Sustainable utilization of industrial by-products spent foundry sand and cement kiln dust in controlled low strength materials (CLSM)

•Industrial by-products SFS and CKD used for developing controlled low strength material.•CLSM properties in fresh and hardened state, leachate toxicity, EE and ECO2 evaluated.•CLSM using 100% by-products fulfills the acceptance criteria for general backfill applications. In the present study, industrial by-products, spent foundry sand (SFS) and cement kiln dust (CKD) were used for developing controlled low strength materials (CLSM) and their various fresh and hardened state properties were examined. Embedded energy (EE), Embedded carbon dioxide (ECO2) as well as leachate toxicity of CLSM were also evaluated. Conventional fine aggregates were completely replaced by SFS; while CKD replaced cement at 0%, 25%, 50%, 75% and 100% levels; with the binder to aggregate ratio as 1:10. All the CLSM mixes were obtained while maintaining the flowability at around 250 mm. Addition of CKD increased flow and bleeding, delayed setting time and reduced compressive strength. The findings also indicate that SFS with even 100% CKD can be successfully utilized to prepare excavatable, eco-friendly and sustainable CLSM with bearing resistance equivalent to well compacted sands, suitable for general purpose backfill and utility trench filling. Mix with 75% CKD and 100% SFS as the only fine aggregate proved most suited from most of the aspects of a practical CLSM. All the proposed CLSM mixes were found to be environment friendly w.r.t leachate toxicity, low EE and ECO2. The study offers CLSM as an important alternative for the sustainable utilization of by-products in large quantities.