ABSTRACT
The results from an experimental work on the shear behavior of concrete beams with natural aggregates (NA) or 100% recycled aggregates (RA) are presented. Full scale 200x250x1900 mm reinforced concrete beams without stirrups were manufactured from two mixtures with C35/45 target class of compressive strength and S4 class of workability. The beams were tested under 4 points bending for a shear span-to-depth ratio (a/d) equal to 1.5 or 3.0. The mechanical properties of the two mixtures were characterized in terms of compressive strength, splitting tensile strength and modulus of elasticity. The experimental results show that, for the same class of compressive strength, the shear failure mechanisms in recycled aggregates concretes (RAC) are the same compared to the natural aggregate concretes (NAC) while the shear strength is lower. The decrease in the shear strength is directly related to the decrease in the splitting tensile strength of the RAC compared to the NAC, when the failure is brittle. When it is not brittle, this decrease is significantly higher than that of the tensile strength. In terms of load–deflection response, RAC beams exhibited higher defection compared to the NAC beams. Fracture surfaces of beams with a/d = 3 were observed by using 368an optical microscope for both NAC and RAC. It was found that the failure surface of NAC beams occurs at the interface between the aggregates and the mortar, whereas it occurs by the rupture of recycled aggregates with a denser cracking network in the case of RAC beams. The experimental shear strengths were compared with the shear provisions of EN 1992-1-1which may need adaptation to be applied to RAC. The final conclusions are supported by the results of other published tests results.
