Study on Mechanical Properties and Damage Evolution of High-Porosity Concrete under Cyclic Loading and Unloading

Dong Zhang,Lei Sun,Xia Wang,Si-yu Gong,Yang Dong,Ran-fang Zuo,Ai-hong Lu,Yu Xia,Ma Jianjun

doi:10.1155/2021/6594889

Abstract

Understanding the mechanical properties and energy response of high-porosity concrete under the cyclic loading and unloading is the foundation of road construction in sponge city. In this study, the concrete with the porosity of 15% was taken as the research object, and the cyclic loading and unloading tests on the high-porosity concrete were performed under the stress amplitude of 25 MPa, 30 MPa, and 35 MPa in the elastic stage. The effects of stress amplitude and cycle number on the mechanical characteristics and damage evolution law of concrete were obtained. The experimental results show the following. (1) With the increase of cycle number, the loading and unloading elastic modulus of concrete under different stress amplitudes first increases and then decreases; the greater the stress amplitude, the faster the growth and deceleration of the loading and unloading elastic modulus. (2) With the increase of the cycle number, the peak strain and residual plastic deformation increase. (3) The greater the stress amplitude, the higher the damage of concrete; with the increasing number of cyclic loading and unloading, the damage of concrete is enhanced gradually. When the damage variable value is 1, the relationship between the cycle number and the initial stress amplitude satisfies a negative exponential function.

Highlights

Sponge city construction is an important opportunity and challenge in China’s new urbanization construction, and it is an important way to solve the water shortage, water environment deterioration, and flood disasters in the current new urbanization construction [1]
The greater the stress amplitude, the less the cycle number required for the maximum of loading and unloading elastic modulus
Due to the limitation of test conditions and the long cycle time of cyclic loading and unloading, the relationship between the cycle number and damage variables can be fitted through effective test data, and the cycle number can be obtained when the damage variable value of the sample is 1 under different stress amplitudes

Summary

Introduction

Sponge city construction is an important opportunity and challenge in China’s new urbanization construction, and it is an important way to solve the water shortage, water environment deterioration, and flood disasters in the current new urbanization construction [1]. Rough the MTS 815 program-controlled servo test system, Xing et al [8] conducted a uniaxial compression test on concrete cylindrical specimens under cyclic loads and studied the effects of the initial load, cyclic frequency, and the increased amplitude of cyclic stress on the mechanical behavior of concrete specimens. Under the same cycle frequency and the same increased amplitude of cyclic stress, the strength of concrete tends to decrease with the increase of initial load [9]. There are few studies on the mechanical properties of highporosity concrete under cyclic load [29] To this end, the experimental method was used to analyze the effects of cyclic number, cyclic load amplitude, and other parameters on the mechanical properties and energy dissipation of high-porosity concrete in this study

Test Equipment and Test Scheme

MPa 10

Damage Evolution Law of HighPorosity Concrete

25 MPa 30 MPa 35 MPa

Findings

Conclusions