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The cement industry has for some time been seeking procedures that would effectively reduce the high energy and environmental costs of cement manufacture. One such procedure is the use of alternative materials as partial replacements for fuel, raw materials or even clinker. The present study explores the reactivity and burnability of cement raw mixes containing fired red or white ceramic wall tile wastes and combinations of the two as alternative raw materials. The results showed that the new raw mixes containing this kind of waste to be technically viable, and to have higher reactivity and burnability than a conventional mix, providing that the particle size of the waste used is lower than 90 μm. The mineralogical composition and distribution in the experimental clinker prepared were comparable to the properties of the clinker manufactured with conventional raw materials. Due to the presence of oxides such as ZnO, ZrO2 and B2O3 in tile glazing, the content of these oxides was higher in clinker made with such waste. The mix of red and white ceramic wall tile waste was found to perform equally or better than each type of waste separately, a promising indication that separation of the two would be unnecessary for the purpose described above., This study was funded by the Spanish Ministry of Education and Science (MEC) under grants for Projects CTM2004-06619-CO2-01 and 02/TECHNO. I. Garcı´a Dı´az and M. Palacios benefited from pre-Ph.D. grants awarded by the MEC and the Region of Madrid (CAM), respectively, and S. Martı´nez-Ramı´rez from a “Ramón y Cajal” contract funded by the MEC and the ERDF.

The rheology of waterglass-(Na 2 O·nSiO 2 ·mH 2 O) and NaOH-activated slag pastes and mortars depends on the nature of the alkaline activator used: in waterglass-activated slag pastes and mortars, the extensive structural breakdown under shear makes the Herschel-Bulkley model a better fit to the down ramp of the flow curve, whereas NaOH-activated pastes and mortars, such as portland-cement pastes and mortars, behaved like Bingham fluids. Admixtures were unable to reduce the yield stress of waterglass-activated slag pastes, but the inclusion of a naphthalene derivative admixture in NaOH-activated slag pastes reduced the yield stress by 80%. The problem of undesirably short setting times for waterglass-activated slag mortars and concretes could be overcome by an extended mixing time, giving an initial set of nearly 3 hours.

15 pages, 6 figures, 6 tables., [ES] El propósito de este artículo es dar a conocer los resultados de la evaluación del comportamiento de mezclas de hormigón producidas a partir de la activación con waterglass (Na2SiO3·nH2O + NaOH) de una escoria siderúrgica granulada de alto horno colombiana. Las propiedades mecánicas y de durabilidad de los hormigones activados alcalinamente (AAS) se comparan con las correspondientes mezclas de hormigón de cemento Portland (OPC) producidas con igual proporción de ligante. Estas proporciones variaron entre 340 y 512 kg por m3 de hormigón. Los resultados obtenidos indican que incrementos en la proporción de la escoria contribuye a la mejora de las propiedades evaluadas., [EN] This article reports the results of related to on the performance of concrete made with waterglass (Na2SiO3·nH2O + NaOH)-activated Colombian granulated blast furnace slag. The mechanical strength and durability properties this alkali-activated slag concrete (AAS) were compared to the properties of ordinary Portland cement concrete (OPC) with the same proportion of binder, which ranged from 340 to 512 kg per m3 of concrete. The results indicated that increasing the proportion of slag led to improvements in the properties studied.

Se ha estudiado el efecto de la incorporación de fibras de carbón en el comportamiento mecánico, estabilidad de volumen y nivel de corrosión de la armadura en morteros de escorias activadas alcalinamente (AAS). Se evalúa la influencia de las fibras de carbón en el comportamiento de morteros alcalinos en comparación con el efecto que producen en morteros de Portland (CP). Los ensayos mecánicos y de estabilidad de volumen se han realizado según lo establecido en la norma UNE que los regula. Se ha utilizado la técnica de la Resistencia a la Polarización para determinar la velocidad de corrosión del acero embebido en las muestras estudiadas. Como consecuencia del estudio realizado, se ha podido concluir que la adición de fibras de carbón a morteros de AAS y CP no mejora las características resistentes de los mismos. En relación con la estabilidad de volumen, la incorporación de fibras de carbón a los morteros de AAS, preparados con una relación líquido/sólido de 0,5, reduce alrededor del 50% su retracción al secado. En los morteros de CP, la influencia de las fibras de carbón difiere de la observada para los morteros de AAS. Los estudios de corrosión han demostrado que en condiciones de carbonatación, los morteros de AAS con fibras de carbón incrementan el nivel de corrosión del acero embebido en los mismos; mientras que mejora sensiblemente el comportamiento de los morteros AAS con un 1% de fibra de carbón frente a la corrosión ante el ataque por cloruros.

The purpose of the present study was to analyze the effect of the structural differences in four polycarboxylate and polyether admixtures on the rheological properties of cement pastes with different chemical and mineralogical compositions and different active additions (CEM I 42.5 R, CEM I 52.5 R, CEM I 52.5 N/SR, CEM II/AV 42.5R, CEM II/B-L 32.5 R, CEM III/B 32.5R, BL I 52.5R and CAC – European standard EN 197-1:2000). The results of the minislump test concurred with the variations observed in the values of the rheological parameters (shear stress and plastic viscosity). The structural characteristic of the admixtures found to play the most prominent role in their fluidizing effect was the proportion of carboxylate (CG) and polyether (EG) group components. In cements characteristics such as fineness and the C3A/calcium sulphate and C3S/C3A ratios were also observed to be essential to admixture effectiveness. In this regard, the rheological parameters varied most widely in CEM I 52.5N/SR pastes and least in BL I 52.5R cement pastes. Of the additioned cements, the CEM III/B 32.5R pastes, which contained granulated blast furnace slag, showed the highest rises in flowability. Finally, the fluidizing effect of polycarboxylate superplasticizers was much more intense in calcium aluminate cements, although flowability declined rapidly in this material., El objetivo de este trabajo ha sido estudiar el efecto de las diferencias estructurales de cuatro aditivos basados en policarboxilatos y poliéteres sobre las propiedades reológicas de pastas de cemento con diferente composición química, mineralógica y con distintas adiciones activas (CEM I 42,5 R, CEM I 52,5 R, CEM I 52,5 N/SR, CEM II/AV 42,5R, CEM II/ B-L 32,5 R, CEM III/B 32,5R, BL I 52,5R y CAC - Norma EN 197-1:2000). Los resultados obtenidos sobre la fluidez de la pasta en el ensayo del “Minislump” coinciden con la evolución de los valores de los parámetros reológicos (esfuerzo de cizalladura y viscosidad plástica) determinados a través de un viscosímetro rotacional. Las características estructurales de los aditivos que más afectan al efecto fluidificante son el contenido de grupos carboxilatos (GC) y de grupos poliéteres (GE). En relación con las características y composición de los cementos, son factores fundamentales, la finura y las relaciones C3A/sulfato cálcico y C3S/C3A. Así, las pastas de CEM I 52,5N/SR son las que presentan una mayor modificación de los parámetros reológicos, mientras que las de BL I 52,5R son las que se ven modificadas en menor medida. Las pastas de CEM III/B 32,5R, con escoria granulada de horno alto, son las que presentan mayores incrementos de la fluidez más acusados. Por último, el efecto fluidificante del aditivo es mucho más marcado en cementos de aluminato de calcio aunque presenta acusadas pérdidas de fluidez con el tiempo.

En el presente trabajo se incluyen los resultados de la resistencia a la penetración de cloruros de morteros de Cemento Portland Ordinario (OPC) adicionados con un caolín colombiano sometido a tratamiento térmico en un rango de temperaturas entre 600 y 800 °C. Los productos del tratamiento térmico, metacaolín (MK), son incorporados en mezclas de morteros de OPC en proporciones del 10 y 20% en relación al peso del cemento. Se comparan sus características físico-químicas, entre las cuales se incluye la microestructura de poros evaluada por la técnica de porosimetría de mercurio, con la absorción capilar y la permeabilidad a cloruros. Se concluye que las muestras adicionadas con un 20% del material tratado térmicamente a 800 °C presentan el mejor desempeño en sus propiedades finales., The present paper discusses the results of chloride resistance tests conducted on ordinary Portland cement (OPC) mortars containing a Colombian kaolin pre-treated at temperatures of from 600 to 800 ºC. The resulting metakaolin (MK) was added to OPC mortar mixes in proportions of 10 and 20% by cement weight. The mortars were compared for physical and chemical properties, including capillary absorption, chloride permeability and pore microstructure as assessed by mercury porosimetry. The best performance was recorded for the samples containing 20% of the material treated at 800 ºC., Los autores agradecen al Departamento de Síntesis, Caracterización y Estabilidad de Materiales del Instituto de Ciencias de la Construcción Eduardo Torroja IETcc (CSIC – España), la Universidad del Valle (Colombia), Colciencias y al Centro de Excelencia en Nuevos Materiales CENM por el apoyo en la realización del presente trabajo.

Publicación en versión impresa: mayo de 2007, The effect of a shrinkage-reducing admixture (SRA) based on polypropylenglycol on the dimensional stability of waterglass-activated slag mortars was studied. The analysis also showed the effect of the admixture on pore structure of the mortars as well as on the mineralogical composition and microstructure of the alkali-activated slag pastes. The SRA reduced the shrinkage by up to 85 and 50% when the alkali-activated slag mortar specimens were cured at relative humidities of 99 and 50%, respectively. The mechanism primarily involved in shrinkage reduction is the decrease in the surface tension of pore water prompted by the admixture. The SRA also modified the pore structure – under both curing conditions – increasing the percentage of pores with diameters ranging from 1.0 to 0.1 μm. Capillary stress is much lower in these pores than in the smaller capillaries prevailing in mortars prepared without admixtures. Microstructurally, the SRA occasioned a slight increase in the proportion of Si units Q2 in the CSH gel and a decrease in the percentage of Al replacing the Si in the gel structure. The admixture did not, however, modify the mineralogical composition of the pastes. Finally, the SRA admixture retarded the alkaline activation of the slag, more intensely at higher admixture dosages. While the admixture did not significantly alter the degree of reaction in pastes cured for 7 days at RH=99%, the value of this parameter dropped by 7% in the presence of the admixture in pastes cured at 50% relative humidity., Funding for project MAT 2001–1490 was provided by the Spanish Ministry of Science and Technology (MCyT). The authors wish to thank A. Gil, J. L. García, I. Sobrados, J. L. Llueca and J. L. Pita for their support in the tests conducted for this study.

12 páginas, 6 figuras, 7 tablas., [ES] La industria cementera mundial está buscando vías experimentales que permitan desarrollar cementos que precisen menor energía en su formación, degraden menos los entornos y emitan menos gases contaminantes a la atmósfera. Esta línea, en España y Europa, coincide plenamente con el concepto de sostenibilidad y alcanzar el cumplimiento del Protocolo de Kioto. El empleo de diferentes residuos y subproductos industriales como materiales alternativos en la fabricación de cemento se ha revelado como un medio muy efectivo para alcanzar, en gran parte, esa sostenibilidad. Estos materiales alternativos pueden ser incorporados en el proceso de fabricación de cemento, por la sustitución parcial de los combustibles convencionales y/o de las materias primas del crudo y por la incorporación de adiciones activas al cemento y/o clínker. En el presente trabajo se exponen los resultados preliminares obtenidos al estudiar la composición y activación alcalina de seis residuos cerámicos cocidos con vistas a su viabilidad de sustituir, parcialmente, algunas materias primas, utilizadas en la preparación de un crudo de cemento. Los resultados obtenidos han mostrado que los seis residuos tienen una composición química y mineralógica adecuada para su posible empleo como materia prima alternativa de un crudo de cemento Portland. No son ni tóxicos ni radioactivos. Como era de esperar estos residuos tienen capacidad puzolánica. A la edad de estudio (8 días) la activación alcalina de los residuos es baja. El contenido en fase amorfa y la naturaleza del activador no parecen ser factores que influyan en dicho proceso de activación. El estudio de caracterización realizado sobre las pastas activadas ha demostrado que las fases feldespáticas son las más susceptibles de disolución y reacción con las disoluciones alcalinas., [EN] The world-wide cement industry is seeking experimental avenues that will lead to cement production that is less energy-intensive, less damaging to the surrounding environment and less prolific in GHG emissions. In Spain and Europe in general, this approach is wholly consistent with the concept of sustainability and compliance with the Kyoto Protocol. The use of different kinds of industrial waste and by-products as alternative materials in cement manufacture has proved to be a very effective way of contributing to such sustainability. These alternative materials may be incorporated during cement production by partial/y replacing conventional fuel and/or the raw materials ground into the raw mix, or by including active additions to the cement and/or clinker. The present paper discusses the preliminary results obtained in a study of the composition and alkali activation of six types of fired ceramic waste with a view to their viability as partial replacements for some of the prime materials used to prepare raw mix for Portland cement. The results show that the chemical and mineralogical composition of the six materials makes them apt for such possible use. They are neither toxic nor radioactive. And as might be expected this type of waste exhibits pozzolanic activity. Alkali activation of the waste, low at the age analyzed (8 days), does not appear to be affected by the vitreous phase content or the nature of the activator. The characterization study conducted on the activated paste shows that the feldspar phases are the ones most susceptible to dissolution and reaction with the alkaline solutions., Los autores agradecen al Ministerio de Educación y Ciencia (MEC) la subvención otorgada al proyecto CTM200406619-C02-01 y 02/TECHNO dentro del cual se han realizado estas investigaciones. M. Palacios también agradece a la Consejería de Educación de la Comunidad de Madrid la concesión de una beca predoctoral y S. Martínez-Ramírez al Ministerio de Educación y Ciencia y al ERDF la financiación del Contrato Ramón y Cajal.

El principal problema tecnológico de los cementos de esconiaactivada alcalinamente (AAS) es su elevada retracción alsecado. Por ello, en el presente trabajo se estudia el comportamientode morteros de escoria activada alcalinamentereforzados con fibras de vidrio alcali-resistentes (AR), especialmentediseñadas para reducir la retracción al secado ensistema cementantes. Para ello se prepararon morteros deescoria activada alcalinamente y de cemento Portland comomaterial de referencia. El porcentaje de fibra AR en los morterosvarió entre 0-1,1% en peso de ligante. Los morterospreparados fueron sometidos a los siguientes ensayos:retracción al secado, resistencias mecánicas a 2, 7 y 28 días,ensayos de tenacidad, resistencia al impacto y comportamientoresistente frente a altas temperaturas. También serealizó un examen microestructural de los materiales a travésde SEM/EDX. Se concluye que el porcentaje de 0,22%de fibra induce una reducción significativa (más de un 20%)en la retracción al secado de los morteros de escoria activada,sin que se produzcan modificaciones negativas en elcomportamiento resistente. Los morteros de escoria activadaalcalinamente recuperan el 20% de sus resistenciasmecánicas iniciales, mientras que dicha recuperación es del50% cuando se incorpora un 0,22% de fibras de vidrio., In light of the practical problem posed by the high drying shrinkage rate exhibited by alkali-activated slag (AAS), due to these materials exhibited a high drying shrinkage the present study analyzes the behaviour of alkali-activated slag mortars reinforced with alkali-resistant (AR) glassfibre especially designed to reduce drying shrinkage in cementitious systems. To this end, both alkali-activated slag and reference Portland cement mortars were prepared, with and without AR fibre (in dosages ranging from 0 to 1.1% by weight of the binder). These mortars were subjected to the following tests: drying shrinkage, mechanical strength after 2, 7 and 28 days, toughness, and high temperature. The microstructure of the materials was also studied by SEM/EDX techniques. At a percentage of 0.22%, AR fibre was found to induce a significant reduction (over 20%) in drying shrinkage, without detracting from the fine resistance strength, of alkaliactivated slag mortar. Moreover, plain activated slag mortars recovered 20% of their initial mechanical strength after exposure to high temperatures, and in specimens reinforced with glassfibre at a rate of 0.22%, recovery climbed to 50%., Los autores quieren expresar su agradecimiento al MEC por la concesión del proyecto MAT2001-1490, con cuya financiación se ha realizado este trabajo. M. Palacios agradece también a la CAM la concesión de una beca predoctoral, en cuyo marco se ha realizado este estudio. Los autores también agradecen a Vetrotrex el suministro de la fibra de vidrio AR.

[EN]This paper shows how several superplasticizers (polycarboxylates, vinyl copolymers, melamine and naphthalene-based) and shrinkage-reducing (polypropylenglycol derivatives) admixtures affect the mechanical and rheological properties and setting times of alkali-activated slag pastes and mortars. Two activator solutions, waterglass and NaOH, were used, along with two concentrations—4% and 5% of Na2O by mass of slag. All admixtures, with the exception of the naphthalene-based product, lost their fluidifying properties in mortars activated with NaOH as a result of the changes in their chemical structures in high alkaline media. The difference in the behaviour of these admixtures when ordinary Portland cement is used as a binder is also discussed in this paper.

This study analyzes the behaviour of waterglass- or NaOH-activated slag mortars after carbonation. The effect of a superplasticizer based on vinyl copolymer and shrinkage reducing polypropylenglycol derivative admixtures on that process was also examined. The same tests were run on cement mortars for reference purposes. The mortars were carbonated in a chamber ensuring CO2 saturation for four and eight months, after which ages the samples were tested for mechanical strength; mercury porosimetry and mineralogical (XRD, FTIR) and microstructural characterization (SEM/EDX) were also conducted. The results obtained indicate that alkali-activated slag mortars were more intensely and deeply carbonated than Portland cement mortars. Carbonation took place directly on the gel, causing decalcification. When waterglass was the alkaline activator used, carbonation caused a loss of cohesion in the matrix and an important increase in porosity and decrease in mechanical strength. When a NaOH solution was used as the alkali activator, carbonation enhanced mortar compaction and increased mechanical strength. Finally, in waterglass-activated slag mortars, the inclusion of organic admixtures had no effect either on their behaviour after carbonation or the nature of the reaction products.

22 páginas, 10 figuras, 3 tablas., [ES] En el presente trabajo se estudia la estabilidad de diferentes aditivos superplastifícantes (policarboxilatos, copolímeros vinílicos, derivados de melamina y nafta leño) y reductores de la retracción (derivados de polipropilenglicol) en medios alcalinos. Se prepararon disoluciones de dichos aditivos en agua. NaOH (pH=11,7 y 13,6), Ca(OH) pH=12,4 y waterglass (pH=13,0). A diferentes edades se midió el pH de las disoluciones y se estudiaron los cambios estructurales experimentados por los aditivos mediante FTIR, FT-Raman y UV-VIS. Todos los aditivos son inestables a pH> 13,0 excepto los aditivos derivados de naftaleno y polipropilenglicol en la disolución de NaOH pH=13,6 y el aditivo derivado de polipropilenglicol en la disolución de waterglass (Na2O-nSiO2-mH2O + NaOH). El resto de los aditivos experimentan modificaciones estructurales que explican la pérdida de sus propiedades fluidificantes en los medios fuertemente básicos., [EN] The present study explores the stability of different superplasticizer (polycarboxylate, vinyl copolymers, melamine and naphthalene derivatives) and shrinkage-reducing (polyproplyene glycol derivatives) admixtures in water and several alkaline media: NaOH (pH= 11.7 and 13.6), Ca(OH)2 (pH=l2.4) and waterglass (pH=13.0) solutions. The pH of the solutions was measured at different limes and the structural changes taking place in the admixtures were studied using FTIR, FT-Raman and UV-VIS techniques. All the admixtures, except the naphthalene and polypropylenglycol derivatives in the NaOH pH=l3.6 solution and the naphthalene derivative in waterglass (NaO2-nSiO2-mH2O + NaOH), are unstable at pH > 13.0. The other admixtures all undergo structural changes in highly basic media that explain the loss of their fluidifying properties under these conditions., Los autores quieren agradecer al Ministerio de Cierncia y tecnología la subvención del proyecto MAT2001-1490, sin cuya financiación no se podría haber realizado este trabajo.

[EN]The objective of this paper was to reproduce the formation of thaumasite due to the reaction of atmospheric SO2 with hydraulic mortars. The research was carried out on mortars made with ordinary Portland cement (OPC), mineralized white Portland cement, hydraulic lime and a mixture of lime and pozzolana. Mortars underwent sulfation by exposing the samples to 300 ppm SO2 at 25 °C and 95% RH for 2 days. Subsequently, half of the sulfated samples were kept for 6 and 12 months in a chamber with 0.3 ppm, SO2 as pollutant (0.50 l min−1 flow gas velocity), 5 °C and 95% RH. The other halves of the sulfated samples were kept partially immersed in water at 5 °C for 4, 9 and 14 months. The process of thaumasite formation in hydraulic mortars due to the interaction of the material with atmospheric SO2 was reproduced in all the hydraulic mortars kept partially immersed in water at low temperature, except in the lime–pozzolana mixture. Gypsum was the first reaction product formed as a result of that interaction. Subsequently, gypsum reacted with calcium carbonate and C–S–H gel resulting in the formation of thaumasite. The formation of thaumasite was easier and quicker in sulfated samples kept at low temperature partially immersed in water. Only in OPC mortars was thaumasite formation observed in samples exposed to 0.3 ppm of SO2 for 12 months.

[EN]Carbonation on waterglass- and NaOH-activated slag pastes was analyzed and compared with carbonation in Portland cement pastes to determine possible differences. Thermogravimetry-differential thermal analysis (TG/DTA), Fourier-transform infrared spectrometry, and nuclear magnetic resonance were used to determine the effects on the main reaction products. According to the TG/DTA results, carbonate precipitation following carbonation is much more intense in Portland cement pastes than in alkali-activated slag pastes. This may be attributed to the fact that in Portland cement paste both the portlandite and the C–S–H gel can be carbonated, whereas in alkali-activated slag pastes, only the C–S–H gel is carbonated directly. In both systems, carbonation leads to the formation of CaCO3, Si-rich C–S–H gel, silica gel, and alumina. The carbonation of waterglass-activated slag pastes is not altered by the presence of either of the organic additives used in the study.

The development of new binders, alternative to traditional cements and concretes obtained by the alkaline activation of different industrial by-products (blast furnace slags and/or fly ashes), is an ongoing study and research topic of the scientific community. The mechanical and durable behaviour of alkaline cement mortars reinforced with polypropylene fibres has been the object of the present investigation. Three different alkaline matrices were used: (a) granulated blast furnace slag activated with waterglass (Na2SiO3+NaOH) with a concentration of 4% Na2O by mass of slag and cured at room temperature, (b) aluminosilicate fly ash activated with 8M NaOH and cured at 85 °C during the first 24 h and (c) 50% fly ash+50% slag activated with 8M NaOH solution at room temperature. In the mechanical tests (flexural and compressive strengths), two different dosages of fibres were used: 0.5% and 1% by mortar volume. Shrinkage tests according to ASTM C 806-87 standard with (1%) and without fibres were also carried out. The durability tests carried out were freeze/thaw and wet/dry cycles. In these tests, the dosage of fibre was 0.5% by mortar volume. The results obtained show that the nature of the matrix is the most important factor to strength development, more than fibre presence and content amount.

This paper examines on the setting time and mechanical strength behaviour of slag cement pastes activated with different alkaline activators. For this purpose three alkaline solutions were used: waterglass solution (27% SiO2, 18 % Na2O and 55% H2O), NaOH and Na2CO3, maintaining always a constant concentration of Na2O (4% by mass of slag). The solutions were prepared with mixes of 0%, 80%/20% and 20%/80%. The activation process was studied at early ages by conduction calorimetric and fourier transform infrared spectroscopy (FTIR). Results show that the initial pH of the alkaline solution plays an important role in the initial slag dissolution. However the factor playing a decisive role in the acceleration or delay of setting times and in the development of mechanical strengths is the nature of the anion present in the solution. SiO4 2− ions act as an accelerator of the setting time, but CO3 2− ions delay the setting time.

14 páginas, 6 figuras, 6 tablas., [ES] Los clínkeres belíticos de sulfoaluminatos se obtienen por cocción de crudos a temperaturas moderadas, hacia 1.250 ºC. Esos crudos se componen de carbonato de calcio mezclados con dos subproductos industriales: cenizas volantes pobres en óxido de calcio y fosfoyeso. Los clínkeres obtenidos se caracterizaron a través de Difracción de Rayos X (DRX), Espectroscopia Infrarroja por Transformada de Fourier (FTIR) y por la determinación de CaO libre. El comportamiento hidráulico de los cementos elaborados de los clínkeres con el 7% de yeso se estudió por DRX, Microscopía Electrónica de Barrido (SEM), FTIR y Resonancia Magnética Nuclear (RMN)., [EN] Sulfoaluminate belite clinkers by burning raw at moderate temperatures near 1250 °C were synthesized. The used mixtures were made by calcium carbonate blended to two industrial wastes: low calcium fly ash and phosphogypsum. The clinkers were characterised by X-Ray Diffraction (XRD), Infrared Spectroscopy (FTIR) and free lime. The hydraulic behaviour of the obtained cements, by adequate clinkers with 7% of added gypsum, was followed by XRD, scaning electronic microscopy (SEM), FTIR and NMR., Los autores quieren agradccer al CSIC/CNCPRST de Marruecos la concesión del proyecto de Cooperación bilateral MA 20000008, a través del cual se ha realizado esta investigación.

A mechanical, mineralogical and microstructural characterisation of the cement pastes obtained by alkaline activation of fly ash/slag mixtures cured at different temperatures has been carried out. The pastes obtained were characterised by XRD, FTIR, MAS NMR, SEM/EDX, atomic absorption and ion chromatography, also the insoluble residue in HCl was determined. The results obtained have proved the existence of two different reaction products in those activated pastes. The average atomic ratios in the main reaction product were Ca/Sinot, vert, similar0.8, Al/Canot, vert, similar0.6, Si/Alnot, vert, similar2–3. Such analysis corresponds to calcium silicate hydrate rich in Al, which includes Na in its structure. Other reaction product which was detected in the pastes as result of fly ash activation, was an alkaline aluminosilicate hydrate with a three-dimensional structure.

The expansion of alkali-activated granulated blast furnace slag (AAS) cement mortars with reactive aggregate due to alkali–silica reaction (ASR) was investigated. The alkaline activator used was NaOH solution with 4% Na2O (by mass of slag). These results were compared to those of ordinary portland cement (OPC) mortars. The ASTM C1260-94 Standard Test Method based on the NBRI Accelerated Test Method was followed. The nature of the ASR products was also studied by SEM/EDX. The results obtained show that the AAS cement mortars experienced expansion due to the ASR, but expansion occurs at slower rate than with OPC mortars under similar conditions. The cause of the expansion in AAS cement mortars is the formation of sodium and calcium silicate hydrate reaction products with rosette-type morphology. Finally, in order to determine potential expansion due to ASR, the Accelerated Test Method is not suitable for AAS mortars because the reaction rate is initially slow and a longer period of testing is required.

[EN]Physico-chemical properties and mechanical behaviour of ternary cements made by Portland cement, fly ash and limestone are studied. The mixtures at various compositions of clinker, gypsum fly ash and limestone are intimately ground and compared to other compositions without fly ash. Blended fly ash cements are also studied. The results show that fly ash acts as grinding agent by reducing the required time to obtain the same percentage of particles retained on a 80-μm sieve as the standard cement. Fly ash cements lead to an important extension of setting time than limestone cements. The replacement of clinker by limestone gives better mechanical strengths than the mixtures containing fly ash at early days; after 28 days, the cements prepared by incorporation of fly ash gain an important strength. From mechanical point of view, an optima dosage was obtained at 77% clinker, 2% gypsum, 7.5% fly ash and 13% limestone composition.

The objective of this work was to determine the mechanisms that govern the setting times of alkali-activated slag (AAS) cement pastes, as a function of the nature of the alkaline activator used. For this purpose three different activators were used: waterglass (Na2SiO2.nHaOH with a SiO2/NaO ratio equal 1·5), NaOH and Na2CO3. The concentration of all solutions was constant = 3% of Na2O by mass of the slag. The pastes were studied through isothermal conduction calorimetry, FTIR and 29Si and 27Al MAS-NMR. Results indicate that pastes activated with waterglass develop faster setting due to the formation of an initial calcium silicate hydrate. Setting, in pastes activated with NaOH is due to the formation of a more polymerised calcium silicate hydrate. Pastes activated with Na2CO3 show longer setting times due to the initial formation of a sodium calcium carbonate which retard the reaction processes.

[EN]Early hydration of portland cement with superplasticizer admixtures of different nature has been studied. These admixtures were: one based on mélanine synthetic, other based on vinyl copolymer and other based on polyacrylate copolymers. The dosage of the formers were constant (1% weigth of cement) and for the third, the influence of admixture dosage was also evaluated, giving dosage values among 1-0.3%. The pastes obtained were studied by conduction calorimetry, XRD and FTIR. Also the apparent fluidity was determined by "Minislump" test. The main results obtained were: a) superplasticizers admixtures used, regardless of their nature and for the polycarboxilate one the dosage, retard the silicate hydration (specially, alite phase), b) The ettringite formation is affected by the nature of the admixture. c)A relationship between the dosage of admixture based on polycarboxilates and the time at the acceleration has been established. A lineal relation (y = 11.03 + 16.05x) was obtained. From these results is possible to know, in function of dosage admixture, the time when the masive hydration products and the setting times are produced. Also the total heat releases in these reactions is independent of the nature and dosage of admixture, saying that in all cases the reactions are the same., [ES]En el presente trabajo se ha estudiado la hidratación inicial de un cemento portland aditivado con superplastificantes de diferente naturaleza. Dichos aditivos fueron: uno basado en melaminas sintéticas, otro en copolímeros vinilicos y otro en policarboxilatos. La dosificación de los dos primeros se fijó constante en 1% en peso con relación al cemento, mientras que para el tercero se evaluó, también, la influencia de la dosificación, tomando proporciones desde el 1% hasta el 0,3%. Las pastas obtenidas se estudiaron por: calorimetría de conducción, DRX y FTIR. También se determinó la fluidez de la pasta a través del ensayo del "Minislump ". Los resultados obtenidos han indicado que: a) Los aditivos superplastificantes utilizados, independientemente de su naturaleza y para el aditivo basado en policarboxilados de su dosificación, retardan la hidratación de los silicatos (especialmente de la fase alita), b) La formación de etringita se ve afectada por la naturaleza del superplastificante. c) Se ha establecido la relación existente entre la dosificación del aditivo basado en policarboxilatos y el tiempo en el que aparece el máximo de la señal de aceleración. Obteniéndose una relación lineal (y = 11,03 + 16,05x). A partir de estos resultados es posible, en función de la dosificación del aditivo, conocer el tiempo en el que se produce la precipitación masiva de productos, así como los tiempos de fraguado. También se ha comprobado que el calor desprendido como consecuencia de las de las reacciones, asociadas a esta etapa, es independiente de la naturaleza y dosificación del aditivo, poniendo de manifiesto que las reacciones que se producen son las mismas.

[EN] This work discusses the results from accelerated tests intended to investigate the ways the different curing methods affect the carbonation of calcium alumínate cements pastes (CAC). The research was focused on the mineralogical composition of hydrated and carbonated samples. The compressive strengths and the porosity of the samples have been determined. Results point out that vaterite and aragonite are formed as a result of carbonation of both cubic and hexagonal calcium alumínate hydrates. The polymorph of calcium carbonate formed does not depend on the curing process. Carbonation rates is higher in hexagonal than in cubic hydrates. Results obtained through this study evidence that, as a consequence of the carbonation process of CAC pastes, in test conditions, an increase of the mechanical strengths occurs., [ES]En el presente trabajo se discuten los resultados obtenidos en los ensayos acelerados llevados a cabo para investigar los efectos de diferentes métodos de curado sobre la carbonatacion de pastas del cemento de aluminato de calcio (CAC). Se estudió la composición mineralógica de las muestras hidratadas y carbonatadas. Además, se determinaron las resistencias mecánicas a compresión y la porosidad de las probetas. Los resultados indican que la vaterita y el aragonito son las polimorfías del CaCO3 que se forman al carbonatar los aluminatos cálcicos hidratos, tanto los de naturaleza hexagonal como cúbica. El polimorfo del carbonato cálcico formado no depende del proceso de curado. La velocidad de carbonatación de los hidratos hexagonales es mayor que la de los cúbicos. Los resultados obtenidos en el presente trabajo han evidenciado que como consecuencia del proceso de carbonatación sobre pastas de CAC, en las condiciones realizadas, se produce un incremento en las resistencias mecánicas.

The aim of the present work was to evaluate the validity of non-calorimetric different methods, used in the determination of reaction degree of alkaline activated slag pastes. The methods used were: (a) chemical separation by methanol-salicylic acid; (b) determination of the weight loss mass between 100-600 °C in TG curves, associated to chemically combined water; (c) quantification of the -74 ppm signal in ^^Si MAS-NMR spectra. The parameters considered in the process were: nature of the alkaline activator (Waterglass, NaJZO^ and NaOH), activator concentration (4% and 3% Nafi in mass with respect to the slag), curing temperature (25 and 45 °C), slag specific surface (460 and 900 m^/kg) and time of reaction (from 7 days to 18 months). The results obtained indicate that none of the three methods is definitive but complementary and they provide to follow the reactive evolution of the alkaline activated slag cements. The method based on the quantification of the -74 ppm signal in the ^^Si MAS NMR is the most suitable method., El objetivo del presente trabajo fue evaluar la validez de diferentes métodos, no calorimétricos, utilizados en la determinación del grado de reacción de pastas de escoria activada alcalinamente. Los métodos utilizados fueron: (a) método de separación química por disolución en metanol ácido-salicilico; (b) determinación de las pérdidas de masa entre 100-600 °C en las curvas de TG, pérdidas asociadas a la cantidad de agua químicamente combinada: (c) cuantificación de la señal de -74 ppm de los espectros de ^^Si RMN MAS. Las variables consideradas en el proceso fueron: naturaleza del activador alcalino (Waterglass, Na^CO^ y NaOH), concentración del activador (4% y 3% de Nafi en masa respecto a la escoria), temperatura de curado (25 y 45 °C), superficie específica de la escoria (460 y 900 m^/kg) y tiempo de reacción (de 7 días a 18 meses). Los resultados obtenidos indican que ninguno de los tres métodos es definitivo pero sí son complementarios y permiten seguir la evolución reactiva de la escoria activada alcalinamente. El método basado en la cuantificación de la señal de -74 ppm de los espectros de ^^Si RMN MAS es el más adecuado., Centro Superior de Investigaciones científicas

[EN]The carbonation process of aluminous cement in presence of high alkali content is studied. In this work, the formation of a compound which formula is close to K^Al/COJjjJOH)JHp) is shown for the studies samples. The aluminous cement carbonation in alkali presence take place, at least, in two stages. In a first stage the aluminium and potassium carbonate hydrate joint to CaCO^ is formed. Later, that aluminium potassium carbonate hydrate is developed toward the aluminium hydroxide formation., [ES] Se realiza un estudio del proceso de carbonatación del cemento aluminoso en presencia de una concentración elevada de álcalis. En el presente trabajo se demuestra la formación, en las muestras estudiadas, de un compuesto cuya fórmula es cercana a K^Al/COJ„JOHjJHp)^. La carbonatación del cemento aluminoso en presencia de álcalis tiene lugar, al menos, en dos etapas. La primera de ellas da lugar a la formación de un carbonato de aluminioy potasio hidratado junio a CaCO^ Posteriormente estecarbonato de aluminio y potasio hidratado evoluciona hacia la formación de hidróxido de aluminio.

[EN] The alkali activation of metakaolin is a way of producing high strength cementitious materials. The processing of these materials has been the subject of numerous investigations. The present paper describes the results of a research project initiated to study the stability of these materials when exposed to aggressive solutions. Prisms of mortar made of sand and alkali-activated metakaolin were immersed in deionized water, ASTM sea water, sodium sulfate solution (4.4% wt), and sulfuric acid solution (0.001 M). The prisms were removed from the solutions at 7, 28, 56, 90, 180, and 270 days. Their microstructure was characterized and their physical, mechanical, and microstructural properties were measured. It was observed that the nature of the aggressive solution had little negative effect on the evolution of microstructure and the strength of these materials. It was also found that the 90-day and older samples experienced a slight increase in their flexural strengths with time. This tendency was most pronounced in those samples cured in sodium sulfate solutions. This behavior may be related to the change in microstructure of the cementitious matrix of the mortars cured longer than 90 days. Some of the amorphous material present had crystallized to a zeolite-like material belonging to the faujasite family of zeolites.

[EN]The alkaline activation of blast furnace slag promotes the formation of new cement materials. These materials have many advantages over ordinary Portland cement, including high strength, low production cost and good durability. However, many aspects of the chemistry of alkaline activated slags are not yet very well understood. Some authors consider that these processes occur through a heterogeneous reaction, and that they can be governed by three mechanisms: a) nucleation and growth of the hydrated phase; b) phase boundary interactions and c) any diffusion process though the layer of hydration products. The aim of this paper was to determine the mechanism explaining the early reaction of alkaline activation of a blast furnace slag through the use of calorimetric data. A granulated blast furnace slag from Avilés (Spain) with a specific surface of 4450 cm2> g-1 was used. The alkaline activators used were NaOH, Na2CO3 and a mix of waterglass (Na2SiO3·nH2O and NaOH. The solution concentrations were constant (4% Na2O with respect to the slag mass). The solutions were basic (pH 11-13). The mixes had a constant solution/slag ratio of 0.4. The thermal evolution of the mixes was monitored by conduction calorimetry. The test time was variable, until a rate of heat evolution equal to or less than 0.3 kJ kg-1 h-1 was attained. The working temperature was 25°C. The degree of hydration (α) was determined by means of the heat of hydration after the induction period. The law governing the course of the reaction changes at a certain degree of hydration. From a generally accepted equation, the values of α at which the changes are produced were determined. These values of α depend on the nature of the alkaline activator. Nevertheless, for high values of α, the alkaline activation of slag occurs by a diffusion process.

[EN]New repair mortars with biocide properties were subjected to acid rain wet/dry cycles in aggressive environment simulation chambers. Those mortars based on lime had a sepiolite addition as a biocide support. The aim of this work was to determine the influence of both the clay and the biocide on mortar behaviour under aggressive solutions. The aggressive solutions used were the following: 1) H2SO4 solution, with pH = 4.5; and 2) “acid rain” solution with pH = 3.5. In the first case (H2SO4 solution), neither the sepiolite nor the biocide had a significant influence on mortar behaviour, while in the second aggressive medium (“acid rain”), sepiolite plus biocide, a decrease in the reaction between the mortar and the “acid rain” were noted.

[EN]The effect of simultaneous addition of varying concentrations of manganese and phosphorus oxides on a C/S ≈ 3 composition has been investigated. Mineralogical changes on synthesized powders were identified by X-ray diffraction, Infra-red spectroscopy and DTA. M3 polymorph's alite formation with Mn and P inclusions less than 0.69 (wt%) Mn2O3 and 0.62 (wt%) P2O5 is shown. The Electron Paramagnetic Resonance investigations of synthesized monoclinic C3S show that Mn ions are in octahedral site as Mn2+ oxidation state. The formed solid solutions could be described with the following cationic vacancies formula: (Ca3−5X Mn4XX)(Si1−2X p2x) O5, with X ≤ 0.005.

[EN]It is well known that the presence of pollution increases the degradation of some building materials. In order to understand the influence of individual pollutants as well as the role of oxidants and water in lime mortar degradation, those materials have been exposed in atmospheric simulation chambers. According to the pollutants used in the chambers (NO, NO2 and SO2), NO2− and NO3− or SO32−and SO42− have been analysed and related with the reaction between the lime mortar and the pollutant. The reactivity order of the different pollutant (NO, NO2 and SO2), in presence and absence of water and/or oxidant has been determined.

The kinetics of hydration of alkali-activated slag (AAS) have been studied for different temperatures. The alkaline activator used was a mix of water-glass and NaOH solution. The degree of reaction was determined by means of the heat of hydration after the induction period. The reaction mechanism determined for AAS pastes was a diffusion mechanism and their activation energy was 57.6 KJ/mol.

[EN]The influence of sand nature on the burnability of white cement raw mixes manufactured using CaF2 and CaSO4 as flux and mineralizer has been studied. A methodology based on a statistical method called Experimental Design is used to establish a model. Raw mixes burnability models have been compared depending on sand nature. An Al2O3 and CaO rich sand enhances raw mix burnability, favouring clinkering. The enhancement is attributed to the different distribution of clayey material in the raw mix.

Se han estudiado los procesos de activación alcalinosulfáticos de una escoria granulada de alto horno española (Avilés, Ensidesa). Las disoluciones activantes utilizadas fueron: H2O desionizada (como disolución de referencia), Ca(OH)2 (3,5∙10-3N), NaOH (1N), Na2CO3 (2N), CaSO4∙2H2O (3,0∙10-3N) a 25ºC. Se ha comprobado la influencia de la naturaleza del catión de la disolución alcalina o sulfática sobre el proceso de activación de la escoria. Las disoluciones sódicas disminuyen el período de inducción, mientras que las disoluciones cálcicas lo incrementan. También se determinó el grado de reacción de la escoria, así como la naturaleza de los distintos productos de reacción formados, en función de la naturaleza de la disolución activante.

Se presenta el estado del conocimiento actual de los cementos y hormigones de escorias activadas alcalinamente, detallándose las características y propiedades de los citados materiales. [es]Se incide especialmente en aquellos aspectos de carácter científico y técnico que permanecen sin resolver y que, por tanto, precisan nuevas investigaciones., [en]The paper presents the state ofthe art in cements and concretes with alkaline-activated slag. Characteristics and properties ofthese materials are given. Special emphasis is made on those scientific and technical aspects which remain unsolved and which, therefore, cali for further research.

In this paper a study on the thermal behaviour of C4A3S̄ (in an open system and up to 1500 °C) is presented as well as the kinetics of decomposition of this compound. At temperatures higher than 1300 °C, the thermal decomposition of C4A3S̄ starts. Such a process is linked to a loss of SO2 simultaneously with a production of CA and CaO. After that CA and CaO reacts giving C12A7. If the temperature is lower than 1400 °C or even being higher than 1400 °C (between 1400 and 1500 °C) although only during the first moments, the decomposition process of C4A3S̄ occurs through a solid-gas reaction. This reaction is controlled by a first order kinetic and can be represented by the following equation: F1 (α) = Ln (1 − α) = − kT having a energy of activation Ea = 538 Kj mol. When the temperature surpasses 1400 °C then a melting of at least C12A7 and CA phases takes place. It occurs in such a way that when α > 0,5, the C4A3S̄ decomposition is produced in the presence of a quantity of liquid enough for considerably modifying its kinetic.

[EN] The influence of KOH presence on the evolution of hydration and carbonation of high alumina cement mortars at two different curing temperatures (4 and 40 ~ has been studied. It has been confirmed that hydration reactions at both temperatures are accelerated with KOH presence and it has a great influence on hydrated and carbonated species. The massive deposition of carbonation products leads, in all cases to a decrease in mortar porosity which leads to an increase of mechanical strengths.

A chemical, physical, mineralogical and mechanical characterization has been made of different bedding and repair mortars in mosaics from the Roman town of Italica, Spain. The main cause of deterioration in the superficial mortars is biological attack. In the repair mortars, situated at the deepest levels, all of which are based on Portland cement, the main causes of deterioration are lixiviation, corrosion of metal reinforcements in the concrete, and crystallization of salts in the cement.

Starting from an industrial cement obtained by milling together a new low energy clinker and gypsum, two blended cements containing 20% wt of fly ashes and 10% wt of limestone respectively, have been prepared. The behaviour of these three cements in Na2SO4 dissolution and sea water has been studied. The method used for testing the specimens has been the Koch-Steinneger one. As a consequence of the study it can be said that the three cements keep a good behaviour in all the aggressive media although the strengths are lower (independently of the age of the specimens) in Na2SO4 and sea water than in distilled water. Also, the composition of the hydrated pastes conserved in the aggressive liquids of different periods of time has been studied. The evolution of the content of Ca(OH)2, gypsum and Mg(OH)2 in the pastes as well as the variations observed in the morphology of C-S-H gel along the time and in function of the aggressive medium, seem to keep a good correlation with the strengths evolution. Finally it has been concluded that those cements prepared with the new low energy cement have such a composition that makes them to be resistant to the sulphate attack.

The reactivity of Ca2AlMnO5 towards water was studied, in the absence as well as in the presence of gypsum, based on a comparative study regarding the hydration process undergone by Ca2AlFeO5 in identical conditions. In the absence of gypsum, the hydration reaction of Ca2AlMnO5 (C4AMn) is more strongly exothermal than that produced in Ca2AlFeO5 (C4AF) hydration, generating hydrates of the hexagonal type which contain Mn in their structure. These hydrates exhibit a high degree of stability, and their conversion into cubic hydrates is very slow, as it does not set in but after the seven first days of hydration. The presence of gypsum does not have any retarding effect on C4AMn hydration, which occurs speedily and with remarkable heat release. The hydration product formed is an ettringite-like phase with Mn incorporated in its structure. The formation rate of this ettringite phase is much faster than in C4AF hydration.

[EN] This paper presents the state-of-the-art on hydraulic behaviour of the blast furnace slags. It analyzes different aspects such as characteristics and influence of its vitreous phase structure, its chemical composition, mechanisms that rule its hydration process, activators and activating process mechanisms, etc. At the same time, the paper presents results obtained from a chemical and mineralogical characterization of Spanish blast furnace slags., [ES] En este trabajo se presenta un estudio del estado del conocimiento en tomo al comportamiento hidráulico de las escorias de alto horno, analizando aspectos tan variados como características e influencia de la estructura de su fase vitrea, de su composición química, mecanismos que rigen su proceso de hidratación, activadores y mecanismos del proceso de activación, etc. Así mismo, se presentan los resultados obtenidos tras realizar una caracterización química y mineralógica de las escorias de alto horno españolas.

Instrumental techniques are indicated and the most adequated methodologies for determining the nature of the binder in concretes are explained. These methods are: a) Determination of the Silicic Moduli through chemical analysis of the sample. This test reveáis very different valúes between cement portland based concrete and high alumina cement based concretes. b) X-ray diffraction. It is considered as the best method. In the present paper the main diffraction Unes corresponding to the components of hydrated portland cement and high alumina cement, are given. As complementary methods having as limited use, DTA and TG are studied. The most significative changes of the hydrated phases of both cements when heated are shown. A valoration of the Oxine test is also done as well as a description of using the characteristic colour of the high alumina cement as a practical indicator for determining its presence in concretes. Finally, comments on the significance of the presence of different CaCO3 polymorhisms in portland cement concrete and high alumina cement concrétete are also done., Se indican las técnicas y se explican las metodologías más adecuadas para determinar la naturaleza del conglomerante aluminoso en hormigones. Estos métodos son: a) Determinación del Módulo Silícico, a través de Análisis Químico de la muestra problema, al considerar la acusada diferencia de aquel valor en hormigones de cemento portland, respecto a hormigones de cemento aluminoso. b) Difracción de Rayos X. Se considera la técnica idónea. Se dan en el presente trabajo las principales líneas de difracción de los compuestos característicos de los cementos hidratados, portland y aluminoso. Como métodos complementarios y de utilidad limitada se estudia el ATD y el TG. Se proponen las temperaturas más significativas de los compuestos hidratados de aquellos cementos, a través de lo cual se puede deducir la presencia de uno u otro tipo de cemento. Se hace una valoración del método de la "oxina", significando el alcance limitado del mismo. Igualmente se describe el color como indicador de gran interés práctico en la determinación del cemento aluminoso. Así como un comentario documentado sobre el significado de la presencia de diferentes polimorfías del CaCO3 en los hormigones de cemento portland y de cemento aluminoso.

Infrared spectra of sodium and potassium alkaline-metal nitrates and magnesium and calcium alkali-earth nitrates in solid phase had been recorded in order to assign the fundamental bands. The influence of the dispersal médium (alkaline halide), employed in the solid sample preparation have been discussed. The quantitative measurements of the band in ten sities at 1387 cm-1 (present in the I.R. spectra of the four nitrates in KBr médium) allowed us to determine the Lambert-Beer law slopes for each compound. These values are differents (bearing in mind experimental random errors), so we have could to affirm the nonexistence of solid solution between the nitrate and the alkaline halide médium. The L-B law obtained by us can be used for the Identification differentiation and quantitative analysis of these nitrates in solid phase, even if they are present in a very low concentration., Se ha realizado la asignación de los espectros infrarrojo (IR) de los nitratos alcalinos, sódico y potásico, y de los alcalinotérreos, magnésico y cálcico, en estado sólido. Se ha visto la influencia del medio dispersante (haluro alcalino), utilizado en la preparación de la muestra sólida. El estudio cuantitativo de la absorbencia de la banda a 1.387 cm-1 (presente en los espectros IR de los cuatro nitratos en medio KBr) permite determinar las pendientes de la Ley de Lambert-Beer Se comprueba que dichas pendientes son diferentes lo que conduce a poder afirmar que no se produce disolución sólida entre el KBr y el nitrato alcalino o alcalinotérreo. La determinación de la ley de Lambert-Beer permite la identificación y el análisis cualitativo y cuantitativo por espectroscopia IR de estos nitratos cuando están presentes en bajas concentraciones en muestras sólidas.

This paper constitutes a compilation as well as an interpretation of the present state of knowledge about the different microstructures developed in the interface areas of concrete, that is, the cement paste-aggregates, the cement paste-reinforcement, the cement paste-fiber, etc. The Chemical reactions taking place in interface areas, the development and morphology of such areas and their strength ^since interfaces are taken as the weakest points of concrete) are the aspects dealt with in some detail in this work., El presente trabajo constituye un resumen y también una interpretación del estado actual del conocimiento respecto de las diferentes microestructuras que se desarrollan en las zonas interfaciales de los hormigones, es decir: pasta de cemento-áridos, pasta de cemento-armaduras, pasta de cemento-fibras, etc. Las reacciones químicas que tienen lugar en la zona interfacial, el desarrollo y morfología de dicha zona y su resistencia (las interfases se consideran como uno de los puntos débiles del hormigón) son los aspectos que con cierto detalle se tratan en el trabajo.

Summary A comparative study of the mineralogical composition of damagedartificial building materials (mortars, plasters, etc.) andefflorescences taken from Toledo's cathedral has been carriedout by X-ray diffraction and IR spectroscopy. By means ofthe IR spectroscopy, several salts (Na 2 SO 4 , Na 2 SO 4 .10H 2 O,K 2 SO 4 ,3K 2 SO 4 .Na 2 SO 4 , CaSO 4 2H 2 O' CaSO 4 .K 2 SO 4 .H 2 O, KNO 3 , etc)have been identified. These compounds are present in verysmall amounts and, as a result, their identification by X-raydiffraction is difficult. The interpretation of these data reveals the existence ofseveral simultaneous mechanisms of degradation of the artificialbuildings materials. This is the case with some mortars containingsyngenite which has been produced by reaction of gypsum andK 2 SO 4 . This inolves the previous existence of gypsum as aproduct of degradation of CaCO 3 .

Ca2AlMnO5 compound has been characterized through the following instrumental techniques: X-ray diffraction; IR spectroscopy, electronic spin resonance and differential thermal analysis. The crystalline structure of Ca2AlMnO5 has been shown to be an orthorhombic type. Its cell parameters have been determined as well. In addition, it was verified that all manganese in this phase is present in the Mn3− form. This element occupies both octahedral positions and tetraedral ones in the mentioned orthombic cell. Finally, the differences existing between Ca2AlMnO5 and Ca2AlFeO5 have been determined: the bases by which both phases can be identified by means of the above mentioned instrumental techniques have been established.

The effect of manganese substitution into the crystal structure of the ferrite phase, Ca//2(Fe//2// minus //xAl//x)O//5, has been studied by X-ray diffraction, analytical electron microscopy and differential thermal analysis. The introduction of manganese into Ca//2Fe//2O//5 and Ca//4Fe//2Al//2O//1//0 produces a distortion of the crystal structure marked by an expansion of the b axis but without changes in crystallographic symmetry. The limits of solid solution of manganese in both phases were determined. The presence of manganese in the Ca//2Fe//2O//5 phase suppresses its ferromagnetic character.

LGTJU

[EN]The effect of quenching in the stability of the phases of different commercial clinkers and so its flexotraction and compression strength at 7 and 28 days curing time have been studied. The clinkers were reheated at 1.576'' C, for a period of thirty minutes, and were quenched in two different ways^outside at air temperature and water submersion. The samples were studied by the techniques: XRD, optical microscopy and dispersive X-ray analysis. All the water quenched clinker had always a trigonal structured alite, which has Mg and Al is solid solution. The air quenched clinkers had a monoclinic alite. The flexotraction and compression strength at 7 and 28 days of the water quenched clinkers were always lower to those of the air quenched ones. This is due to that the trigonal structured alita hydrates with much more difficulty than the monoclinic alite., [ES] Ha sido estudiado el efecto del templado en la estabilidad de las fases de diferentes clinkeres comerciales y los resultados de sus resistencias a flexotracción y compresión a los 7 y 28 días. El clinker fue recalentado a 1.576 C durante treinta minutos y templado al aire y por inmersión en agua. Las muestras se estudiaron por las siguientes técnicas: D.R.X. Microscopía y por análisis dispersivo de rayos X. El clinker templado al agua tiene alita de estructura trigonal con Mg y Al en disolución sólida. Los clinkeres templados al aire tienen alita monoclinica. Las resistencias de flexotracción y compresión a 7 y 28 días de los clinkeres templados al agua fueron siempre más bajas que las de los clinkeres templados al aire. Esto demuestra que la alita trigonal se hidrata más lentamente que la monoclínica.

It has been verified that high manganese content in raw mixes causes alters the mineralogical composition of clinkers. New phases like 2 CaO.Mn0 2 and Ca 2 AIMnO 5 are developed and C 3 A formation can be inhibited. Manganese is a flux similar to iron in the traditional raw mixes. The presence of manganese will modify the expressions of the lime saturation factor (LSF), silica modulus (Ms) and aluminum modulus (Mf). This has as consequence an increase of the proportion of interstitial phase in the obtained clinkers.