Effect of quick lime addition for improving compressive strength of fly ash based (cement free) geopolymer concrete

Abstract

In this current investigation, a comprehensive exploration has been undertaken to advance the development of “Class F” fly ash-based Geopolymeric mortar and concrete, utilizing fly ash that has been sourced from the Satpura Thermal Power Station in Sarni, District Betul, Madhya Pradesh, India. The study has systematically investigated the influence of Quick Lime addition in the formulation of fly ash-based Geopolymeric mortar and concrete, with a particular focus on enhancing compressive strength within the constraints of ambient atmosphere conditions. The Geopolymeric binder has been meticulously crafted using sodium hydroxide and sodium silicate as alkaline activators. Systematic variations of Quick Lime dosages (ranging from 0% to 10% by weight of fly ash) have been introduced, and the ensuing specimens have undergone scrutiny for standard consistency and setting time under ambient temperature curing. The outcomes have underscored a discernible trend wherein the judicious addition of 7 to 9 wt.% calcium oxide (Quick Lime) to the fly ash matrix has precipitated a noteworthy reduction in setting time at room temperature, concurrently manifesting a substantial enhancement in compressive strength for Geopolymeric mortar and concrete formulations. The elucidation of the binder's microstructural phases and their chemical characteristics has been pursued through rigorous analytical methodologies, encompassing X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and field emission scanning electron microscopy (FE-SEM). Cost analysis has also been conducted for 1m³ of concrete, comparing conventional concrete (M25) and fly ash-based Geopolymer concrete