Utilization of Water Treatment Plant Sludge With High Calcium Fly Ash As Geopolymer Precursor For Paving Cement-Free Bricks

Abstract

The construction industry is facing challenges in terms of sustainability as lot of virgin natural materials are utilized every year. On one hand, construction needs more material and on the other, waste material from anthropogenic activities produces large volumes of byproducts like fly ash and water treatment plant sludge that requires proper disposal.  Two waste by-products namely, drinking water treatment plant sludge of Bhandup Water Complex of Brihanmumbai Municipal Corporation and high calcium fly ash from Trombay Thermal Power Plant have been used in synthesis of geopolymers. Mixture of Sodium silicate and sodium hydroxide solutions were used as the liquid alkaline activating solution. Influence of various factors such as molar ratios of SiO₂:Na₂O of activating solution, SiO₂:Al₂O₃ of the mix, Na:Al of the mix, curing temperature and time period were studied. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) tools were used   to understand the influence of various factors on geopolymer specimens. Statistically, molar ratios of Na/Al affect the geopolymerization process as reflected in the measurement of compressive strength of the samples. The others did not show any statistically significant influence on the process. The results obtained demonstrate the feasibility of recycling of aluminosilicate rich wastes, revealing a highly promising area for recycling and a broader perspective for their application.