Thermodynamic Modeling of Binary Binders with Agricultural Residues for Hydration Analysis

N. S. Ajeesh Kumar and K. L. Radhika

Abstract
Supplementary cementitious materials (SCMs), such as fly ash, blast furnace slag, rice husk ash (RHA), and sugarcane bagasse ash (SBA), are increasingly used to promote sustainable construction practices. However, understanding how the chemical composition, fineness, reactive phases, and pore solution content of SCMs affect the reaction process and hydration of cement is challenging. Researchers are developing models, including thermodynamic modelling (TDM), to better understand these effects. TDM is a useful tool for predicting the composition of pore solution and understanding the composition of hydrated cement and SCMs. This study investigates two types of ordinary Portland cement (OPC1 and OPC II) with varying chemical and mineral compositions mixed with two SCMs (RHA and SBA). Using TDM, the impact of cement content on hydrate generation in binary mixes is studied. The results revealed that OPC l and OPC ll hydration models predicted CSH gel, ettringite, hydrotalcite, calcite, and portlandite. In comparison to OPC1, OPC II predicts 21 % more CSH gel and 25 % less hydrogarnet. The study also found that jennite-like CSH transforms into tobermorite-like CSH with an in crease in RHA, and a decrease in portlandite was observed in SBA blended systems. The TDM results were validated using experimental data, providing valuable insights into the type and composition of hydrates that develop during cement hydration and its blends with SCMs.

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Keywords
cement, hydration, modelling, sustainable concrete-making materials