Preliminary approach to bio-based surface healing of structural repair cement mortars

Mitigating the maintenance and repair costs of structures and infrastructures is a major problem in all countries. The aim of this research work is to analyse the performance of surface healing technique for crack control of cement-based mortars for structural repair in maritime environments. Microbiologically induced calcite precipitation (MICP) with ureolytic bacteria Sporosarcina pasteuri DSM 33 was introduced for crack-healing. Only main cracks were filled with the bioagent (bacterial cells and nutrients) for cost-saving purpose. It is intended to analyse the effectiveness of this technique for structural application in areas exposed to cyclic moisture changes. Hygric properties and their relation to durability increase were analysed through moisture buffering tests, capillary, porosity, compressive strength, SEM and microscopy analysis before and after bio-agent application to evaluate the evolution of the precipitation. For the first time, moisture buffering value (MBV) was used to evaluate the performance of the self-healed mortar and time needed for bacterial precipitation. The treated material can be classified as good in terms of MBV, and there was a general increasing trend of moisture buffering behaviour in self-healed samples. SEM analysis showed distinctive differences between the treated and non-treated cracks. The results show that bio-agent had remarkable effect on compressive strength recovery (over 87% of original value) after 21 days of healing and positively affected the initial stage of capillary absorption.