Evaluating the performance of thermomechanically beneficiated fly ash blended mortar

Abstract

This study explores the performance of beneficiated and reclaimed landfilled fly ashes (LFA) from three active landfills in Wyoming and Colorado. The LFAs that did not meet the physiochemical requirements of ASTM C618 underwent thermal and mechanical beneficiation processes to increase their fineness and reduce their carbon content. Subsequently, the performance of mortar samples incorporating these LFAs was thoroughly assessed in terms of compressive strength, electrical resistivity, resistance against alkali-silica reaction-induced expansion, water absorption, and chloride permeation. The results demonstrated that the beneficiation processes employed effectively improved the properties of the off-spec ashes, leading to all of the beneficiated ashes meeting the requirements set by ASTM C618. In most cases, the mortar specimens containing beneficated LFA exhibited comparable or even superior mechanical and durability performance compared to those containing ASTM C618-compliant fly ash. These findings highlight the potential of beneficiated LFAs as viable alternatives in concrete production, particularly in the face of the anticipated fly ash scarcity in the US and worldwide.