CM 920 Design

The substrate should be clean and free of dust, cement skin, grease and other impurities that can prevent adhesion. Adhesion and surface resistance of the substrate should be no less than 1.5 MPa. Always prime the underlying substrate with PP 600 and allow to dry before pouring. In terms of the primer forming a film and the curing of the self-leveling, the temperature of the substrate must not fall below 10 °C. For best results, the ambient temperature in the work area should be between 10 and 25 °C. At higher or lower temperatures, the time for curing will shorten or extend. With the risk for cracks due to shrinkage or settings in the subfloor, a concrete surface should not be leveled within the first 28 days after casting. As a recommendation the RH in the concrete should have reached RH 90 % as the upper limit for pouring the CM 920 Design. Use the Combimix form foam for edging. In order to avoid drainage pipes from getting clogged, always make sure the drains are properly sealed before pouring.

Mix the dry powder with 3.8–4.0 liters of water (19–20 %) per 20 kg bag. Mix with a drilling machine and a whisk, or a mixing pump intended for this purpose. Best results are achieved when mixing in a barrel. The correct water mixture can be tested using a slump test with a cylinder with Ø 30 mm and a height of 50 mm on a 300 x 300 mm plexiglas plate. With the correct water mixture, the spread should be max 140 mm. The slump test also checks that the material is well blended and that there is no separation.

The mixed material is applied by hand, or pumped out onto the substrate in lengths. Each new ribbon is added to the old one as soon as possible so that the material can blend together and create an even surface. The width of the ribbons can be adjusted to the capacity of the mixing pump and the thickness of the covering. The material requires a light treatment with a trowel to provide maximum smoothness.

You can easily shape or cut the semi-hardened self-leveling underlayment material before it fully dries. The product is paintable with epoxi or similar after 2–5 days depending on the thickness. Always make sure that the material is sufficiently dry before it gets overcoated. The guiding value assumes a curing temperature of approximately 20 °C, 50 % RH and proper air flow.