In this study, a new type of mortar was prepared through biomimetic carbonate precipitation (BCP) with L-Aspartic acid (L-Asp) as a modifier. Direct shear tests were performed on BCP-treated mortar, and the effects of L-Asp addition on shear properties were evaluated. To describe the shear stress-displacement relations, a sigmoid-hyperbolic shear model (SHM) was used. Results show that the L-Asp modifier significantly improves the shear strength of the mortar. SHM can well describe the shear stress-displacement relations of BCP-treated mortar with an R2 value higher than 0.98, which realizes competitive performance among the ever-developed models.