Elastic modulus of reinforced concrete from bending test

This study demonstrates an experimental approach for direct measurement of RC elastic modulus. This work considered the transformed moment of inertia as an input variable. The planned laboratory study involves subjecting reinforced concrete beams with varying reinforcement ratios from 0.43% to 1.77% and grades of concrete (M7.5, M10, M15, M20) to bending tests. Two equations for elastic modulus determination were developed based on beam theory. The first crack load and the corresponding deflection were measured from the load-deflection curve. The uncracked transformed moment of inertia (Iun,tr), cracking moment (Mcr), and deflection ( at first crack were computed. By substituting the Mcr, and Iun, tr into the deflection equation based on the test setup, the elastic modulus (E) of RC was determined. Results showed that as the concrete grade increases, so does its modulus of elasticity, and it demonstrated a direct correlation between the increase in concrete grade and its modulus of elasticity. It was also observed that as the percentage of reinforcement increases, the elastic modulus of RC increases due to increased flexural stiffness. The derived equations were able to accurately compute the elastic modulus capturing the composite behavior of concrete and reinforcement.