Properties of sustainable high-strength concrete containing large quantities of industrial wastes, nanosilica and recycled aggregates

This research aims to study the effect of adding nanosilica (NS) on the properties of sustainable high-strength concrete (SHSC). The SHSC was produced using recycled aggregates from concrete debris as a 100% alternative to coarse aggregate, and industrial waste was used as supplementary cementitious materials at 50% and 75% of Ordinary Portland cement (OPC) weight. A total of 25 mixes, including control mix (The first mix was made as the reference by using only cement without replacement materals), binary mixes (OPC and fly ash (FA)), ternary mixes (OPC, FA and ground-granulated blast-furnace slag (GGBS)) and quaternary mixes (OPC, FA, GBFS and silica fume (SF)) were developed. The dosage of NS was 0%, 1%, 3% and 5% by binder ratio. The fresh properties of SHSC were evaluated by slump test, and the mechanical properties were assessed by testing the compressive strength, splitting tensile strength, flexural strength and modulus of elasticity. The transport properties were evaluated by water permeability, water sorptivity and chloride permeability tests. Results showed that compared with the reference mixture, the SHSC containing 75% of the quaternary blends with 3% NS achieved enhanced mechanical properties at 28 and 91 days, indicating that this mixture can achieve the highest sustainability performance. The SHSC mixture containing 3% NS and 50% quaternary mixtures achieved the highest performance of 80.7, 6.46 and 10.09 MPa for compressive strength, split tensile strength and flexural strength, respectively, at 28 days. This SHSC mixture also achieved water permeability; chloride permeability was 2.54 × 10−11 (cm/sec) and 1370 coulombs at 28 days.