The marketplace is constantly producing new and better products than ever before and thus we need to keep abreast of such products. In this blog, Paul Uno outlines two systems that are making an impact in Australia, namely ‘Biax’ and ‘E5 Internal Cure’.
Whilst at the Cement and Concrete Association of Australia (CCAA) in the 1990’s, I met various entrepreneurs who were trying to introduce the waffle pod system into AS2870 (Residential Slabs and Footings Standard), however, they wanted to use polystyrene rather than cardboard boxes used earlier.
Once this system was accepted into the Code, builders and concrete placers saw the savings they could make in reduced concrete volumes (compared to raft slabs). It then quickly took over the residential slab market in Australia.
A new company has come up with a thinner, domed-shaped “100% recycled reprolene” pod which still provides the 3D advantage of the waffle system in reducing deformation, but with fewer environmental negatives. Extensive FEM modelling on these biaxial pods has been carried out on the system by European and Australian engineers. Quite a number of jobs have used this system on-site and the system itself has received quite a few awards recently. I would refer engineers to read more about this via www.biax.com.au
Another innovative product has come into the marketplace called ‘E5 Internal Cure’. As many concrete suppliers, placers and engineering professionals will know, once you place concrete on site you have to cure it. This is to reduce the risk of early drying shrinkage cracking as well as any issues with reduced compressive strength and abrasion resistance.
Using a hose, wet hessian, plastic membrane or sprayed compounds was the standard method of curing at the end of a pour (i.e., once the slab had reached final set). Spray compounds included Wax emulsions, Chlorinated Rubber solutions, Hydrocarbon Resins, Acrylic Emulsions and PVA formulations. Each of these products had advantages and disadvantages (e.g. PVA’s did not comply with the liquid membrane curing Standard AS3799 which requires at least 90% water retention over 72 hours).
In the last 10 years, researchers at Purdue University in the USA have found that introducing nano silica into a concrete mix vastly improves its ability to self-cure. It primarily works on the principle of producing more nucleation sites. As the particles of nano silica are so small, they produce more nuclei upon which better hydration and pozzolanic activity can occur. This reduces drying shrinkage and crack formation, while also providing better curing within the matrix. I would refer readers to https://www.mcclay.au/e5-tech for further information.
If you would like to find out more about cement and concrete technology or practice, or would like to learn more about designing in accordance with AS2870 Residential slabs and footings, then you should attend the one (1) and two (2) day ETIA workshops on these topics (some presented via Zoom and others Face to Face). For further information on our workshops, refer to www.etia.net.au
Image courtesy McClay Industries | ©2023
This blog is the latest in a series produced for Construction Engineering Australia by globally respected engineering educator and reinforced concrete specialist, PAUL UNO BE MBdgSc MIE(Aust) CPEng NER RPEQ APEC Engineer IntPE(Aus), Director, ETIA (Engineering Training Institute Australia).