Wet–Dry Performance of Fat Clay Treated with Sludge Ash of Wood and Paper

Abstract

This study aims to evaluate the durability and long-term performance of clayey soil treated with sludge ash of a wood and paper (SAWP) mill in response to wetting and drying (w-d) cycles to elucidate its efficiency as a sustainable construction material in earthwork applications. For this purpose, height change measurements, P-wave velocity (Vp), and unconfined compressive strength (UCS) tests were carried out at different w-d cycles. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted to identify the mineralogical and microstructural changes in treated samples. The height change and Vp of the SAWP-treated samples were measured at each cycle and continued for 12 w-d cycles, or until the cycles ended were possible. The UCS tests were carried out after 0, 1, 3, 5, 7, and 12 w-d cycles. The height change ratio increased with the increased w-d cycles. Experimental results revealed that the Vp and UCS results generally decreased by increasing the number of w-d cycles. Crack propagation caused by desiccation kinetics and degradation of the cemented structure led to the formation of a weak plane and a significant reduction in Vp and UCS. Unique relationships were developed between Vp, UCS, and the number of w-d cycles for different SAWP contents and curing periods. These relationships can be considered as estimating the UCS based on Vp values with good accuracy to achieve sustainable design requirements. The XRD analyses demonstrated that calcite (CaCO3) was the main cementitious compound which is a key factor for the strength enhancement.