Evaluation and beneficiation of high sulfur and high alkali fly ashes for use as supplementary cementitious materials in concrete

Coal-fuel power plants with semi-dry or dry flue gas desulfurization (FGD) systems produce high sulfur and/or alkali fly ashes due to comingling of ash FGD products. Such do not meet the SO3 content limit (5.0% max.) ASTM C618 are unable mitigate alkali-silica reaction. The mineralogy present in these can vary significantly (e.g., CaSO4, CaSO3, Na2SO4) based on technology used and this affects performance concrete. Thus, single SO3% is capture complexity ash, results elimination potentially viable pozzolans for This study performs a systematic investigation effect type various parameters cement-fly pastes mortars, including workability (flow flow retention), pore fluid pH, setting time, strength development, potential deleterious expansion. To better quantify understand effects, considers both real doped (i.e., blend specification-compliant target compounds). poor observed case time pH was successfully mitigated using chemical admixtures.