There is an old base made of cement-sand mixture (CSM). Very strong and reliable. I want to fill the top with leveling screed. I heard from a neighbor that you need to weld the layers together, use some kind of cement milk. Explain what we might be talking about here?
Vovka, your neighbor is advanced!
As I understand it, he was talking about adhesive milk based on cement, latex additive and water. They need to be mixed in certain proportions. Next, treat the old DSP or concrete base with this milk, and then fill in the leveling screed. The main thing here is to carry out the work “wet on wet” until the milk dries. As a result, the screed will be “welded” to the base.
I agree, we are talking about adhesive milk. It must be prepared in the ratio of components cement + latex additive + water - 1:1:1 . There is disagreement among workers about the proportion: by mass or by volume . On real objects, for convenience, we use the proportion by volume. In cases of shortage of latex additive or its absence, you can use cement laitance in a 1:1 ratio, although cement laitance dries faster than adhesive laitance. Therefore, we apply it to a small area.
Grachik , could you explain which latex additive you are working with (name, manufacturer).
Also interesting is the opinion of those who used latex additives based on an aqueous dispersion of synthetic resins. Provide specific examples of products.
Slavny Zhuk , in my practice I use a latex additive based on an aqueous dispersion of synthetic resins IDROKOL X20-m (manufactured by Litokol). This product is easy to use and also reliable in use. I use IDROKOL X20m to prepare adhesive cement laitance, which I use to treat the surface to continue pouring between old and fresh concrete. also use adhesive cement laitance to bond new cement-based screeds to old substrates .
For those who want to carry out the work of preparing and applying adhesive milk on their own, I will give a few recommendations.
When performing thin-layer putty or adjacent screeds, before work it is necessary to treat the existing surface with adhesive cement “milk” prepared from IDROKOL X20, water and cement, taken in equal proportions (1:1:1). Apply adhesive laitance with a brush, roller or brush. Immediately apply the cement mortar mixed with IDROKOL X20, fresh on fresh, before the adhesive cement “milk” forms a surface film. After application, level and compact the mortar.
Preparation of adhesive milk
Mix in a clean container 1 part of clean water (t° from +10° to 20°C), 1 part of IDROKOL X20-m. Pour 1 weight part of cement into the resulting liquid while continuously mixing with an electric drill with a special mixing attachment until a homogeneous liquid solution without lumps is obtained.
As a latex additive for adhesive milk, you can use a product from Kerakoll - Keraplast Eco P6. It improves the adhesion of bonding layers of mortars, ensuring the density and uniformity of mineral mortars and mineral screeds.
Mode of application . First mix Keraplast Eco P6 with water in the required ratio, and then add cement and aggregates. Mix thoroughly to avoid the formation of lumps. Recommended proportions:
Additionally, read the technical data sheet for the product.
Over the weekend, in the dressing room I poured a leveling screed onto the old cement base. To adhere the layers, I used adhesive milk based on IDROKOL X20, prepared and applied it as recommended by aden. I used Litoliv Basis as a leveling screed. All work was done by hand, including kneading. The layer thickness was 30 mm. The area of the dressing room is 6 m2. A total of 14 bags were used. Overall it was comfortable to work with. The cost of the material was 6,000 rubles.
Next I continued leveling the old cement base in the boiler room. The dimensions of the boiler room are quite large: 6x2.5 m. The thickness of the screed layer was again taken to be 30 mm. To adhere the layers, I used adhesive milk based on IDROKOL X20, the preparation technology is described above. This time I used cement-sand mortar as a screed. The placement of beacons, mixing of components, application and leveling of the solution were carried out manually. Compared to the Litoliv Basis screed, it was more difficult to work, less comfort, more physical labor. The cost of the materials used (cement, sand, screenings) was approximately 2,000 rubles. If the work is carried out using Litoliv Basis, then 36 bags will be needed and the cost today will be 16,560 rubles.
It is true that it is worth noting that the surface from Litoliv Basis is flat, smooth, blue-black in color without additional rubbing, I believe it will not accumulate dust for a long time. For a screed made from a cement-sand mixture, additional reinforcement is required if pedestrian traffic is planned on its surface.
To prepare adhesive cement-latex milk you need:
Before preparing the solution, it is recommended to first dilute IDROKOL X20M in water, observing the proportions specified in the recipe, and use the resulting liquid to prepare the solution. Adhesive milk can be applied with a brush, roller or brush.