Traditional OSB is a problem for resilient and wood flooring installations because of the nature of its construction. Traditional OSB is made from large chips of wood that will swell when exposed to humidity and moisture, causing the texture of the chip structure to show through on resilient floors. According to the Engineered Wood Association, OSB is only suitable as a substrate for stretch-in carpet, which isolates the texture of the OSB from the flooring with a layer of carpet pad. The association goes on to recommend applying a 1/4" layer of underlayment over the OSB for installation of resilient and wood flooring. The main thing to remember about traditional OSB is that it is very absorptive and swells when exposed to moisture (such as rain). This swelling is not good for floor installation. Having said that, there are new OSB products out there that are “engineered” materials, making them different from traditional chip/strand OSB. Some of these new engineered OSB boards have much better moisture resistance and can handle water contact without a change in dimensional properties.
ACI provides guidelines as suggestions or recommendations on the water content to provide the desired compressive strength. Never add more water than what is necessary to provide the desired workability. More water equals lowered strength.
Concrete is very good in compression but poor in tension. Reinforcement allows the concrete structure to maintain its compressive integrity while still providing good resistance to tensile or flexural stresses.
Adding air to the concrete (air entrainment) allows the concrete to withstand freezing and thawing cycles as it provides room for the water present in concrete to expand without putting stresses on the concrete itself.
Concrete can be placed in a wide range of ambient conditions. ACI guidelines explain the range of these conditions. Avoid placing concrete below 40°F or above 120°F without proper protective measures. Also avoid windy conditions without a wind break as this will expose the fresh concrete to premature surface drying, which can lead to cracking or a weakened surface that is prone to “dusting” and discoloration.
After creating a slope with a fresh mud bed using MAPEI's 4 to 1 Mud Bed Mix, the area should be allowed to cure for at least 24 hours per inch (centimeter) plus one day before application of MAPEI's Mapelastic AquaDefense. For example, if the mud bed is at 2" (5 cm) depth at its highest level, then you must wait three days before the application of Mapelastic AquaDefense. Curing time is based on a temperature of 73°F (23°C). Cooler temperatures will require longer curing times. If your project is on a fast track, consider Planislope RS mortar, which can receive waterproofing in a matter of hours.
Curing is one of the most important steps in protecting your concrete and ensuring a long service life. The use of sprinklers, wet burlap and curing agents allow the concrete to gain structural integrity (strength) while protecting it from premature surface drying. Utilizing curing compounds and using sealing agents are the best ways to keep the concrete surface protected from the environment and ambient conditions, which would otherwise deteriorate the concrete surface.
There are many causes for cracking in concrete. Concrete goes through many changes as it hydrates or hardens. Allowing the concrete to harden and achieve strength before these stresses arise will eliminate a large portion of these cracks. Proper curing, a good mix design, use of shrinkage-reducing admixtures and the addition of fibers are all good ways to help minimize some types of cracking.
New cement board will often come with a fine dust on the surface of the board. So, it is very important to clean the surface of the cement board and to allow the surface to dry before applying Mapelastic AquaDefense. Usually, wiping the cement board with a damp (not wet) sponge will effectively remove the dust.
Admixtures enable concrete producers and placers to easily mix, place and/or finish the concrete in multiple environments and conditions. Admixtures also provide a way to produce higher-quality concrete without increasing the cementitious content of the concrete mixture, which keeps the cost of the concrete down.
When applying MAPEI's Mapelastic AquaDefense, it is important to allow it to dry in between coats. It is also important to avoid applying Mapelastic AquaDefense too thick. When applying Mapelastic AquaDefense over a mud bed, the mud bed must be dry before application. After using MAPEI's 4 to 1 Mud Bed Mix, the area should be allowed to cure for at least 24 hours per inch (centimeter) plus one day before application of Mapelastic AquaDefense. For example, if the mud bed is at 2" (5 cm) depth at its highest level, then you must wait three days before the application of Mapelastic AquaDefense. Curing time is based on 73°F (23°C). Cooler temperatures will require longer curing times. If your project is on a fast track, consider Planislope RS mortar, which can receive waterproofing in a matter of hours.
After treating corners and seams of cement board with mesh tape and a polymer-modified, cement-based tile mortar, the area should be allowed to cure for at least 24 hours before the application of MAPEI’s Mapelastic AquaDefense. Note: If time is an issue, use a MAPEI rapid-set, polymer-modified mortar with the mesh tape and allow the area to dry for at least four hours before the application of Mapelastic AquaDefense.
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