Prediction of Modulus of Rupture of Concrete

Abstract

Tensile strength of concrete is an important parameter for determining deflection and minimum flexural reinforcement. Many design codes use the modulus of rupture as the cracking strength. Relations giving the modulus of rupture as a function of concrete compressive strength are based on tests on concrete with a compressive strength lower than 40 MPa. This study presents a statistical study on 395 data points from a large number of research programs with concrete compressive strength ranging from 20 MPa to 130 MPa. It further reveals that the data are largely scattered and that minimum, mean, and maximum values for the modulus of rupture should be defined. New relations are proposed by giving the modulus of rupture as a function of the square root of the compressive cylinder strength of concrete and the compressive cylinder strength of concrete raised to the 2/3 power. The use of the new relations in design codes is illustrated.