Shear performance of reinforced concrete deep beams using different coarse aggregates under the effect of elevated temperatures

Abstract

This paper describes experimental tests of the shear performance of high-strength reinforced concrete deep beams produced with different coarse aggregates, conducted at an ambient temperature of 25 °C and after heating to 600 °C. Three types of coarse aggregates of 10 mm maximum size were considered: limestone-based normal weight aggregate, quartzite-based normal weight aggregate, and steel slag-based heavyweight aggregate. Additionally, 20 mm maximum size aggregate was used for the steel slag concrete only. Eight beam specimens were designed to fail in shear, eliminating the possibility of flexural failure. Four beam specimens were tested at ambient temperature, and the corresponding four specimens were exposed to a temperature of 600 °C for 3 h. The results showed that the shear capacity of the deep beams tested at the ambient temperature was closely correlated with the abrasion resistance of the coarse aggregate. Exposure to an elevated temperature led to variable reduced shear strength, depending upon the type of aggregate. Compared to the beams tested in ambient conditions, the best performance was achieved by the limestone aggregate, followed by steel slag aggregate then quartzite aggregate, recording shear strength losses of 23.1%, 37.9% and 40.5%, respectively. This reduction in shear capacity was due to the reduction in compressive strength by 53–61% for the concrete exposed to 600 °C. The mid-span deflection at peak load was in general reasonably comparable for the beams tested at 25 °C and after exposure to 600 °C. The trend of stiffness loss after elevated temperature exposure for the various types of aggregate was very consistent with shear strength.