Bearing characteristics of recycled concrete aggregate encased column composite ground

This paper investigates the bearing characteristics of a recycled concrete aggregate encased column (RCAEC) composite ground with the objective of better-utilizing construction waste. A large-scale model test was conducted, in which recycled concrete aggregate (RCA) was employed as the column material and geosynthetics were encased with varying lengths and layers, with the similarity scale factor assumed to be 10. The impact of various factors, including encasement length, encasement stiffness, length-to-diameter ratio (l/d), and optimal replacement ratio, on the load-bearing characteristics was examined. The findings indicate that the maximum bearing capacity of the composite foundation can be achieved when the encasement length of RCAEC is approximately six times the column diameter, the l/d is 6 ∼ 7, the stiffness of the encasement material is approximately 100 kN/m, and the area replacement rate is around 13%. Lateral compression tests revealed a strong correlation between crushing degree, column-bearing capacity, and aggregate gradation. Increasing pressure led to significant destruction of 10 ∼ 5 mm particles, while particles smaller than 2.5 mm increased, alongside a rise in relative density. For optimal column construction and bearing processes, it is crucial to optimize RCA gradation and limit column loads to below 14,000 kN to prevent excessive crushing of RCA.