Study on the improvement of vegetated concrete substrate by biochar and limestone calcined clay cement

Vegetated concrete has proven to be an effective technique for restoring the ecological environment of rocky slopes, but conventional formulations often suffer from excessive cement content and limited plant growth. This study proposes the use of biochar (BC) and limestone calcined clay cement (LC3) to form an improved vegetated concrete mix. Twenty-five different formulations were tested for their compressive and shear strength, pH values, and Bermuda grass growth. Microstructural studies using scanning electron microscopy (SEM). The results show that LC3 significantly increases the stress at small strains, while BC increases the strain at peak stresses. LC3 hydration produces cementitious material that coats soil particles, filling voids and leading to a linear increase in cohesion. The optimal mixture, with 12% LC3 and 6% BC, showed a 227% increase in cohesion and a 146% increase in internal friction angle. While LC3 increased pH, reducing the germination and growth performance of Bermuda grass, BC effectively improved these parameters, promoting faster and healthier plant growth. This study provides a reference for the application of LC3 and BC in future vegetated concrete development.