Reinforced Concrete Beams Capacity with Various Concrete Compressive Strengths

Abstract

The use of high-strength concrete (HSC) started about four decades ago in world. Using (HSC) supports the applications in civil engineering such as reduce the size of buildings columns, increase the girders length, increase the buildings stores as well as the economics benefits. The paper aims to investigate the effect of using various compressive strength of concrete mixes on the behavior and load capacity of reinforced concrete beams in terms of cracking, yield, failure loads, deflection and ductility. The experimental program included the cast of six reinforced concrete beams with 1.75 m length and cross section of 200 ϗ 300 mm. The beams specimens were tested under two points loads. Several concrete mixes were tried to obtain the concrete compressive strengths 30.9, 40.3, 51.2, 60.1, 71.6 and 89 MPa that used for every specimen beam. The experimental results showed that the increase of concrete compressive strength developed the load capacity strength and ductility. By increasing the compressive strength ratio with (30%, 67%, 95%, 132%, and 188%) caused increase in cracking load by 25%, 66%, 94%, 116% and 152% respectively, and increased the yield and failure loads by (18%, 31%, 41%, 51%, and 69%), (14%, 32%, 47%, 59% and 77%) respectively. As well as the deflection in yield was decreased by (13%, 22%, 33%, 26% and 13%), while it was increased by 10%, 16%, 23%, 26%, and 39% respectively in failure stage as a result of increased of load failure. Adding to that, ductility is increased by 27%, 50%, 84%, 70% and 61%, respectively with the of increasing of compressive concrete strength in ratios mentioned above.