Mechanical properties evaluation of sustainable engineered cementitious composites containing recycled fine powders

Abstract

Recycled fine powder (RFP) can be used as supplementary cementitious material or fine aggregate in concrete to reduce environmental pollution. This work investigated the mechanical properties of sustainable engineering cementitious (RFP-ECCs) with concrete and brick mixed powder (RMP) and recycled glass powder (RGP). The fresh flowability, hydrate heat, mechanical properties and the microstructure of RFP-ECC were investigated. It was found that the introduction of RGP improved the flowability of the fresh paste without PE fibre, while tiny effect on that of the fresh paste with PE fibre. A higher RGP substitution ratio resulted in a decrease in the hydration rate and the accumulated heat release of RFP-ECC. However, hydration rate and accumulated heat release of binders are not affected by the particle size of RGP. The compressive strength and flexural strength decreased with the increase of RGP substitution ratio. All specimens presented excellent deformation ability and multi-cracking behaviour under flexural loading. The mid-span deflection at peak load of RFP-ECC increased with RGP% but decreased with increasing RGP particle size (0–300 μm). SEM results show that the use of RGP will lead to loosen microstructures of RFP-ECC samples and deteriorate the bonding properties between the fibre and the matrix, resulting in an increased probability of fibre pull-out. The flexural toughness of RFP-ECC during the deformation-hardening stage and damaging stage were evaluated by introducing equivalent flexural toughness ratio and residual flexural toughness ratio. Finally, the cost assessments and environmental impact facts of RFP-ECC indicate that the utilization of RMP and RGP in ECC mixtures is sustainable and economical.