Q: What is steel reinforcement and why should I use it in my slab?
A: Concrete is strong in compression (squashing) and weak in tension (stretching). The introduction of steel reinforcement in concrete improves the strength of concrete in tension. In a slab-on-ground reinforcement increases the tensile strength and helps control the width of shrinkage cracks.
Q: What is curing and how do I cure my new concrete slab?
A:Concrete hardens as a result of hydration, that is the chemical reaction between cement and water. Hydration occurs only if water is available and if the concrete’s temperature stays within a suitable range. After placing concrete, the concrete surface needs to be kept moist for a period of time to permit the hydration process. this period is referred to as the curing period and is usually 5-7 days after placing conventional concrete. New concrete can be wet with sprinklers, covered with wet hessian or plastic sheets. Another alternative is to water with commercially available curing compounds which seal in moisture. In addition to this, usage of the new concrete should be avoided and left to cure for at least 8 days (for vehicle use), 1 day for foot traffic.
Q: Will the colour or Exposed rocks of my new concrete slab match the existing?
A: Regarding coloured concrete and exposed, there are no guarantees. As concrete ages it oxidizes and changes colour, Even the same mix from the same concrete plant may not be the same colour at a later date. With Exposed, as this is from the Earth and not manufactured in a shed, the rocks may look slightly different in colour or shape to and existing slab. The concrete plant does not assume responsibility for mix through colours or exposed, so we don’t either. Even though colours are usually close (Maybe just a shade or so lighter/darker). If you picked a colour from the chart and the end result is different from what you had in mind, we do not consider that our responsibility. The same applies if you ask for a certain colour to match some feature of your house we can by no means guarantee that it is going to be successful, although we have gained considerable experience with this and will do our best.
Q: When can we walk/drive on the concrete?
A: With Plain concrete Normal foot traffic can be walked on the next day. With Coloured or exposed, it still needs to be sealed so not advisable un-till 24hours after sealing, if required to walk on then take care not to make scuff marks. Vehicle areas should be left to cure for at least 8 days.
Q: Why does concrete crack?
A: The nature of concrete is that it cracks, which should not matter as long as it does in the designated spots. We do however, go to great lengths to minimise the chance of cracking in the wrong places, by using tool joints or saw cut joints with the first 24 hours. (Expansion joints)
Like all other materials, concrete will slightly change in volume when it dries out. This change in volume brings about tensile stresses with the concrete which causes it to crack. This is the reason that contractors put joints in concrete pavements and slabs to allow the concrete to crack in a neat, straight line at the joint, allowing it to move when the volume of the concrete change due to shrinkage. The prevailing weather conditions may also contribute to cracking with the risk most likely on warm days, dry days with low humidity and/or windy days.