12This paper investigates the bond performance of recycled coarse aggregate (RCA) concrete with un-13 corroded/corroded reinforcing steel bars, with the main parameters being RCA content, corrosion level, 14 bar diameter and embedment length. For this purpose, 60 pull-out specimens containing different 15 percentages of RCA (i.e. 0%, 25%, 50% and 100%) and steel bars of two diameters (12 and 20 mm)
16and different embedment lengths were tested. In order to establish various levels of corrosion, 17 specimens were exposed to an electrochemical corrosion for 2, 5, 10 and 15 days. The bond strength 18 between RAC concrete and un-corroded/corroded steel are compared to current codes and equations 19 proposed by other researchers.
20Experimental results showed that larger corrosion rate of steel bars was observed with the increase of 21 the replacement level of RCA due to its high porosity and water absorption. The use of RCA had a slight 22 influence on bond strength for un-corroded specimens compared to that obtained from conventional 23 concrete. Furthermore, the bond strength of RCA concrete was strongly affected by corrosion products; 24 bond strength slightly enhanced for up to 2% corrosion rate, and then significantly decreased as the 25 corrosion time further increased, similar to that of conventional concrete. However, the rate of bond 26 degradation between RCA concrete and corroded steel bars was much faster than that observed in 27 corroded conventional concrete.
29
Introduction
30With the increase of concrete utilization, there is a rapid growth in the consumption of natural 31 aggregates that is the largest concrete component. It is estimated that the global consumption of natural 32 aggregates (NCA) approximately 48.3 billion tons every year [1]. Simultaneously, the increasing amount 33 of construction wastes has created a significant concern from the environmental aspect. It has been 34 reported that about 850 million tonnes of construction and demolition wastes (CDW) are generated in the EU countries every year, which are about 31% of total waste generation, causing serious 1 environmental issues accompanied by a shortage in landfills [2]. The use of recycled aggregate (RCA) 2 produced from CDW seems not only a promising solution for these serious issues, but can also assist 3 in reducing aggregate cost [3]. However, the quality of concrete containing RCA from CDW might be 4 inferior to those made with conventional aggregate [4, 5] due to the presence of old adhered mortar to 5 original concrete, leading to a porous, a higher absorption and cracks on the surface of RCA [6]. This 6 higher absorption capacity may cause some difficulties to control the fresh properties of concrete, and 7 consequently affects concrete durability and mechanical properties [3, 7]. However, results obtained 8 from some studies indicated that RCA can be partially used up to 30% as an alternative to natural 9 aggregate in concrete without affecting its properties [8].
10Bond between steel reinforcement and surrounding concrete...