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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.
Slick Brick Properties
Bond Strength
Bond strength is a good indication of the overall robustness of a masonry wall. Inadequate bond strengths result in mortar joints acting as a plane of weakness where cracking can occur. Table 2 provides the flexural tensile strength of Slick Bricks determined using the bond wrench test carried out at CSIRO, Division of Building, Construction and Engineering, on sets each of a minimum of six samples. The values in Table 1, although only a selection of the results, demonstrate that the target strength of 0.34 MPa (clause 11.7.3 AS3700- 1998) is well exceeded.
Table 1. Average Flexural Tensile Strengths.
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1
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1.56
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0.26
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0.16
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2
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1.21
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0.15
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0.12
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3
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1.42
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0.17
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0.12
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4
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1.23
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0.46
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0.38
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5
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1.57
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0.30
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0.19
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6
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1.35
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0.11
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0.08
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Bond is influenced by many factors including the suction of the masonry unit, the water retention of the mortar, the ingredients of the mortar and any additives used. The thin-bed mortar formulated to be utilised with Slick Bricks removes the on site variability of the quality of the mortar. The mortar ingredients are pre-defined, require no additives and provide sufficient water retention to allow for hydration to occur.
Masonry Strength
Mortar is relatively weak compared to clay bricks, so that the removal of the mortar increases the masonry strength as shown in the results achieved with Slick Bricks in Table 2. The selection of results from tests carried out at the University of Newcastle shown in Table 3 indicate that the Slick Bricks have load-bearing capabilities far in excess of those for conventional masonry.
Table 2. Compressive Strength of Masonry Prisms.
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299 x 90 x 128
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32.0
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2.4
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0.15
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24.2
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299 x 90 x 171
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29.8
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3.4
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0.15
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21.9
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219 x 110 x 128
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31.6
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2.0
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0.15
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24.7
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219 x 110 x 171
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30.6
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3.4
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0.15
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21.2
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299 x 150 x 128
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21.9
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1.9
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0.15
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16.4
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Fire Resistance Levels
Fire resistance tests were undertaken at BRANZ, The Building Research Association of New Zealand, to AS 1530.4 – 1997 on three thicknesses of Slick Bricks with a 10mm render on one face. The results are given in Table 3.
Table 3. Fire resistance loading of Slick Brick walls.
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90
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240
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240
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60
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30
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110
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240
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240
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90
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45
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150
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240
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240
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120
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50
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Figure 1. Structural adequacy chart for 110mm single leaf wall.
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Accessories
Special Ties for Window and Door Frames
The 1mm mortar beds prohibit the use of conventional masonry components and required a range of special ties and connectors to be developed, manufactured and tested. A range of stainless steel cavity and veneer ties, galvanised ties for concrete frames, windows, sliding doors and metal door frames are available.
Precast Concrete Lintels
A range of pre-cast reinforced concrete lintels to match course heights of Slick Bricks equivalent to single, double and triple Slick Brick heights is also available. The minimum bearing length is 100mm each end for lintel spans less than 1200mm and 150mm for longer spans.
Certification
BRANZ (Building Research Association of New Zealand) has independently assessed the Slick Brick Wall System as meeting the requirements of the Building Code of Australia (BCA 96). BRANZ Appraisal Certificate No. 99/014 covers the system.
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
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