Yes, you can plaster over expanding foam.
Having the right amount of expansion joints between concrete slabs is essential, but large openings exposed to the elements can cause many different problems over the lifetime of the concrete. For this reason, it's important to fill or seal your expansion joints.
High Expansion is mostly used on dry product fires or enclosed areas to drawn large volume surfaces and fill cavities such as warehouse, cellars, aircraft hangar or engine/pump rooms aboard ships. Less water used produces a very large amount of foam in a short time, resulting in fire extinguishment by smothering.
Waterproofing and moisture control: Expanding foam can seal gaps and cracks, preventing water and moisture infiltration. It is commonly used to seal around plumbing fixtures, windows, and roofs, protecting structures from water damage and mould growth.
Avoid using the foam near any ceiling lights or heating appliances. If you spray the foam near a ceiling light, for example, there is a chance that it could catch fire due to the flammable nature of the spray. Additionally, it could also cause damage to the light itself if it cures around any wiring.
Three main applications for expansion foam joints in construction: To create a gap in new concrete, preventing concrete from sticking to existing structures; or, To allow concrete to expand and shrink freely without applying pressure to adjacent structures.
Expanding foam is not as strong as concrete when supporting load-bearing posts. A local fence installation professional can help you decide which post hole filler is best depending on the type of fence and uses you need.
Low-expansion foam expands less than 20 times when properly proportioned and agitated with air. The normal expansion range for low-expansion foams is usually 8 to 12 times. High-expansion foam is usually formed by blowing air through a solution-wetted netting or wire mesh.
On average, it can take anywhere between 8-24 hours for spray foam to completely cure and expand, though it usually takes anywhere between 5 minutes and 1 hour to become tack-free. For the best results, review your spray foam's product label to determine the optimal curing time for your specific brand and application.
Tips for placing concrete expansion joints
Place joints around 30 times the slab thickness apart. So, for a slab which is 100mm thick, the joints should be placed around 3,000mm (3 metres) apart. Make sure joints are cut deep enough: they need to be at least a quarter of the thickness of the slab.
Epoxy has rapidly become a go-to solution for concrete joint filling over traditional options like asphalt or rubber. Unlike those materials, epoxy is designed to be strong, flexible, and incredibly durable. Plus, its waterproof seal prevents water damage and grime accumulation.
Large Gaps and Expansion Joints (Over 1/4″)
All sections should be measured before the filling process. Materials for large concrete gaps and expansion joints include: Non-Sag Caulk: Thick, easy-to-control caulk ideal for larger areas. It requires smoothing but stays in place and works well with a backer rod.
Squirt a little expanding foam around a loose shower arm, and it'll be solid as a rock. Let the foam set up until it's stiff and carve off any excess around the shower arm.
Drill and Fill
In FriendnFamily's video, they simply drill holes in the concrete, then put the nozzle into the holes and inject the foam under the slab. It slowly lifts, although it does not become perfectly even with the neighboring slab. Notice how it lifts both the sunken and raised slab at the same time.
The finished foam is also less prone to be affected by wind, and the finished foam will spread out more rapidly on the spill surface. A disadvantage of such low expansion foam is its rapid drain time.
The answer lies in a critical but often overlooked component: Expansion Foam. This particular material is indispensable and ensures the longevity and durability of your construction projects by accommodating the natural movements of concrete.
Despite the many advantages of foam concrete, its main disadvantages are lower strength & shrinkage. Shrinkage can be reduced by the effective use of natural fibers while in order to increase strength, synthetic fibers have a vital role.
Fill the hole with Fast-Setting Concrete up to 3 to 4 inches below ground level. Pour about a gallon of water per 50 lb bag into the hole and allow the water to saturate the concrete mix. Wait about 4 hours to begin constructing your fence or applying heavy weight to your post.
This is another temporary solution. The real reason your concrete slab is sinking is due to poor settlement, poor compaction, or tree roots. You need to stabilize and strengthen the ground underneath your slab. The only way to do that is by filling the voids beneath the slab with a strong expanding foam.
This means that when applied beneath concrete spray foam can help keep the surface of the concrete cool during the summer months and warm during the winter months. It also helps reduce condensation on the surface of the concrete which can cause damage over time if left unchecked.
High Expansion foam is suitable for use in combating fires in buildings, process areas, warehouses, and aircraft hangar systems. High expansion foam systems can be used for protection of LNG storage areas by quickly blanketing the flammable liquid surface and helping to control vapor release.