Innovative Approach to Enhance Self-Healing in Cementitiously Stabilized Soils and Mitigate Shrinkage Cracking
Dr. Muhunthan Balasingam, Washington State University
Although cementitious stabilization offers great advantages, such as beneficial utilization of the in-situ inferior materials or waste/byproducts, it suffers from shrinkage cracking which limit the widespread use of this technology. The proposed study is on an innovative approach that couples self-healing effects of bacterial spores with sequential hydration methodology that could mitigate the development of shrinkage cracking of stabilized mixture while sustaining the development of high strength. Traditionally, there is a tradeoff between high strength and susceptibility to shrinkage cracking which typically happens soon after the construction. High strength is desired from the standpoint of providing support to structure on the stabilized materials. However, high strength of stabilized materials leads to high potential to shrinkage cracking. Traditionally, optimum moisture content of the stabilized material is specified at the time of mixing to reach the strength needed. The mixture with optimum moisture content, however, suffers from shrinkage cracking. Sequential hydration is a concept for which moisture content below optimum is provided for partial hydration. The mixture will develop initial strength, but low shrinkage strain, due to partial hydration and limited moisture to evaporation. The relaxation of stabilized mixture reduces the shrinkage stress of stabilized mixture when it is restrained from free movement. The subsequent supply of moisture will allow for stage-two hydration to develop a high strength. The final shrinkage strain and shrinkage stress is also reduced, due to developed strength and relaxation during partial hydration. In addition, the stage-two hydration will arrest cracks, if any, during initial hydration which is an autonomic self-healing function. The stabilized mixture with sequential hydration has potential to develop high strength and low shrinkage cracking potential. The mixes containing bacterial microcapsules which enhance self-healing is expected to benefit immensely from the sequential hydration and lead to a novel design for cementitious stabilization.
Dr. Muhunthan Balasingam