ABSTRACT
The aim of the present work is to investigate the bond strength and cracking properties of recycled aggregate concretes (RAC) with steel reinforcement. For this purpose, six recycled concrete aggregate mixtures and two reference conventional concrete mixtures (NAC) with C25/30 and C35/45 strength classes and S4 class of workability were chosen. Specimens were fabricated with different incorporation ratios of fine and coarse recycled aggregates or only coarse recycled aggregates. A total of 96 pull-out specimens were prepared using 10 mm and 12 mm diameter deformed steel bars concentrically embedded in concrete cylinders with two embedment lengths of five and ten times the rebar diameter. To study the cracking behavior, four 200x300x3000 mm reinforced concrete beams were prepared with two ribbed bars of 12 mm in diameter. The mechanical properties of the studied concretes were characterized in terms of compressive strength, splitting tensile strength, and Young’s modulus. Concerning reinforced elements, two types of tests were performed: direct tension for pull-out tests and 4-point bending for beams. Test results for pull-out specimens showed that for the same strength class the bond strength and related failure mechanisms remain the same and the obtained values are, at least, five times higher than the predicted values by Eurocode2 when safety factors are considered. For flexural members, RAC showed more cracks (in number) and smaller spacing than NAC. Flexural tests showed, however, that crack openings remain in the same order of magnitude whatever the class of compressive strength (C25/30 or C35/40). These results show only slight differences between RAC and NAC which may 314be due to the difference in tensile strength and allow concluding that the Eurocode2 (EC2) predictions for the control of cracking remain valid for the studied RAC as well as the bond characteristics, without questioning significantly the security level that it provides.
