Slick Bricks - The Development and Laying of Slick Bricks

Over recent decades everything to do with construction has been improved to enable the builder to increase the speed of construction, that is, everything except bricklaying.  Conventional masonry construction is labour intensive and although construction of brick walls on site has many advantages, at the same time this can prove to be the weakness of the masonry building system.  Mortar constitutes only a relatively small proportion of the masonry, but the quality and workmanship can seriously affect the overall performance of the masonry.

The New Slick Brick System

A new system, namely Slick Bricks, has been developed using precision, diamond ground clay bricks with an interlocking key that eliminates the vertical joint and utilises thin-bed jointing technology.  This article discusses the development and evaluation of the Slick Brick System, which makes bricklaying easier, quicker and stronger, resulting in productivity gains, improved on-site quality and cost savings.

Introduction

Mortar Joints

The basic technology of laying clay bricks in mortar has been in use for thousands of years.  Conventional masonry construction is labour intensive as the number of mortar joints directly influences the speed of construction and imposes restrictions on the height of masonry laid per day.  Mortar joints, traditionally 10mm in size, serve a number of purposes including binding the bricks together and taking up size variations in masonry units. 

Advantages and Disadvantages of Mortar Joints

Masonry is a composite material consisting of masonry units and mortar joints. This not only accounts for its inherent appeal, but can also be its inherent weakness.  The achievement of an effective bond between the brick and mortar is the most important aspect of masonry construction, and this bond is reliant on the workmanship and mortar ingredients.  Mortar is also relatively weak compared to bricks so the removal of the traditional 10mm joint, not only increases the speed of construction, it also drastically improves the strength of the masonry. 

Development of Slick Bricks

Machining and Tight Tolerances

To use thin-bed mortar technology it was necessary to develop a system to control the size of the fired clay bricks.  A technique of precision diamond grinding the bedding surfaces of clay bricks after firing, was developed over a number of years, to provide masonry units with tolerances, sufficiently tight, to facilitate the use of a 1mm mortar bed. Controlled manufacturing methods, batching and meticulous testing afford clay masonry units that, after grinding, have a tolerance of ± 0.2 mm on the bedding faces.

Interlocking Tongue and Groove Ends

The development of an extruded cored clay brick with interlocking, tongue and groove ends provides additional gains in speed by eliminating the need to fill the perpendicular joints, which is quite acceptable for a wall which is to be rendered.  The shallow tongue and groove headers provide horizontal alignment.

Varying Brick Heights to Speed Up Construction Times

With these specifications, a range of products has evolved, based on 90mm, 110mm and 150mm wide clay units, available in heights, up to three times that of a conventional brick height.  The heights are equivalent to conventional brick coursing heights to permit the use of standard masonry alongside Slick Bricks.  Dimensional details, unit weights and the number of bricks per square metre are given in Table 1.

Table 1. Slick Brick product specifications.

Product Range

Dimensions
L x W x H (mm)

Weight
(kg)

No. of bricks/m2

Slick 90 single

299 x 90 x 85

3.2

38.8

Slick 90 one & a half

299 x 90 x 128

4.8

25.8

Slick 90 double

299 x 90 x 171

6.5

19.4

Slick 90 triple

299 x 90 x 257

9.7

12.9

Slick 110 single

219 x 110 x 85

2.9

52.9

Slick 110 one & a half

219 x 110 x 128

4.3

35.2

Slick 110 double

219 x 110 x 171

5.8

26.4

Slick 110 triple

219 x 110 x 257

8.7

17.8

Slick 150 single

299 x 150 x 85

5.3

38.8

Slick 150 one & a half

299 x 150 x 128

8.0

25.8

Slick 150 double

299 x 150 x 171

10.7

19.4

A New Brick Laying Technique

Dipping as Opposed to Trowelling

To further increase the speed of construction, it was necessary to discard the traditional method of laying mortar beds using a trowel and instead apply the mortar to the base of the bricks by a simple method of dipping.  The mortar is applied by dipping the bottom bearing face of the brick in a tray of adhesive.

Laying The First Course

The base course needs to be laid in conventional mortar to ensure a plumb, level surface for the subsequent laying of Slick Bricks.  The first course must be level and plumb as construction tolerances of subsequent courses are minimal compared with conventional mortar, due to the 1mm bed joint.

Thin-Bed Mortar

Benefits of Thin-Bed Mortar

Not only does the number of mortar joints influence the speed of construction, the large number of joints in standard brickwork imposes restrictions on the height of masonry constructed per day.  Slick Bricks with 1mm horizontal bed joints permit masonry to be laid with no daily height restrictions.

What is Thin-Bed Mortar?

The thin bed mortar is a polymer modified, cement-based system that has been specifically formulated and developed to have the necessary handling properties while providing sufficient strength in the joints to satisfy Australian Standards.

How Does Thin-Bed Mortar Compare to Conventional Mortar?

The move to a polymer modified thin-bed mortar has increased the bond strength and overall masonry strength whilst at the same time reducing the volume of materials handling and storage on site.  To lay 1000 standard bricks, 1 tonne of sand and 160 kg of cement are required.  In contrast, to lay 1000 Slick Bricks, only 150kg of mixed thin-bed mortar is needed, significantly reducing the quantity of material needed on site.

Summary

Austral Bricks have developed a wall system using precision diamond ground clay bricks with tolerances, sufficiently tight, to enable the bricks to be laid using thin bed mortar, and with a unique interlocking key to eliminate the need for filling perpendicular joints.  Slick Bricks are laid using a polymer-modified cement based mortar applied to the brick by a simple method of dipping.  The end result is a significant boost to the speed of construction making it possible to increase productivity up to three times the speed of laying conventional bricks while at the same time improving quality control over the masonry. 

The Slick Brick System, independently certified by BRANZ, includes bricks, thin-bed mortar, ties, connectors and lintels.  The result is a complete building system providing everything the builder needs to construct clay brick walls in less time than ever before.  By simplifying the laying of bricks, Slick Bricks make bricklaying easier, quicker and stronger, providing significant cost savings.

Note: References are available by referring to the original text.

Primary author: C. Inglis

Source: Abstracted from the Journal of the Australasian Ceramic Society, Vol. 39, No. 1. pp. 60-65, 2003.

For more information on this source please visit The Australasian Ceramic Society.

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