BEHAVIOUR CHARACTERISTICS OF FACE SHELL MORTARED BLOCK MASONRY UNDER AXIAL COMPRESSION

Abstract

<p>Although face shell mortared blockwork constitutes the main construction practice in North America, its behaviour characteristics are relatively undefined and has traditionally been assumed to behave in asimilar manner to brick and solid block masonry. Only recently has it been reported that face shell mortared concrete blockwork failed differently and the failure theories developed for these cases may not be applicable to face shell mortared blockwork. It is the main objective of this investigation to provide a better understanding of behaviour of face shell mortared blockwork and to arrive at the reasonably accurate measure of its strength under axial compression.</p> <p>A total of 461 concrete block prisms incorporating a broad base of material properties and sources (29 block plants) were tested in axial compression normal to bed joints. In addition over 1400 auxiliary block compression and tension tests and mortar tests were carried out. The experimental investigation included a comprehensive study of the properties of the constituent materials, re-evaluation of current test methods for measuring the compressive strength of the blockwork, detailed deformation monitoring of the behaviour, parametric study of the variables affecting the strength of face shell mortared blockwork, comparison to other types of concrete masonry construction and quantitative assessment of specified strengths for hollow concrete blockwork.</p> <p>Regardless of the block size or shape,cracking of the webs is the expected failure pattern in face shell mortared blockwork and failure criteria attributing the dilation of mortar as the cause of failure are not applicable in this case. Since much reserve strength is available after initial observation of web cracking, models which predict cracking should not necessarily be expected to predict ultimate strength. Although the block's compressive strength can be related to blockwork compressive strength, a strong relationship existed with the block tensile strength. While web cracking in face shell mortared blockwork initiates in a mechanism independent of mortar, it cannot be concluded that the ultimate strength is independent of the type or strength of mortar. Employing 2-course prisms for measurement of blockwork compressive strength would result in an unrepresentative failure and overestimated strength. Currently employed relationship for determining the modulus of elasticity of concrete block masonry is clearly an overestimation.</p>