FLEXURAL BEHAVIOR OF REINFORCED HIGH-STRENGTH LIGHTWEIGHT CONCRETE BEAMS

The use of lightweight concrete of higher compressive strengths is increasing faster than the development of appropriate design recommendations. This paper reports limited experimental data on the flexural behavior of high-strength lightweight concrete beams. Flexural tests were conducted on six singly reinforced beams. The variables were strength of concrete [5200 psi < f'(c) < 11,000 psi (35.9 < f'(c) < 75.9 MPa)] and the ratio of tensile steel content r as a ratio of the balanced steel content [0.18 < rho/rho-(b) < 0.54). No compression or lateral reinforcement was used in this study. Test results are presented in terms of load-deformation behavior, ductility indexes, and cracking patterns. It is concluded that to achieve a ductility index of 3, rho/rho-(b) should not exceed 0.40 for beams with concrete strengths of 8000 psi (55.2 MPa) or 0.20 for beams with concrete strengths of 11,000 psi (75.9 MPa). The flexural design provisions of the ACI Building Code are found to be adequate to predict the strength of reinforced high-strength lightweight concrete beams.