Water transport mechanisms in concretes bearing mixed recycled aggregates

Abstract

Aggressive agents present in the environment that penetrate concrete through its pore structure induce deterioration, compromising the service life of concrete members. Determining the viability of using recycled materials in structural concrete calls for a prior understanding of their effect on water transport, the primary vehicle for external agent ingress. This article describes durability indicators such as electrical resistivity, water permeability (pressure testing), total water absorption, effective porosity and sorptivity that directly or indirectly measure water penetration and consequently performance across the service life of concrete bearing 20% to 100% mixed recycled aggregate (MRA). The 28 d concretes studied here with up to 75% MRA exhibited <7% weight gain due to water absorption, <15 vol% porosity and <30 mm maximum depth of water penetration under pressure, all indicative of high quality concrete. In 90 d materials, the values of the aforementioned parameters were 40% lower. Even in concrete with up to 100% MRA (with 28 d readings of 50 Ω m to 100 Ω m), electrical resistivity remained unaffected, The present findings reveal that high quality high durability structural concrete can be viably manufactured with up to 75% MRA.