Use of Recycled Asphaltic Concrete Coarse Aggregate in High-Early-Strength Concrete Incorporating Fine Fly Ash and Microsilica

Abstract

This study investigates the utilization of recycled asphalt concrete coarse aggregate in the production of high early strength concrete incorporating fine fly ash and micro silica. The mixtures consisted of ordinary Portland cement, superplasticizer, river sand, natural coarse aggregate, and recycled asphalt concrete coarse aggregate with a particle size range of 4.75–19.0 mm. The recycled aggregate was used to replace natural coarse aggregate at levels of 0, 20, and 40 % by weight. The performance of the concrete was further enhanced using supplementary cementitious materials, namely micro silica and fine fly ash, each used to replace 15 % of cement by weight. All specimens were water-cured at ambient temperature. Compressive strength was evaluated at 24 hours, 7 days, and 28 days, while water absorption, porosity, flexural strength, and modulus of elasticity were determined at 28 days. The results indicate that the mixture containing 15% microsilica and 40% recycled asphalt concrete aggregate achieved a compressive strength of 365 ksc at 1 day and 728 ksc  at 28 days, with water absorption of 0.48%, porosity of 1.19%, flexural strength of 87.1 ksc , and a modulus of elasticity of 29.1 GPa. This mixture is suitable for early-strength high-performance concrete in accordance with ACI 363.2R-11. And the mixture incorporating 15% fine fly ash and 40% recycled aggregate exhibited a compressive strength of 305 ksc at 1 day and 504 ksc at 28 days, with water absorption of 1.02%, porosity of 2.50%, flexural strength of 55.4 ksc, and a modulus of elasticity of 28.5 GPa. This mixture is appropriate for precast wall and slab applications in accordance with TIS 848-2546. Furthermore, the combined use of recycled asphalt concrete aggregate and fly ash enhances the utilization of waste materials, reduces cement consumption, and promotes sustainability in the construction industry.