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The use of admixtures in mortars to improve both their physical-chemical and ornamental features has become increasingly common in recent years. The varying origin and composition of these products, some sourced from waste produced in other industries, poses the question of whether they modify the activity concentration index (ACI) of the construction materials to which they are added. Seven pigments, some of natural and others of artificial origin, and two water repellents were characterised both chemically and radiologically in this study. Neither the synthetic pigments nor the water repellents exhibited significant radiological content. The pigments based on Fe2O3 of natural origin had detectable activity concentrations of naturally occurring radionuclides from the 238U series. Those levels were attributable to the raw material used, namely the bauxite red mud generated in aluminium production. In addition to Si, Al, Fe, Ca, Ti and Na as majority elements, this sludge also contains traces of K, Cr, V, Ba, Cu, Mn, Pb, Zn, P, F, S and As, among others, including naturally occurring uranium. The public and occupational radiological risk due to exposure to pigment-modified construction materials were consequently assessed. Neither the doses for the public at large and for workers were found neither to be significant nor constitute any perceptible hazard, essentially in light of the small amounts of pigment used to prepare mortars., This study was funded by the Spanish Ministry of the Economy, Industry and Competitiveness under project BIA2016-77252-P.

The main aim of this paper is to measure the induced torque needed to rotate a steel fiber, hence an experimental and parametrical analysis of factors governing steel fiber alignment in cement pastes and mortar, rotating from static position and rotating in a dynamic fluid is here presented. To aim this objective, a set of rheological tests has been conducted to assess the torque necessary to rotate steel fibers immersed into different fresh cement paste and mortar mixes with Bingham fluid behaviour. Fibers of different aspect ratios (length/width) and different geometry, straight and hooked-end, have been evaluated as they are the more commonly used. On the other hand, different parameters (type of mixture, size of aggregates, volume fraction of aggregates) affecting cement mixtures are also analysed and their influence in fiber orientation discussed. Fiber alignment depends on external torques applied to fibers, immersed into a cement-water-aggregate viscous system, that can be produced during or after casting. The flowability of the fresh suspension with fibers produces a load/pressure that generates a torque that can align them. Fiber alignment is a main goal to pump the fresh material. Hence, the factors that govern fiber alignment are studied which increase the post-cracking strength of cement-based composites under load along its life service due to casting or pumping. To that end, a set of tests has been conducted to assess the torque necessary to rotate steel fibers immersed into different fresh cement paste and mortar mixes with Bingham fluid behaviour. Fibers of different aspect ratios(length/width) and different geometry (straight and hooked-end) have been evaluated. On the other hand, different parameters (type of mixture, size of aggregates, volume fraction of aggregates) affecting cement mixtures are also analysed and their influence on fiber orientation is discussed. The values obtained here are between 1 and 14 N . mm min of dynamic yield torque and 0.1 and 0.5 N . mm min for viscoplastic torque per fiber, depending on fiber geometry, are helpful to improve the fiber alignment in cement-based composites reinforced with fibers through a design and production based on these parameters., Special acknowledgment, appreciation and recognition to the IETcc-CSIC collaboration using the Viskomat™ NT rheometer within the framework of the Excellence Project MINECO BIA2013-47876-C2-1P. The authors want also acknowledge the laboratory of Materials of Architecture, Universidad Poiltécnica de Madrid.

A methodology including software tools for analysing NORM building materials and residues by low-level gamma-ray spectrometry has been developed. It comprises deconvolution of gamma-ray spectra using the software GALEA with focus on the natural radionuclides and Monte Carlo simulations for efficiency and true coincidence summing corrections. The methodology has been tested on a range of building materials and validated against reference materials.

Partial or total replacement of Portland cement clinker by SCMs (Supplementary Cementitious Materials) is a priority for the cement industry in its pursuit of global sustainable development and eco-friendly binder manufacture. The most widely used SCMs include industrial by-products such as blast furnace slag, fly ash and red mud. Alkali-activated cements manufactured with SCMs may reduce the need for Portland clinker by up to 90 wt%–100 wt% with no significant decline in material strength. The trade-off, however, is the risk of higher than legally allowable levels of radioactivity and unbound heavy metals (Cd, Hg, Ni, Pb, Cr), which may leach into the soil with the concomitant adverse implications for human health and the environment. This study assessed the mechanical strength, leachability and natural radioactivity of alkali-activated cement paste containing industrial waste-based SCMs (blast furnace slag, fly ash and red mud) and Pb and Ni compounds. Strength was highest in alkali-activated slag and slag/fly ash pastes and lowest in the red mud-containing materials. The addition of Pb or Ni sulphates had no adverse effect on this parameter. Alkaline and OPC pastes showed a high level of immobilization of both lead and nickel ions. According to the radiological findings, the Activity Concentration Index (I) was higher in red mud than in OPC, blast furnace slag or fly ash. With (I) values lower than 1, however, all the hydrated/activated materials studied would be EU directive-compliant. Nonetheless, the use of these new materials will depend not only on the activity concentration index, but also on their physical and chemical properties and the quality tests that must be passed to conform to legal requirements., Anton Pasko worked at the Eduardo Torroja Institute (IETcc-CSIC) under a short-term (2016) scientific mission (STSM) obtained through the institute and sponsored by COST Action TU 1301 (NORM4Building). The authors thanks also to Spanish Ministry of Economy, Industry and Competitiveness for funding the BIA2013-47876-C2-1-P and BIA2016-77252-P, where tests of this study were conducted.

The behaviour of fresh and hardened alkali-activated slag (AAS) and OPC concretes was compared and the effect of mixing time assessed. OPC and AAS concrete slump and rheological results proved to differ, particularly when the slag was activated with waterglass (WG). The nature of the alkaline activator was the key determinant in AAS concrete rheology. Bingham models afforded a good fit to all the OPC and AAS concretes. In OPC and NaOH-activated AAS concretes, longer mixing had an adverse effect on rheology while improving hardened performance only slightly. In WG-AAS concrete, longer mixing times, improved mechanical properties and also rheological behaviour was enhanced, in which those conditions were required to break down the microstructure. Longer mixing raised thixotropy in OPC and NaOH-activated AAS concretes, but lowered the value of this parameter in waterglass-activated slag concrete., This study was funded by the Spanish Ministry of the Economy under Projects BIA2013-47876-C2-1-P and BIA2014-58063-R.

The production and characterization of a cement and mortar based on the alkaline activation of a high content (≥70%) of natural volcanic pozzolan (NP) and the synergic effect of the addition of granulated blast furnace slag (GBFS) up to 30% were performed. NaOH and a mixture of NaOH + Na2SiO3 were used as activators. The results of this study highlight the possibility of obtaining a binder with a compressive strength of up to 125 MPa at 28 days of curing (25 °C). The optimal alkaline cement that was obtained can be categorized as GU- and LH-type cement according to the ASTM C1157 standard.

Workability and rheology in alkali-activated materials (AAMs) have been scarcely studied and differ substantially from ordinary Portland cement (OPC) systems. This study aims to explore the workability and rheology of alkali-activated slag (AAS) and fly ash (AAFA) mortars, ascertaining the effect of the precursor, the nature and concentration of the alkaline activators and the aggregate content. Mortars were prepared varying the aggregate/binder and liquid/binder ratios. OPC mortars were used as a reference. Mortar workability was determined by flow table measurements. The rheological tests included the stress growth test and torque at constant shear rate. Mortars were tested for 7 day compressive strength. AAS and AAFA mortar workability was more sensitive to changes in the liquid/solid ratio than OPC mortars. In AAM mortars, fluidity was found to be proportional to the liquid/solid ratio and dependent upon aggregate content. When in a plastic state, AAS and AAFA mortars activated with waterglass solutions exhibited larger spreads and greater workability than OPC mortars, confirming the fluidising effect of waterglass. Rheology of AAS mortars was more influenced by the nature and concentration of the alkaline activator than that of AAFA mortars. Rheological behaviour of AAS and AAFA mortars fits the Bingham model.

The aim of this article was to study the kinetic, the mechanical development and the microstructure of an alkali-activated blended Portland cement produced from the mixture of a granulated blast furnace slag and Portland cement in proportion 80% and 20% respectively. The hybrid cement reported compressive strength 4.5 and 10.8 times higher than the reference (100% Portland cement) when is activated with NaOH and waterglass (sodium silicate + NaOH) respectively. Similarly, the heat of hydration was reduced and the material presented a fairly dense and compact microstructure. The main products observed were gel C-S-H, C-A-S-H and hydrated gehlenite.

This work describes the effect of metakaolin on the microstructure and compressive strength of geopolymeric systems based on natural volcanic pozzolans. The effect of the molar ratios of SiO2/Al2O3 and Na2O/Al2O3 and the percentage of metakaolin present in the mixture was studied. The proportion of MK varied between 0 and 30%. A mixture of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) was used as an alkaline activator. The mechanical strength of the geopolymeric pastes and the microstructural properties were evaluated, and techniques such as X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used. The optimum proportion of MK was 20%, incorporated as a replacement of the natural pozzolan. The results obtained in the present study reveal the possibility of obtaining a geopolymeric cementing material with a compressive strength of up to 68 MPa at 28 days of curing at room temperature (25 ± 3 °C).

The aim of this study has been to determine the activity concentrations of 40 K and radionuclides from the 238 U and 232 Th decay series in commercial cements, some industrial wastes and geopolymers (also called alkaline cements) and to calculate their activity concentration levels after the cement hydration/activation at 28 days to ascertain the effect of these processes on their final activity concentrations. The highest activity concentration levels of radionuclides from uranium and thorium series have been obtained in the fly ashes, slags and calcium aluminate cement. When a blend among industrial wastes and cement is realised, the radionuclides activity concentration are calculated on the grounds of their percentages in the blend material and tested by its experimental measurement. Once the hydrated/activated cements and geopolymers have been obtained, a proportional decrease to the percentage of added water is observed in the radionuclides activity concentration for the hydrated cements and no-correlation in the case of 40 K in geopolymers pointing to an increase of this isotope in the sodium compounds used for its activation.

Pursuant to European Directive 2013/59, materials additioned with NORM waste must be characterised radiologically to determine their acceptability for use in construction. The radionuclides studied to judge that acceptability, 232Th, 226Ra and 40K, are normally measured with gamma spectrometry. Gamma detectors are calibrated by using standards as similar as possible in dimensions and chemical composition as the matrix in the samples to be measured. In light of the broad spectrum of chemical and physical characteristics of NORM samples, experimental calibration is often beyond the means of gamma spectrometry laboratories. As a result, Monte Carlo-based methods are deployed to simulate the experimental setup consisting in detector and sample, both geometrically and chemically. Canberra Industries’ LabSOCS (Laboratory Sourceless Calibration Software) is one of the tools available for such calculations. This study verified the accuracy and precision of the counting efficiency delivered by LabSOCS, both with the standard powder geometry and a new geometry consisting in a 5 cm cubic specimen of Portland cement paste. The findings showed that in both geometries the accuracy and precision of LabSOCS-calculated efficiency (by specimen height and activity), across an energy range from 45.64 keV (210Pb) to 1460.82 keV (40K) met the acceptability criteria routinely applied in environmental radioactivity laboratories. The geometry proposed yielded activity values for the end construction material closer to the true indices than the conventional method consisting in summing the partial activities of the unreacted components., This study was funded by the Spanish Ministry of Science, Innovation and Universities' Research Agency and the European Regional Development Fund (AEI/ERDF/EU) under project BIA2016-77252-P. Author Ana María Moreno de los Reyes participated in the study under Spanish Research Agency pre-doctoral grant BES-2017-081306.

Alkali activated materials have a variety of niche applications (other than as a large-scale civil infrastructure material) in which alkali-activated binders and concretes have shown potential for commercial-scale development. The majority of these applications have not yet seen large-scale alkali activated materials utilisation, moreover, there have been at least pilot-scale or demonstration projects in different areas and each provides scope for future development and potentially profitable advances in science and technology. This paper explores the feasibility of generating geopolymers from fly ash using waste glass as an alkaline activator (waterglass family). The mechanical properties of the cementitious geopolymers obtained by alkali-activating fly ash with three solutions: sodium hydroxide 8 M, sodium hydroxide 10 M + 15% waterglass and sodium hydroxide 10 M + 15 g of waste glass were determined, along with their microstructural characteristics using Fourier Transform Infrared Spectroscopy, X-Ray Diffraction, Mercury Intrusion Porosimetry, Mass Nuclear Magnetic Resonance, Scanning Electron Microscopy and Back Scattering Electron Microscopy. The main reaction product in all the systems studied was the alkaline aluminosilicate hydrate gel to which geopolymers owe their mechanical properties. The gel formed when the system contained an extra source of silicon was shown to prompt compositional differences, while the degree of reaction, microstructure and Si/Al and Na/Al ratios were very similar in the former two systems. Waste glass proved to be an effective alkaline activator in geopolymer preparation.

C3A is the most highly reactive phase in clinker and the one with the greatest affinity for superplasticiser admixtures. The amount of C3A in cement, the sulfate content in the medium and the type and amount of admixture largely determine paste, mortar and concrete rheology. Many unknowns remain, however, around the effect of SP structure on admixture adsorption onto (cubic or orthorhombic) C3A polymorphs. Isotherms were found for polycarboxylate ether and naphthalene-based admixture adsorption onto synthetic cubic and orthorhombic C3A to determine that effect, given their different structure and nature. The impact of sulfates on adsorption was also explored. The conclusion drawn was that admixture structure and sulfate content in the media were the factors with the greatest impact on adsorption onto cubic C3A. Orthorhombic C3A was observed to react more intensely to the presence of sulfate and consequently to have less affinity for the admixtures. In the presence of soluble sulfates the addition of superplasticisers was shown to retard the appearance of the main cubic-C3A calorimetric signal more effectively when admixture-sulfate competition was more intense. The presence of SP admixtures has no impact on the peak heat flow time in orthorhombic-C3A hydration. The affinity of this polymorph for sulfates is so high that admixture adsorption is much smaller than observed in cubic-C3A. Therefore, the SPs have a scant effect on orthorhombic-C3A hydration.

An understanding of the rheological behaviour of OPC-based products has been widely studied, for it is essential to determining and predicting the fresh and hardened characteristics and properties of pastes, mortars and concretes. The rheology of alkali-activated material (AAM) systems has been much less intensely researched, however. The present study aimed to ascertain the effect of factors such as the nature and concentration of the alkaline activator on the rheological behaviour of alkali-activated slag (AAS) pastes, with a comparison between the rheological parameters and fluidity of these pastes to the same parameters in OPC. More specifically, the study explored how paste rheology was affected by the nature of the alkaline activator (NaOH, 50/50 wt% NaOH/Na2CO3 or waterglass – Wg), its concentration (3–5% Na2CO3 of slag weight) and, in the waterglass solution, the SiO2/Na2O ratio. The findings showed that AAS paste rheology is affected by the nature of the activator. The rheological behaviour in AAS pastes activated with NaOH alone or combined with Na2CO3 was similar to the rheology observed in OPC pastes, and fit the Bingham model. Conversely, the AAS pastes activated with waterglass fit the Herschel–Bulkley model and their rheology proved to depend on both the SiO2/Na2O ratio and the Na2O concentration. Moreover, regardless of the activator used (NaOH, Na2CO3 or waterglass), an increase in Na2O concentration implies a raise of shear stress. The formation of primary C–S–H gel in Wg–AAS and its effect on paste rheology were confirmed. Gel formation was likewise shown to be related to the SiO2/Na2O ratio and activator concentration.

The rheological behaviour of fresh cement has a direct effect on the microstructural development of mortar and concrete. Inasmuch as the presence of mineral additions impact cement paste rheology and consequently its permanent microstructure and strength, a full understanding of blended cement behaviour should be pursued. The present study addresses the joint effect of mineral additions (limestone and fly ash) and superplasticisers admixtures on the viscosity and water demand of cement pastes. Cement pastes were prepared with 10, 30 or 50 wt% limestone or fly ash as mineral admixtures. Melamine-, naphthalene- and polycarboxylate-based superplasticisers were used. Paste rheology was studied in terms of variations in yield stress and viscosity with the solids content and amount of mineral additions added. The strength and microstructure of the blended cement pastes were determined at viscosity values of 1.5 Pa·s. in the presence of superplasticisers. The findings showed that the Krieger–Dougherty equation could be used to determine the effect of solids content on the apparent viscosity of limestone- and fly ash-blended cement suspensions, as well as the effect of superplasticisers. Adding less than 30% limestone to cement had no effect on paste rheology: i.e., the w/c ratios for minimum and optimal workability were similar to the ratios for ordinary cement. However, adding fly ash did lower the minimum water demand, and the optimal amount of water needed for suitable fluidity. The inclusion of 10% of either addition raised paste strength, while higher proportions 30 or 50%) had the opposite effect. The use of mineral additions reduced the effectiveness of cement superplasticisers.

This study compared the resistance of Triclinic-C3S, grey (OPC) and white (WOPC) Portland cement paste to decalcification induced by accelerated leaching in concentrated ammonium nitrate solutions. Paste microstructure was studied with scanning and backscattering electron microscopy (SEM and BSEM) and nitrogen BET surface area techniques. Ca2+ leached content was quantified by ICP, XRD and FTIR techniques were used to study phase mineralogy. The conclusions drawn from the findings were that calcium leaching-induced decay in the cementitious materials studied (C3S, OPC and WOPC), accelerated by immersion in ammonium nitrate, affected the main calcium phases in the samples (CH, C–S–H gel and ettringite), i.e., both the anhydrous and the hydrated phases. The present study showed that the Ca/Si ratio of C–S–H gels declines on a gradient from the sample core outward. Specimen surface area and nanoporosity rose in cementitious materials after Ca leaching-induced decay and subsequently declined as a result of the collapse of the structure of the hydrated cement, and in particular of the C–S–H gel. C3S paste was impacted more quickly and intensely by leaching than the WOPC and OPC pastes. Further to the findings of this study, the leaching resistance of these three materials, in descending order, is: OPC > WOPC > C3S.

For first time, an experimental and computational study has been conducted to define a structural model for the C-A-S-H gel forming in alkali-activated slag (AAS) pastes that would account for the mechanical properties of these materials. The study involved a comparison with the C-S-H gel forming in a Portland cement paste. The structure of the C-A-S-H gels in AAS pastes depends on the nature of the alkali activator. When the activator is a NaOH, the structure of the C-S-H gel falls in between tobermorite 1.4 nm with a mean chain length of five, and tobermorite 1.1 nm with a mean length of 14. When waterglass is the activator the structure of the C-A-S-H gel is indicative of the co-existence of tobermorite 1.4 nm with a chain length of 11 and tobermorite 1.1 nm with a chain length of 14. This very densely packed structure gives rise to excellent mechanical properties.

[EN] In the present work, the use of three Slovak poor metakaolin sands with different metakaolin content (36.0% (MK-1), 31.5 (MK-2) and 40.0% (MK-3)) and specific surface has been deeply studied as mineral addition for Portland cement. The percentage of metakaolin sands in the blended cements was 10%, 20% and 40%. The pozzolanic tests confirm that the three metakaolin sands show a high pozzolanic activity, comparable to a commercial metakaolin and silica fume. With respect to the rheological behaviour, metakaolin sand–blended-cement pastes fit to Herchel–Bulkley model and their yield stress increases as the metakaolin content increases. MK-3 sand with the highest pozzolanic activity and highest specific surface induces the highest increase of the yield stress. From the calorimetric results it is concluded that the addition of MK-1 and MK-2 sands to Portland cement induces a delay up to 2 h of the precipitation of the main hydration products in the blended-cement pastes and decreases the maximum heat evolution rate. On the contrary, the incorporation of 40% of MK-3 sand shortens 6 h its apparition and increases significantly the maximum heat evolution rate. Additionally, the presence of the metakaolin sands reduces the heat released during the hydration process with respect to non-blended-cement pastes. The incorporation of metakaolin sand induces a decrease of the mechanical strength, being the decrease higher as the metakaolin sand content increases although they also produce a refinement in the pore structure and a decrease of the permeability.

[EN]A clinker and a cement obtained from a raw mix containing ceramic waste as an alternative raw material were characterized in the present study. Their hydration, physical–chemical properties and leaching behaviour in different acid media were also explored. The findings showed that both the clinker and the cement met all the requirements set out in European standards EN 197-1 [1], although they had higher ZnO, ZrO2, and B2O3 contents than an industrially produced reference product. According to the hydration studies, initial hydration was somewhat retarded in the new cement, which exhibited longer initial and final setting times and lower 2-day mechanical strength. The SEM/BSE/EDS microstructural study showed, however, that morphologically and compositionally, the hydration products formed were comparable to unadditioned Portland cement paste products. While low concentrations of Zn and B were observed to leach in acid media, the biotoxicity trials conducted confirmed that these concentrations were not toxic. Zr was retained in the cement pastes.

The alkali–silica reaction in waterglass-alkali-activated slag (waterglass-AAS) and ordinary Portland cement (OPC) mortars was evaluated using three types of (siliceous and calcareous) aggregates. The tests were conducted to the ASTM C1260-94 standard test method. The mortars were studied by volume stability, mechanical strength and Hg intrusion porosity. The ASR products were studied with XRD, FTIR and SEM/EDX techniques. According to the results obtained, under the test conditions applied in this study, waterglass-AAS mortars are stronger and more resistant to alkali-aggregate reactions than OPC mortars. When the mortars were made with a reactive siliceous aggregate, expansion was four times greater in the OPC than in the AAS material. When a reactive calcareous (dolomite) aggregate was used, no expansion was detected in any of the mortars after 14 days, although the characterization results showed that the dolomite had reacted and calcareous-alkali products (brucite) had in fact formed in both mortars. These reactive processes were more intense in OPC than in AAS mortars, probably due to the absence of portlandite in the latter. When the calcareous aggregate was non-reactive, no expansions were observed in any of the mortars, although a substantial rise was recorded in the mechanical strength of AAS mortars exposed to the most aggressive conditions (1 M NaOH and 80 °C)., This research was funded by the Spanish Ministry of Education and Science under Project No. BIA2007-61380. The authors thanks to M.M. Alonso and J. Llueca for their support in tests conducted for this study. M. Palacios worked under a postdoctoral contract awarded by the CSIC.

This paper describes the behaviour of sulphate resistant cement paste hydrated at temperatures ranging from 4 to 85 °C. A number of techniques and methods were used to study hydration: compressive strength, thermogravimetry, X-ray diffraction, mercury intrusion porosimetry, backscattered electron imaging in conjunction with energy dispersive X-ray analysis and nuclear magnetic resonance (NMR). Early age compressive strength was found to be higher in cement pastes cured at 40 and 85 °C than in the materials hydrated at 4 and 22 °C, due to the formation of larger quantities of hydrated product in the former. The MAS NMR findings showed that this higher early age strength was related to increased CSH gel polymerization rates, and a concomitantly larger average number of units in the SiO4 chains. The formation of CSH gels with very long chains at early ages hindered the uptake of further hydration products, however. This in turn generated more porous and less cohesive structures, causing a decline in mechanical strength, as confirmed by the backscattered electron imaging and porosity results., Dr. I. Elhadiri participated in this study under a Spanish Agency for International Cooperation (AECI) Grant. The research was funded by the Spanish Ministry of Education and Science under Project CTM2004-06619-C02-01. The authors thank Professor Antonio Aguado (Polytechnic University of Catalonia) and M. Palacios for their comments and support. They are likewise grateful to J.L. García, A. Gil, M.M. Alonso and J. Llueca for their assistance with the mechanical, spectroscopic and microscopic tests and I. Sobrados and M. Palacios for the NMR studies.

[EN]Potassium dawsonite is formed as an intermediate compound during the alkaline hydrolysis (AH) in calcium aluminate cements (CACs). A synthesis method of potassium dawsonite has been developed. The crystal structure of potassium dawsonite KAl(CO3)(OH)2 has been solved by direct methods from X-ray powder diffraction data and refined with the Rietveld method. It crystallises in the orthorhombic Cmcm space group with unit cells parameters a=6.3021(3) Å, b=11.9626(5) Å, c=5.6456(3) Å and Z=4. The structure consists of carboaluminate chains, formed by the basic unit [Al2(OH)4(CO3)2]2− arranged along the c axis. The carbonate groups are placed in an alternate manner at both sides of the carboaluminate chains. The carboaluminate chains are also held together by the K+ cations that are located in the middle of three such chains. Finally, the chemical reactions explaining the AH process in CACs are postulated.

[EN]Different types of ancient and recent hydraulic mortars were collected from well-documented archaeological, historic and modern buildings in various geographical locations (urban, suburban, rural and maritime) of Italy, Spain and Belgium, representative of different environmental impacts, types and degrees of deterioration. A synthesis of the characteristics of the collected samples is presented, along with the identification of the formation products that occurred on the sample surfaces as a result of the reaction of the mortars with atmospheric pollutants. The analyses were performed by means of optical microscopy (OM), X-ray diffractometry (XRD), scanning electron microscopy (SEM-EDX) and ion chromatography (IC). The results obtained prove that sulphation processes takes place on hydraulic mortars, leading to gypsum formation on the external surface of the samples. Through the reaction of gypsum with the aluminate hydrate of the binder, ettringite formation was found to occur on a cement-based restoration mortar sampled in Antwerp.

The activation of fly ash/slag pastes with NaOH solutions have been studied. The parameters of the process studied are: activator concentration (NaOH 2 and 10 M), curing temperature (25°C and 65°C), and fly ash/slag ratios (100/0, 70/30, 50/50, 30/70, and 0/100). The equations of the models describing the mechanical behaviour of these pastes have been established as a function of the factors and levels considered. The ratio of fly ash/slag and the activator concentration always result to be significative factors. The influence of curing temperature in the development of the strength of the pastes is lower than the contribution due to other factors. At 28 days of reaction, the mixture 50% fly ash/50% slag activated with 10 M NaOH and cured at 25°C, develop compressive mechanical strengths of about 50 MPa. The nature of the reaction products in these pastes has been studied by insoluble residue in HCl acid, XRD, FTIR and MAS NMR. It has been verified that slag reacts almost completely. It has also been determined that the fly ash is partially dissolved and participates in the reactive process, even in pastes activated at ambient temperature. The main reaction product in these pastes is a hydrated calcium silicate, like CSH gel, with high amounts of tetracoordinated Al in its structure, as well as Na ions in the interlayer spaces. No hydrated alkaline alumino-silicates with three-dimensional structure characteristics of the alkaline activation of fly ashes were formed.

The physical and chemical interaction between a solid industrial waste from aluminium refining and saturated Ca(OH)2 solution, as well as the effects of substituting siliceous sand for the waste on the physical and mechanical properties of mortars were studied. The waste is a solid that contains reactive alumina capable of combining with the calcium hydroxide. These reactions result in stable and insoluble compounds. This alumina, together with the halite (also present in the waste composition), chemically react with a saturated solution of Ca(OH)2, giving as a main reaction product the so-called Friedel's salt (Ca4Al2Cl2O6 · 10H2O). Stratlingite and Si-hydrogarnets were among other products detected. The waste has a high specific surface area. The cement/waste mixtures therefore require a higher quantity of mixing water than cement/sand mixtures. The result is a decrease of the mechanical strengths and an increase of the total porosity. However, a decrease of the average size of the pores occurs, which can have a positive effect on the durability of the final material.

The objective of the present work is to know the joint influence of a series of factors (specific surface of the slag, curing temperature, activator concentration, and the nature of the alkaline activator) on the development of mechanical strengths in alkaline-activated slag cement mortars. To reach this aim, a factorial experimental design was carried out (a complete 2 3 × 3 1 design) for every age studied (3 to 180 days). Through the variance analysis, the most significant factor on the response turned out to be the alkaline activator nature. The activator used, Na 2 SiO 3 · nH 2 O + NaOH, was the factor that gave the highest mechanical strengths in all tests. The next most statistically significant factor was the activator concentration, followed by curing temperature, and, finally, the specific surface of the slag. The equations of the model describing the mechanical behaviour for flexural and compressive strengths and their relationships for each age studied were established

[EN]Burnability of white cement raw mixes made using CaF2 and CaSO4 as fluxes/mineralizers is studied and modelled. A methodology based on a statistical method called experimental design is used to establish the model. An equation that explains the burnability of these new raw mixes is established. Through this equation, it is deduced that limestone particle size, fluorite and gypsum content have a major influence on burnability, while silica modulus has little effect.

[EN]Sepiolite is a clay mineral (Si12Mg8O30(OH)4(OH2)4) which due to its fibrous structure has considerable absorbent and adsorbent properties making of it an ideal material for supporting different products, such as toxines, oil, biocides, etc. In this work, the influence of the sepiolite on the carbonation process of lime mortars with sand/lime3/1 ratio, and also on the physical, chemical, mechanical and rheological properties as well as the microstructural characteristics of the same mortars has been studied. It has been proved that sepiolite slows down the rate of carbonation process in these lime mortars due to its capacity for water adsorption without affecting the mechanical behaviour of the mortars. However, it has been observed that sepiolite affects the microstructural development of the composite. The influence of the sepiolite on the rheological behaviour of these lime mortars has also been established by a mathematical equation which correlates the viscosity and the content of sepiolite in the mortar. This equation can also determine, for different water/(lime + sand) ratios, the optimum amount of sepiolite which could be added to the mortar for achieving the best plasticity.