Durability Evolution of Low Liquid Limit Clay-Based CLSM Incorporating Industrial Wastes Under Freeze–Thaw, Wet–Dry, and Drying Actions

Abstract

A sustainable controlled low-strength material (CLSM) was developed using ground granulated blast-furnace slag, steel slag, and flue gas desulfurization gypsum in combination with cement to synergistically utilize engineering excavated soil and industrial solid wastes for stabilizing low liquid limit clay. However, the long-term durability evolution of this material under harsh and coupled environmental conditions—particularly freeze–thaw cycles, wet–dry cycles, and prolonged drying—has not been systematically investigated. In this study, systematic freeze–thaw cycling (up to 11 cycles), wet–dry cycling (up to 11 cycles), and natural drying (until mass stabilization) tests were conducted on specimens with binder contents ranging from 8% to 16%. The evolution of mechanical performance was evaluated via unconfined compressive strength (UCS) tests, while microstructural changes were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results revealed a distinctive “S-shaped” fluctuation in UCS under freeze–thaw cycles. High-binder (16%) specimens maintained strengths of 1783–2395 kPa with intact surfaces and no visible cracking—significantly outperforming low-binder specimens. Under wet–dry cycles, strength initially increased after the first cycle and then declined progressively, with the lowest strength loss observed at 10% binder content. During drying, both water loss rate and drying shrinkage strain decreased with increasing binder content: from 8% to 16% binder, the water loss rate dropped from 34.16% to 29.03%. Microstructural analysis revealed that higher binder content promoted the formation of a dense, interwoven network of C–S–H gel and ettringite, which effectively filled intergranular pores and encapsulated soil particles, thereby enhancing macroscopic durability. This study provides a sustainable material solution for utilizing industrial solid wastes in the stabilization of low liquid limit clay for CLSM applications under severe environmental conditions, supporting the broader adoption of waste-to-resource strategies in construction engineering.