Mechanical performance of concrete blended with high-strength capsules prepared by a novel method

The incorporation of self-healing capsules in concrete can negatively affect its mechanical properties, limiting their large-scale utilization in real world. To minimize the potential impacts, a novel method than can prepare high-strength capsules was proposed in this study. The basic performance of capsules and the influence on the mechanical performance of concrete was tested, and the underlying mechanisms was explored through microstructural analysis of the concrete matrix. Experimental results indicate that the novel high-strength capsules exhibit superior hardness and strength, resulting in a survival rate of 93.6 % after stirring of concrete. Meanwhile, the negative impact of the capsule on compressive strength is very limited, but the capsules significantly enhance flexural strength. Specifically, at dosages up to 7 %, compressive strength is reduced by no more than 1.5 %, while flexural strength notably increases by up to 18.3 %. Moreover, samples blended with capsules present the same exothermic characteristic peaks and phase composition as those without capsules, and the cumulative isotherms and phase content are similar, suggesting that capsules have a negligible effect on the types and quantities of hydration products in the matrix. The microscopic pore structure of the matrix is largely unaffected. More importantly, the capsules integrate more effectively with the matrix than fine aggregates, as evidenced by similar or narrower interfacial transition zones and comparable elastic moduli.