Utilization of recycled concrete powder in modification of the dispersive soil: A potential way to improve the engineering properties

Abstract

Recycled concrete was used in dispersive soil as admixture in this paper to improve the mechanical properties and dispersivity of dispersive soil. Recycled concrete blocks were collected, ground to powder and mixed into dispersive soil with the weight ratios of 1%, 2%, 3%, 4%, and 5%. Soil samples were prepared and cured in a curing chamber for 0, 1, 3, 7, 14, and 28 days with temperature and humidity at 20 °C and 98%, respectively. Dispersivity, pH, and electronic conductivity of soil samples were determined at different curing time. Flow speed of seepage water and eroded soil weight were measured during pinhole test. Unconfined compression test and splitting test were performed to determine compressive strength and tensile strength of soil samples. Microstructures and mineral changes were obtained by SEM, XRD and TG/DTG tests. Validation test was performed on a natural dispersive soil to prove the effectiveness of recycled concrete powder on the dispersivity. Experiments show that dispersive soil turns into nondispersive soil with increase content of recycled concrete powder. Results of remoulded sphere sample crumb test are more conservative due to the remoulding process of soil during the test. Compressive and tensile strength of soil samples present a significant increase tendency with both the mixing ratio of recycled concrete powder and curing time. Results indicate that recycled concrete powder can be used to improve both the dispersivity and mechanical properties of dispersive clay, simultaneously help to solve the disposal of abandoned construction concrete waste. Enhancing of water stability of dispersivity soil would also ensure the safety and normal operation of both agricultural irrigation facility and hydraulic engineering.