Elucidation of rapid reduction of water flow through concrete crack regarded as self-healing phenomenon

Abstract

ID No : 75 ABSTRACT The development of self-healing concrete has witnessed several strides in the last three decades. Among these is the understanding of the mechanisms of self-healing concrete, as well as the realization of new technologies of enhancing crack selfhealing in concrete. Previous research suggests that crack closing mechanism occurs due to mainly 1) Hydration of anhydrous cement, 2) Formation and crystallization of Calcium Carbonate, 3) Swelling of cement matrix and 4) Sedimentation of particles in the crack interstices. In this research however, after a one by one investigation, it was found that these mechanisms do not fully explain the drastic water flow recovery that occurs in the initial stages of water permeation through cracked concrete. This preliminary finding then prompted direct visual observation of water flow through cracks’ narrow spaces. This was achieved by using acrylic resin and glass as transparent media over the concrete surface of split and machine cut cracks respectively. With this, an interesting observation was made – the creation of air bubbles (waterless spaces inside the interstices) following the condition of full water saturation. It was observed that water flow through the narrow crack openings creates air bubbles by probably various water action mechanisms. The created air bubbles narrow water flow paths in the crack, causing significant water flow reduction in the initial and later stages of water supply condition.