What’s wrong with brickie’s sand?
- Simple shake test surveys of common “brickie’s sands” show that almost all typically exceed (some by up to three times) the maximum (10%) clay content permitted by Australian Standards (AS4773.2, Section 3.2.3) for use in mortars for bricklaying or blockwork.
- Bricklayers should ask their sand supplier for a “Sieve Analysis” Test Certificate or “Material Quality Report” to confirm the clay content of their “bricklaying sand”.
- Most sand suppliers are either unwilling or unable to supply a Certificate for the sand and therefore bricklayers often have to turn a blind eye to the Australian Standards (AS4773.2 Mortar Mix Tables 3.1 and 3.2).
- The industry is almost completely accustomed and addicted to the use of the “fatty”, non-compliant sands which are “perceived” to make the job of laying bricks easier. Unfortunately, this practice can have a detrimental effect on the quality and longevity of the finished building and with serious implications for the Bricklayer, Builder, Architect or others involved in the building process.
What’s bad about high clay content in brickie’s sand?
- High clay content can result in brickwork that looks messy and can be difficult to clean. Acid washing only cleans off the cement residue, it then takes a lot of hard scrubbing and effort to clean off the clay residue from new brickwork. High pressure water washing can also further the mortar and brick face .
- High clay content also affects the durability of the brickwork. As the clay in the finished mortar joints reacts over time with rain and moisture, it can expand, leach out and dissolve, requiring expensive re-pointing to rectify in the future.
- High clay content can reduce mortar bond strength and result in weaker brickwork, making it more prone to cracking, water penetration and failure.
- If the clay content in the sand exceeds the Australian Standards requirement for mortar mixes, then it also follows that the brickwork and building does not comply. As a consequence the Client, Certifier or Superintendent may reject the work or to withhold payment pending rectification or rebuilding.
So, how do you mix mortar according to Australian Standards?
- Ensure that the Mortar Classification for the site and building, Mortar Mix Proportions and Mortar Mix Ingredients are all accordance with Australian Standards e.g. AS4773.2 Table 3.1 and Table 3.2.
- Use “washed sand” with approved “water thickener” for workability.
- Assume that “bush sand” or “brickies sand” will comply without modification or blending unless a Sieve Analysis Certificate or Report can be provided to show otherwise.
Even when the Builder or Client supply the Sand for the site, the bricklayer needs to be careful! The Job Specifications, Contracts or ultimately a Court of Law, may determine that the responsibility rests with the “Professional Bricklayer” to ensure Sand and any other materials, are checked and modified where required, to meet the relevant Australian Standards.
Always ask the Supplier for a Sieve Analysis Certificate or Material Quality Report for the sand and check for compliance before using.
Refer to The Australian Standard AS4773.2:2015 Masonry in small buildings for the correct material qualities.