The exact opposite happens with your favorite cold beverage. This is how saunas work, by increasing the heat they allow for higher water content in the air. Lower ambient temperatures decrease this. Ambient Temperature: Higher ambient temperatures increase the air’s capacity to hold water.Temperature – This has two different mechanisms that should be addressed.Frequent rain/snow showers or high relative humidity will lengthen your drying time significantly. Weather – Daily weather conditions will have a dramatic impact on drying time for your concrete wall/slab.Steel troweling a surface will “lock it down” and cause the drying to take significantly longer. A smoother surface (like a steel trowel surface) not only reduces the surface area, but also decreases the ease of vapor transmission. Surface Profile – A rougher surface profile increases the available surface area of the concrete to allow for drying.Here are some of the not so obvious factors Changing the water:cement ratio from 1:2 to 1:1 can add months onto the necessary dry time due to the additional free water that will need to evaporate. Water:Cement Ratio – The single biggest impact to drying time necessary for concrete.The primary reason is because water trapped deeper in the concrete will not be impacted by other elements like solar load and ambient temperature as quickly as water that was closer to the surface. However, this is not linear a 4 inch thick slab will not cure 4 times slower than a 1 inch thick slab, although that is the current rule of thumb. Thickness of the concrete slab - Thicker slabs will take longer to dry obviously.The primary reasons for this is that different types of concrete will require different water:cement ratios and finishes. Each of these types of concrete will impact the amount of time necessary to achieve an appropriate moisture content. Type of Concrete - Standard, Decorative, Accelerated Set, Fiber Reinforced, Flowable, Roller Compacted, Self-Consolidated, Pervious, Insulated or High Strength.Here are the ones most people think about when you ask them how long it will take for a wall/slab to dry. What factors impact concrete’s ability to dry? What if it rains all 28 days after the concrete has been poured? Is it still considered dry enough for the membrane or coating to be installed just because the literature said it needed a 28 day cure?.Probably not. That 28 day cure rule is however a general rule of thumb for when the concrete should achieve 80% of its structural strength. That's correct, but that has nothing to do with moisture content in the substrate. Most manufacturers literature references a 28 day cure (and sometimes as low as 7 days) prior to their materials being installed. While we won't be able to answer them all here, or definitely for that matter, I hope the following information can be used as a tool to assist the project team with estimating the recommended minimum time needed for the concrete substrate to dry prior to an installation of most deck coatings, air barriers, or waterproofing membranes. I have a CMU wall, will the fact that it is fully grouted impact when I can start installing materials? How do I know if the wall is too damp for your products approved to be installed onto a damp substrate? It just rained, how long do I need to wait before I can start installing your products again? We just poured the wall, how long do I have to wait before I can install your product? Some of the most common questions I get asked as it relates to concrete construction are:
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