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Development of new products from rehydration of Portland cement phases

Abstract

The increasing human concentration in urban environments and the consequent necessity of building the infrastructures of the cities makes Civil Construction today responsible for most of the raw materials extracted worldwide. Such infrastructures require intensive use of concrete, and construction waste, consisting largely of cementitious materials, is commonly disposed in landfills. The fine fraction of these wastes is cement rich, mainly in hydrated condition. Hydrated cementitious compounds (such as hydrated calcium silicates, sulfoaluminates and portlandite) can be recycled by heat treatment at temperatures much lower than those required for clinker production without generating CO2 by decarbonation during calcination. Such materials, when exposed again to water, have the ability to rehydrate once again acquiring mechanical strength. Thus, recycling the fine fraction of cementitious waste has the potential to produce a new type of supplementary cementitious addition, or a new type of cement. The main objective of this project is to investigate by employing various analytical techniques (including XRD, TGA, calorimetry and rheological methods) the dehydration and rehydration mechanisms of each of the main hydrated phases of cement as pure phases synthesized for this purpose. It is expected that the results obtained from the observation of pure phases behavior will explain the hardening (consolidation) and mechanical strength evolution processes of rehydrated cements. Understanding these processes is necessary to enable the large-scale use of dehydrated cements as new cementitious binders, and/or as OPC additives (eg, accelerators for additive manufacture - "3D printing"). (AU)

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