Self-healing bacterial mortar with improved chloride permeability and electrical resistance

Abstract

Abstract Mortar is known as a constituent of concrete structures. Its properties can be used as indicators of concrete properties. Owing to the production of calcium carbonate sediments via the self-healing mechanism, mortar permeability can be reduced to enhance its durability. The present study was designed and implemented to explore not only the effects of urease bacteria as a self-healing agent incorporated in mortar mixing water but also those of different curing environments on mortar durability as reflected in improvements gained in mortar compressive strength, electrical resistance, water absorption, and chloride ion permeability. Using sundry methods for measuring durability, electrical resistance which is a simple, fast and non-destructive testing method is regarded as an impressive criterion of the mortar permeability. For the purposes of this study, specimens were cast using S. pasteurii bacteria and maintained in either of the two urea-calcium chloride or urea-calcium lactate curing environments. Experimental results demonstrated that adding bacteria as a self-healing agent to mortar and curing the specimen in a proper environment led to its enhanced compressive strength and electrical resistance. The greatest improvement of 60% in 28-day compressive strength was obtained with specimens containing bacteria and cured in the urea-calcium chloride solution. Water absorption of the self-healing mortar was observed to decrease by 32–55% relative to that of the control. Meanwhile, the results of chloride ion permeability test revealed a decrease in chloride ion penetration into the bacterially-treated mortar, which is another indication of improved mortar durability.