Development of an Alternative Cementitious Materials Based on Calcium Carbide Residue and Silica Fume

The present study evaluated the engineering properties and microstructure of an alternative binder composed of calcium carbide residue and silica fume. The cementitious mechanisms of this alternative binder based on the pozzolanic reaction in raw materials. The ratio of calcium carbide residue and silica fume was decided based on the chemical composition of raw materials and their chemical reaction. The calcium carbide residue-silica fume mortar was prepared and tested for its compressive strength at several curing periods, with results then compared to conventional mortar made with ordinary Portland cement. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to investigate the microstructure of hardened mortars. The test results suggest that the compressive strength of calcium carbide residue-silica fume mortar continuously developed throughout the curing period. The relative compressive strength of calcium carbide residue-silica fume mortar reached 72.78% of the ordinary Portland cement mortar strength at 28 days curing age.

Strength Development and Microstructural Investigation of Calcium Carbide Residue and Fly Ash Prepared with Optimized Alternative Green Binders

The development of new environmentally friendly binder from calcium carbide residue and fly ash wastes were investigated in this study. The key point of this work is difference to several previous investigations in that the optimized mixture proportion of the raw materials were calculated based on their chemical composition and their reaction. The compressive strength development over the curing age was also compared with reference mortar created with OPC binder. Mortar cubes were cast from the mix containing the calcium carbide residue and fly ash, at the optimized ratio. The compressive strength of the mortar was then monitored over an extended period: at 56 days it was 10.66 MPa, which is approximately 47% of the reference mortar. The morphologies and chemical compositions of the developed mortar showed the presence of spherically shaped of unreacted fly ash powder particles embedded in a cement C–S–H gel resulting from the pozzolanic reaction of raw materials.

Mechanical Properties and Durability Performance of Concrete Containing Calcium Carbide Residue and Nano Silica

Calcium carbide residue (CCR) is the end-product of production of acetylene gas for the applications such as welding, lighting, ripening of fruits, and cutting of metals. Due to its high pH value, disposing of CCR as a landfill increases the alkalinity of the environment. Therefore, due to its high calcium content, CCR is mostly blended with other pozzolanic materials, together with activators as binders in the cement matrix. In this study, cement was partially substituted using CCR at 0%, 7.5%, 15%, 22.5% and 30% by weight replacement, and nano silica (NS) was utilized as an additive by weight of binder materials at 0%, 1%, 2%, 3% and 4%. The properties considered were the slump, the compressive strength, the flexural strength, the splitting tensile strength, the modulus of elasticity, and the water absorption capacity. The microstructural properties of the concrete were also examined through FESEM and XRD analysis. The results showed that both CCR and NS increase the concrete’s water demand, hence reducing its workability. Mixes containing up to 15% CCR only showed improved mechanical properties. The combination of CCR and NS significantly improved the mechanical properties and decreased the concrete’s water absorption through improved pozzolanic reactivity as verified by the FESEM and XRD results. Furthermore, the microstructure of the concrete was explored, and the pores were refined by the pozzolanic reaction products. The optimum mix combination was obtained by replacing 15% cement using CCR and the addition of 2% NS by weight of cementitious materials. Therefore, using a hybrid of CCR and NS in concrete will result in reduction of cement utilization in concrete, leading to improved environmental sustainability and economy.