Practical approach production of bacteria-based agent-contained light weight aggregates to make concrete self-healing

Abstract

A functional experimental concrete system has been developed in our lab, in which a two component bacteria-based healing agent contained in a protective reservoir is included in the concrete mixture. Incorporated bacteria have the potential to produce copious amounts of calcium carbonate based crystals from supplied mineral precursor compounds. Precipitates of the carbonate mineral seal and block occurring cracks. Particles of expanded clay, a type of light weight aggregate (LWA), were chosen as protective reservoir in which the bacteria and precursor compound are contained. Most effective method for intrusion of healing agent in LWA is by vacuum impregnation, a rather expensive process. In this work a more economically feasible in-situ approach is proposed, still gaining the required healing capacity. Prior to mixing LWA are pre-wetted with a warm liquid impregnation solution (80°C) carrying bacterial spores and mineral precursor compounds. This alternative production process is economical and practically more straightforward and functionally additionally beneficial as water-saturated LWA contribute to internal curing. Benefit of the novel approach is the reduced cost of healing agent production and improved practicality directly at a concrete plant, as commonly available equipment can be used. First tests indicate sufficient healing capacity remains after the wet mixing stage and internal drying by cement hydration.