Durability and Cost Analysis of High-Volume Fly Ash Blended Self-Compacting Mortar

In the present study, the effect of high-volume fly ash blending in the concentration of 15%, 25%, 35%, 45%, and 55% with different effective water-to-cement (W/C) ratios has been investigated for rheology, compressive strength (CS), and durability of self-compacting mortar (SC-mortar). The rheology of SC-mortar was evaluated in terms of slump flow diameter, v-funnel flow time, and developed yield stress and plastic viscosity. The CS of SC-mortar was evaluated at 7 and 28 days of curing, whereas the water permeability and rapid chloride penetration tests were performed to evaluate the durability of SC-mortar at 28, 90, and 180 days. The consumption of ordinary portland cement was reduced using the k-factor or cementing efficiency factor in mix design, where the value of the k-factor decreases with increasing fly ash content. The experimental study revealed that the addition of a high volume of fly ash has a significant impact on rheology and durability, whereas CS of SC-mortar was affected marginally. Scanning electron microscopic (SEM) examination revealed that the fly ash blending has improved the packing and reduced the pore density to compensate for the loss of CS on account of lower cement content. An increase in W/C has increased the porosity, causing a negative impact on CS and durability. The durability of SC-mortar has increased with increasing fly ash content, and there was an exceptional increment in water ingression time (T25) with an increase in fly ash content from 25% to 35%, but with higher content of fly ash (above 35%) and low value of W/C, SC-mortar become very sticky, thus reduced the workability significantly. Compared with the control mix, there is a significant reduction in the cost of SC-mortar with fly ash blending of 15%, thereafter, the cost reduction is marginal with a further increase in fly ash dosage which is due to the rise in admixture dosage. Based on the rheology (within EFNARC limits), CS, and durability of SC-mortar, the optimized dosage of fly ash has been recommended in the range of 25%-40% with different W/C.