cementitious mateals it was shown that this water anomaly was the resuswelling associated with the hydration and rehydrationunreacted and dehydrated components of the hardenement paste. On the other hand, in the case of limestthere was no indication of microstructural change or retivity in the samples to explain this behavior. ESEM aextensometric measurements ruled out swelling as anplanation of the low water sorptivities, and there wasevidence from long-term capillaryrise tests of pore blockinor particle migration effects[2]. Additional tests with aqueous ethanol solutions suggested that the low affinity oflimestone samples for water was evidence of a finite conangle, possibly caused by the adsorption of organic surcontaminants favoring partial wettability to water.

-

-

Liquid water has a strong molecular cohesion and, thfore, must interact strongly with a solid material in orderspread across it. Hence, a high-energy (hydrophilic) suris necessary for complete wetting. Organic liquids, howehave weaker cohesion than water (reflected in a lowerface tension), and spread across a low-energy (hydrophsurface more easily.

Pure mineral calcite (CaCO3) has a high-energy surfac[9] and is naturally hydrophilic[10]. However, there is alarge amount of published data[11–13]to suggest that carbonate minerals exposed to the natural environment reaacquire organic adlayers. A layer of organic contaminaif it is present, can strongly modify the wettability of calciby reducing the affinity of its surface for water. Thus,ganic material can be used to generate a low-energy suand establish a hydrophobic state.

The literature also contains a variety of suggested teniques for destroying or removing organic material in cbonate specimens. Gaffey et al.[14] have provided evidencthat skeletal carbonate samples subjected to heating dsignificantly from similar materials as they occur in nture. Heating of skeletal samples to high temperatures (u400◦C) can degrade organic material, expel water and O−,reduce the concentration of some trace elements, and chthe mineralogy and texture of the material.

Boisseau and Juillet-Leclerc[15] have used hydrogeperoxide solution (30% w/w) to eliminate organic materin coral skeletons. H2O2 is more acidic than water. The acpH of hydrogen peroxide promotes some dissolution ofbonates, thus allowing the enhanced removal of the orgawhich are finely disseminated throughout the carbonatintercrystalline and intracrystalline voids[15].

Varying degrees of success have been reported for tments used in the removal or destruction of organic matecontained in carbonate samples. Although many researccontinue to assume that heating or soaking in hydrogenoxide solution effectively removes organic material, otherhave warned that this is not the case. Love and Woro[16] suggested that all the treatments used in experimfor the removal/destruction of organic material (includiheating for 2 h at 400◦C and soaking in a 30% hydrogen peroxide solution for 24 h) were unsatisfactory, becathey failed to accomplish the complete removal of theganic matter. The amounts of organic material remainafter each treatment differed. Harsher procedures or mple chemical treatments removed more organic material, buthey were also more likely to alter the chemical compositof the sample.

3. Experimental work

3.1. Materials and short-term sorptivity measurements

Two specimens of freshly quarried Lépine limestone wused for the capillary absorption experiments. Lépine (a

230 I. Ioannou et al. / Journal of Colloid and Interface Science 279 (2004) 228–234

(mm)

Table 1Details of limestone specimens

Specimen Limestone Origin Volume fraction porosity Dimensions (mm) Absorbing face

A Lépine France 0.21 50× 52× 80 52× 80B Lépine France 0.21 51× 54× 96 51× 96

e-geion

rou

omeses

neandtererieainsothtones on

uslyea-

onesor-nol,

y

-nvis

per-eur-

d byr to

ningec-16 hper

tileiner.con

to

a-laryure-afte

rox-

asrox-

set2 h.houtsedachd thecup-

eter-

rial.pedallyfeltingd totingper-the

ap-ot

veyndry-tion

vi-petal

known as Lavoux à grain) is the widely used name for limstone exported from the Lépine quarry at Lavoux, a villalocated 14 km east of Poitiers in the Rhône-Alpes regof France. The stone occurs inthe Callovien or Oxfordienstages of the Jurassic period and is a moderately poöolitic limestone with some shells[17]. It has uniform off-white appearance and a fine rounded texture showing snodules. Micropores occur in both the particulate phaand the matrix, which is partly well crystallized. Lépilimestone has been used extensively for constructionrestoration work both in the UK (for example, ChichesCathedral, West Sussex) and France (for example, GalLafayette, Paris). The stone is almost pure calcite. It contonly a small amount of contaminants and no dolomite. Bspecimens were cut from the same bar of Lépine limesand had previously been used by Taylor in experimentthe water absorption properties of limestones[2,7]. Speci-men details are given inTable 1.

Experiments were undertaken to confirm the anomalolow water sorptivity of each specimen. These involved msurements of the capillary absorption properties of the stusing a range of organic liquids and distilled water. Theganic liquids used were three alcohols (methanol, ethaand propan-2-ol) and a hydrocarbon (n-heptane). Laboratorreagent materials were used as received.

The experiments were carriedout at different temperatures in a temperature-controlled cabinet to provide data othe effects on the absorption process of changes in thecosity and surface tension of the liquids. A standard eximental arrangement[6,18,19]was used in which one facof the specimen was placed in contact with the liquid sface and the amount of liquid absorbed was determineweighing the specimen at appropriate intervals. In ordecontrol evaporation, the four sides of the specimen adjoithe inflow face were sealed with epoxy resin. Both the spimens and the liquids were placed in the cabinet at leastbefore each experiment to stabilize the temperature. Eximents that involved the capillary absorption of the volaorganic liquids were carried out in a sealed glass contaBetween experiments, the specimens were reduced tostant weight at 105◦C. The organic liquids were allowedevaporate in a fume cupboard before final oven drying.

3.2. Hydrogen peroxide treatments

In order to investigate the effect of chemical modifiction of the internal pore surfaces of the stone on its capilabsorption properties, a further series of sorptivity measments was carried out on one of the test specimens (A),

s

s

-

-

-

r

the latter had been repeatedly treated with hydrogen peide.

During the individual treatments, the specimen wpartly immersed in a beaker containing hydrogen peide (AnalaR, 30%) stored in the dark. The beaker wasin a sealed container at room temperature for at least 1The container was covered to maintain darkness througthe soaking period. The solution of hydrogen peroxide ufor the chemical treatments was not refreshed. After etreatment, the sample was removed from the beaker anhydrogen peroxide was allowed to evaporate in a fumeboard before final oven drying (at 50◦C). The sorptivity ofthe dry test specimen at room temperature was then dmined.

3.3. Heat treatment

Test specimen B was heated in a furnace at 400◦C forapproximately 5 h in an attempt to remove organic mateIn view of the high temperatures, the sample was stripof epoxy resin before heating. The furnace was gradubrought to the target temperature of 400◦C. Preheating othe specimen at 105◦C also took place to further minimizthe risk of any potential damage, such as cracking, resufrom the high temperatures. The specimen was allowecool down to room temperature and the epoxy resin coawas then replaced on the four sides of the specimenpendicular to the absorbing end face. The sorptivity ofsample was measured at room temperature.

4. Results and discussion

4.1. Short-term sorptivity measurements

For each specimen and for all liquids the cumulative cillary absorptioni increases linearly with the square roof the elapsed timet1/2, as illustrated inFig. 1. This re-sult allows a sorptivityS (= i/t1/2) to be derived fromeach absorption experiment. Repeated measurements hashown clearly that precise and reproducible sorptivities mabe measured. The results arenot influenced by the order iwhich the liquids are absorbed. Repeated wetting anding also seems to have no effect on the capillary absorpproperties of the specimens.

When sorptivity values are plotted against(σ/η)1/2, thedata points fall into two groups, with the water sorptities lying on a straight line of significantly smaller slo(Fig. 2). This confirms the findings of previous experimen

I. Ioannou et al. / Journal of Colloid and Interface Science 279 (2004) 228–234 231

Fig. 1. Cumulative capillary absorptioni versus t1/2 for water and organic liquids into Lépine limestone. (1) water; (Q) ethanol; (+) propan-2-ol;(2) n-heptane.

Fig. 2. SorptivityS versus(σ/η)1/2 graphs for water and organic liquid absorption into two different Lépine limestone specimens. (1) water; (Q) ethanol;(+) propan-2-ol; (2) n-heptane.

rate

nic

,

heedly

n in

ntne,hichex-s of, arene.tss.

ar-

ersity

heased

Table 2Intrinsic sorptivities and water-wetting indices

Specimen Intrinsic sorptivity (10−5 m1/2) Wetting index

A 1.92 0.33B 1.85 0.37

work [7], which first showed that the limestones demonsta marked water anomaly.

The linear plots illustrated inFig. 2 define the wettingindex β . We see that, for the low surface tension orgaliquids, as a group, the sorptivityS scales as(σ/η)1/2. Weare, therefore, justified in assuming that for these liquidsthere is complete wetting and the wetting indexβ = 1. Us-ing Eq.(2), we then calculate the intrinsic sorptivities of ttwo limestone specimens. For water, the slopes are marklower, indicating partial wetting. The wetting indexβ forwater absorption into the two limestone samples is giveTable 2.

A wetting indexβ < 1 in a porous medium is equivaleto a finite dynamic contact angle. In the Lépine limestowe ascribe this to an adlayer of organic contaminants wproduces a low energy hydrophobic calcite surface. Thetent of this effect may depend on the amounts and typeorganic material present in the specimen. These, in turnaffected by the grain size and the mineralogy of the stoMüller and Suess[20] found that fine-grained sedimengenerally contain more organic matter than coarser one

4.2. Hydrogen peroxide treatment

The results of the capillary absorption experiments cried out after 17 hydrogen peroxide treatments (Fig. 3) pro-vide further evidence that naturally occurring surface layof organic contaminants are responsible for the low affinfor water of Lépine limestone. The water sorptivity of ttreated specimen, measured at room temperature, incresteadily with the number of treatments (Table 3). Conse-

232 I. Ioannou et al. / Journal of Colloid and Interface Science 279 (2004) 228–234

nictreat-

one

altedfec-nal

pec-e toicalon onic

on

enical

inor-

ntsrox-

d innaler-ven

nflu-ctssid-hegen

beugh-ult,ial.gleche orn themine-nengtane,

de-entanicat-ed,

iq-ment.t-

Fig. 3. S versus(σ/η)1/2 graph for the absorption of water and orgaliquids into Lépine limestone specimen A, before and after seventeenments with hydrogen peroxide. (2) water, (Q) ethanol,(+) propan-2-ol,(1) n-heptane (all before H2O2 treatments); (!) water, (—) n-heptane,(P) ethanol (all after H2O2 treatments).

Table 3Short-term sorptivity data for the absorption of water into Lépine limestspecimen A, after individualhydrogen peroxide treatments

Number of hydrogen peroxide treatments Sorptivity (mm min−1/2 )

0 0.741 0.793 0.826 0.89

11 0.9312 0.9513 0.9715 0.9817 0.99

Note. The data have been normalized to a reference temperature (21◦C) byapplying the correction factor(σRηT/σTηR)1/2 [6].

quently, the wetting indexβ also increased from the originvalue of 0.33 to a final value of 0.59. This can be attributo the fact that the strong oxidant hydrogen peroxide eftively removed organic material, thus modifying the interpore surfaces of the stone.

The change observed in the sorptivity of the treated simen (and the wetting index) could also have been duthe alteration of carbonate material itself by the chemtreatment or, indeed, by some unassessable combinaticarbonate composition modification and removal of orgamaterial[16]. However, the results of capillary absorptimeasurements using organic liquids (Fig. 3) show that the in-trinsic sorptivity is unchanged after treatment with hydrogperoxide. This is an indication that no significant chemor structural changes occurred in the test specimen.

As shown by the experimental results, multiple (17number) hydrogen peroxide treatments were required inder to destroy significant portions of organic contaminaand increase the sorptivity of the Lépine sample by app

f

imately 35%. Despite the measurable change observethe sorptivity of the test specimen, the fact that the fiwetting indexβ < 1 suggests that soaking in hydrogen poxide failed to remove completely the organic material, eafter consecutive treatments. Grattoni et al.[21] note thatthe thickness of the adsorbed contaminant does not ience wettability. As long as a film is preserved, no effeof partial dissolution can be expected. Hence, a little reual contamination is likely to influence the wettability of tlimestone, even after a series of treatments with hydroperoxide.

Removal of organic material by bleaching is likely toincomplete, since organics are finely disseminated throout the surface of the entire sample. This makes it difficif not impossible, to eliminate all of the adsorbed materGant and Anderson[22] suggest that, in many cases, a sinsolvent is relatively ineffective in cleaning a sample. Mubetter results can, therefore, be obtained with a mixturseries of solvents. The best choice of solvents depends oparticular mineral surface, because the latter helps deterthe amount and type of wettability altering compounds adsorbed. Cuiec[23] found that both sandstone and limestocores could be effectively cleaned by flowing the followiseven solvents through the core: pentane, hexane, hepcyclohexane, benzene, pyridine, and ethanol.

4.3. Heat treatment

Fig. 4 suggests that the heat treatment succeeded instroying most of the organic contaminants originally preson the surface of test specimen B. The water and orgliquid data fall almost on a single straight line after the trement. Whilst the intrinsic sorptivity remained unchang

Fig. 4.S versus(σ/η)1/2 graph for the absorption of water and organic luids into Lépine limestone specimen B, before and after the heat treat(2) water, (Q) ethanol,(+) propan-2-ol, (1) n-heptane (all before treament); (!) water, (—)n-heptane, (P) ethanol,(×) propan-2-ol (all afterthe heat treatment).

I. Ioannou et al. / Journal of Colloid and Interface Science 279 (2004) 228–234 233

alhatce aultsthe

tent

td

bateeralhen

radatelyrallynal

e-onlyonsthis

en

nictom-O

ef-in

t thein

y bene,wa

rs, bey ofingrtiala-

ur-

ncer-thesis

ss,e-nce

ndpur-imilar

inay

he

st toding

nrbed

nee andnatesur-ionedbutneer re-hiche one be-ence

rys-theand,,s-

anic

liq-thetogen

rp-videf or-

ve ation.the

the wetting indexβ for water increased from the originvalue of 0.37 to a final value of 0.92, hence indicating tthe limestone specimen behaves as a high energy surfater the destruction of organic contaminants. These resprovide strong evidence that the anomaly observed inwater sorptivity of Lépine limestones was to a great exthe result of a contact angle effect.

Both Anderson[13] and Thomas et al.[12] suggest thamost of the wettability-altering compounds exhibit enhancesolubility at elevated temperatures. Hence, some adsormay desorb from the surface of the sample, as the tempture increases. Gaffey et al.[14] argue that organic materiacontained in carbonate samples breaks down rapidly wheated to temperatures of 100◦C or higher. Even thoughdetails of the processes and mechanisms of thermal degtion of organic compounds are complex and not compleunderstood, it is believed that thermal degradation geneinvolves depolymerization, bond scission, loss of functiogroups, formation of free radicals and evolution of H2O, CO,and CO2.

Love and Woronow[16] state that heating does not rmove the organic material from carbonate samples, butchars it. This view is strongly supported by the observatimade during the heat treatment experiments described inpaper: after the sample was heated at 400◦C for 5 h, a layerof black crust appeared on the top surface of the specimpossibly indicating the formation of a carbon residue.

The measurements of the capillary absorption of orgaliquids by the heat-treated specimen (Fig. 4) also suggesthat heating has no significant effect on the chemical cposition of the limestone. This is due to the fact that CaC3is stable at temperatures greater than 350–375◦C [14]. Itmay, therefore, be concluded that heat treatment is anfective method of destroying organic material containedlimestone or other carbonate material.

4.4. Practical significance of the results

Taken together, the results provide good evidence thacapillary absorption of water into Lépine limestone usedthe construction of stone buildings and monuments maretarded by the effects of partial wetting. Lépine limestotherefore, has a degree of natural resistance to capillaryter absorption.

This finding is significant in relation to practical mattein stone construction and especially stone conservationcause many of the processes which control the durabilitthe built fabric are mediated by water. Naturally occurrsurface contaminants protect the stone by favoring pawettability to water. Because of the anomalously low wter sorptivity of Lépine limestone, the time to reach sface saturation,ts, in absorption at constant flux,V0 (forexample, driving rain), is expected to be reduced, sits = 0.64S2/V 2

0 [24]. The reduction in sorptivity due to patial wetting is also expected to have a similar impact oncapillary rise of water in stone buildings. A simple analy

f-

s-

-

,

-

-

shows that the height of capillary riseH , which is a dynamicequilibrium between the upward flow and evaporative lois given byH = S/(2ef )1/2, wheree is the evaporation ratand f the porosity of the solid[1]. The organic contaminants are, therefore, generally beneficial to the performaof a stone building.

The results also hint that, for both freshly quarried aold limestones, there may be value for conservationposes in chemical treatments based on substances sto those which are known to adsorb strongly on calcitenature. Organic acids (such as fulvic and humic acid) mbe used to modify the wettability of calcite by reducing taffinity of its surface for water; artificial oxalate and tartratetreatments have been used in a similar way in the paprotect stone against acid rain and enhance surface bonwith silica gel consolidants[25]. Organic acids are found isoils and groundwater and can be coprecipitated or adsoon to the surfaces of growing calcite crystals[26]. Chem-ical modification of the internal pore surfaces of the stousing such substances is expected to be able to reinforcenhance the naturally occurring alteration of the carbomineral surface, by building up permanent monolayerface films, whilst avoiding, at the same time, the formatof pore blocking deposits. Hence, not only will unimpedvapor diffusion occur during the later stages of drying,also liquid water movement will occur from within the stoto the surface. The latter is suppressed by the use of watpellents (silicones/siliconates or aluminum stearates) ware the protective surface treatments currently availablthe market. As a result, salts are encouraged to crystallizhind the treated surface and the resulting cryptoflorescusually leads to damage.

Finally, we note that Scherer has argued[27] that themagnitude of the stress which develops during the ctallization of salts within building stones depends onshort-range forces acting at the salt–mineral interfacetherefore, on the mineral surface chemistry. If this is sothe stress, and therefore the damage, caused by salt crytallization in limestones may depend on whether an orgadlayer is present or not.

5. Conclusions

Data on the capillary absorption of water and organicuids in two specimens of Lépine limestone confirm thatwater sorptivity of this stone is anomalously low. Heatinghigh temperatures and numerous treatments with hydroperoxide, followed by a further series of capillary absotion measurements using water and organic liquids, prostrong evidence that naturally occurring surface layers oganic contaminants are responsible for the partial wettabilityof this type of limestone.

The experimental results suggest that limestones hadegree of natural resistance to capillary water absorpChemical modification of the internal pore surfaces of

234 I. Ioannou et al. / Journal of Colloid and Interface Science 279 (2004) 228–234

rbeet-for

Rendail-ar-

te,

e

.1.

i.

)

01.

.

-

ch-

g.,

ini,ton-

)

stones with substances similar to those which are adsofrom the natural environment could further reduce the wtability of limestones. Such a treatment could be of valueconservation purposes.

Acknowledgments

The authors acknowledge support from the Overseassearch Students Awards Scheme, the A.G. Leventis Foution, and the Royal Society. They also thank Dr. Moira Wson and Dr. Vicky Pugsley for their comments and Dr. Mgaret Carter for advice on chemical treatments.

References

[1] C. Hall, W.D. Hoff, Water Transport in Brick, Stone and ConcreSpon Press, London, 2002.

[2] S.C. Taylor, C. Hall, W.D. Hoff, M.A. Wilson, J. Colloid InterfacSci. 224 (2000) 351.

[3] J.R. Philip, Adv. Hydrosci. 5 (1969) 215.[4] C. Hall, Mater. Struct. 27 (1977) 117.[5] R.J. Gummerson, C. Hall, W.D. Hoff, Construct. Pap. 1 (1980) 17[6] R.J. Gummerson, C. Hall, W.D. Hoff, Build. Environ. 15 (1980) 10

d

--

[7] S.C. Taylor, PhD thesis, UMIST, Manchester, 1998.[8] S.C. Taylor, W.D. Hoff, M.A. Wilson, K.M. Green, J. Mater. Sc

Lett. 18 (1999) 1925.[9] T. Okayama, D.S. Keller,P. Luner, J. Adhes. 63 (1997) 231.

[10] W. Jang, J. Dreuch, J.D. Miller, Langmuir 11 (1995) 3491.[11] P.W. Carter, R.M. Mitterer, Geochim. Cosmochim. Acta 42 (1978

1231.[12] M.M. Thomas, J.A. Clouse, J.M. Longo, Chem. Geol. 109 (1993) 2[13] W.G. Anderson, J. Pet. Technol. 38 (1986) 1125.[14] S.J. Gaffey, J.J. Kolak, C.E. Bronnimann, Geochim. Cosmochim

Acta 55 (1991) 1627.[15] M. Boisseau, A. Juillet-Leclerc, Chem. Geol. 143 (1997) 171.[16] K.M. Love, A. Woronow, Chem. Geol. 93 (1991) 291.[17] Honeyborne, D.B., The Building Limestones of France, Building Re

search Establishment Report, HMSO, London, 1982.[18] C. Hall, T.K.M. Tse, Build. Environ. 21 (1986) 113.[19] C. Hall, Mag. Concrete Res. 41 (1989) 51.[20] P.J. Müller, E. Suess, Geochim. Cosmochim. Acta 41 (1977) 941.[21] C.A. Grattoni, E.D. Chiotis, R.A. Dawe, J. Chem. Technol. Biote

nol. 64 (1995) 17.[22] P.L. Gant, W.G. Anderson, Soc. Pet. Eng. Paper 14,875, Soc. Pet. En

Richardson, TX, 1985.[23] L.E. Cuiec, J. Can. Pet. Technol. 16 (1977) 68.[24] C. Hall, A.N. Kalimeris, Build. Environ. 17 (1982) 257.[25] E. Hansen, E. Doehne, J. Fidler, J. Larson, B. Martin, M. Matte

C. Rodríguez-Navarro, E.S. Pardo, C. Price, A. de Tagle, J.M. Teuico, N. Weiss, Rev. Conserv. 4 (2003) 13.

[26] S.F. McGarry, A. Baker, Quaternary Sci. Rev. 19 (2000) 1087.[27] G.W. Scherer, R. Flatt, G. Wheeler, Mater. Res. Soc. Bull. 26 (2001

44.