Alkali-Activated Controlled Low-Strength Material Utilizing High-Calcium Fly Ash and Steel Slag for Use as Pavement Materials

This study investigated the performance of alkali-activated, cement-based controlled low-strength materials (CLSMs). The CLSM was produced by mixing fly ash, steel slag, sodium hydroxide, and water with bottom ash (BA) aggregate. Properties of fresh and hardened composites were measured, and tests were conducted to determine their microstructure characteristics. Highlighted properties including slump flow, bleeding, unit weight, unconfined compressive strength, and resilience modulus were reported. The results indicated that the inclusion of 10%–30% slag resulted in a stronger CLSM with a higher Ca/Si ratio in the cementitious matrix of its microstructure. Higher slag content in the CLSM also shortened setting time and led to a lower bleeding rate. A mixture containing slag up to 20% of fly ash was recommended for pavement applications. Finally, the economic and environmental impacts were also preliminarily studied.