Internal curing and improved chloride resistance of high-strength concrete amended with coal bottom ash

Abstract

Bottom ash is one of the combustion residues produced during thermal coal electricity production. Its morphology is characterized by agglomerated particles with an angular and porous structure. Compared with fly ash, bottom ash is seldom recycled due to its unique characteristics, such as very irregular shape, high porosity, and low abrasion resistance. However, there is demand to develop a novel method to consume a large amount of bottom ash as its direct disposal gives rise to both economic and environmental problems. The main objectives of this study are to propose an advanced application target for bottom ash and verify the advantages that can be obtained by the unique characteristics of bottom ash. This dissertation presents the utilization of coal bottom ash in high-strength concrete for internal curing and chloride resistance. The research in this dissertation can be divided into the following five areas : 1) Characterization of high-strength mortar/concrete incorporating fine bottom ash : The effects of FBA aggregates on the density, compressive strength, dynamic modulus of elasticity, and flow characteristics of the mortar are investigated, and the porosity and water capillary absorption of the mortar are measured to evaluate the properties of moisture transport, which may affect the durability of the mortar. Moreover, the effects of fine and coarse bottom ash on the flow characteristics and density of concrete mixture are investigated in relation to particle shapes and paste absorption of bottom ash. Mechanical properties, such as compressive strengths and modulus of elasticity and flexural strength of high-strength concrete with bottom ash are also evaluated; 2) Internal curing of high-strength concrete with bottom ash : The microstructure, shrinkage, an hydration kinetics, and their effects on the mechanical properties of high-strength concrete with bottom ash are evaluated and compared to those of concrete with artificial lightweight aggreg...