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 clay content permitted by Australian Standards (AS4773.2, Section 3.2.3) for use in mortars for bricklaying or blockwork.
-Usually if a bricklayer asks their sand supplier for a Test Certificate or Material Quality Report to confirm the content of their “brickie’s sand”, they are greeted with just a blank look.
-Many bricklayers therefore turn a blind eye to Australian Standard AS4773.2 Mortar Mix Tables 3.1 and 3.2. and non-compliance is therefore widespread on building sites.
-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?
-First, the 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 water a scrubbing brush and elbow grease to clean off the clay residue from new brickwork. High pressure water washing may work but needs to be done with caution, because it can further damage the mortar joints and brickwork.
-Second, the high clay content affects the durability of the mortar. 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.
-Third, the high clay content can affect the mortar bond strength and result in weaker brickwork which can be more prone to cracking, water penetration and failure.
-Last and most important, if the clay content in the sand is too high and does not meet Australian Standards requirement for mortar mixes, it then follows that the brickwork and building will not comply either. As a consequence the Certifier, Builder or Client may have good reason and motive to knock back the work or to withhold payment from the unfortunate bricklayer.
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 where required for workability. Be careful if using “bush sand” or “brickies sand” assume that without further modification or blending, these do not comply, unless a Certificate or Report showing otherwise is available from the supplier.
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 Builder or Client for a Test Certificate or Material Quality Report when they supply the sand. Be careful and check for compliance before using.
Refer to The Australian Standard AS4773.2:2015 Masonry in small buildings for the correct material qualities.