Search

Glass from the solid urban waste is presented mainly in amber, green and transparent colour. Regarding their reactivity, several studies argue that there are differences among each colour when they...

Optimisation of the packing density of cementitious materials by the addition of supplementary cementitious materials (SCMs) is a way of obtaining the same service properties with less embodied energy and reduced carbon dioxide emissions. In this paper, ternary cement pastes containing metakaolin (MK) and limestone filler (LF) finer than ordinary Portland cement (OPC) were studied to evaluate the effects of these SCMs on packing density and water film thickness (WFT). The flowability of the pastes at different water to cementitious material ratios by volume ((w/cm)v = 0·5 to 1·0) was evaluated by mini-slump and Marsh cone tests to evaluate the opposite effects caused by the incorporation of finer particles (increase of free water to lubricate the particles due to higher packing and increase of specific surface area). The incorporation of LF and MK increased the flowability when (w/cm)v was increased over the optimum water demand corresponding to the maximum packing density. The rheological properties of the pastes were primarily dominated by the relative solid packing fraction and the flowability was found to be mainly governed by the WFT. The incorporation of finer particles accelerated the setting time. The reactive particles (OPC and MK) can be replaced by LF up to 20% to obtain a similar compressive strength, as validated by Powers’ model.

This paper analyzed the eco-efficiency of concretes (water/cement ratio = 0.50; cement content=350 kg/m3, and slump = 7 cm) with blended cement containing 25% by weight calcined pozzolan o...

Se estudió una brecha vítrea con cantidad variable de mordenita para su uso como puzolana. El material se caracterizó por micros- copía óptica y electrónica de barrido (MEB), difracción de rayos X (DRX) y el contenido de zeolita se estimó mediante la técnica de tinción por azul de metileno. Luego de su molienda se determinaron las características físicas, la capacidad de intercambio catiónico (CIC), la puzolanicidad y el índice de actividad puzolánica a compresión (IAP). La técnica de tinción y la determinación de la CIC se utilizaron para evaluar el contenido promedio de zeolita. La brecha vítrea tiene actividad puzolánica después de 7 días, la demanda de agua aumenta ligeramente y su adición estimula la hidratación temprana del cemento portland. A edades tardías, la reac- ción puzolánica alrededor de los granos, observada mediante MEB, mejora la resistencia a la compresión del cemento mezcla alcanzando un IAP > 0,85 a los 28 días. A vitreous breccia with variable amount of mordenite was studied for its use as pozzolan. The raw material was characterized by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and the zeolite content was estimated by the methylene blue staining technique. After being ground, physical characteristics, cation exchange capacity (CEC), pozzolanicity, and the compressive strength activity index (SAI) were determined. The staining technique and the CEC measurement were used to evaluate the average content of zeolite. The vitreous breccia has pozzolanic activity after 7 days, the water demand increases slightly, and its addition stimulates the early hydration of portland cement. At later ages, the pozzolanic reaction around the grains, as revealed by SEM studies, improves the compressive strength of blended cements having a SAI > 0.85 at 28 days. Fil: Bonavetti, Viviana Lidia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Tandil. Centro de Investigaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires. Sede Olavarria del Centro de Investifaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires | Universidad Nacional del Centro de la Pcia.de Bs.as.. Centro de Investigaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires. Sede Olavarria del Centro de Investifaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires.; Argentina Fil: Rahhal, Viviana Fátima. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Tandil. Centro de Investigaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires. Sede Olavarria del Centro de Investifaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires | Universidad Nacional del Centro de la Pcia.de Bs.as.. Centro de Investigaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires. Sede Olavarria del Centro de Investifaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires.; Argentina Fil: Locati, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Irassar, Edgardo Fabián. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Tandil. Centro de Investigaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires. Sede Olavarria del Centro de Investifaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires | Universidad Nacional del Centro de la Pcia.de Bs.as.. Centro de Investigaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires. Sede Olavarria del Centro de Investifaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires.; Argentina Fil: Marfil, Silvina Andrea. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Centro de Geología Aplicada, Agua y Medio Ambiente; Argentina Fil: Maiza, Pedro Jose. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Centro de Geología Aplicada, Agua y Medio Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Previous studies revel that calcined illitic clay acts as potentially supplementary cementitious materials in Portland cement. Packing and workability are improved; the hydration products are like that corresponding to Portland cement and it also produces a pore size refinement improving the mechanical performance at later ages. The illitic clays have a high activation temperature and its pozzolanic activity is slow; however, it is the most abundant type of clay in several regions of the world, and therefore, their used as supplementary cementitious materials must be improved. Therefore, compression resistance values denote the effect of dilution at early ages. On the other hand, materials containing silica and alumina can be activated in an alkaline form, which would help to compensate the dilution generated by the addition. In this work, the alkaline activation of cement mixtures with calcined illitic clays is presented. As an alkaline activator, finely ground discarded glass is used. The finely ground glass, due to its amorphous nature, reacts quickly contributing to early hydration, while providing the alkalis necessary for an alkaline activation. In this paper, the blended cements with 30% of calcined illitic clays were analyzed and the effect of different percentages of replace by glass powder wastes was studied.

In this paper, durability parameters (water sorptivity, water penetration, chloride penetration and natural carbonation) are studied on conventional mixtures (w/cm = 0.50). Concretes were elaborated with Portland cement (PC) and blended Portland cements, containing 25% replacement by illitic calcined clay (ICC) and low-grade kaolinitic calcined clay (KCC). They were characterized by slump, compressive and tensile strengths and bulk porosity. Water sorptivity (ASTM C 1585) was determined on concretes cured 2, 7 and 28 days; water penetration test (EN 12390) and chloride penetration (ASTM C 1556) were determined on concretes cured 28 days. Carbonation depth undergoing a good and very good curing was assessed using a phenolphthalein indicator at 3 and 6 months of natural exposition. Results show that water sorptivity is reduced when concrete is curing for 2, 7 and 28 days for all concretes. KCC has a significantly lower sorptivity than PCC and ICC. At 28 days, the water penetration is deeper for ICC and lower for KCC concrete. All concretes have similar apparent chloride diffusion coefficients. After six months, the natural carbonation of all concretes is less than 2 mm, with a slightly lower performance of ICC and KCC than PCC.

A large amount of ceramic sanitary ware wastes (SW) results from the production and after demolition processes. This study proposes the use of SW as supplementary cementing materials (SCM) in concrete to contribute with construction and demolition waste management. Experiments were carried out on concretes and pastes using different proportions of SW-replacement. Physical, mechanical, and durable behavior of concrete was evaluated and how concrete was affected by the cement hydration process. The incorporation of SW to Portland cement to make concrete reduces the permeability in the matrix and refines the capillary pores, improving the mechanical properties and the behavior in aggressive environments, such as chlorides. The results show that it is recommended the use of SW as SCM to produce concretes with mechanical properties and durability comparable to those of a conventional concrete, at 28 days. Fil: Zito, Silvina Vanessa. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Irassar, Edgardo Fabián. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Rahhal, Viviana Fátima. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina

The thermal transformation (100–1100 °C) of two shales containing illite-chlorite (I/Ch), feldspars and quartz from La Cabañita quarry (Olavarria, Argentine) was studied by TG-DTA, XRD and FTIR. It included dehydration; dehydroxylation (350–800 °C) and the structural collapse of illite (950 °C); while the neoformations were hematite and iron spinel. For rotary kiln production, the glass formation due to feldspars melting at 1100 °C was the upper temperature limit. For the calcination temperature range of 900–1100 °C, grindability increased when calcination temperature increased, but the specific surface area decreased. The high Fe-content caused a reddish color of particle surface, but their cores were black. The pozzolanicity test was satisfied at 7 days and strength activity index was 0.84–0.97 and 0.94–1.04 at 28 and 90 days, respectively. The addition of calcined shale did not affect the mortar flow and the hydration products assembly. Calcined I/Ch shale was a slow reactive pozzolan with good strength at 90 days. Fil: Irassar, Edgardo Fabián. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Bonavetti, Viviana Lidia. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Castellano, Claudia Cristina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría; Argentina Fil: Trezza, Mónica Adriana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Rahhal, Viviana Fátima. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Cordoba, Gisela Paola. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría; Argentina Fil: Lemma, Roxana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina

Clayminerals are the most abundant raw materials for calcined pozzolans. Thermaltransformation includes dehydration, dehy­droxylation, mineral collapse, andneo-formation. Depending on the type and amount of clay mineral, and the natureand amount of associated minerals, the thermal treatment determines the pozzo­lanicactivity. In this paper, 10 natural shales or clays (six illite, two kaolin,and two loess) from Buenos Aires Province (Argentina) were identified using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), andthermogravimetry (TG). The thermal transformation was checked by XRD or FTIR and the elec­trical conductivity (EC) at the calcination window. The pozzolanicactivity was evaluated using the Frattini test and strength activity index (SAI). The Frattini test gives positive results after 7 days and SAI is greaterthan 0.90 at 28 days, but the compressive strength development depends on mainclay mineral. The EC was effec­tive to evaluate the Ca(OH)2 fixationduring the first time and it is related to the specific surface obtained. Fil: Irassar, Edgardo Fabián. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría. Departamento de Ingeniería Civil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Tironi, Alejandra. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría. Departamento de Ingeniería Química; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Bonavetti, Viviana Lidia. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría. Departamento de Ingeniería Civil; Argentina Fil: Trezza, Mónica Adriana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría. Departamento de Ingeniería Química; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Castellano, Claudia Cristina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría. Departamento de Ingeniería Civil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Rahhal, Viviana Fátima. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría. Departamento de Ingeniería Civil; Argentina Fil: Donza, Horacio Ariel. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría. Departamento de Ingeniería Civil; Argentina Fil: Scian, Alberto Nestor. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina

The aim of this study is to evaluate the behavior of glass powder waste as alkaline activator of slag when both are used in blended cement. The slag blended cement was prepared with 70% slag, and then the slag was replaced with 10-20% glass powder by mass. The self-activation concept is here introduced. Ground glass releases alkalis through dissolution in a slow and sustained way over time. This would activate slag. Ground glass improves fluidity of mortars and the compressive strength overcomes dilution and increases with age due to the combined pozzolanic action of slag and glass. The proposed blended cement has better mechanical properties than slag-cement. The proposed blended cement has better mechanical properties than slag-cement and due to less use of slag, it becomes more sustainable and it contributes to waste management. El objetivo del presente trabajo es evaluar el comportamiento de un residuo molido de vidrio como activador interno de la escoria cuando ambos son usados en un cemento mezcla. El cemento de escoria fue preparado con un 70% de escoria y luego la escoria se reemplazó en un 10 y 20% en masa por vidrio molido. Este trabajo introduce el concepto de auto-activación. El vidrio molido libera álcalis por disolución, en forma lenta y sostenida en el tiempo que activarían la escoria. La presencia de vidrio molido mejora la fluidez de los morteros y la resistencia a compresión supera la dilución y crece con la edad por la acción puzolánica combinada de la escoria y el vidrio. El cemento mezcla propuesto tiene mejores propiedades mecánicas que el cemento de escorias pero con menor contenido de escoria por lo que es más sustentable y contribuye al manejo de residuos.

In this paper the rheological behavior of fresh Portland cement pastes mixed with different calcined clays was analyzed. For this purpose, two samples of Portland cement with different mineral composition (one with low C3A and high C3S content and another with low C3S and high C3A) were used combined with different replacement percentages of two calcined clays (two different metakaolin). Grounded α-quartz was used as control as well. Both mineral admixtures had different crystallinity and morphology: the α-quartz is fully crystalline while metakaolin is completely amorphous with a very small crystalline fraction giving very high pozzolanic properties in the vitreous state. All determinations were performed in the hydration latency period. The results show that the fresh Portland cement paste with low C3A(%) content and high C3S(%) content present great shear strength and the replacement with calcined clays affects the rheological behavior of the fresh pastes depending on the greater or lower pozzolanic reactivity of the mineral addition.

This paper studies the addition (0–40% w/w) of natural zeolite (NZ, 84% clinoptilolite) in blended cements made with Portland cement (PC) with low and medium C3A content. The isothermal calorimetry was used to understand the effect of NZ on the early cement hydration. For low C3A cement, the addition of NZ produces mainly a dilution effect and then the heat released curve is similar to plain cement with lower intensity. For medium C3A cement, the curve shows the C3S peak in advance and a high intensity of third peak attributed to C3A hydration. The high cation fixed of NZ reduces the ions concentration (especially alkalis) in the mixing water stimulating the PC hydration. The flowability decreases when the NZ replacement level increases. Results of Fratini’s test show that NZ with both PCs used presents slow pozzolanic activity. At early age, XRD and FTIR analyses confirm that hydration products are the same as that of the corresponding PC and the CH is progressively reduced after 28 days and some AFm phases (hemi- and monocarboaluminate) appear depending on the NZ percentage and the PC used. For low replacement levels, the compressive strength is higher than the corresponding PC from 2 to 28 days. For high replacement levels, the early compressive strength is lower than that of corresponding plain PC and the pozzolanic reaction improves the later compressive strength of blended cements. Fil: Rahhal, Viviana Fátima. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Pavlík, Zby?ek. Czech Technical University in Prague; República Checa Fil: Tironi, Alejandra. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Castellano, Claudia Cristina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Trezza, Mónica Adriana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Černý, Robert. Czech Technical University in Prague; República Checa Fil: Irassar, Edgardo Fabián. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina

The effects of two illitic calcined shales as supplementary cementitious materials (SCMs) on the performance of ordinary Portland cement (OPC)-based pastes and mortars were investigated. The packing density of blended cement pastes and mortars were predicted with compressible packing model (CPM). The water film thickness (WFT) and flowability were calculated and measured. Early hydration was described by calorimetric curves and the hydration microstructure was identified by X-ray diffraction (XRD), differential thermal analysis (DSC/TG), and pore size distribution (MIP). The compressive strength was tested at 2, 7, 28, and 90 days. The results showed that the partial replacement of OPC by illitic calcined shale decreased the packing density and the flowability of cement pastes but this does not occur for standard mortars. For blended cements, the hydration products were similar to that corresponding to OPC, the pozzolanic reaction contributed from 28 days to the densifying of solid structure and it was also noticed the pore size refinement that improved the compressive strength at later age.

RESUMEN Por su alto contenido de sílice en estado amorfo, los vidrios en teoría pueden comportarse como materiales puzolánicos cuando se muelen finamente. Esto abre una interesante vía de reutilización de estos residuos en la industria del cemento portland (CP), sobre todo si se considera que los residuos sólidos urbanos (RSU) en Argentina contienen entre el 3 y 5% en peso de vidrio. Este trabajo estudia el comportamiento de residuos de vidrio blanco molido, procedente de botellas en comparación al correspondiente a la microsílice (MS), de reconocida actividad. El objetivo de este trabajo es analizar las diferencias estructurales, composición mineralógica, tamaño y forma de partícula de la MS y el vidrio molido en cuanto a su reactividad y actividad puzolánica. Se presentan resultados experimentales sobre pastas y morteros con porcentajes variables de ambas adiciones (8, 16 y 24% en peso). Se analiza la cinética de hidratación temprana por calorimetría de conducción, la potencial puzolanicidad por el ensayo de Frattini y el seguimiento de la hidratación de las pastas por difracción de rayos X (DRX). Se presentan resultados de fluidez y resistencia a compresión sobre morteros normalizados a 2, 7 y 28 días. Los estudios realizados muestran que la incorporación de vidrio molido como adición, desarrolla más lentamente actividad puzolánica y en menor medida que la MS, sin embargo no reduce la fluidez de los morteros y contribuye significativamente a la resistencia mecánica. ABSTRACT Due their high content of silica in an amorphous state the glass, in theory, can behave as pozzolanic material when are finely ground. This opens up an interesting way of reusing these materials in the Portland cement industry (CP), especially considering that solid urban waste (RSU) in Argentina contains between 3 and 5% by weight of glass. This paper studies the behavior of ground white glass from bottles, in compares that corresponding to microsilice (MS), with recognized activity. The objective of this paper is analyzed the structural differences, mineralogical composition, size and particle shape of the MS and the ground glass in terms of reactivity and pozzolanic activity. Experimental results on pastas and mortars with variable percentages of both additions (8, 16 and 24%) are presented. The kinetics of early hydration by conduction calorimetry, the potential pozzolanity by the Frattini test and the X-ray diffraction (DXR) paste hydration monitoring are analyzed. Fluidity and compressive strength results are shown on standar mortars at 2, 7 and 28 days. In general the incorporation of ground glass develops its reactivity more slowly and to a lesser extent than the MS, however it does not reduce the fluidity of the mortars and contributes significantly to the compressive strength.

We study the hydration and pozzolanic reactions of cement pastes made from Argentinian and Czech Portland cements as a function of age, using thermogravimetry. The measurements are done for 2, 7, 28, and 90 days cured samples in order to monitor the rate of hydration. The investigation is performed in the temperature range from 25 °C to 1000 °C with a heating rate 5 °C/min in an argon atmosphere. The mass change during the decomposition of calcium silicate hydrate gels, portlandite, and calcite are determined, and the changes in the portlandite amount are estimated in dependence on the time of hydration.

Illite-chlorite clay from quarry located at Buenos Aires Province (Argentine) was characterized by XRD, FTIR and TG-DTA. Mineralogical transformations during clay firing under oxidizing conditions were studied from 100 to 1100 °C by XRD and FTIR. From select temperatures, calcined clay was ground (85% passing to 45 µm sieve) and the pozzolanic activity of blended cements (25% w/w) was evaluated by the Frattini test and the strength activity index (SAI). Finally, the hydration phase assemblage of blended cements was studied using XRD analysis.

In this paper, the paste workability and hydration progress of blended cements containing different calcined illitic clays were studied. For blended cements with different replacement percentages, the particle packing, the water film thickness (WFT) and the flow spread was modelled and measured. Results indicate that blended cement with ground illitic calcined clays maintain or reduce the packing, so the flow spread of blended cement pastes decrease when the replacement percentage increases. For blended cements with 25% of calcined illitic clay, the early hydration was described by the calorimetric curve, and later the hydration products were analysed by XRD and TG analysis and the pore size distribution (MIP) at 2, 7, 28 and 91 days. Finally, the performance of blended cements was evaluated by the compressive strength. For blended cements, the hydration products are similar to that corresponding to ordinary Portland Cement (OPC) and it also produce a pore size refinement that improve the compressive strength at later age.

The rheological behaviour of fresh Portland cement (PC) pastes with different chemical and potential mineralogical compositions was analysed when were blended with crystalline mineral additions (fillers). These two fillers were very different: a siliceous, Q, α-quartz type, and another limestone, C. Trials were conducted during latent hydration at 25 °C. The findings showed that apparent viscosity was higher in the PC with low C 3 A and high C 3 S content, consequently , the Na 2 O eq .(%) content of everyone also contributed very significantly. Moreover, it was also observed that the incorporation of each filler affects differently the rheological behaviour of fresh cement pastes. The different influence is due to the different physical and chemical properties of each filler (nature, chemical composition and character and texture intimate of the particles), and also of the type of PC to interact. Finally and at these very early ages, both fillers stimulated the hydration of the PC which they were mixed by direct and non-direct way, and in the case of C filler by indirect way as well, but without any pozzolanic activity. Despite the fact that blended cement P1/Q 60/40 has proved to be a “false positive” in Frattini test.

The mineralogical composition of special purpose Portland cements must conform to certain requirements. Sulphate-resistant Portland cements, for instance, the tricalcium aluminate (C 3 A) and tetracalcium aluminoferrite (C 4 AF) phase’s contents must be very low to minimize the consequences of the hydration of large amounts of sulphates and the wide fluctuations in volume that would entail. At the same time, for economic, technical and environmental reasons, primarily pozzolanic additions, some of which are aluminic in chemical character, are included in Portland cements. When thermally activated clays such as metakaolin ( aluminic pozzolan) are added to Portland cements with low (to nil) C 3 A content, an AFt phase of pozzolan origin may also form. The present study corroborated previous reports of the formation, but at very early ages (48 h), of such an AFt phase of pozzolan origin, mainly, in a Portland cement blend containing minimal C 3 A content, an aluminic pozzolan in chemical character ( metakaolin , M pozzolan) and excess gypsum, 15.05% (=7.0% SO 3 ); and if C 3 A content in OPC is high, the AFt phase originated is of pozzolan origin as well, and in addition, of such C 3 A content, generating so greater or lesser Expansive Synergic Effect , ESE, according to the greater or lesser pozzolanic activity amount originated previously by M pozzolan in this case, and for this reason, being the ettringite from M pozzolan its chief direct and indirect cause. On the other hand, it also proved that such excess gypsum acted as a setting regulator in blended cements with metakaolin and a retarder in all the other cements tested, whether they were pure Portland cements or blends containing a crystalline mineral addition, Q , and also some blended cements with metakaolin can be regarded as being “ hydraulic expansive cements ” according to ASTM C 845-90 Standard.

The standard use of admixtures in Portland cements (with and without mineral additions)-based concrete manufacture today has made the physical–chemical interaction among the various components a highly topical issue. One way to analyse the resulting effects is discussed in this paper, which substantiates the importance of a careful selection of the parameters used to evaluate the rheological behaviour of plain fresh pastes of Portland cements. To this end, the pastes studied in this research contained no mineral additions. The initial analysis explored the variations in rheometer response depending on angular velocity and phase duration. Ramp direction, number of angular velocities and the size of the inter-velocity steps were also studied. Lastly, the importance of allowing the cement paste sample to rest during the measurement sequence was also analysed. These trials were conducted on two types of Portland cements with completely different mineralogical compositions. They were repeated every 20 min prior to the initial setting time, more exactly up to the first nadir on their heat of hydration release curves, determined in earlier conduction calorimetry studies. The results showed that parameter selection in designing a scheme to evaluate the rheological behaviour of fresh Portland cement pastes had a substantial effect on the response obtained. That response was also highly dependent upon the degree and type of hydroxy-induced alkalinity in the liquid phase of the pastes, in turn a result of the mineralogical and chemical composition of the PCs, in particular their N 2 O and K 2 O (%) contents, which therefore proved to play a prominent role in rheological behaviour.

Two waste fired brick powders coming from brick factories located in Argentine and Czech Republic were examined as alternative mineral admixtures for the production of blended cements. In pastes composition, local Portland cements (Argentine and Czech) were substituted with 8&ndash, 40%, by mass, with powdered ceramic waste. For the ceramic waste-Portland cement system, workability, the heat released, pozzolanity, specific density, compressive strength, hydrated phases, porosity, and pore size distribution were tested. The relevance of the dilution effect, filler effect, and pozzolanic activity was analyzed to describe the general behavior of the pozzolan/cement system. The properties and performance of cement blends made with finely ground brick powder depended on the composition of ceramic waste and its reactivity, the plain cement used, and the replacement level. Results showed that the initial mini-slump was not affected by a low ceramic waste replacement (8% and 16%), and then it was decreased with an increase in the ceramic waste content. Brick powder behaved as a filler at early ages, but when the hydration proceeded, its pozzolanic activity consumed partially the calcium hydroxide and promoted the formation of hydrated calcium aluminates depending on the age and present carbonates. Finally, blended cements with fired brick powder had low compressive strength at early ages but comparable strength-class at later age.

Supplementary cementitious materials (SCMs) affect the packing density and water film thickness (WFT) of blended cement paste. Herein, the effects of limestone filler (LF) and metakaolin (MK) on the packing density, WFT, flowability, heat of hydration, setting time and compressive strength of blended cement paste were studied. It was found that the addition of LF and MK would increase the packing density but whether it would increase the WFT is dependent on the change in solid surface area. Moreover, dispersion caused by finer particles stimulates the early hydration and reduces the setting time for the same SP dosage. However, the early compressive strength depends on the stimulation and dilution effects of SCM and retarding effect of SP.

Cement industry belongs to the business sectors characteristic by high energy consumption and high \(\hbox {CO}_{2}\) generation. Therefore, any replacement of cement in concrete by waste materials can lead to immediate environmental benefits. In this paper, a possible use of waste ceramic powder in blended binders is studied. At first, the chemical composition of Portland cement and ceramic powder is analyzed using the X-ray fluorescence method. Then, thermal and mechanical characterization of hydrated blended binders containing up to 24 % ceramic is carried out within the time period of 2 days to 28 days. The differential scanning calorimetry and thermogravimetry measurements are performed in the temperature range of \(25\,^{\circ }\hbox {C}\) to \(1000\,^{\circ }\hbox {C}\) in an argon atmosphere. The measurement of compressive strength is done according to the European standards for cement mortars. The thermal analysis results in the identification of temperature and quantification of enthalpy and mass changes related to the liberation of physically bound water, calcium-silicate-hydrates dehydration and portlandite, vaterite and calcite decomposition. The portlandite content is found to decrease with time for all blends which provides the evidence of the pozzolanic activity of ceramic powder even within the limited monitoring time of 28 days. Taking into account the favorable results obtained in the measurement of compressive strength, it can be concluded that the applied waste ceramic powder can be successfully used as a supplementary cementing material to Portland cement in an amount of up to 24 mass%.

The production of a cement binder generates a high amount of CO2 and has high energy consumption, resulting in a very adverse impact on the environment. Therefore, use of pozzolana active materials in the concrete production leads to a decrease of the consumption of cement binder and costs, especially when some type of industrial waste is used. In this paper, the hydration of blended cement pastes containing waste ceramic powder from the Czech Republic and Portland cement produced in Argentina is studied. A cement binder is partially replaced by 8 and 40 mass% of a ceramic powder. These materials are compared with an ordinary cement paste. All mixtures are prepared with a water/cement ratio of 0.5. Thermal characterization of the hydrated blended pastes is carried out in the time period from 2 to 360 days. Simultaneous DSC/TG analysis is performed in the temperature range from 25 °C to 1000 °C in an argon atmosphere. Using this thermal analysis, we identify the temperature, enthalpy and mass changes relat...

The effects of mineral additions, quartz (Q) and limestone (C) fillers, on Portland cement (PC) hydration are ultimately reflected in the mechanical behavior and durability of the resulting concrete. The physical and chemical interactions involved may expedite or retard the hydration rate. The present paper describes the hydration mechanism in Portland cements containing crystalline mineral additions (fillers, non-pozzolanic), based on the reaction rates and amount of products formed. The mineralogical composition of the Portland cements used determines their differential behavior when exposed to sulfate or attacked by chloride, separately. Ground quartz, Q, and limestone, C, were the mineral additions chosen. The results show that direct and non-direct stimulation of the hydration reactions increase with the replacement ratio and, obviously, as a result of the concomitant physic dilution effect. Mixing water would be responsible for direct stimulation. non-direct stimulation, in turn, would occur very early in PC hydration, for the positive and negative electrostatic charge acquired by the particles of filler during grinding and/or initial mixing, and subsequently the zeta potential is generated as PC hydration progresses. On the other hand, it has also been demonstrated that both of the fillers interact chemically as specified below. Hence, Q filler is influenced by the portlandite of any PC, OPC and/or SRPC (due to its randomly inner texture totally compact, but above all, to its acid chemical character) to originate CSH-gels, although in a very slowly way, and for this reason, its chemical interaction is specific for the portlandite and generic for any PC of C3A significant content. Whereas, C filler interacts chemically mainly with the C3A to originate different carboaluminate types, and for this reason, its chemical interaction is specific for the C3A only. Consequently, overall system behavior varies depending on the crystalline mineral addition, the type of PC and the replacement ratio.

The Friedel’s salt (Fs) is often formed when reinforced concrete is attacked by chlorides from marine environmental and/or thaw salts. In this investigation, a semi-quantitative analysis and study of the Fs (2θ range = 11.16–11.34°) in the solid phase of the Frattini test was made by XRD analysis. For this purpose, two Portland cements (PC) P1 (14% C3A) and PY6 ( 1. All the pozzolans exhibited different pozzolanic activity depending on the mineralogical composition of the Portland cement with which they were tested, although such differences were attributable more to their Al 2 O 3 r - (%) content than to their SiO 2 r - (%) content for the case of the pozzolans A, C, M1 and M0 specially. Thus, M0, M1, C and A pozzolans mainly, tend to sustain [OH−] content and react readily with Ca2+. On the contrary, for the SF and D pozzolans was due to their SiO 2 r - (%) content only, which react with both, Ca2+ and OH− ions, in the same way. But despite what the physical state of D pozzolan is like SF, vitreous mainly and its SiO 2 r - content as well (practically), the size and shape of their respective particles (“frustules” for D, empty, perforated sheaths) are totally different, and as a consequence, their respective behaviour in the Frattini test has been different as well. 2. In this investigation, the Friedel’s salt (Fs) owns its formation to two different origins: the C3A of PC and to the reactive alumina, Al 2 O 3 r - , of pozzolans which reaction with chloride ions, pointing the latter as a preferential (see point 3); but it is also possible C4AF reactivity involved at later ages. 3. The role of the reactive alumina, Al 2 O 3 r - , and reactive silica, SiO 2 r - , (vitreous and/or amorphous fractions of the pozzolanic additions) during the Friedel’s salt formation has been specified and, as a result, the formation rate of Fs from Al 2 O 3 r - of pozzolan turns out to be notably higher than the formation rate of Fs from C3A of PC. For this reason, both have been termed rapid forming Fs or Fs-rf and slow forming Fs or Fs-lf, respectively, but in any case, topochemical mechanism with prior dissolution must be preponderant over through-solution mechanism. 4. The Friedel’s salt formation in all the PC/pozzolan blends have coincided quantitatively in the vast majority of the cases with the respective reactive alumina, Al 2 O 3 r - (%), content of each pozzolan. The number of these coincidences was greater for the PY6 blends, due to its C3A practical absence in these samples, since its presence in the P1 blends can stimulate directly, non-directly, but above all, indirectly the chemical reaction of the C3A hydration with NaCl solutions (3.75% and 3.00% in this study) and influence like that in the velocity of the compound formation: Fs. 5. The physical state of the reactive alumina, Al 2 O 3 r - , in C natural pozzolan must be more amorphous than vitreous, resembling metakaolin more than fly ash. That notwithstanding, pozzolan composition must have conditioned the water/cementitious material ratios obtained for their respective P1 and PY6 blended cements (a finding that could be used in the future for speedy, easy, reliable, reproducible and inexpensive characterization of natural and artificial pozzolans, and logically for this purpose, its previous physics-chemical analysis, Frattini test at 2 and/or 7 and/or 28 days-age and/or mechanical strengths will also be previously needed), as well as its specific pozzolanic activity.

The calorimetric technique provides continuous, direct, and general measurements of the course of coexisting reactions and their interactions during hydration of blended cement at early age. In this article, this technique is used to analyze the influence of compositional and process variables on the early age hydration of Portland limestone cements (PLC) made by intergrinding in a full size-cement plant. Eight cements, the vertices of 23 factorial design, were made with a limestone filler content (LF) of 0 and 24%, a gypsum content (GC) of 2.5, and 5.0%; and a fineness, measured as that fraction retained on a 45 μm sieve (R45), of 5 and 18%, to study their effects on the heat released. In addition, a PLC with a composition nearly to the center point of 23 designs was analyzed. Measurements were performed on cement pastes (w/cm = 0.4) using a semiadiabatic differential calorimeter operating at 20 °C during 48 h. At different time, the heat released was determined and it was modeled using a linear mathematical model including the three variables (LF, R45, CG) and their interactions. The significance of the model, the variables and the interactions was judged using the analysis of variance. Results of model show that heat released is reduced by LF due to physically dilution phenomenon, which is directly proportional to LF content. The R45 exerts its major influence during the development of second peak (12–21 h) but later its effect declines to null contribution. GC retards and attenuates the hydration reactions moderately until 30 h, and then its increase contributes to Qt due to the formation of ettringite and its transformation. The only significant interaction was LF with R45 during the second peak development. Results present good correlation with the isolate measurement of compressive strength at 12, 24, and 48 h.

This paper examines the behavior of Portland limestone cements (PLCs) made by inter-grinding clinker, gypsum and limestone in a full size-cement plant, while varying the content of limestone filler (LF – 0% and 24%), content of gypsum (GC – 2.5% and 5.0%) and PLC fineness, measured as that fraction retained on a 45 μm sieve (R45 – 5% and 18%). The influence of the combined action of these variables on the particle size distribution (PSD) and early age properties of blended cement was studied using a 23 experimental design. Fineness evaluated by the parameters of the Rosin–Rammler–Springer–Bennett (RRSB) distribution function shows that the uniformity index (n-parameter) depends strongly on LF content; while the characteristic diameter (x′-parameter) depends on R45 and LF content. As for the inter-grinding process, water demand is reduced by incorporation of LF and increased by reduction of R45, producing a compensation. Setting time is mainly affected by R45; LF produces a few modifications and the influence of gypsum content and gypsum–limestone interaction are not as obvious. Calorimetry studies show that LF decreases the height of the main peak and the total heat released, while gypsum content modifies the time of acceleration and the post-peak hydration, specifically for fine cements. In accordance, chemical shrinkage decreases when R45, LF content and gypsum content increase. Up to 2 days, strength is mainly governed by the R45 and the LF in PLC, which act inversely. At early ages, the influence of gypsum content on early properties increases up to 48 h. XRD analysis shows its stimulation of calcium silicate hydration during the first hours and ettringite formation after 24 h.

37 páginas, 5 figuras, 6 tablas., [ES] Este trabajo ha tenido por objetivo determinar la viabilidad de uso de dos residuos agroindustriales incinerados, cenizas C1 y C2, como posibles adiciones puzolánicas artificiales, para fabricar cementos y/o de sus productos derivados, hormigones y morteros tradicionales y especiales, principalmente; de aquí su estudio comparativo con el humo de sílice español, HS. Y la conclusión que se obtuvo fue que las dos cenizas pueden ser consideradas como adiciones puzolánicas artificiales con carácter químico silícico cierto, pero sólo una, la C2, podría llegar a ser considerada como “microsílice”, porque su pérdida por calcinación se encuentra dentro de su límite permitido. En cambio la C1, no, porque dicha pérdida fue demasiado elevada, aún cuando, su contenido de sílice reactiva, SiO2r-, era mayor por lo que en su caracterización química y sulfática se mostró más cercano al del HS que la C2. Finalmente se ha podido justificar también que, la adopción de cualquier método de ensayo para determinar la resistencia potencial a los sulfatos de los cementos portland con filler calizo carece de sentido., [EN] This study attempted to determine the viability of using incinerated agro-industrial waste, ashes C1 and C2, as possible artificial pozzolanic additions in traditional and highperformance concretes and mortars, mainly, and for this reason, a comparative study was likewise conducted with Spanish silica fume (HS). The conclusion drawn from the findings was that the two ashes used could be regarded to be centainly, silicic artificial pozzolanic additions but only C2, which had a higher SiO2 content, could be regarded to be a “microsilica”, however, because its loss on ignition, L.O.I., fell within the acceptable range of variability. In contrast, C1 could not be so regarded because its L.O.I. was too high, despite its higher reactive silica SiO2r- content. For this reason, ash C1 had to be ruled out for any of the proposed uses, even though in terms of chemical and sulfatic characterization it was closer to HS than C2. By contrast, the mechanical strength values of C2 and HS were comparable, making the former initially acceptable for any of such uses. Finally, it has also been justified that, adoption of any method of trial to determine potential resistance to the sulfates of the Portland cements with calcareous filler lacks of sense.

The present paper analyses the influence of three siliceous mineral admixtures or mineral additions, on hydration reactions of two Portland cements with very different mineral composition, but focussing it on the heat hydration parameter, mainly. The main techniques used in the study were conduction calorimetry and Frattini test and the ancillary analytic tests included the determination of setting times and the chemically combined water amount as well as X-ray diffraction analysis of the plain PC and their blended cement pastes. The results show how size, morphology and crystalline or vitreous state of the siliceous mineral additions affect its pozzolanicity and hydraulicity and, concomitantly, the hydration reactions in Portland cements with widely varying mineralogical characteristics. On the other hand, the findings also differentiate the effects of direct , non-direct and indirect stimulation of the hydration reactions by these siliceous mineral admixtures. In addition, it is sustained that when these types of effects occur jointly under certain conditions, they may induce results that can be regarded to be the comparable to a Calorific Synergic Effect .

The need for cements or other cementitious materials that afford high early age mechanical strength has led to the use of extremely reactive pozzolanic additions such as silica fume, nanosilica, metakaolin and similar. The inclusion of the right proportion of such pozzolanic additions stimulates portland cement hydration, i.e., directly, as they are initially moistened by the mixing water, non-directly when they act as “seed crystals”, and indirectly, because of the pozzolanic reaction between the addition particles and the portlandite forming from the portland cement components hydration; since this reaction is characterized by its intensity and speed, when its occurs it prevails over the other two. Indirect stimulation also causes the fraction of portland cement in the blend to release more heat of hydration than pure portland cement, and its does so on a scale consistent with the existence of a calorific synergic effect. Such greater heat is released in the early stages of hydration primarily by C3A and C3S that react with the mixing water to respectively generate ettringite and hydrated calcium silicates. When portland cements have a low to nil C3A content, less heat of hydration is released due to the absence of an AFt phase that could be transformed into AFm. However, when extremely active pozzolanic additions, such as silica fume, are used, ettringite forms from C4AF, further contributing to origin amounts of hydration heat released comparable to the above calorific synergic effect.

This research reports on the effects of including natural pozzolans in two Portland cements with different mineralogical compositions, with and without excess gypsum at amounts equivalent to 7.0% SO3. The main analytical techniques used to study these effects were: the amount of water needed to make a paste of normal consistency, the 2-day Frattini pozzolanicity test and conduction calorimetry. The results obtained showed that these natural pozzolans caused contradictory (accelerating and retarding) effects on the rheology of the resulting cements, depending on the mineralogical composition of the respective Portland clinkers as well as the reactive chemical composition of the pozzolans, in particular their reactive alumina content (Al2O3r−). The addition of gypsum also caused acceleration and delays in the calorimetric evolution of the resulting pastes, which proved to be heavily dependent upon the more or less aluminic chemical character of the natural pozzolans studied. This, in turn, was conditioned by the higher or lower Al2O3r− content (for the SiO2r− content was of a very similar order of magnitude in all three pozzolans analyzed). The Al2O3r− content was likewise responsible for paste behaviour in the afore-mentioned trials and analyses, and the pozzolanic activity exhibited by the compound was found to be more specific than generic, indirectly stimulating C3A hydration more intensely and rapidly than C3S hydration in PC1, one of the two Portland cements used. Indeed, when these natural pozzolans exhibited such prior pozzolanic activity in the second cement studied, PC2, the hydration of its 79.5% of C3S was not indirectly stimulated to the same degree; rather, the contrary effect was observed, i.e., this cement was physically diluted by the three pozzolans. Pozzolan O stimulated hydration directly and non-directly more than indirectly, while pozzolan C acted conversely, and A exhibited varying combinations of the two patterns. The physical state of the reactive alumina, Al2O3r−, in these three natural pozzolans, must be more amorphous than vitreous, i.e., resembling metakaolin more than fly ash in this regard. That notwithstanding, the reactive alumina content in each pozzolan must have conditioned the water/cementitious material ratio obtained for the respective blends with both types of Portland cement (a finding that could be used in future for speedy, simple, reliable and economical characterization), as well as their specific pozzolanicity developed and the rate and total heat of hydration generated by such blended cements.

This paper analyzes the effect of fly ash chemical character on early Portland cement hydration and the possible adverse effects generated by the addition of gypsum. Behaviour was analyzed for pure Portland cements with varying mineralogical compositions and two types of fly ash, likewise differing in chemical composition, which were previously characterized under sulphate attack as: silicic-ferric-aluminic or aluminic-silicic ash in chemical character, irrespective if they are in nature, siliceous or siliceous and aluminous materials according to the ASTM C 618-94a. The experimental results showed that water demand for paste with a normal consistency increased with the replacement ratio in fly ash with a more aluminic than silicic chemical character, whereas it declined when silicic-ferric-aluminic ash was used. On the other hand, the differences between the total heat of hydration released at the first valley and the second peak also clearly differentiated the two types of ash. While the relative differences increased in the more aluminic than silicic ash, they declined in the more silicic than aluminic. In another vein, the findings indicate that within a comparable Blaine fineness range, the reactive alumina (Al2O 3 r− ) content in pozzolanic additions has a greater effect on mortar strength than the reactive silica (SiO 2 r− ) content, at least in early ages up to 28 days. Finally, the adverse effect generated in the presence of excess gypsum is due primarily to the chemical interaction between the gypsum and the C3A in the Portland cement and the reactive alumina (Al2O 3 r− ) in the fly ash.

The use of active mineral additions is an important alternative in concrete design. Such use is not always appropriate, however, because the heat released during hydration reactions may on occasion affect the quality of the resulting concrete and, ultimately, structural durability. The effect of adding up to 20% silica fume on two ordinary Portland cements with very different mineralogical compositions is analyzed in the present paper. Excess gypsum was added in amounts such that its percentage by mass of SO3 came to 7.0%.

Different illitic clays (Buenos Aires Province, Argentine) were selected to study their potential pozzolanic activity. Clays were characterized by X-ray diffraction (XRD), Fourier transformed infra-red spectroscopy (FTIR) and thermal analysis (TG). Clays are calcined at 300, 600 and 950 °C and ground until 85 % mass passed through a 45 µm sieve. The pozzolanic activity was evaluated by the Frattini test and the strength activity index (SAI) at 2, 7 and 28 days on blended cements containing 25 % by weight of calcined clay. Results indicates that calcined illitic clays are suitable as raw material to prepare calcined clay pozzolan when they are fired at 950 °C as revels the Frattini test and they have a SAI from 0.75 to 0.94 at 28 days depending the amount of clayed minerals in the raw shale-stone. Secondary clay minerals don’t change significantly the pozzolanic behavior of illitic calcined clays.

The properties and hydration of blended cements containing from 8 to 40 % by mass of ceramic waste (CW) from different countries (Argentine and Czech Republic) are investigated. The mini slump, the heat released rate up to 48 h, the pozzolanic activity and the compressive strength at 2, 7 and 28 are determined. Hydration process is characterized by XRD analysis and the pore size refinement is accessed by MIP. Results show that both CWs increase the water demand with increasing the cement replacement level, and they possess pozzolanic activity after 7 days. At early age, the heat released and the compressive strength are lower than that of the Portland cement (PC) for all replacement levels. At 28 days, the pozzolanic reaction significantly improves the compressive strength. From XRD analysis, it is evident that CW reacts to form AFm phases (hemicarboaluminate at 7-28 and later transformed to monocarboaluminate) depending on the replacement level and CW used. CH peak reduction due to the pozzolanic reaction appears at 28 days. The reduction of porosity up to 16-24 % of CW replacement is in accordance with the compressive strength results.

This research presents the effects of finely divided crystalline mineral additions (quartz and limestone), commonly known as filler, on the early hydration of portland cements with very different mineralogical composition. The used techniques to study the early hydration of blended cements were conduction calorimeter, hydraulicity (Fratini's test), non-evaporable water and X-ray diffraction. Results showed that the stimulation and the dilution effects increase when the percentage of crystalline mineral additions used is increased. Depending on the replacement proportion, the mineralogical cement composition and the type of crystalline addition, at 2 days, the prevalence of the dilution effect or the stimulation effect shows that crystalline mineral additions could act as sites of heat dissipation or heat stimulation, respectively.

Fly ashes from the combustion of coal thermal power stations are commonly incorporated into portland cements and/or concretes and mortars. The chemical and morphological composition of fly ashes, together with their particle size, make them suitable as pozzolanic(non-calcic) or pozzolanic/hydraulic(highly calcic) additions to manufacture such building materials. This work focuses on the incorporation of two different fly ashes (non-calcic but of very different Fe2O3(%) contents, fineness and morphology) to two ordinary portland cements (of very different mineralogical composition as well), to determine the effects those have and the interactions they produce in the hydration reactions of portland cement. The main techniques employed for this study have been: conduction calorimetry and Frattini test; secondary techniques applied have also been: determination of setting times and analysis by X-ray diffraction and SEM. Analysis of the results obtained permitted to find different effects of fly ash addition on the hydration reactions of portland cements. Thus, dilution and stimulation effects augment with the increased fly ash percentage. Delay and acceleration of the reactions depend mainly on the type of portland cement and are accentuated with increased fly ash contents. Their behaviour as concerns heat dissipation mainly, depends on the type of fly ash used and is more pronounced with increased cement replacement. On the other hand, the pozzolanic activity of these fly ashes has been revealed at 7 and 28 days, but not at 2 days. Finally, pozzolanic cements can be manufactured using different portland cements and/or types of fly ashes, in the appropriate proportions and compatible qualities, depending on the effect(s) one wish to enhance at a specific age, which is according to previous general conclusions drew out of sulphate attack and chloride attack researches.

In this paper, the hydration mechanism of portland cement pastes with limestone, quartz and natural pozzolan (80/20 weight) was analized. The techniques used were nonevaporable water content, pozzolanic activity and X-ray diffraction. Results show that filler effect increases initially the amount of hydration products in all pastes. For limestone pastes, the dilution effect is significant at long time, for quartz and pozzolan pastes the dilution effect was lower due to the contribution of the pozzolanic reaction.

This paper analyses the influence of portland cement replacement by silica fume (up to 10%) and/or granulated blast furnace slag (up to 70%) on the hydration cement (XRD, heat of hydration, non evaporable water content and calcium hydroxide content) curing under sealed conditions and their effect on the mechanical strength. The obtained results indicate that binary cements containing silica fume and ternary cements there was a significant increase of hydration rate at early age. At later ages, most of studied cements have an equivalent or greater strength that those obtained in the plain portland cement. En este trabajo se analiza la influencia de la incorporación al cemento portland de humo de sílice (hasta 10%) y/o escoria granulada de alto horno (hasta 70%) sobre la hidratación (DRX, calor de hidratación, contenido de agua no evaporable y de hidróxido de calcio), bajo condiciones de curado sellado y su incidencia sobre la resistencia mecánica. Los resultados obtenidos indican que en los cementos binarios con humo de sílice y en los cementos ternarios se produce un importante aumento de la velocidad de hidratación en las primeras edades, mientras que a edades más avanzadas la mayor parte del dominio estudiado alcanza o supera la resistencia obtenida por el cemento portland sin adición.

Carboaluminates are hydration products of limestone-blended cements and they compete with monosulfoaluminate stability and ettringite transformation. In this paper a study about the hydration of pure C3A phase with CaCO3 in the presence or not of gypsum and in a calcium hydroxide solution is related to the hydration products of portland and limestone-blended cements. Results show the formation of monocarboaluminates in systems containing C3A and CaCO3 while the tricarboaluminate was not found. Calcium hydroxide intervenes in these systems to form a calcium hemicarboaluminate hydroxide. In limestone-blended cements, calcium monocarboaluminate is immediately detected after hydration begun and the transformation of monosulfoaluminate to monocarboaluminate occurs at 28 days while the conversion of ettringite to monosulfoaluminate is deferred.

Sulphate performance of concrete depends primarily on permeability. Under severe conditions of sulphate exposure, low-permeability concrete is prescribed and it must also be made with high sulphate resisting cement. For portland cement, the sulphate resistance depends on the C3A content and the amount of CH produced at early stages of hydration. Some parameters that modify the quantity of early CH in the hardened cement paste are investigated in this paper. Two type V cements with quite different C3S content and blended cements containing natural pozzolana or limestone filler were used. Expansion, flexural and compressive strength of mortar, immersed until 1 yr in sodium sulphate solution, with pH-controlled are presented. Results show that the sulphate performance of portland cement with high C3S content is very poor compared with low C3S portland cement. Addition of natural pozzolana provides the maximum sulphate resistance while the addition of 20% limestone filler declining sulphate performance of low C3A cements. This behaviour can be attributed to the reaction between sulphate ions with CH into the paste that produces an alteration of the predominant mechanism of sulphate attack.

This paper describes the effect of duration of initial curing on the mechanical properties (compressive strength, tensile strength, and modulus of elasticity) and the chloride penetration of concretes containing limestone blended cements. Three concrete mixtures (water/cementitious=0.5) containing a portland and two limestone blended cements were subjected to three different initial curing regimens (full, wet, and air curing). Results show that mechanical properties of concrete containing limestone blended cement are less affected by the cessation of moist curing at early ages. This is attributed to the hydration acceleration owing to limestone presence and the increase of fineness in the clinker fraction of the blended cement. A prolonged initial moist curing reduces this advantage of limestone blended cements and the dilution effect produced by limestone addition impairs the potential mechanical properties. For concretes cured for an initial 7 days, there was no substantial difference in mechanical properties and chloride penetration resistance of cements with and without limestone filler.

The hard, strong and durable cement−based product required by the user is only achieved following a period of plasticity but the attention paid to its fresh properties is small, despite the far−reaching effects of inadequate fresh performance. Pumping, spreading, moulding and compaction all depend on rheology and thanks to an increasingly scientific approach it is becoming possible to predict fresh properties, design and select materials and model proc‐ esses to achieve the required performance. Rheology is now seriously considered by users, rather than being seen as an inconvenient and rather specialised branch of cement science.

The present study deals with a characterization of metakaolin pozzolanic activity and its chemical character exhibited in the Ordinary Portland Cement (OPC) blends by means of Transmission Electron Microscopy (TEM) and Selected-Area Electron Diffraction (SAED) techniques principally. Metakaolin sample was prepared by calcination of kaolin rock (Guadalajara, Spain) at 780°C. Two OPC of different chemical composition from the tricalcium aluminate content point of view were chosen and Portland cement blends series elaborated and then submitted to the pozzolanic activity test (EN 196-5 or Frattini test). The main mineralogical components of the metakaolin are determined qualitatively: χ-alumina and quartz. The chemical character of the metakaolin is described because of its final composition as well as due to its Al atoms possible coordination. The crystalline order of the material is found to be of both amorphous and polycrystalline, being an intimate amorphous mixture of alumina and silica. Finally, all the alumina capable of reacting chemically is denominated and classified as reactive alumina component, Al2O3r−, of pozzolans, as well as the aluminic chemical character of metakaolin in OPC blends is once again proved and exhibited by means of Friedel's salt formation studied already at 4 h-age.

In this work two aluminic pozzolans (metakaolins) and a non-pozzolan were added to two Portland cements with very different mineral composition, to determine the effect on the rate of heat release and the mechanisms involved. The main analytical techniques deployed were: conduction calorimetry, pozzolanicity and XRD. The results showed that the two metakaolins induced stimulation of the hydration reactions due to the generation of pozzolanic activity at very early stage, because of their reactive alumina, Al2O3r− contents, mainly. Such stimulation was found to be more specific than generic for more intense C3A hydration than C3S, at least at very early on into the reaction, and more so when 7.0% SO3 was added, and for this reason, such stimulation is described as ‘indirect’ to differentiate it from the ‘direct’ variety. As a result of both stimulations, the heat of hydration released is easy to assimilate to a Synergistic Calorific Effect., We would like to thank the Fundación Rotaria, the Universidad Nacional del Centro de la Provincia de Buenos Aires, for financial support, and the Instituto de C. C. ‘Eduardo Torroja’-CSIC from Spain as well, for having provided the authors with necessary cementing materials and some analytical and experimental techniques.

For reasons of market demand and Portland cement production,the manufacture of cements with two or more separately ground additions to produce customized cements is becoming common practice.When pozzolan or slag content in this type of cements is high, however, the initial strength of the resulting product may be adversely impacted. This problem can be minimized by activating one or both of the replacement materials. The present study analyzes the effect of Portland cement additions such as physically activated natural pozzolan(up to 20%) and/or granulated blast furnace slag (up to 35%) on mortar flexural and compressive strength. The results show that higher strength is attained in ternary than binary cements. Initially (2 and 7 days), the highest compressive strengths are reached by mortars with up to 13% natural pozzolan and 5% slag, whereas at later ages mortars with larger proportions of additions are found to perform best., Debido a las exigencias del mercado y de la producción de cemento Portland, es cada vez más frecuente la elaboración de cementos con dos o más adiciones a partir de la molienda separada de sus constituyentes, dando origen a la formulación de los cementos a medida.Cuando el contenido de adiciones es alto, la utilización de puzolana y escoria en este tipo de cementos presenta la peculiaridad de disminuir la resistencia inicial del cemento resultante. Sin embargo, si algunas o ambas adiciones se activan, este problema puede minimizarse. En este trabajo se analiza la influencia de la incorporación al cemento Portland de puzolana natural (hasta 20%) activada físicamente y/o escoria granulada de alto horno (hasta 35%) sobre la resistencia a flexión y a compresión de morteros. Los resultados indican que los cementos ternarios presentan un mejor comportamiento resistente que los cementos binarios. Las máximas resistencias a compresión en las primeras edades (2 y 7 días)se alcanzan con hasta 13% de puzolana natural y 5% de escoria, mientras que a edades más avanzadas se trasladan a mayores contenidos de puzolana y escoria.