Durability Properties of Concrete Made with High Volumes of Low-Calcium Coal Bottom Ash As a Replacement of Two Types of Sand

Two types of concrete mixtures (Concrete A and Concrete B) were prepared with sands having different fineness modulus. Sand was replaced with coal bottom ash (CBA) at 20, 30, 40, 50, 75, and 100% levels in both concrete mixtures. Laboratory tests were performed to study the effect of CBA on compressive strength, sorptivity, chloride permeability, drying shrinkage, and sulfate and acid resistance of concrete. At 7days, for both grades of concretes, concrete mixtures incorporating CBA showed lower compressive strength. At 28days, for Concrete A, no significant effect of CBA on compressive strength was observed. However, in case of Concrete B, concrete mixtures containing more than 50% CBA displayed lower 28-day compressive strength than that of control concrete. With age, compressive strength of bottom ash concrete mixtures increased at faster rate. Bottom ash concrete mixtures displayed higher sorptivity, lower chloride permeability, and drying shrinkage. For both grades of concretes, resistance to sulfate and acid exposure of control and bottom ash concrete mixtures were almost identical. Compressive strength of concrete mixtures increased up to 180days of immersion in sulfate solution. Under acid attack, control and bottom ash concrete mixtures experienced almost equal weight loss.