Crack healing in cementitious materials including tests methods

Abstract

If concrete is crack free, deleterious substances can be avoided entering the body of the material, that may corrode the rebar or encourage freeze/thaw damage. This paper examines a self healing system of cementitious materials. Microbial induced calcite precipitation was used to heal cracks in concrete with calcite using bacillus bacteria in alkaline conditions to generate a calcite filling material. Self healing of cracked prisms was determined using a water flow and absorption test and the results were expressed to record the healing as a percentage. The findings of the tests showed that a significant degree of self healing had taken place after 56 days after inducing a crack to the concrete prisms and the water flow test was appropriate to determine the degree of self healing taking place. Limitations of this process are such that the process requires a biological laboratory to create the spore impregnated aggregate. Once the aggregate is prepared, the batching process is essentially the same as any normal concrete. A practical use of this system could be developed using cover panels of self healing material to act as permanent formwork, thus placing the healing ingredients where they are needed at a minimum cost. The system has huge potential for the creation of a self repairing sustainable infrastructure.