Stress-strain behavior of cementitious materials with different sizes.

Jikai Zhou,Xudong Chen,Pingping Qian

doi:10.1155/2014/919154

Abstract

The size dependence of flexural properties of cement mortar and concrete beams is investigated. Bazant's size effect law and modified size effect law by Kim and Eo give a very good fit to the flexural strength of both cement mortar and concrete. As observed in the test results, a strong size effect in flexural strength is found in cement mortar than in concrete. A modification has been suggested to Li's equation for describing the stress-strain curve of cement mortar and concrete by incorporating two different correction factors, the factors contained in the modified equation being established empirically as a function of specimen size. A comparison of the predictions of this equation with test data generated in this study shows good agreement.

Highlights

It is widely believed that the true fracture properties of concrete structures can be unequivocally determined only by means of uniaxial tensile stress [1]
The flexural strength of cement mortar and concrete measured from different sizes of beams are shown in Figures 5 and 6
A strong size effect in flexural strength is found in cement mortar than in concrete

Summary

Introduction

It is widely believed that the true fracture properties of concrete structures can be unequivocally determined only by means of uniaxial tensile stress [1]. Experiments on notched specimens of homothetic sizes made of concrete, rocks, and ceramics by Bazant et al [17, 18] and Man and Van Mier [19] demonstrate that the nominal tensile and shear strengths depend on the size of the specimens All these experiments show two key points: (1) the flexural strength of cement-based materials as predicted by elasticity or limit analysis is a function of the volume of the specimen and of the stress field in the structure. Part of this size effect can be attributed to the existence of initial defects in the material before any stress is applied to it, and (2) the fracture toughness measure from notched specimens varies with the size of the structure. This paper brings together the results of past studies and the results of new experiments and interpretations

Experimental Program

Test Results and Discussion

Modeling Stress-Strain Relationship Based on Continuous Damage Mechanics

Conclusions