Clinkering, processing and characterisation of Alite-Belite-Ye’elimite eco-cements: from basic to applied science

Abstract

An eco-friendly industrial production is essential to protect our environment. The synthesis process of PC generates greenhouse gas emissions. Because of that, the cement industry is under increasing scrutiny to reduce CO2 emissions, including the energy used in the production of PC. This PhD thesis is focused in the production and characterisation of cements with alite, belite and ye’elimite phases. It has been gathered in two blocks: on the one hand, a deep characterisation of the hydration of the main phases of this type of cements, alite and ye’elimite pure phases, has been performed to understand them. The corresponding hydration products (which contain nanocrystalline and crystalline phases) have been characterized through PDF methodology. On the other hand, the synthesis, hydration understanding, processing and the corresponding characterisation of ABY cements and mortars have been performed. Here, both standard (ABY, composed by beta-belite) and doped (dABY, with alpha-belite) cements/mortars have been prepared and characterised. Summarising, this first part of the PhD has enabled us to establish a multi-r range methodology for the analysis by PDF of mixtures of crystalline/nanocrystalline/amorphous components. Moreover, C-S-H gel has been characterised and described as nanocrystalline defective tobermorite, monolayers of portlandite and water pore, independently of the polymorphism of alite, particle size, water to solid mass ratio or temperature. Finally, aluminium hydroxide gel obtained from the hydration of ye’elimite has also been described. The type and amount of the sulphate source seems not to have any influence on the nanocrystalline nature of this phase.