This paper presents a study on the stress-strain relationship of cement mortar under triaxial stress state. The influence of confining pressure on peak-stress, peak-strain, volume change, modulus of elasticity, and Poisson’s ratio were studied using experimental results and data from limited studies in the literature. Cement mortar samples having compressive strengths of 38 MPa and 45 MPa were tested under four levels of confining pressures (i.e., 0, 5, 10, and 15 MPa) and a stress-strain model for confined cement mortar was subsequently developed. It has been shown that the model has good agreement with both the experimental results. The results not only show that confinement significantly improves the strength and ductility of the cement mortar samples, but also reveal a linear relationship between the observed lateral and axial strain. In this regard, the mathematical relationship for confined cement mortar was developed as a function of the stress and strain parameters of the unconfined state and a new linear relationship between modulus of elasticity, Poisson’s ratio and lateral stress is proposed.

Introduction

Cement mortar materials are widely used in normal construction, mining and 3D concrete printing applications [1,2]. In order to design and safety assessment of structures, the mechanical properties under complex stress conditions due external loadings are required. For cement mortar made of same materials, the mechanical properties are different when the material mixture ratio is different, and the mechanical properties of the specimens are also different when the loading is different [3]. Hence the accurate prediction of stress-strain behaviour of cement mortar under various stress state is required to be developed for the accurate estimate of the structural performance. Specifically, considering the performance of mortar under triaxial compression and/or tension is useful for masonry structures for the determination of strength, deformation and failure modes. A comprehensive review of past literature on the mechanical behaviour of unconfined and confined cement mortar reveals that limited models are available to describe partially the mechanical behaviour of cement mortar. However, none of these models develop the complete stress-strain behaviour of cement mortar under triaxial stress states.