Study on strength and microstructure of multi‐source solid waste ultrafine powder concrete

Abstract In order to improve the resource utilization rate of slag, phosphogypsum, and steel slag, full solid waste groups (ultrafine grinding group A, B, C and ungrinding group E) and full cement group D were used to prepare concrete in laboratory experiments. The influence laws of grinding and dosage on the slump, compressive strength, and pore structure of concrete were studied. The results showed that the slump of group E was the largest, reaching 216 mm. At the curing age of 3 days, the strength of group D was the greatest, with a value of 31.77 MPa, while group E was the smallest, with a value of 15.6 MPa. The compressive strength of groups A, B, and C was much higher than that of ungrinding group E, which indicated that ultrafine grinding had an excellent effect on improving the early strength of concrete. Within the curing age of 28 days, the early compressive strength of group A with the minimum amount of ultrafine slag powder was the highest, reaching 40.2 MPa. The compressive strength of group C was the highest at the curing age of 60 and 90 days, which were 43.2 and 45 MPa, respectively. The formation of ettringite was the main source of concrete early strength. Ettringite and C‐S‐H gel were generated in large amounts and intertwined with each other; the hydration product structure of the ultrafine grinding groups was denser, the paste structure was filled more fully, the pores were smaller, and the concrete compressive strength was greater.