Abstract
Abstract The main goal of this research is to determine the mechanical properties of bedding mortar by assessing the mortar damage onset, the stiffness plasticity degradation and the apparent Poisson´s ratio under compression. Two mortar types, 1:0.5:4 and 1:1:6 (cement:lime:sand ratio), were used and tested at 28 days; specimens had diameter-to-height (d/h) ratios of 0.3 and 1.0. These diameter-to-height (d/h) ratios were chosen to evaluate the effect of confinement caused by the friction between the steel plates of the testing machine and the sample. Numerical models were developed, and their response compared with the experimental results. From the experimental results, it was concluded that there are meaningful differences in their responses with weak and strong mortar types and different d/h ratios. The d/h ratio influences the relationship between the stress and strength and the apparent Poisson´s ratio of the specimen, which is defined herein as the ratio of the horizontal to vertical strain, regardless of cracking of the specimen. The mortar damage onset and stiffness plasticity degradation for both mortar types and d/h ratio are different and depend on the stress/strength ratio level. All samples with a d/h ratio of 0.3 show a constant decrease in the volumetric strain until failure but with negligible expansion on the horizontal deformation. In contrast, samples with a d/h ratio of 1.0 present an increase of stiffness after development of the first crack, which causes the increase of the sample volume. Numerical simulation and experimental results for mortar 1:0.5:4 with a d/h ratio of 0.3 are similar until approximately 10 MPa, after which the numerical results diverge from the experimental results. For the d/h ratio of 1.0, the vertical strain results are also similar, but the horizontal strains results near failure are very different. The model can not represent the nonlinear increase of the horizontal strain near failure probably because the crack propagation and the stiffness plasticity degradation could not be controlled. For mortar 1:1:6, vertical strains from numerical and experimental results are similar, but again the model can not reproduce the nonlinear increase of horizontal strain near failure.
Highlights
Several theoretical and experimental studies have been conducted to describe the behaviour of concrete under a complex state of stresses and most of these studies depicted the nonlinearity of concrete through plasticity models, damage models or a combination thereof [1,2,3,4,5,6]
The relationship between stress-strength ratio and the apparent Poissons ratio is affected by the mortar type and the d/h ratio
The stress-strain behaviour and, the specific volumetric variation, Poisson’s coefficient and derivative of the strain-stress, were dependent on the type of mortar and level of confinement applied, that is, the dynamics of crack formation and propagation was dependent on the type of mortar and confinement. n Damage onset and stiffness plasticity degradation can be visualised using the derivative of the strain-stress curve
Summary
Several theoretical and experimental studies have been conducted to describe the behaviour of concrete under a complex state of stresses and most of these studies depicted the nonlinearity of concrete through plasticity models, damage models or a combination thereof [1,2,3,4,5,6]. A few studies have been conducted on the failure mechanism of masonry under a complex state of stresses and these studies have focused on the testing of the components [726]. The primary goal of this research is to evaluate the mechanical properties of bedding mortar by assessing its damage onset, stiffness plasticity degradation and apparent Poissons ratio under compression for different diameter/height (d/h) ratios, focusing on the material strain behaviour under loading until failure. The results of the pilot testing presented are preliminary and require further validation
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