Performance and microstructure of grade 40 self-compacting concrete with agricultural waste ashes ternary blends

This study evaluates sawdust ash (SDA) and millet husk ash (MHA) as partial substitutes for Portland cement (PC) in Grade 40 self-compacting concrete (SCC). Ashes were combusted between 600 and 650 °C and used at 0–30 % replacement in 5 % increment. An optimized blend of 10 % MHA, a superplasticizer dosage of 7.49 kg m −3 and a water–cement ratio of 0.38 to obtain SDA–MHA–SCC. Trial mix 7 (T7) fulfilled the criterion for grade 40 SCC, having 657 mm slump, 0.81 passing ability and 15 % segregation resistance was adopted. Scanning electron microscopy at 2,419,200 s was carried out on SCC, SDA–SCC, and SDA–MHA–SCC. The outcome of the chemical analysis of MHA and SDA indicated that the summation of SiO 2 + Al 2 O 3 + Fe 2 O 3 yielded 73.16 % and 28.27 % respectively. The initial and final setting times of PC, were recorded as 4,080 s and 9,600 s, while, at 5 % and 30 % SDA–MHA–SCC gives 5,580–12,540 s and 15,300–23,340 s, respectively. The outcome from this study, exposed MHA is a good reactive pozzolana and enhanced the characteristics of grade 40 SCC for sustainable civil engineering construction.