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

Abstract 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.