Influence of Early Age on the Wave Velocity and Dynamic Compressive Strength of Concrete Based on Split Hopkinson Pressure Bar Tests

Shiming Wang,Longjun Dong,Jian Zhou

doi:10.1155/2018/8206287

Abstract

The effect of early age on the mechanical properties of concrete was investigated in this study. A uniaxial compression test was performed on split Hopkinson pressure bar (SHPB) equipment with a large diameter of 75 mm. The experimental results indicated that before 7 days, concrete showed viscoelasticity and had good deformation ability and low sensitivity to incident energy. In addition, the concrete exhibited the characteristics of quasi-brittle materials, and the sensitivity of the incident energy improved with age. The threshold value of the incident energy at early ages had an insignificant effect on the stable age concrete. The threshold value was 50% of the corresponding age’s critical incident energy, while it was 75% after 7 days.

Highlights

As one of the most commonly used building materials, the mechanical properties of concrete must meet design requirements after 28 days of curing, which is in contradiction with modern construction methods that are dedicated to shortening the construction period
Kim and Han [6, 7] as well as Kanstad and Hammer studied the correlation of compressive strength and the elastic modulus with the change of curing temperatures, ages, and cement types and proposed a model that could predict the splitting tensile strength and elastic modulus on the basis of experiments without knowing the compressive strength [8]
The mechanical properties including compressive strength, splitting strength, and modulus of elasticity of early-age concrete cured under both temperaturematching curing and isothermal 20∘C curing were investigated by Wang and Yan[16]; they created a model that can predict the compressive strength, splitting strength, and elasticity modulus by finite element method measurements or calculations

Summary

Introduction

As one of the most commonly used building materials, the mechanical properties of concrete must meet design requirements after 28 days of curing, which is in contradiction with modern construction methods that are dedicated to shortening the construction period. Bertagnoli and Gino [13] proved a simplified approach for determining the time evolution of stresses developing at the early age of curing concrete slabs of composite beams and the different types of cement. This approached featured a variable time evolution of the hydration process, and different external temperatures were taken into account. Jin and Li [17] obtained the complete strain-stress cure for young concrete and studied the effect of static load level, curing conditions, and loading age at early ages on the mechanical properties of stable concrete. The results were compared and analyzed systematically to illustrate the effect of the different impact levels and ages of 1, 3, 7, and 14 days on the mechanical properties of concrete (28 days)

Experimental Program

Experimental Results and Discussion

28-2 Logarithm Fitting 28-8 Logarithm Fitting

Conclusions