Mechanical performance and cementation uniformity of sand stabilized with bone meal-derived calcium phosphate compounds: An eco-friendly biocementation technology

During the process of sand cementation using the traditional biocementation technology EICP/MICP (Enzyme/Microbially induced carbonate precipitation), the significant release of ammonium ions and ammonia gas poses environmental concerns. This study proposes an eco-friendly approach: Soybean urease induced calcium phosphate compounds precipitation (SICCP). This method employs bone meal, soybean, and urea as raw materials to stabilize sand. The effectiveness of SICCP-stabilized sand was assessed using a variety of analytical methods, including unconfined compressive strength test, precipitation content analysis, three-dimensional reconstruction of CT images, microstructural observation, and mineral composition analysis. Results indicate that optimal sand column strength, reaching up to 625 kPa, was achieved with an initial cementation solution pH of 3 and a soybean urease solution ratio of 0.2. Increasing the initial pH of the cementation solution and the soybean urease solution ratio led to decreased uniformity of calcium phosphate compounds (CPCs) and a corresponding reduction in strength. Compared to EICP/MICP technology, the cost of SICCP is lower, and the amount of ammonia gas and ammonium ions released into the environment can be reduced by approximately 96 % and 57 %. The findings of this study provide novel insights and a theoretical foundation for advancing biocementation technologies toward a more environmentally sustainable direction. ● A new sand stabilization method SICCP has been proposed, which makes full use of waste bone resources. ● Compared to EICP, SICCP can reduce the NH 3 release per liter of grout solution by at least 96 % and the production of NH 4 + by at least 57 %, making it more environmentally beneficial. ● The cost of SICCP is lower than that of EICP, making it suitable for extensive site applications.