Study on axial compressive behavior and damage constitutive model of manufactured sand concrete based on fluidity optimization

Due to the adsorption effect of manufactured sand on water reducer, the method of adding water reducer is often used to improve the fluidity of concrete mixture, which may change the strength of manufactured sand concrete. This paper systematically studies the manufactured sand concrete with different strength grades of C30, C40, C50, C60, C70, C80 prepared with basic water reducer dosage (1 time) and optimized water reducer dosage (1.65 times), and designs slump, slump loss, uniaxial compression and pore content tests for manufactured sand concretes with the same strength grade. The results show that optimized dosage of water reducer can signifi-cantly increase the fluidity, peak stress and elastic modulus of manufactured sand concretes with the same strength grade and reduce their slump loss, peak strain and pore content. Combined with Lemaitre damage mechanism, the total damage of manufactured sand concrete is divided into initial damage and load damage. The initial damage is caused by different fluidity of manufactured sand concrete. The greater the fluidity, the less initial damage will be. The influence of initial damage on the concrete stress-strain relationship is analyzed. As the initial damage increases, the total damage will increase, the strength and elastic modulus of the concrete will decrease. This is due to the fluidity changes the pore structure inside the concrete.