Biological Solutions for the Remediation of Cracks in Ancient Earthen Structures: Experimental Studies

Abstract

The aim of this research is to investigate two biological solutions, namely, soybean urease induced calcite precipitation (SICP) and xanthan gum (XG) biopolymer, for the remediation of cracks in ancient earthen structures. In this study, soil crack patterns captured by a high-resolution camera are quantified using image processing software. Optical microscopy and wind erosion tests were utilized to analyze the surface cementation effect in the repaired earth samples. Experimental results show that repaired samples treated with SICP solution (a mixture of soybean urease and urea-calcium chloride solutions), XG solution, and SICP-XG solutions (a mixture of SICP and xanthan gum solutions) can significantly decrease the surface crack ratio, and both the total length and the average width of the cracks, especially for the sample treated by the SICP-XG solution. In the wind erosion test, the repaired cracks in these three earthen samples remain stable under wind speeds of 15 m/s. In addition, scanning electron microscopy and X-ray diffraction tests confirmed the cementation effect induced by CaCO3 crystals and xanthan gum.