Constitutive model and healing agent optimisation for microbial concrete

To ensure the application of microbial self-healing concrete (MSHC) in practical engineering, it is imperative to investigate its constitutive model and the effect of microbial self-healing agent (MSHA) dosage on concrete properties. In this study, a constitutive model for MSHC is established using a Weibull-lognormal statistical distribution, and the effect of MSHA dosage on concrete performance is investigated. Results show that MSHA dosages of 0.30 m³ and 0.45 m³ serve as critical thresholds for compressive strength and splitting tensile/flexural strength, respectively, beyond which mechanical properties decline sharply. The optimal MSHA content was determined to be 0.33 m³ per unit volume of concrete. Based on the constitutive model and ordinary concrete parameters, the mechanical behaviour of MSHC at any MSHA dosage can be effectively predicted. With the optimal dosage, MSHC healed cracks narrower than 1.02 mm after 28 days, achieving area and permeability repair rates of 96.02% and 77.65%, respectively.