Mechanical and durability properties of concrete based on recycled coarse and fine aggregates produced from demolished concrete

International audienceFaced with aggressive environments, the durability of recycled aggregate concretes constitutes one of the most unknown aspects. The employment opportunities of recycled concrete aggregates will inevitably remain cautious due to the absence of well-established performance criteria. This paper is to investigate the influence of different granular compositions (recycled coarse and fine aggregate) on the mechanical characteristics and durability of concrete. Five series of concrete mixes, manufactured with various granular combinations (natural/recycled), were studied The formulation of the reference concrete was based on a constant quantity of 400 kg/m3of cement and a constant workability of fresh concrete securing S2 class of flowability and C25/30 concrete class, according to European standards.The experimental program consisted of comparing the long-term mechanical strength of concrete conserved in different types of water baths: fresh tap water sourced directly from the supply network, deionized water, and salt water. Also, the durability indicators were observed, such as capillary water absorption, porosity accessible to water, helium gas permeability, and an ammonium nitrate leaching test.The obtained results have highlighted the superiority of concrete composed of natural aggregate over concrete incorporating recycled aggregate for mechanical behaviour, case-observed with three types of water used as a conservation bath. The replacement of natural aggregate by recycled aggregate does not provide any substantial improvement in terms of durability. The use of recycled sand in concrete increases its porosity and vulnerability to an aggressive environment