Modification of Concrete Mix Design with Crystalline Admixture for Self-healing Improvement

Abstract

Current practice reveals that no adaptation of self-healing concrete mix designs are made for the introduction of healing agents. However, the inclusion of healing agent may downgrade the concrete properties to some extent. Therefore, an optimization of mix design is necessary in order to eliminate the possible negative effects induced by the healing agents and also to potentially improve the self-healing and self-sealing abilities. In this paper, seven concrete mix designs were studied with crystalline admixture (CA) as a prospective healing agent to stimulate the autogenous healing mechanism. Several design parameters were opted namely (1) dosage of CA from 0 to 2% by cement mass, (2) water-cement (w/c) ratio between 0.46 and 0.52, and (3) cement content in the range of 320 to 360 kg/m³. The self-healing and self-sealing performances were investigated by the indicators of crack closure and the permeability rate, respectively. Results showed that the addition of CA demonstrated an advanced progress on the crack closure with increasing the healing time. The size of the crack considerably influenced healing performance. All in all, the effects of mix design parameters in terms of improvements of healing and sealing efficiencies are discussed and a recommendation for optimizing the mix design is proposed.