A study of high-flowability steel fiber reinforced small-aggregate concrete with high-resistance to early cracking and shrinkage for paving layer of slab/plates

Cracking of concrete paving layer for slab/plates is a vexed problem in civil engineering, which is trying to be solved by developing a high-flowability steel fiber reinforced small-aggregate concrete (SFRSC) with dominant properties of high resistance to early cracking and shrinkage. This paper carried out a series of experimental studies on twenty-two mix proportions of SFRSCs with high-flowability represented by a slump of 160 ± 20 mm. The variables were steel fiber content varying from 0 to 75 kg/m 3 , shrinkage-reducing admixture content from 0.2 % to 2 % by weight of binders, maximum size either 10 mm or 16 mm of coarse aggregate, and strength grade of concrete matrix from 30 MPa to 50 MPa. Early cracking from casting to 14 days, early shrinkage from casting to 3 days, and long-term drying shrinkage up to 180 days were measured, while the microstructures of SFRSC were detected. The results indicate that steel fibers obviously reduce the early cracking in SFRSC, producing a cracking reduction coefficient of 29.5 %-100 % for SFRSC at 24 h, with steel fiber content of 15 kg/m 3 -75 kg/m 3 . Steel fiber presents a coupling effect with shrinkage-reducing admixture on enhancing early cracking resistance, making SFRSC with 30 kg/m 3 steel fibers and 0.6 % shrinkage-reducing admixture reach a cracking reduction coefficient of 89.4 %. Steel fiber contributes to reducing the drying shrinkage of SFRSC as their content increases, and also creates a coupling effect with the shrinkage-reducing admixture. The drying shrinkage of SFRSC decreases using aggregate with a maximum size of 16 mm, along with increasing the strength grade. Formulas based on a modification of GL2000 model, accounting for the effects of test variables, are proposed for predicting the drying shrinkage of SFRSC. • High-flowability steel fiber reinforced small-aggregate concrete for paving layer of slab/plates. • Optimal mix proportion design of the concrete with high-resistance to early cracking and long-term shrinkage. • Identified the coupling effects of steel fibers with shrinkage-reducing admixture. • Determined cracking reduction coefficients for early cracking resistance. • Formulas for predicting the drying shrinkage accounting the effects of studied variables.