Self-healing Behavior of Expansive Mortars with Fly Ash and Bottom Ash

Abstract

In this paper, the effectiveness of fly ash (FA) and bottom ash (BA) on the self-healing (S-H) behavior of expansive concrete was experimentally investigated by using the crack closing ratio and water flow rate as indicators of the self-healing ability. To heal cracks that may be caused by shrinkage, high CaO-SO₃-free lime fly ash (FAB), high CaO fly ash (FAA), and low CaO fly ash (FAR), and one type of expansive additive were used as the partial binder replacement materials. A pre-soaked bottom ash with high water retainability was used as a water-providing agent for the internal curing (IC) technique, to reduce shrinkage and enhance long-term hydration. Pre-cracked mortar samples were prepared in a disc shape with a fixed crack width of 0.1 mm. After crack creation, the crack width ratio and water flow rate were monitored every 7 days for 3 months. It was observed that expansive mortars with 30% fly ash showed significant improvement in the self-healing ability when compared to the non-fly ash mortar.   The use of 10% bottom ash showed enhanced self-healing ability in expansive mortar. Moreover, using both fly ash and bottom ash showed significant improvement in the self-healing behavior.