Which mixture to choose for a semi-dry floor screed and what other materials are required for pouring?

The quality and longevity of your flooring can be significantly affected by selecting the appropriate mixture for a semi-dry floor screed. Choosing the right screed mixture is essential whether you’re building a new project or remodeling an existing area. Semi-dry screeds are a popular option for many flooring jobs because they provide a practical solution that strikes a balance between robust performance and ease of application.

Which combination then should you choose? The secret is to comprehend the fundamental elements that constitute a high-quality semi-dry screed. This mixture usually consists of cement, sand, and occasionally aggregates combined with just enough water to make a workable but not excessively moist consistency. This lessens the chance of shrinkage or cracking and speeds up the screed’s setting process.

To complete the task correctly, you’ll need a few more supplies and equipment in addition to the screed mixture itself. These consist of a trowel or screeding board to level the surface, a mixer to prepare the screed, and a primer to guarantee good adhesion between the screed and the substrate. A moisture meter is also useful for determining whether the screed is dry before adding any finishing layers.

A smooth, long-lasting floor that endures over time can be achieved by using the right mixture and materials. With the appropriate resources and some preparation, you should have no trouble submitting a successful screed application.

Mixture Type Other Required Materials
Semi-Dry Concrete Mix Plasticizers, Water, Aggregate (sand and gravel), Cement
Self-Leveling Compound Primer, Mixing Bucket, Trowel or Spreader, Water
Rapid-Setting Screed Bonding Agent, Water, Aggregate, Cement
Fiber-Reinforced Screed Fibers, Water, Aggregate, Cement

For a semi-dry floor screed to be smooth and long-lasting, the proper mixture must be chosen. A proper primer, reinforcement mesh, and curing compound are necessary for a screed application, as well as a mixture of sand and cement with the ideal moisture content. This article will assist you in choosing the best combination and materials for your project, enabling you to produce a long-lasting, high-quality finish.

Composition of the solution

Given that the wet floor screed method is used as a foundation, the composition will be identical. Since varying the proportions is necessary to achieve the desired consistency, that is the only difference. In this instance, the solution becomes more plastic with less water added.

What exactly is included in the composition of the mixtures:

  • Water. Acts as a binding component that liquefies its ingredients and makes them homogeneous, it binds them together.
  • Cement. Acts as a composite raw material and also binds other ingredients, additionally strengthening the overall mass, making it durable.
  • Plasticizer. It is an additive to concrete solutions, it allows to increase the fluidity and plasticity of the mixture. Often used when reducing the proportion of water and cement.
  • Coarse sand. Added to the solution in order to provide the volume of the material and the interaction of the components with each other. Coarse sand distributes stress on the floor, as a result of which the screed will not crack.
  • Polypropylene fiber. Fiber increases the strength and elasticity of the mixture, it protects the semi-dry screed from cracks when drying. Also, this component increases the impact resistance of the floor and makes it resistant to dynamic loads.

Requirements for components

It is not advised to use raw materials not meant for this purpose to prepare a solution for a semi-dry screed. Every component will have specific needs.

  1. Cement. Cement grade M500 is used. This is a binder for the solution. According to GOST 31108-2003, this type of cement can be labeled as CEM I 42.5 (for D0). The letter index D means the addition of ground slag: in this case, this slag should not be. This raw material is frost-resistant, waterproof and durable. It sets in the solution no earlier than 45 minutes after preparation.
  2. Sand. Must be coarse-grained, washed or sifted. It should not contain large inclusions and various residues. The most optimal option is first-class sand with a fineness modulus of 2.5-3 mm.
  3. Water. The ideal option would be non-chlorinated water from a well. It should be cold or at room temperature, you cannot use water from unverified sources, since the liquid may contain various waste particles and impurities.
  4. Plasticizer. Selection based on the needs of the solution.

The fiber fiber imparts flexibility and resilience to the screed against mechanical strain. For a floor that is 50 mm thick, you need to calculate this material by taking about 40 grams of fiber per square of mortar.

How to choose a ready-made?

When selecting a pre-made mixture for a semi-dry screed, it is advised to consider the following:

  • filling thickness;
  • composition;
  • setting time;
  • complete hardening time.

The best balanced composition is achieved in the production of ready-made mixtures for semi-dry screed. Here, choosing the proportions independently is not necessary. It is crucial to determine the appropriate number of squares to pour in order to determine the total number of bags. Mixtures are offered for sale in 20–25 kg bags.

When selecting a prefabricated composition, it’s important to consider whether the screed is intended for automated or manual (mechanized) pouring.

Compositions from the following manufacturers are available in hardware stores:

  1. Besto. Fiber fiber ties containing all the necessary components in their composition. Available in 25, 40 and 50 kg bags. Price for a 25 kg bag is 120 rubles.
  2. ArmMix Floor – suitable for manual and automated flooring. Does not form cracks when drying, layer thickness is from 30 to 150 mm, can be used on outdoor areas. Price for a 50 kg bag is 342 rubles.
  3. Perfekta Fibrosloy. Reinforced screed, available in 25 kg bags. Strength — 30 MPa. Layer 10 — 200 mm. Cost — 224 rubles per bag.

You can use any of the listed compounds to prepare the subfloor for parquet, laminate, linoleum, and tiles.

Independent preparation

When preparing a mixture for a floor screed by semi-dry method, all proportions must be followed. Additionally, it’s critical to adhere to the detailed preparation guidelines for both the manual and automated methods of laying.

Proportions of ingredients

Following the principle of proportion is one of the most crucial guidelines when working with concrete. The technique will no longer be referred to as "semi-dry" if too much water is added; instead, it will be a typical wet screed, which may not be important in this situation.

If you were to take 10 kg of M500 cement, the preparation amounts would be as follows:

  • 25-30 grams of polypropylene fiber (reinforcing fiber);
  • 35 kg of coarse-grained sand of 2.5-3 mm fraction;
  • 4-4.8 liters of clean cold water.

You should add plasticizers as you see fit, taking into account the surrounding temperature and other variables.

Proportional calculations are also influenced by the type of sand and cement brand. Even though this type of screed typically calls for M500 cement and coarse-grained sand, it’s important to take the type of room and the nature of the work into consideration when planning the floor.

Another widely used guideline is to use 4.5–6 parts sand for every 1 part cement.

To help with comprehension, here’s an example: 1 meter of semi-dry screed that is 5 cm thick will require:

  • 15 kg of cement;
  • 0.065 cubic meters of sand;
  • 2-3 liters of water and 40 grams of fiber;
  • plasticizer is added at the rate of 50 ml per 1 square of screed.

Step-by-step instructions

It is advised to adhere to the detailed preparation instructions in order to achieve the desired consistency in the solution.

Manually

When preparing a solution for laying on the floor manually, it is worth observing not only the proportions, but also the sequence of adding and mixing them together.

This is how the algorithm appears:

  • dry components;
  • add fiber;
  • add water and plasticizer.

The first step is to combine all of the dry ingredients, which are cement and sand, in the predetermined quantity.

Next, you must take the reinforcing fiber and use your hands to fluff it up. The fiber itself resembles tiny bits of gray or white material.

Using a shovel, the fiber is added to the dry ingredients and combined. Next, gradually add cold, clean water. It’s crucial to add water in tiny amounts while keeping the precise ratios in mind.

Pouring the entire amount of water at once could make the mixture too liquid. The plasticizer needs to be added at the water-adding stage. You have two options: either mix it with all the water at once or measure out a small amount, combine it with the additive, pour it into the mixture, and then add the rest of the water.

When preparing the solution by hand, you’ll need a big bucket, similar to a plastic trough, and a drill attachment for a mixer.

If large volumes are anticipated, the builders advise mixing the solution directly on the floor, which can be accomplished with a shovel.

Mechanized

You can use a concrete mixer to speed up the procedure and ensure that the solution is prepared to a more consistent outcome. If there are significant volumes to be screeded, this method works well.

The order will be a little different in this case:

  1. Sand and cement are poured into the concrete mixer in measured proportions, mixed a little.
  2. Fiber is mixed separately with the required amount of water.
  3. Water with fiber is poured into the concrete mixer with the cement-sand mixture. Mix mechanically.

A shovel must be used to load the material into the concrete mixer. A semi-dry solution is the end product. By using this method, you can mix the raw materials evenly and handle large volumes of material in a short amount of time.

Remember that you must initially prepare the volume of solution that can be handled until it starts to solidify and harden.

What other materials are needed for the work?

For semi-dry screed, an additional special insulating material is required in addition to the materials mentioned above. It is available in various forms:

  • polyethylene film;
  • soundproofing backing;
  • damper tape;
  • penoplex;
  • izolon.

To help shield the semi-dry screed from moisture, a polyethylene film will be used. A robust substance that is at least 200 microns thick is used for this. A thinner film won’t offer enough defense against moisture.

Isolon is occasionally used as a moisture and loud noise shield. This material needs to be able to tolerate temperatures between -60 and +100 degrees in order to be used both indoors and outdoors.

The floor will expand during the hardening process, and the damper tape will help make up for it. This backing is made of 5 mm polyethylene foam. It separates the solution’s deforming effects from walls, columns, and other projecting structures.

Choosing the right mixture for a semi-dry floor screed is essential for ensuring a durable and smooth floor finish. For most projects, a blend of cement, sand, and a small amount of water works best. This mixture provides the ideal balance between strength and ease of application. When selecting a mixture, make sure to consider the specific needs of your project, such as the load the floor will bear and the desired finish.

To finish the project, you’ll also need a few other supplies in addition to the mixture. To guarantee strong adhesion between the screed and the base layer, this also includes a primer. The screed can be made more stable and less prone to cracking by using reinforcement fibers or mesh. Furthermore, a smooth and even surface requires the use of tools like a trowel and leveling screed.

Remember the importance of correct preparation and curing. Make sure the base surface is dry and clean before adding the mixture. It’s critical to keep the screed moist after pouring to avoid it drying out too soon, which can result in cracks and weak spots.

You will put yourself in a position to have a successful flooring project if you choose your mixture and materials carefully and adhere to the recommended procedures. Selecting the appropriate screed for a residential or commercial project guarantees a sturdy base that endures over time.

Video on the topic

Ideal beacons for semi-dry floor screed using mechanized technology

All about semi-dry screed for heated floors

Floor screed. Which one is better and why. Subtleties of screeding.

Which aspect of concrete application are you most interested in?
Share to friends
Andrey Ivanov

Experienced civil engineer with more than 20 years of experience. Specializing in the construction of industrial and civil facilities. Author of many publications in professional journals.

Rate author
StroyComfort1.com
Add a comment