I'm a little late to the party, but I thought I'd add some observations...The product has been mixed incorrectly. Too much water. When this happens, all of the additives (the stuff that allows the product to be flexible and not crack) wash to the surface and you see what we often call "powdering". That's what all of that white stuff is.This will cause two major problems. One, the cracking that you are already seeing. Two, if you were to adhere something to the surface, it would not bond properly. I would bet that if you were to pH test this as it sits, the pH would be pretty high.That white stuff is actually latex or acrylic in a dry powder form. Sometimes, depending on the product, you may also see fibers in it. Some self-leveling can contain Kevlar fibers for reinforcing the product against movement. It kind of works like a teeny tiny version of rebar to provide dimensional stability.Self-leveling is not like thin set mortar or really even trowelled patches. It has a very specific ratio of water to powder. If you get outside of that, either way, you severely affect the performance of the product. You cannot mix it to "feel".It also has a very specific amount of time that you should mix the product. It then needs to set for a set amount of time to slake off. This allows any entrained air that's trapped in the mix to rise to the top and escape so that you don't have a lot of "fish eyes" (bubbles) in the mix that leave little pock marks in the finished surface.When done correctly, it's like coordinating a symphony. Complicated but almost artistic and beautiful.It's definitely a defective pour. It needs to come out and be replaced.Whatever you do, DO NOT LET THEM POUR OVER THIS!!! It will be an absolute nightmare. It needs to be removed, re-primed, and repoured correctly.If the product is not being run through a pump, then a typical self-leveling crew should really be 3 people minimum. 1 guy mixing, 1 guy controlling the product on the floor, and 1 guy prepping bags for the mixer and taking the mixed material and dumping it out. You can do it with 2 people if they know what they're doing but it can get pretty hairy if you run into a problem. You only have so much time, generally around 10-12 minutes to get the next mixed material down so that you are working with wet edge to wet edge. The exception to this is if you are using a type of self-leveling that is reactivatible. If that's the case, then you can use a set of self-leveling star rollers and reactivate the product. This returns it back to a more flowable state and then you can re-blend your wet edges if you started to "lose' the pour. The rollers break down the early bonding legs that start to form in the product and allow it to flow again. You can do this reactivation once and then that's it. It gives you about another 8-10 minutes of time to work with that wet edge.I'm sorry that you had this experience. Please know there are many good quality mechanics in our industry who do good work and would never leave somebody in this situation. I wish you well getting it replaced and hopefully this time everything is done correctly and the job goes smoothly (no pun intended).
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I&#;m Andy Parkin, Managing Director of the Multi-Award Winning Speed Screed. I&#;m here to talk about laying Self Levelling Screed.
I would say that I don&#;t believe there is a &#;Self Levelling Screed&#; per say, yes a self-smoothing, but not self-levelling, please don&#;t lay the screed and expect it to level itself. However the term &#;self-levelling&#; is used extensively in the industry and I will use it here.
For the purpose of this video I will also assume that &#;laying Self Levelling Screed&#; is a levelling compound normally laid between 1-10mm.
When laying vinyl, ceramic tiles, carpet and other floor coverings. Self levelling screed levels out uneven substrates leaving a smooth flat surface to bond to.
Before laying self levelling screed, its suitability needs to be determined. Most projects will have one of three different types of substrate as follows:
When bonding I think it is important to highlight the process. When looking at the substrate, it needs to be sound. When we say &#;sound,&#; it needs to be solid. If you have crumbling, cracking, or other issues, then action needs to be taken before laying the screed. There is no point in laying self-levelling screed onto something that isn&#;t stable, because it will only result in the screed cracking and/or de-laminating.
Checks should be made to ensure that the substrate is not contaminated. Contamination can be a variety of things, oils, grease, dust, anything that may have gone into the pores of the screed (the capillaries of the screed). If there is contamination it may require some mechanical surface preparation, which may be grinding/scabbling or shot blasting. If there is paint on the substrate then it will need to be removed, before laying self-levelling screed.
The surface needs to be clean and vacuumed if there is dust/dirt on the surface. Before laying self-levelling screed a primer needs to be applied to the substrate to assist in the bonding of the self levelling screed and the substrate. Sometimes it can go down without the primer, always read the instructions before laying. Either way you are going to need some penetration of the surface. It needs to bond, so it may be that you must grind off the first couple of millimetres of the matrix to get down to something that is bond-able.
If the substrate is power floated concrete, then the top of the matrix will need to be removed to get to the more open textured concrete that will allow the primer to penetrate. There are certain products that may go down directly onto it a power floated surface, but again, you would have to look at the requirement for each individual product. In general, you would be looking at mechanically altering the surface to allow for better adhesion between the screed and the substrate.
When laying self-levelling screed, the thickness varies from product to product, however as a general guideline please find the depths below:
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Generally, when laying self-levelling screed the substrate should be 75% relative humidity or less, if above a liquid damp proof membrane maybe required to suppress the available moisture.
I would recommend that the surface is always tested for moisture before proceeding.
When completely happy with the substrate, you are now ready to apply the primer which assists with the bonding of the screed and substrate.
Each product will have a tested recommended primer and may have different ratio&#;s to water. Always check with the manufacturers guidelines before proceeding.
Generally, the primer needs to be dry before laying self-levelling screed, however it wouldn&#;t normally be left too long (always check the product for instructions).
When applying the prime use a brush, and make sure there is no pooling of the primer.
If mixing by hand using an electric drill, the powder is added to the correct amount of water (again work from the manufacturers guidelines for their product), whilst mixing thoroughly until a lump free mortar is produced.
The screed is then poured onto the substrate, laying self-levelling screed is then carried out by using a steel trowel or float to spread the mortar and finish off.
Generally, the screed will self-smooth for the first 15 minutes and have a total working time of around 30 minutes, depending on site temperatures.
Site conditions will effect drying times, however 3 mm of screed would normally be dry within 24 hours, and walk-able within 3-4 hours.
I hope this helps with your &#;laying self-levelling screed&#; questions, if you would like any further help please get in touch.
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