Influencia de la naturaleza del cemento en la compatibilidad con aditivos superplastificantes basados en carboxilatos

An empirical study was conducted to gain a fuller understanding of the interactions taking place in cementsuperplasticiser systems. To this end, two clinkers of known chemical and phase composition were prepared in this study to gain insight into such interactions. One contained no tricalcium aluminate (C1), while the other had a 9% C3A content (C2). These clinkers were ground to approximately 340 m2/kg and blended with gypsum only or gypsum and Klein compound (3CaO·3Al2O3·CaSO4) (1, 2). Sufficient compound was added to C1 to ensure the formation of about the same amount of ettringite after 0.5 and 1 h of hydration as found in cement C2 + gypsum. The admixture used was a carboxylate superplasticiser. Rheology measurements showed that while paste yield stress was correlated to ettringite formation, no such simple relationship was observed for plastic viscosity. Plastic viscosity depended on the total hydrates formed, i.e., not only as ettringite but also as C-S-H gel. The findings revealed that in clinkers with very low sulfate and potassium contents, the rheology of carboxylate-containing cement paste is primarily controlled by ettringite formation.En el presente trabajo se ha realizado un estudio empírico con el objetivo de profundizar en el conocimiento de las interacciones del sistema cemento-superplastificante. Con este fin, se prepararon dos clínkeres con una composición química y de fases conocida: el primero (C1) sin aluminato tricálcico y el segundo (C2) con un contenido en C3A del 9%. Ambos se molieron hasta obtener una superficie específica aproximada de 340 m2/kg y se emplearon con dos adiciones: yeso y el compuesto de Klein (3CaO·3Al2O3·CaSO4) (1, 2). Se añadió la cantidad necesaria del compuesto de Klein a C1 para garantizar la formación, tras 0,5 y 1ª h. de hidratación, de aproximadamente la misma cantidad de etringita en dicho cemento que en la mezcla de cemento C2 y yeso. Se empleó un superplastificante basado en carboxilatos. Los resultados reológicos obtenidos han demostrado que si bien el esfuerzo de cizalla umbral de las pastas muestra una buena correlación con la formación de la etringita, no existe una relación tan clara entre dicho parámetro y la viscosidad plástica. Ésta depende de la cantidad total de hidratos que se generen, es decir, no sólo en forma de etringita sino también como gel C-S-H. A partir de los resultados de los ensayos realizados, se puede afirmar que la formación de etriginta es el factor determinante en la reología de las pastas de cemento preparadas con clínkeres con bajo contenido en sulfato y potasio y aditivadas con un superplastificante basado en carboxilatos

Low-Emission, Cementless Binders and Concrete: Future Proof Materials

In the chapter, the results of testing the possibility of obtainment of the high-performance binder and concrete based on alkali activated fly ash and other aluminosilicate wastes or industrial wastes are presented. The discussed topic is framed in terms of requirements and actions taken by the cement industry, which lead to a decrease in carbon dioxide emissions. In terms of carbon footprint, cementless, geopolymer concrete is determined as a more advanced material for civil engineering because of its ability to not contain the clinker component and still be able to reach, by its properties, the level of high-performance cementitious materials. In the presented paper, some of the properties of hardened geopolymer composite material are improved. It was established that the addition of thermally processed waste material, containing metakaolin, radically increases the strength and durability of geopolymer concrete. By means of completed research methods, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy X-ray dispersion spectroscopy (EDS) and thermal analysis DTA-DTG, the influence on changes in the structure of hardened geopolymer material due to the increase in its strength and durability during low-temperature exposure is explained

Oil-Based Mud Cutting as an Additional Raw Material in Clinker Production

Oil-Based Mud (OBM) cutting is a hazardous by-product generated during oil-well drilling. Its chemical composition suggests that it might be suitable as a raw material in cement manufacturing. It is rich in calcium oxide, silica, and aluminium oxide, which are the major oxides in raw materials for cement manufacturing. In this research, OBM cutting is used as a constituent of the raw meal for cement clinker production. Raw meal mixtures were prepared by mixing different ratios of raw materials increasing OBM content. The impact of the addition of OBM cutting on the resulting clinker has been investigated. The results demonstrate that OBM cutting could be recycled in the manufacturing of Portland cement clinker. Clinker prepared using OBM cutting had very similar properties to that prepared from limestone. This result could represent an opportunity for solving an environmental problem. The addition of OBM cutting lowers the calcination temperature, and increases the rate of carbonate dissociation. However, it also leads to a higher free lime in clinker, which is a result of the presence of trace elements, such as barium. Overall, its use as a raw material in cement production could provide a cost-effective, environment-friendly route for the management of OBM cutting