Improving the compressive strength of mortar from a binder of fly ash-calcium carbide residue

- We created a binder from two kinds of waste materials.
- Finenesses of binder, curing temperatures, and cement contents were studied.
- The more fineness of the binder yields large increases in compressive strength of mortar.
- The mortar cured at a high temperature attained a greater strength in the short term.
- The mortar containing 10% Portland cement of a binder yielded 31.2 MPa.

The aim of this research is to improve the compressive strength of mortar made from fly ash (FA) and calcium carbide residue (CR) as a binder. FA is a by-product from a thermal power plant while CR is a by-product from an acetylene gas industry. They were used together to form a new binder material for concrete. Due to low strength at the early age, several processes were introduced to increase the compressive strength of the new binder. Finenesses of binder, curing temperatures, and cement contents were the studied parameters in this study. Mortars cast for 24 h were oven-cured at temperatures of 30, 45, 60 and 75 °C for 24 h, and then cured in water at room temperature until the testing age. The results showed that the fineness of CR-FA binder is the most important factor to increase the compressive strength of CR-FA mortar. At 90 days, the compressive strength could increase from 15.6 MPa to 26.0 MPa as a result of an increased fineness of the binder. In addition, a high curing temperature enhanced the compressive strength of mortar at an early age but was less effective at a later age. Moreover, substituting some of the GCR-GFA binder with Portland cement can accelerate and increase the mortar strength at various rates. The mortar SC0T30 (no cement) has a compressive strength of 26.0 MPa at 90 days and could be increased to 30.3 and 31.2 MPa with 5 and 10% of cement in the binder, respectively.

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