Investigation of steel fiber reinforced high-performance concrete with full aeolian sand: Mix design, characteristics and microstructure

High-performance concrete with full aeolian sand (FA-HPC) has the characteristics of low water binder ratio, large cementitious materials content and no restriction of coarse aggregates, resulting in a high risk of shrinkage cracking. Aiming at reducing the shrinkage of FA-HPC and improving its cracking resistance, mechanical properties and durability, steel fibers with different lengths are employed to reinforce FA-HPC and develop a new type of cement-based composites (FA-HPFRC). For this purpose, the modified Andreasen & Andersen (MAA) model was adopted to determine the volume fractions of aeolian sand (AS), cement, fly ash (FA) and silica fume (SF). Then, the water binder ratio (W/C), superplasticizer (SP) and steel fiber content of FA-HPFRC were optimized through wet packing compactness, flowability, mechanical properties and shrinkage tests. Furthermore, the cracking resistance and microstructure of the developed FA-HPFRC were tested and analyzed from macromicro perspectives. The results show that the volume fractions of AS, cement, FA and SF are determined as 0.482:0.316: 0.109:0.093 when the powder materials in FA-HPFRC are stacked to the most compact state. The wet packing compactness decreases with a higher W/C ratio while it increases first and then decreases with the increase of SP content. Considering the influences on mechanical properties, the W/C and SP content shall be 19% and 1% of the cementitious material separately. The introduction of steel fibers in FA-HPC reduces the concrete's flowability, destroys its dense packing system and lowers its wet packing compactness. However, the characteristics such as high toughness, and large elastic modulus of steel fibers endow FA-HPFRC with excellent mechanical properties, chloride resistance and shrinkage resistance. Especially steel fibers with 12 mm length perform well in improving the comprehensive performance of FA-HPFRC and increasing the cracking resistance 15.03% higher than that of 6 mm steel fibers. This research further improves FA-HPC's mechanical properties and durability, especially the shrinkage cracking resistance, and provides technical and theoretical support for the application of FA-HPFRC.