Concrete and Masonry Research Group, Sustainable Technology Research Centre, Faculty of Engineering, University of Kingston, UK

This paper reports on a program of testing work to investigate the properties of thin layer masonry formed using solid dense concrete blocks. The type of mortar used was ARDEX X7G PLUS POWDER which was made broadly in accordance with the manufacturers instructions i.e. 1¾:1 (mortar: water) by volume. This mortar has a very high yield therefore significantly less powder is required per m³ compared to traditional adhesives.
The variables investigated include: the effect of ageing on flexural strength; the impact of initial unit moisture content on flexural strength; the effect of different forms of constructing thin joint masonry on tensile flexural strength and how the consistency of the mortar affects tensile strength. With respect to this latter point, the mortar consistency was altered by, increasing or decreasing the water content. In addition the wet and hardened properties of the mortar were monitored.
Test results show that significant gains to the tensile flexural strength of masonry can be achieved when thin layer mortar technology in conjunction with solid dense concrete blocks is employed. Preliminary findings did not indicate that dampening units prior to construction improves bond strength, but did indicate constructing thin joint block work by applying mortar to one surface of the block using a scoop and to the other face a second very thin layer with a trowel improves bond and using less water in the mix than is recommended by the manufacturer also improves bond although when the mix becomes very dry, constructing specimens becomes difficult. Whilst applying mortar to both faces is not practical it is a technique used to achieve the maximum possible bond. This enables other factors to be examined and altered to optimise bond strength.