Resistance of mortar with coal bottom ash to carbonation and chloride penetration

Abstract

The importance of recycling coal bottom ash has increased as the number and size of coal power plants increased. This study investigates mechanical characteristics and chloride penetration resistance of mortar that incorporates bottom ash as aggregate when the mortar is subject to single (chloride penetration only) or coupled deterioration (chloride penetration and carbonation). This study can be divided into two parts: 1) workability and compressive strength of mortar incorporat-ing bottom ash, and2) chloride penetration depth and total chloride contents of mortar incorporating bottom ash when exposed to single or coupled deterioration. First, workability of mortars incorporating coal bottom ash or mortars incorporating cold-bonded bot-tom ash was higher than that of normal mortar, and compressive strength of coal bottom ash mortar and cold bonded bottom ash mortar was not significantly different from that of the normal mortar. Although coal bottom ash mortar and cold bonded bottom ash mortar initially had lower compressive strength than the normal mortar, their strength improved over time to match that of the normal mortar, potentially due to the internal curing effect. Second, coupled deterioration made mortar more susceptible to chloride penetration. While the total amount of chloride ions penetrated under coupled deterioration was not different among coal bottom ash mortar, cold bonded bottom ash mortar, and the normal mortar, the chloride penetration depth of coal bot-tom ash mortar and cold bonded bottom ash mortar was less than that of the normal mortar. This may be due to pozzolanic reactions occurring in the interfacial transition zone between cement paste and the surface of bottom ash and paste. These reactions not only create pozzolanic walls on the surface of aggregate but also increase the cation concentration in cement, both of which slow down the rate of corrosion of reinforce-ment bars in concrete structures. In conclusion, this study co...