Experimental Study of Interface Shear Characteristics of Pervious Concrete and Carbonated Soil in the MgO-Carbonated Composite Pile

Abstract

Regarding a novel and low-carbon composite pile, the MgO-carbonated composite pile (MCP) is formed by a pervious concrete pile (inner core) at the center of a deep magnesia (MgO) mixing column (outer core) subjected to forced carbonation. The shaft resistance of the MCP is primarily governed by the interface of pervious concrete–carbonated soil. Understanding the interface’s shear behavior and strength is crucial for the design and safety assessment of the MCP. In this paper, a series of direct shear tests were conducted to analyze the shear behaviors of the pervious concrete–carbonated soil interface. The aim was to evaluate the impact of key influence factors such as carbonation time, MgO content, and initial water content on the interface friction capacity. Furthermore, a practical prediction model for interface shear strength was proposed, taking into account the aforementioned factors. The test results revealed that the peak shear strength of the specimen under 12 h of carbonation time reached 508 kPa, representing a 94% increase compared to the specimens without forced carbonation. The curves of shear stress versus tangential displacement of the inner–outer cores interface exhibited both strain-hardening and -softening behaviors. The proposed linear model exhibited excellent predictive accuracy for interface shear strength, with a regression coefficient exceeding 0.8. Based on multiple linear analysis, MgO content emerged as the most significant factor affecting the interface shear strength of the MCP, followed by vertical effective stress.