Synergistic application of modified zeolite and biochar in improving the performance of sandy vegetation concrete

The combined use of zeolite (ZL) and biochar (BC) can effectively address the problems of poor anti-erodibility and fertility retention capacity of vegetation concrete (VC) prepared from sandy soil. Natural ZL (NZL), especially clinoptilolite, has some disadvantages, such as presence of numerous impurities distributed in the pores and low surface activity, which lead to insufficient adsorption ability. To fully utilize the synergistic effect of ZL and BC, NZL was modified into physical (PZL), chemical (CZL), and composite-modified ZL (SZL). Results showed trend in the average pore size was SZL > CZL > PZL > natural ZL, and the changes in the functional groups on the surface of SZL was the most significant. Modified ZLs enhanced VC performance: PZL had the strongest effect on anti-erodibility, while SZL was most effective in improving fertility and retention. Our results provided a useful method for treating engineering defects in VC prepared using sandy soil. • Modified zeolite (ZL) could better fulfill its synergistic effect with biochar (BC) than natural ZL. • Composite modified ZL (SZL) had the best adsorption effect on aging cracked BC particles. • SZL had the best effect on improving fertility and plant growth of sandy vegetation concrete (VC). • Physical modified ZL (PZL) and SZL were better in mechanical strength enhancement of sandy VC. • 2 wt% SZL with 2 wt% BC was the recommended proportions.