Understanding Cement: An Experimental and Theoretical Approach

Ordinary Portland Cement (OPC) is widely used as a construction material in modern world. Cement is an inorganic material and is highly complex due to its multi-component, multi-phase nature. Cement powder readily reacts with water, undergoing hydration process which results into the formation of a number of reaction products, all embedded into a system called cement paste. The major reaction products are calcium silicate hydrate and calcium hydroxide. Calcium silicate hydrate is the dominant hydration product (constitutes about 70% of the cement paste) and is primarily responsible for the binding properties of cement. In order to tailor the final performance of cement it is necessary to understand the structure and properties of the principal hydration product. However, calcium silicate hydrate is also a very complex phase as it evolves both structurally and chemically as a function of time throughout the hydration process and its exact constitution is not yet known. Efforts were made in this work to develop an insight and understand the nature, composition, structure of the calcium silicate hydrate phase of a commercially manufactured OPC cement by combining different analytical techniques viz: XRF, SEM, FTIR, Solid State NMR, XRD  and theoretical modeling by Quantum Chemical techniques. Based on the comparison of experimental and theoretical results, a basic structural model has been proposed which could be further developed in order to elucidate the exact structure of calcium silicate hydrate formed in the OPC cement used in this work