Comparison of different types of self-healing concrete under extreme conditions

Abstract

Extreme environments are aggressive for concrete structures, hence a performance-based design is crucial to guarantee the durability during the service life. Nonetheless, there is a knowledge gap regarding the influence of cracks on standard and self-healing concrete. This research focuses on monitoring cracked self-healing concrete with two commercial healing agents: a bacteria-based healing agent (BAS) and a crystalline admixture (CA). After crack formation and a healing process of three months in wet/dry conditions (4 days/3 days), several extreme conditions were considered: (1) submerged in artificial seawater, (2) submerged in a solution with 33 g/L sodium chloride and (3) freeze-thaw (FT) cycling with de-icing salts. Microscopic images were used to quantify the healing efficiency of the two different healing agents, while chloride ingress and scaling were measured to determine durability. The results of the microscopic measurements indicated significant healing efficiency for both healing agents after the healing regime reaching 72% for CA, and 67% for BAS. After exposure to a marine environment, this efficiency increased to 95% and 92%, respectively. The uncracked BAS samples achieved a scaling reduction of 93% under FT exposure relative to the uncracked REF samples, while this was 49% for the CA samples. In cracked samples, scaling was reduced by 50% for BAS and 24% for CA, relative to the cracked REF samples. In all tested conditions, the BAS samples partially prevented the chloride ingress through the crack, while CA samples showed a great reduction. Overall, both healing agents reduced the degradation and could decrease the chloride ingress.