Q: Should my concrete slab be steel reinforced?
A: If a material with high strength in tension, such as steel, is placed in concrete, then the composite material, reinforced concrete, resists not only compression but also bending and other direct tensile actions. A reinforced concrete section where the concrete resists the compression and steel resists the tension can be made into almost any shape and size for the construction industry. In a slab-on-ground reinforcement increases the tensile strength and helps control the width of shrinkage cracks.
Q: How do I ‘cure’ my new concrete slab?
A: Concrete hardens as a result of the chemical reaction between cement and water known as ‘hydration’. Hydration will only occur if water is available and the temperature of the concrete stays within a suitable range. After pouring concrete, the surface must be kept moist long enough to permit the hydration process. This ‘curing’ period is usually 5-7 days after pouring. You can keep your concrete moist with sprinklers, or by covering it with wet hessian or plastic sheets, depending on the size of the pad. Another alternative is to water with commercially available curing compounds which seal in moisture.
Q: Will the colour or exposed rocks of my new concrete slab match the existing?
A: Regarding coloured concrete and exposed rocks there are no colour guarantees. As concrete ages it oxidizes and changes colour, and even the same mix from the same concrete plant may not be the same colour at a later date. Colours are usually close but can easily be just a shade or so lighter or darker. Keep this in mind when selecting your colours. We will do our best to colour match but we are unable to guarantee it will be exact.
Q: When are we allowed on the concrete slab?
A: With plain concrete, you can allow normal foot traffic on the slab the next day. With coloured or exposed concrete, you will need to wait 24 hours after it has been sealed. Vehicles should not be allowed on the slab for at least 8 days.
Q: Why can concrete crack?
A: It is not unusual for concrete to crack, which should not matter as long as usually it has been prepared for and will crack in only the designated spots. We do try to minimise the chance of having the slab cracking in the wrong places by using expansion joints. Like all other materials, concrete will slightly change in volume as it dries out. This change in volume will bring about tensile stresses within the concrete and this is what causes the cracks. A good contractor will allow for these tensile changes by putting expansion joints in concrete pavements and slabs to allow the concrete to crack in a neat, straight line at the joint, and allowing it to move when the volume of the concrete changes due to shrinkage. The existing weather conditions will usually also contribute to having your concrete cracking with the risk higher on warmer days, dry days when the humidity is low and windy days. Basically anything that is going to dry your concrete out faster than it normally would, where the moisture level is low, will give you a higher chance of slab cracks.