Development of binary and ternary binders made from industrial by-products for producing controlled low-strength materials

This study investigated the properties of controlled low-strength materials (CLSM) from industrial by-products, i.e., bottom ash (BA), calcium carbide residue (CR), and fly ash (FA) as binary (BA-CR and BA-FA mixtures) and ternary (BA-CR-FA mixture) binders. The flowability, density, hardening time, unconfined compressive strength (UCS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were investigated. The results indicated that high flowability ( 200–265 mm ) was achieved by incorporating FA into the CLSM mixture. Increasing the replacement of BA with CR content from 15 to 45% by weight led to longer hardening times by approximately 49% , as well as lower density and UCS at early ages. In contrast, increasing the replacement of BA with FA content to 45% by weight reduced the hardening time by 27%, while both the density and UCS of the CLSM increased. The XRD and TGA analyses of CLSM pastes at 28 days revealed the formation of calcium silicate hydrate, along with residual portlandite and calcite from the precursor materials. For a binary binder, the CLSM sample made with 55% BA and 45% FA is recommended , achieving a 28-day UCS of 5770 kPa . The CLSM sample with a ternary binder of 55% BA, 15% CR, and 30% FA achieved the highest 28-day UCS of 13916 kPa, exceeding the highest-strength binary mixture by more than 130%. Finally, the results suggested that the industrial by-products used, including FA, CR, and BA, could be upcycled as raw materials to produce CLSM.