Surcharges & Product Guides
SURCHARGES AND CONDITIONS OF SALE
Please click on the links below to download and read:
To assist you, we have uploaded some industry guidelines to our website.
Guide to Concrete Placing Best Practice
Click below to read the CCAA Guide which outlines industry standard best practice for concrete placing.
This guide is written primarily as a reference guide for house builders and tradespeople working with concrete.
Concreting in Hot Weather & Tips to Minimise Plastic Shrinkage Cracking
The warmer months, with its strong heat and winds, are known to be the prime plastic shrinkage cracking season for concrete, with special care and planning required to protect your project. Please see below an extract of information from the 2005 CCAA ‘Plastic Shrinkage Cracking’ Data Sheet, available to read by clicking here:
“Rapid drying of the surface of the plastic concrete causes it to shrink and crack, but the cracks are not always evident during finishing operations and may not be discovered until the next day.
WHAT CAUSES PLASTIC SHRINKAGE CRACKS?
Simplistically, plastic shrinkage cracking occurs when the rate of evaporation of moisture from the surface exceeds the rate at which moisture is being supplied to it (via bleeding from the concrete).
The concrete surface dries out and shrinks at a time at which it has little strength and hence it cracks. It can be likened to the cracking that occurs in clay soil as it dries. Water is lost from the concrete mass in two main ways:
- Drying from the top - Moisture rises to the top surface of a concrete element during placement – a process known as bleeding. Bleed water dries out mainly from evaporation; when the rate of evaporation exceeds the rate of bleeding, the surface dries and tends to crack.
- Drying from the base - Water in a concrete slab may be absorbed into the subgrade or ground below. In addition to affecting bleeding this could significantly increase settlement of concrete and the risk of associated cracking.
PRACTICES TO MINIMISE PLASTIC SHRINKAGE CRACKING
- Dampen the subgrade and formwork, ensuring that any excess water is removed prior to placing concrete.
- Protect concrete surfaces from drying out -
- Erect wind breaks to reduce wind velocity over the concrete surface. This is often impractical, but can be accomplished when frames or walls are erected prior to a floor being placed.
- Apply aliphatic alcohols over the surface immediately after screeding and while there is plenty of bleed water on the surface; repeat the application in severe conditions. These products reduce the rate of evaporation from the surface. They are not a substitute for curing.
- Commence curing regime promptly after finishing and continue for the specified period.
- The use of sufficient proportions of synthetic or steel fibres in concrete can provide improved control of plastic cracking”.