Experimental study on the synergistic reinforcement of silt using EICP and magnesium oxide

In response to the challenges of high silt content, poor cohesion, and loose structure in the Yellow River floodplain, this study proposes a combined reinforcement method using enzyme-induced carbonate precipitation (EICP) and MgO to enhance mechanical properties. By adjusting the cementation solution concentration and MgO amount, the mechanical characteristics of the reinforced silt were systematically analyzed, and the reinforcement mechanism was thoroughly investigated. Results show that while cementation solution concentration significantly affects calcium carbonate precipitation during EICP, excessively high concentrations inhibit urease activity. The addition of MgO promotes magnesium carbonate hydroxide formation, improving mechanical properties and increasing unconfined compressive strength to a maximum of 5000 kPa, with distinct brittle failure characteristics. Residual strength, elastic modulus, and peak strength also improved. Although MgO delays flocculation and precipitation processes, it increases carbonate production. SEM and XRD analyses reveal that increasing cementation solution concentration and MgO content reduces inter-particle porosity and enhances soil microstructural stability. Overall, the combined EICP–MgO method shows exceptional strength improvement in silt, highlighting its practical applicability and innovative advantage over EICP alone.