Alkali-activated, cementless, controlled low-strength materials (CLSM) utilizing industrial by-products

•The CLSM containing fly ash, slag and bottom ash were activated by a NaOH solution.•The CLSM showed a compressive strength of 1.0–2.0MPa at 56days, a flow of 200–250mm and a bleeding rate of 1.0–1.5%.•An increase in the amount of slag resulted in a reduction of the bleeding rate.•The solid NaOH/total binder ratio was determined to be 1.5–2.5% for the maximum strength requirement. A series of characterization tests were conducted to systematically investigate the characteristics of alkali-activated, cementless, controlled low-strength materials (CLSM) utilizing industrial by-products in the present study. Three different industrial by-products (fly ash, slag and bottom ash) were used as component materials in the CLSM mixture. The flow, bleeding, settlement and air content of fresh CLSM mixture were measured, and hardened CLSM mixtures were tested to measure their compressive strength and density. The results showed that NaOH solution as an alkaline activator had very little effect on the flowability of CLSM mixtures, whereas an increase in the amount of bottom ash (fine aggregate) resulted in a considerable reduction in the flowability of CLSM mixtures. An increase in the amount of slag resulted in a reduction of the bleeding rate. The solid NaOH amount which satisfies the maximum strength requirement for future re-excavation as suggested in ACI 229R was found to be 1.5–2.5% by weight in the CLSM mixture when a bottom ash/total binder ratio and a slag/total binder ratio were 1.5 and 0.2, respectively.