Desiccation cracking in clay-bottom ash mixtures: insights from crack image analysis and digital image correlation

Desiccation cracking considerably impairs the hydraulic and mechanical properties of clays and is critical to the long-term performance of infrastructure foundations and earth structures. This study resorts to image-based characterization techniques to investigate the potential of using bottom ash admixtures, as a cost-effective and sustainable stabilization solution, for soil cracking reduction. Three types of samples were prepared by mixing clays with different amounts of bottom ash (0% BA, 20% BA, 40% BA) for desiccation tests. Images of soil surface cracks are captured by a high-resolution camera at certain time intervals to track the spatiotemporal evolution of crack morphology. Experimental results demonstrate that adding bottom ash into clay significantly reduces the extent of moisture loss in 48 h, which can help reduce the development of cracking. In situ strain measurements, facilitated by digital image correlation (DIC), indicate that the minor principal strains induced by the desiccation process decreased from 0.08 to 0.05, further revealing that bottom ash reduced volumetric changes in samples. Moreover, the addition of bottom ash maintains the structural integrity of the soil intact and slows down the crack formation, with a more intensive crack network formed in sample 0% BA. With higher dosage of bottom ash, crack area ratio, average crack length, and total crack length also decrease in the soil samples. These findings are useful to improve the fundamental understanding of the governing mechanisms during soil desiccation cracking and highlight the possibility of recycled usage of bottom ash for soil improvement.