6. Conclusions
This paper describes the experimental measurement of tensile Young’s modulus of concrete at early age using a direct tension setup. Moreover, a predictive composite model was developed to estimate the age-dependent tensile modulus of concrete using the volume fractions and properties of the constituents. The main conclusions are summarized as follows.(1)The tensile stress-strain response of concrete was observed to be very linear even at early ages (e.g., 1 day old). The residual strains after repeated loading of specimens up to strains of 6 0 × 1 0− 6were negligible. The tensile Young’s modulus obtained from the stress-strain response develops according to the water-cement ratio and the age of concrete.(2)The tensile modulus of concrete is approximately 1.0–1.3-times larger than its compressive modulus within the material’s first week of age. As such, estimation of the tensile modulus based on empirical correlations with the compressive strength of concrete can be inaccurate.(3)The age-dependent tensile moduli of concrete could be predicted appropriately by the proposed composite model as long as the volume fractions of coarse aggregates, mortar, and air, and the modulus of aggregates are known. In comparison with the experimental results, the model predictions showed accuracy better than ± 1 5 %.