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.

A lack of proper base and subbase materials in pavement construction is one of the common problems in the tropical region worldwide. In many countries such as Thailand, cementitious materials are usually used for ground improvement. Controlled Lowstrength Material (CLSM) was considered in this study as a pavement base material. The CLSM mixes were prepared by varying cement, fly ash and fine aggregate content. Each mixed component was studied for their physical and chemical properties. After mixing, properties of the CLSM were investigated based on the standard testing of fresh concrete and cement-treated base material. The flowability, setting time and bleeding were checked to ensure that the CLSM were self-compacting. The mechanical properties of hardened CLSM were determined by means of CBR, unconfined compressive strength and resilient modulus tests. The resilient modulus results were used in the analytical design of flexible pavement with CLSM base. The critical traffic data under high-volume road collected by the Thailand Department of Highway was adopted in this study. Results show that the CLSM base considerably increased the performance as well as design life of asphalt pavement compared with the conventional crush rock base pavement.