Mechanistic insights across curing regimes for enzymatic and biopolymer-optimized reinforcement in rock masses

Biocementation is an innovative and sustainable technique for reinforcing weak and weathered rock masses in natural and engineered geological settings, and yet, the influence of curing temperature on the mechanical behavior of treated rock masses has not yet been constrained. Biocementations, like enzyme-induced calcite precipitation (EICP) and biopolymers (BP), have gained prominence for enhancing rock properties, particularly to support underground infrastructure. This study systematically investigates how curing regimes affect the mechanical (elastic and inelastic) behavior and reinforcement performance of rock masses for underground engineered applications using EICP and a novel technique, biopolymer-modified enzymatic precipitation (BP-EICP). Results demonstrate that BP-EICP can significantly enhance bulk stiffness (E) by +187% and uniaxial compressive strength (UCS) by +210%, while EICP alone yields comparable improvements (E: +178%; UCS: +216%). Curing temperature plays a critical role in biomineralization, with lower temperature curing producing greater reinforcement in BP-EICP-treated specimens (E: +192%; UCS: +220%) compared to higher curing temperature (E: +178%; UCS: +199%). The modulus ratio (MR) suggests that curing temperature has a minimal effect on stiffness ratios, whereas the biocementation type has a more pronounced impact, with the EICP-treated specimens yielding a 20% decrease in MR, versus a 13% reduction with BP-EICP. Failure modes in biocemented specimens become more complex with increased curing regimes and enzyme activity, showing transitions between axial and shear failure. This work provides new insights into the role of curing temperature and biocementation type in modifying the mechanical behavior of rock masses subjected to stress conditions, with implications for the stability and design of underground natural and built infrastructure.