Australian Standard 3799 is titled “Liquid membrane-forming curing compounds for concrete”. It describes itself thus: “This Standard is a means by which curing compounds can be classified and described, and their performance assessed”.
AS3799 is intended to maintain the manufacturers’ quality of curing membranes, and thus it looks at a raft of factors; for example solids content, reflectivity and so on. Included in the test regimes is a comparative test for water retention, i.e. hydration quality. Because this is the only Australian Standard which contains such a definition, this standard has become something of an industry benchmark – “Does this curing method comply with AS3799?”
AS3799 is not intended as a standard for concrete curing
This standard is, by its own definition, not intended to define the quality of all methods of concrete curing. It is ONLY about classification of ‘liquid membrane-forming curing compounds’. Curing methods which are not ‘liquid-membrane forming’ are therefore excluded before any testing has even taken place.
By its own definition, AS3799 is not intended as a general curing benchmark. But that’s what the construction industry is using.
And that’s the nub of the problem. By asking “Does this comply with AS3799?” a whole raft of quality curing methods are excluded through being non-membranous.
Water-curing and steam-curing excluded by the Standard
Water-curing, whether by ponding or by hosing, has long been the tacit standard for curing quality on in-situ concrete. 14 days water ponding will almost completely remove the risk of hydration issues; but it delays construction schedules severely. Alternatively, keeping a supply of running water flowing over the slab is also effective, but labour-intensive. Hence these methods are losing popularity, despite the quality of the result.
Steam-curing, on the other hand, is in common use for speeding the manufacture of precast elements.
And guess what? Neither of these very effective methods are covered by AS3799 at all. They’re not intended to be.
What do international standards require?
ASTM and ISO have standards for making and testing samples (ASTM C114 and ISO 1920 respectively) which in no wise limit the method used for such. This is an important point: they focus on the intended result rather than the nature of the method.
What should be done?
An Australian Standard which genuinely focuses only on concrete curing, would be the most practical outcome.
While we’re waiting for that, construction industry professionals should stop asking the question “Does this method comply with AS3799?” and instead focus on hydration levels: “Does this method exceed 90% water retention over 72 hours?”
They should also ask
“Will the curing method need to be mechanically removed later?”
“Will the curing method hold up my construction schedules?”
Fact is, AS3799 has effectively turned the Australian construction industry away from advanced curing methods which are much more practical and cost-effective than liquid membrane-forming products. And that situation doesn’t need to continue.
Interested in saving time and money, but maintaining high curing quality, on your site? Get in touch!