A study on the effect of mortar joint strength and placement on masonry blockwork wall capacity

Abstract

In the past decades there has been a boom in construction on the Maltese Islands. This has led to multiple cases of poor workmanship in local projects. Masonry walls are key components in construction; however, an aspect that is often overlooked locally is the mortar joint, relying more on the brick for structural strength. In both the local MSA annex of Eurocode 6 and international versions of Eurocode 6 it is specified that both the blocks and the mortar used have to be specified to accommodate certain standards. While masonry units are covered under standards such as EN 771-5:2011 and more specifically EN 771-3:2011 for aggregate concrete masonry units, this dissertation focuses more on the mortar. The mortar to be used with masonry similarly has to conform to EN 998-2, which outlines relevant tests such as EN 1015-11 for compressive strength, among other standards such as EN 1052-2 and EN 1015-3 which address mortar properties. However, the effects of mortar placement and workmanship remain under-investigated in the local context, with only brief mentions in Eurocode 6. Mortar placement influences not only the compressive strength of a wall but also its overall performance , including water penetration, shear resistance, flexural strength and insulative characteristics. Hence the identification of the effects of laying of mortar in masonry walls within construction is of interest. The variation of mortars (general-purpose, lime based, cement based etc) have been well standardised in EN 1015:1999, however, different mortar types impact the strength and composite behaviour of the masonry wall differently, making this the key parameter of the investigation. Locally speaking for Hollow Concrete Blocks (HCB) typically, a 1:3: cement to sand ratio is used according to the local licensed mason’s handbook. That being said the national annex specifies mortar based on its strength. For concrete units, a general-purpose mortar of strength M2, M6, M10 or M20 is to be used.