Linear energy storage and dissipation laws of concrete under uniaxial compression at different ages

Abstract

To investigate the influence of age on energy storage and dissipation laws, uniaxial compression (UC) and single–cyclic loading–unloading uniaxial compression (SCLUC) tests were conducted on C35 concrete specimens with ages of 3 d, 7 d, 15 d, 28 d. The experimental results showed that the input strain energy (ISE), elastic strain energy (ESE), and dissipated strain energy (DSE) increased nonlinearly with the stress level during the pre-peak loading stage. Analyzing the relationship between the three strain energies, both ESE and DSE increase linearly with the increase of ISE in the pre-peak loading stage at different ages, namely, linear energy storage and dissipation laws exist in every ages. Based on the linear energy storage and dissipation laws, a novel method was proposed to calculate the DSE and ESE at the ultimate strength point of the concrete at different ages. In addition, we found that the DSE was greater than the ESE of concrete in the loading stage, because the energy was mainly dissipated in forming cracks, grain dislocation, and producing plastic displacement during compression. The value of compression energy storage coefficient represents the capacity of the concrete to store ESE, whereas energy dissipation coefficient represents the strain energy dissipation capacity of concrete. In the future, based on the linear energy storage and dissipation laws of concrete, the new method for calculating the damage variable may be proposed.