Study on Self-healing Mortar Using Microbial Induced Calcium Carbonate Precipitation Process

Abstract

This study presents the self-healing cracked mortar by applying a microbially induced calcium carbonate precipitation process. First, find the suitable cultivation conditions of 5 pure bacteria strains from the Thailand Institute of Scientific and Technological Research (TISTR), i.e., Bacillus thuringiensis TISTR 126, Bacillus megaterium TISTR 067, Bacillus sp. TISTR 658, Proteus mirabilis TISTR 100, and Staphylococcus aureus TISTR 118. From the results, Bacillus thuringiensis TISTR 126 is promising to be the selected strain in the amount of calcium carbonate crystals, high urease activity, and nonpathogenic. The mortar specimens were precracked by a thin plastic sheet to prepare a 0.2 mm narrow crack width. A pre-cracked sample was treated by injecting buffer solution, bacterial suspended solution, and calcium chloride solution, respectively, directly daily into the crack for 28 days. The observation of crack width has been performed before injection of the solution and after 28 days of treatment, mortar samples were performed for the compressive strength and water absorption test. The results are shown in the case of a relationship between treatment days and tested results.