Ready mix concrete is a combination of cementitious material, natural aggregates and water. Admixtures may be added to aid workability and placing characteristics or to improve the long term durability and properties of the concrete.
This combination of materials releases alkalis and is very abrasive and is harmful to the skin. This can cause CEMENT BURNS or IRRITATION AND ALLERGIC CONTACT DERMITITIS.
Always wear appropriate clothing that will prevent direct skin contact with the concrete when placing or finishing. Wear abrasive resistant gloves. Safety glasses or goggles. Long trousers or overalls are ideal. Boots or wellingtons.
If you do come into contact with the wet concrete. Wash off thoroughly and immediately with clean water and remove any contaminated clothing.
IF EYES ARE AFFECTED THEY SHOULD BE WASHED OUT IMMEDIATELY AND MEDICAL ATTENTION SOUGHT.
PLACING, COMPACTION & CURING
The aim of good concrete placing is quite simple. It is to get the ready mixed concrete into position quickly. Allowing compaction and achieving the required finish.
When concrete is placed, air is trapped. This must be removed. Failure to do so will result in a weakened and less permeable concrete. This trapped air may also manifest itself as blowholes and honeycombing on the finish of the hardened concrete. Mechanical poker vibrators or beam vibrators, depending on the nature of the structure, will remove the entrapped air. Compaction is generally complete when the air bubbles stop rising to the surface. A glistening film of mortar on the surface is another good sign. However be wary that over compaction can result in surface laitance.
Concrete develops its full potential strength only when it is efficiently cured and protected from premature drying. Well cured concrete is stronger, more resistant to chemical attack, traffic wear and more watertight. It is also less prone to damage by frost and abrasion.