A simple technique for recording load-strain curves for concrete beams loaded in flexure

A method is described for automatically recording load versus strain using a commercial X-Y plotter. Typical curves are given showing the results obtained with pavement-quality concrete and with lean concrete. The modulus of elasticity of the lean concrete was derived from the tangent to the load-strain curve at the origin and was found to be less than that obtained by resonance tests. A reasonable correlation was found between the elastic modulus and the strains at which micro-cracking was assumed to begin.