Recycling of dredged river silt reinforced by an eco-friendly technology as microbial induced calcium carbonate precipitation (MICP)

• The recycling of the dredged river silt used as building materials is proposed. • An efficient, economical and environmentally friendly protection method (MICP) is selected to treat the dredged river silts. • The effects of cementation solution concentration and treatment times on the solidification effect of MICP were studied. A large amount of river silt is continuously dredged and usually dumped in landfills or oceans, resulting in land occupation and environmental pollution. Traditionally, cement-based materials are used to cement dredged river silt as building materials, which not only increases carbon dioxide emissions but also uses very little dredged silt. In order to realize the resource utilization of dredged river silt, microbial induced calcium carbonate precipitation (MICP) technology, which has the advantages of lower energy consumption, less environmental pollution and lower carbon emissions, is adopted to solidify the dredged river silt as roadbed materials in this paper. The unconfined compressive strength (UCS) test, calcium carbonate (CaCO 3 ) content test and microstructure test are carried out to analyze the mechanical properties of the solidified dredged river silt. The test results show that the MICP mixing method can be employed to solidify loose dredged river silt into high-strength construction materials. The concentration of the cementation solution has a significant effect on the solidification effect, and the most reasonable concentration of the cementation solution is 1.5 mol/L. With the increase of treatment times, the pores in the soil are filled with CaCO 3 , and the UCS of the specimens after 10 times of treatment can reach 6.75 MPa with a relatively uniform CaCO 3 content of 27.8 %. The main crystal form of CaCO 3 is calcite, which can fill the pores and make the river silt particles cement as a whole, which is the main reason for the improvement of mechanical properties of dredged river silt.