leor an unproven issue?

b

c

d

a

AR raw materials, transportation or orientation and polycondensation of the reaction products. Publications

ated binders, state that this new material is likely to have high potential to

This paper presents a review of the literature about the durability of alkali-activated binders. The subjectsof this paper are resistance to acid attack, alkalisilica reaction, corrosion of steel reinforcement, resis-

. . . . . .

. . . . . .

The production of one tonne of OPC generates 0.55 tonnes of chem-ical CO2 and requires an additional 0.39 tonnes of CO2 in fuel emis-sions for baking and grinding, accounting for a total of 0.94 tonnes ofCO2 [2]. Other authors [3] reported that the cement industry emit-ted in 2000, on average, 0.87 kg of CO2 for every kg of cement

carbon dioxide emissions and the fact that OPC structures whichhave been build a few decades ago are still facing disintegrationproblems points out the handicaps of OPC. Portland cement basedconcrete presents a higher permeability that allowswater and otheraggressive media to enter leading to carbonation and corrosionproblems. The early deterioration of reinforced concrete structuresbased on Ordinary Portland cement (OPC) is a current phenomenonwith signicant consequences both in terms of the cost for the reha-bilitation of these structures, or even in terms of environmental

Corresponding author. Tel.: +351 253 510200; fax: +351 253 510213.

Construction and Building Materials 30 (2012) 400405

Contents lists available at

B

evE-mail address: torgal@civil.uminho.pt (F. Pacheco-Torgal).3. Alkalisilica reaction (ASR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4024. Corrosion of steel reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4025. Resistance to high temperatures and to fire. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4036. Resistance to freezethaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4037. Efflorescences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4038. Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404

1. Introduction

With an annual production of almost 3 Gt Ordinary Portland ce-ment (OPC) is the dominant binder of the construction industry [1].

produced. As a result the cement industry contributes about 7% ofthe totalworldwide CO2 emissions [4]. The projections for the globaldemand of Portland cement show that in the next 40 years it willhave a twofold increase reaching 6 Gt/year [5]. The urge to reduceKeywords:Alkali-activated bindersOrdinary Portland cementEco-efciencyDurabilityEforescences

Contents

1. Introduction . . . . . . . . . . . . . . . . .2. Resistance to acid attack . . . . . . .0950-0618/$ - see front matter 2011 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2011.12.017tance to high temperatures and to re, resistance to freezethaw. Special attention is given to the caseof eforescences, an aspect that was received very little concern although it is a very important one.

2011 Elsevier Ltd. All rights reserved.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401Accepted 4 December 2011 become an alternative to Portland cement. While some authors state that the durability of these materialsconstitutes the most important advantage over Portland cement others argue that its an unproven issue.Received in revised form 28 November 2011 on the eld of alkali-activUniversity of Minho, C-TAC Research Unit, Guimares, PortugalUniversity of Minho, Department of Civil Engineering, Guimares, PortugalDepartment of Polymer, Building and Housing Research Center (BHRC), Amirkabir University of Technology, Tehran Polytechnic, IranState Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China

r t i c l e i n f o

rticle history:eceived 6 September 2011

a b s t r a c t

The alkali activation of alumino-silicate materials is a complex chemical process evolving dissolution ofF. Pacheco-Torgal , Z. Abdollahnejad , A.F. Camesaa, a b, M. Jamshidi c, Y. Ding dReview

Durability of alkali-activated binders: A c

Construction and

journal homepage: www.elsll rights reserved.ar advantage over Portland cement

SciVerse ScienceDirect

uilding Materials

ier .com/locate /conbui ldmat

nd Bimpacts associated with these operations. Research works [68]carried out so far in the development of alkali-activated cementsshowed that much has already been investigated and also that anenvironmental friendly alternative to Portland cement is rising.Davidovits et al. [9] was the rst author to address the carbon diox-ide emissions of these binders stating that they generate just 0.184tons of CO2 per ton of binder. Duxson et al. [10] do not conrm thesenumbers; they stated that although the CO2 emissions generatedduring the production of Na2O are very high, still the productionof alkali-activated binders is associated to a level of carbon dioxideemissions lower than the emissions generated in the production ofOPC. According to those authors the reductions can go from 50% to100%. Duxson andVanDeventer [11]mention an independent studymade by Zeobond Pty. Ltd. in which a low emissions Portland ce-ment (0.67 ton/ton) and alkali-activated binders were compared,reporting that the latter had 80% lower CO2 emissions. Weil et al.[12] mentioned that the sodium hydroxide and the sodium silicateare responsible for the majority of CO2 emissions in alkali-activatedbinders. These authors compared Portland cement concrete and al-kali-activated concrete with similar durability reporting that latterhave 70% lower CO2 emissions which conrmed the aforemen-tioned reductions. McLellan et al. [13] reported a 44% to 64% reduc-tion in greenhouse gas emissions of alkali-activated binders whencompared to OPC. Habert et al. [14] carry out a detailed environ-mental evaluation of alkali activated binders using the Life CycleAssessmentmethodology conrming that they have a lower impacton globalwarming thanOPCbut on the other side they have a higherenvironmental impact regarding other impact categories. The highcost of alkali-activated binders is one of themajor factorswhich stillremain a severe disadvantage over Portland cement [14]. Therefore,investigations about the replacement of waterglass by sodic wastesare needed [15]. Currently alkali-activated binders only becomeseconomic competitive for high performance structural purposes,because the cost of alkali-activated concretes is locatedmidway be-tween OPC concretes and high performance concretes. Since theaverage ERMCO concrete class production lies between C25/30and C30/37 and only 11% of the concrete ready-mixed productionis above the strength class C35/45 [16], this means that alkali-acti-vated binders are targeting a small market share. Therefore, in theshort term the above cited disadvantage means that the study of al-kali-activated applications should focus on high cost materials suchas, commercial concrete repair mortars. Pacheco-Torgal [1720]showed that alkali-activated mortars can be as much as 7 timescheaper than current commercial repair mortars thus pointing aviable alternative for alkali-activated binders. These materials arestill at the beginning stages of development and hence need furtherresearchwork in order to become technically and economically via-ble constructionmaterials. Besides the durability of alkali-activatedbinder is a subject of some controversy, while Duxson et al. [10]state this is the most important issue on determining the successof these newmaterials and other authors [21] mention that the factthat samples from the former Soviet Union that have been exposedto service conditions for in excess of 30 years showing little degra-dation means that geopolymers do therefore appear to stand thetest of time. But since those materials were of the (Si + Ca) type thatconclusion cannot be extended to geopolymers dened as alkalialuminosilicate gel, with aluminium and silicon linked in a tetrahedralgel framework [11]. On the other side Juenger et al. [1] argue thatThe key unsolved question in the development and application of alkaliactivation technology is the issue of durability andmore recently VanDeventer et al. [22] recognized that whether geopolymer concretesare durable remains the major obstacle to recognition in standardsfor structural concrete. In this work relevant knowledge about the

F. Pacheco-Torgal et al. / Construction adurability alkali-activated cements will be reviewed. The subjectsof this paper are as follows:2. Resistance to acid attack

Several authors reported that chemical resistance is one of themajor advantages of alkali-activated binders over Portland cement.Glukhovsky [23], used alkali-activated slag mortars noticing thatthey showed increase tensile strength even after being immersedin lactic and hydrochloric acid solutions (pH = 3). Other authors[24] studied the exposure of alkali-activated slag mortars duringsix months in 5% acid solution concentration, reporting that for cit-ric acid changes were low, for nitric and hydrochloric acid changeswere moderate although severe changes was noticed when sul-phuric acid was used. Davidovits et al. [9] reported mass lossesof 6% and 7% for alkali-activated binders immersed in 5% concen-tration hydrochloric and sulphuric acids during 4 weeks. For thesame conditions he also reported that Portland cement based con-cretes suffered mass losses between 78% and 95%. Palomo et al.[25] studied metakaolin mixtures activated with NaOH and water-glass when submitted to, sulphuric acid (pH = 3), sea water(pH = 7) and sodium sulphate (pH = 6), during 90 days. They re-ported a minor exural strength decrease from 7 to 28 daysimmersion, between 28 and 56 days exural strength rises,decreasing again from 56 to 90 days and rising from that day for-ward. They reported that behaviour was similar to the several acidsolutions. According to these authors, unreacted sodium particlesare not in the structure of the hardened material, remaining in asoluble condition thus when in contact with a solution they areleached increasing the binder porosity and lowering mechanicalstrength. On the other hand, strength increase after 3 months indi-cates that the reaction process is still evolving, with the formationof zeolitic precipitates (faujasite) thus lowering porosity andincreasing strength. Shi and Stegmann [26] compared the acidresistance of several binders; alkali-activated slags (AASs), OPCbinders, y ash/lime binders (FAL) and high alumina cement(AC), when immersed in nitric (pH = 3) and acetic (pH = 3 e 5) acidsolutions. They reported that OPC binders presented higher masslosses than AAS and FAL binders while AC pastes were completelydissolved. According to these authors, OPC pastes are more porousthan AAS but less porous than FAL pastes, so chemical attack ismore inuenced by the nature of hydration products than fromporosity. They also reported that low pH acids are responsible forthe highest chemical attack. Bakharev et al. [27] also comparedOPC and alkali-activated slag concrete resistance to sulphat attack,reporting that the former showed a lower strength reduction, thatcould be explained due to the binder structure chemical differ-ences. Bakharev et al. [28] studied OPC and slag concretes activatedwith NaOH and waterglass, immersed in an acetic acid solution(pH = 4) during one year. They reported a 33% strength loss forthe former and 47% for OPC concretes. They claim that the strengthloss is inuenced by Ca content, 64% for OPC concretes and just 39%for alkali-activated slag concretes. Besides slag compounds havelower Ca/Si molar ratio and are more stable in acid medium. Asfor OPC concrete calcium compounds, they possess high Ca/Si mo-lar ratios and react with acetic acid forming acetic calcium com-pounds which is very soluble. They concluded that concreteswith less free calcium have a higher performance in acid medium.The work of Song et al. [29] also conrm that alkali-activated yash concretes possess high chemical resistance, when immersedin a 10% concentration sulphuric acid solution during 8 weeks, theyshowedmass and strength losses respectively of 3% and 35%. Gour-ley and Johnson [30] mentioned that a Portland cement concretewith a service life of 50 years lose 25% of its mass after 80 immer-sions cycles in a sulphuric acid solution (pH = 1) while an alkali-activated concrete required 1400 immersions cycles to lose the

uilding Materials 30 (2012) 400405 401same mass, thus meaning a service life of 900 years. Pacheco-Torgal et al. [31] mentioned an average mass loss of just 2.6% after

being submitted to the attack of (sulphuric, hydrochloric and ni-tric) acids during 28 days, while the mass loss for Portland cementconcretes is more than twice that value. Those authors mentionthat weight loss results for mine waste binders are not very depen-dent from the type of acid, however, other authors [3234] reportdifferent results for geopolymers based on y ash and blast furnaceslag.

3. Alkalisilica reaction (ASR)

The chance of ASR may take place in alkali-activated binders isan unknown subject. For OPC binders, however, the knowledge ofASR has been intensively studied; therefore some explanationscould be also applied to understand the possibility of ASR when al-kali-activated binders are used. ASR was reported by the rst timeby Stanton [35] and needs the simultaneous action of three ele-ments in order to occur: (a) enough amorphous silica, (b) alkalineions and (c) water [36]. The ASR begins when the reactive silicafrom the aggregates is attacked by the alkaline ions from cementforming an alkalisilica gel, which attracts water and starts to ex-pand. The gel expansion leads to internal cracking, what have beenconrmed by others [37] reporting 4 MPa pressures. Those internaltensions are higher than OPC concrete tensile strength, thus lead-ing to cracking. However some authors believe that ASR is not justa reaction between alkaline ions and amorphous silica but also re-quires the presence of Ca2+ ions [38]. Davidovits [39] compared al-kali-activated binders and OPC binders when submitted to theASTM C227 mortar-bar test, reporting a shrinkage behaviour inthe rst case and a serious expansion for the OPC binder. Other

authors [40] reported some expansion behaviour for alkali-acti-vated binders although smaller than for OPC binders. However,Puertas [41] believe ASR could occur for alkali-activated slag bind-ers containing reactive opala aggregates. Bakharev et al. [42] com-pared the expansion of OPC and alkali-activated binders reportingthat the rst ones had higher expansion. This is clear from themicrostructure analysis (Fig. 1). Garca-Lodeiro et al. [43] showedthat alkali-activated y ash is less susceptible to generate expan-sion by alkalisilica reaction than OPC. They also showed thatthe calcium plays an essential role in the expansive nature of thegels. Recent investigations [44] show that siliceous aggregatesare more prone to ASR than calcareous aggregates in alkali-acti-

resistance similar to the one OPC binders. Miranda et al. [47] even

402 F. Pacheco-Torgal et al. / Construction and Building Materials 30 (2012) 400405Fig. 1. Alkali-activated concrete after 10 months curing. (A) Reactive aggregate. (G)Alkalisilica gel [42].Fig. 2. Transverse sections of carbonated alkali-activated slag concretes after 1000 h ofphenolphthalein indicator. Samples are 76.2 mm in diameter [50].demonstrated that alkali-activated y ash binders have superiorpH conditions than OPC binders. They reported that pH decreasedwith hydration reaction development, however an alkaline condi-vated mixtures. Therefore the study of ASR, in alkali-activatedbinders is not a closed subject, at least for the mixtures containingcalcium.

4. Corrosion of steel reinforcement

The corrosion of steel reinforcement is one the causes that inu-ences the structural capability of concrete elements. As concreteattack depends on its high volume and therefore is not of greatconcern, an attack to the steel reinforced bars is a serious threateased by the fact that steel bars are very near of concrete surfaceand are very corrosion sensitive. In OPC binders, steel bars are pro-tected by a passivity layer, due to the high alkalinity of calciumhydroxide. The steel bars corrosion may happen if pH decreasesthus destroying the passivity layer, due to carbonation phenome-non or chloride ingress. The steel corrosion occurs due to an elec-trochemical action, when metals of different nature are inelectrical contact in the presence of water and oxygen. The processconsists in the anodic dissolution of iron when the positivelycharged iron ions pass into the solution and the excess of nega-tively charged electrons goes to steel through the cathode, wherethey are absorbed by the electrolyte constituents to form hydroxylions. These in turn combine with the iron ions to form ferrichydroxide, which then converts to rust. The volume increase asso-ciated with the formation of the corrosion products will lead tocracking and spalling of the concrete cover. For alkali-activatedbinders the literature is small about its capability to prevent rein-forced steel corrosion. Some studies about chloride diffusionclearly show that alkali-activated binders are able to prevent theingress of harmful elements that could start steel corrosion. Royet al. [45] compared chloride diffusion for OPC and alkali-activatedbinders reporting that the former presented almost half of the dif-fusion values of the OPC binders. Saraswathy et al. [46] studied al-kali-activated y ash mixtures reporting a steel corrosionexposure to a 1% CO2 environment, with the extent of carbonation revealed by a

search about reinforced steel corrosion is therefore needed, con-

spalling behaviour. The internal pore structure of the latter allows

7. Eforescences

The subject of eforescences in alkali-activated binders is rela-tively new, since very few authors have addressed this problem.According to Skvara et al. [65,66] the bond between the sodiumions (Na+) and the aluminosilicate structure is weak and that ex-plains the leaching behaviour. According to those authors in thecrystalline zeolites the leaching of sodium is negligible contraryto what happens in the aluminosilicate polymers. It is the presenceof water that weakens the bond of sodium in the aluminosilicatepolymers, a behaviour that is conrmed by the alkali-activatedbinder structure model. Pacheco-Torgal and Jalali [67] also foundthat sodium eforecences are higher in alkali-activated bindersbased on aluminosilicate prime materials calcined at a tempera-ture range below the dehydroxylation temperature with the addi-tion of sodium carbonate as a source of sodium cations (Fig. 3).Temuujin et al. [68] refer that although ambient cured y ash alka-li-activated binders exhibited eforescences that phenomena doesnot occur when the same alkali-activated binders are cured at ele-vated temperature which means the leachate sodium could be asign of insufcient geopolymerisation. Recently Van Deventeret al. [69] recognized that current two part geopolymers sufferfrom severe eforescence which is originated by the fact thatalkaline and/or soluble silicates that are added during processingcannot be totally consumed during geopolymerisation. Only re-cently Kani et al. [70] showed that eforescences can be reducedeither by the addition of alumina-rich admixtures or by hydrother-mal curing at temperatures of 65 C or higher. These authors foundthat the use of 8% of calcium aluminate cement greatly reduces themobility of alkalis leading to minimum eforescences (this cementhas 28% of CaO) (Fig. 4). These results are very important because

nd Building Materials 30 (2012) 400405 403a quick escape of the water vapour resulting in lower internal porepressure.

6. Resistance to freezethaw

According to Yunsheng and Wei [59] alkali-activated y ash canwithstand 2.2 times more freezethaw cycles as compared to con-crete made from OPC with the same compressive strength. Dolezalet al. [60] reported the loss of only 30% of the resistance in alkali-activated y ash binders after being subjected to 150 freezethawcycles. Other authors [61] analyzed the resistance of alkali-acti-vated slag-waste shales based binders reporting a high compres-sive strength even after freezethaw 100 cycles. Slavik et al. [62]obtained high freezethaw resistance in alkali-activated bindersbased on uidized bed combustion bottom ash. The investigationsof Brooks et al. [63] conrm the high resistance to freezethaw ofcerning alkalinity stability with curing time, as well as aboutchloride diffusion and carbonation resistance.

5. Resistance to high temperatures and to re

Concretes based on Portland cement show a weak performancewhen subjected to a thermal treatment and when the temperaturerises above 300 C they begin to disintegrate. As to the alkali-acti-vated binders they show a high stability when submitted to hightemperatures even around 1000 C [52]. Other authors [53] studiedthe activation of metakaolin and shale wastes reporting a highmechanical performance after a thermal phase. The specimensshow some slight strength loss between 600 C and 1000 C, how-ever in some cases they show a strength increase at 1200 C. Konget al. [54] studied alkali-activated metakaolin binders observingthat the residual strength after a thermal phase up to 800 C isinuenced by the Si/Al ratio. The higher residual strength was ob-tained by the mixtures with a Si/Al ratio between 1.5 and 1.7. Kri-venko and Guziy [55] found that alkali-activated binders show ahigh performance in the resistance to re, thus suggesting that thismaterial is suitable for use in works with a high re risk like tun-nels and tall buildings. Pern et al. [56] conrmed that alkali-acti-vated binders can be used as a 120 min anti-re material inaccordance with related standards of the Czech Republic. Theanti-re material must show a temperature lower than 120 C inthe opposite side of the re action. Temuujin et al. [57] used alka-li-activated binders as steel coatings stating that they maintainedhigh structural integrity even after being submitted to a heat treat-ment by a gas torch. Zhao and Sanjayan [58] compared the perfor-mance of OPC concrete and alkali activated concrete under thestandard curve re test mentioning that only the former exhibittion remained even after 5 years, since carbonation phenomenonad not take place. Aperador et al. [48] mention that alkali-activatedslag concrete is associated to poor carbonation resistance a majorcause for corrosion of steel reinforcement. Bernal et al. [49] showsthat the activation of granulated blast furnace slag (GBFS)metaka-olin (MK) blends have low carbonation resistance. The sameauthors [50] found that alkali-activated slag concretes presentsome susceptibility to carbonation which depends on the bindercontent (Fig. 2). Lloyd et al. [51] show that geopolymer cement isprone to alkali leaching leading to a reduction in the pH which isessential to prevent steel corrosion. They also mention that thepresence of calcium is crucial for having durable steel-reinforcedconcrete which is a setback for SiAl geopolymers. Further re-

F. Pacheco-Torgal et al. / Construction athe alkali-activated binders. More recently Fu et al. [64] studied al-kali-activated slag concrete reporting an excellent freezethawresistance.Fig. 3. Alkali-activated mine mortars specimens after water immersion: Above

mortars based on plain mine waste mud calcined at 950 C for 2 h; Below mortarsbased on mine waste mud calcined at different temperatures with sodiumcarbonate [67].

nd Bthey constitute a step back in the development of alkali-activatedbinders. For one the use of hydrothermal curing has serious limita-tions for on-site concrete placement operations. On the other handthe use of calcium based mixtures reduces the acid resistance andraises the chances for the occurrence of ASR. Besides the use ofsuch calcium content reduces the global warming emissionsadvantage over Portland cement.

8. Conclusions

The literature review about the durability of alkali-activatedbinders shows that:

(a) New investigations are needed on the use of sodic wastes toreplace sodium silicate in order to reduce the cost of thesematerials.

(b) The new binders present higher chemical resistance, how-

Fig. 4. Effect of admixtures on alkali leaching (as a proxy for eforescence extent)[70].

404 F. Pacheco-Torgal et al. / Construction aever it seems that depends more on the low content of sol-uble calcium compounds than it is from their lowpermeability.

(c) Although these binders contain a high level of alkali ele-ments, they do not appear to be associated with the occur-rence of ASR, which may be due to the fact that themajority of alkali elements are associated with other reac-tion products. However that explanation forgets the crucialrole played by calcium in the ASR development meaningthat although its rather natural the absence of ASR in freecalcium alkali-activated binders, that problem must betaken under consideration when calcium based binders wereused.

(d) As to the capability to keep an alkaline environment troughtime, which is crucial to maintain reinforced steel safe fromcorrosion, the current studies are not enough to prove it, as amatter of fact their resistance to carbonation is lower thanOPC binders and recent investigation show that it is difcultto synthesize a low-Ca geopolymer capable of preserving thesteel reinforcement passivation lm.

(e) The use of calcium in alkali-activated binders is indispens-able to keep a high pH but at the same time could be theresponsible for triggering ASR.

(f) Contrary to standard OPC binders alkali-activated bindersshow a high stability when submitted to high temperatureswhich dependent on the Si/Al ratio. The investigations onthe re behaviour of alkali-activated binders show thatthese materials are specially recommended for works witha high re risk like tunnels and tall buildings.

(g) Alkali-activated binders show a high resistance to freezethaw cycles.

(h) Alkali-activated binders are prone to the formation of efo-rescences however this disadvantage can be greatly reducewhen using hydrothermal curing treatments or calcium alu-minate admixtures. Nevertheless, hydrothermal curing haslimited applications for on situ concrete placement opera-tions and the use of a calcium based admixture raises issuesabout its acid resistance. Furthermore, alkali-activated bind-ers containing calcium based admixture have a higher globalwarming impact than alkali-activated SiAl mixtures.

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Durability of alkali-activated binders: A clear advantage over Portland cement or an unproven issue?1 Introduction2 Resistance to acid attack3 Alkalisilica reaction (ASR)4 Corrosion of steel reinforcement5 Resistance to high temperatures and to fire6 Resistance to freezethaw7 Efflorescences8 ConclusionsReferences