Influence of micromechanical property on the rate-dependent flexural strength of ultra-high performance concrete containing coarse aggregates (UHPC-CA)

Shaohua Li,Qingliang Yu,Ole Mejlhede Jensen,Zhengzhi Wang

doi:10.1016/j.compositesb.2021.109394

Abstract

The flexural strength of ultra-high performance concrete with basalt aggregates (UHPC-CA) strongly depends on the micromechanical property of CA, interfacial transition zone (ITZ) and matrix. However, the influence of micromechanical property on the rate-dependent flexural strength of UHPC-CA has not been well understood. Here, different initial micromechanical property distributions are produced by controlling the hydration development, and its influences on the rate-dependent flexural strength of UHPC-CA are investigated by a multi-scale analysis method. The results show that a more homogeneous micromechanical property of UHPC-CA results in a higher flexural strength, but a lower dynamic increase factor (DIF) of flexural strength. The lower DIF can mainly be attributed to the lower increasing rate of mesoscale fracture of CA. Moreover, based on a meso-mechanical model, it is revealed that higher fracture toughness ratios of ITZ/CA and ITZ/Matrix result in lower critical angles ( β c r ) of fractures of CA and matrix, consequently, higher mechanical contribution from CA and matrix.

Highlights

With superior mechanical performance under dynamic loading, ultra-high performance concrete (UHPC) is considered as a promising new building material for structures, which is vulnerable to extreme load, e.g. earthquake, blasting and impact [1,2,3]
The results show that a more homogeneous micromechanical property of ultra-high performance concrete with basalt aggregates (UHPC-coarse aggregates (CA)) results in a higher flexural strength, but a lower dynamic increase factor (DIF) of flexural strength
Based on a mesomechanical model, it is revealed that higher fracture toughness ratios of interfacial transition zone (ITZ)/CA and ITZ/Matrix result in lower critical angles of fractures of CA and matrix, higher mechanical contribution from CA and matrix

Summary

Introduction

With superior mechanical performance under dynamic loading, ultra-high performance concrete (UHPC) is considered as a promising new building material for structures, which is vulnerable to extreme load, e.g. earthquake, blasting and impact [1,2,3]. Due to the high cement content, UHPC is costly, causes high environmental impact, and most importantly, has the problem of severe autogenous shrinkage [4,5,6]. To address these issues, recently, coarse aggregates (CA) have been successfully introduced into UHPC without sacrificing the me chanical performance [7,8,9]. The excellent flexural strength is one of the basic and important char acteristics of UHPC [11,12,13,14]. The rate-dependent flexural performance of UHPC-CA without fiber has not been well un derstood, especially from micro-mechanics point of view

Objectives

Results

Discussion

Conclusion