What Is Concrete Screed?
Concrete screeding is a process of applying a well-blended mixture of ordinary Portland cement, fine aggregates (sand), and water to hydrate cement mixture, to form a solid and a leveled sub-floor that is capable of receiving the final floor finish.
Concrete screed is applied to a concrete floor base to provide a suitable flooring or a base for installation of the suitable finished flooring. The final layer of the flooring like tiles, marble, wood, etc. is rested on concrete screed. It provides a leveled surface and a required height for the flooring. This layer of concrete is suﬃciently rigid and is capable to resist the load acting on it.
Mix Proportion Of Concrete Screed
Concrete is made up of cement, sand aggregates, and water. Their proportions vary according to the required properties like strength and to suit various requirements.
Concrete screed is diﬀerent from the normal concrete. It is a thin layer of mixture of materials like cement, sand, and water as per the requirement. The proportion of concrete screed is 1 part cement and three to five parts of sand. The sand should be of 0 to 4 mm size washed sand for levelling screeds.
In some cases, heavy duty screed is used. For heavy duty screed, the proportion of cement and sand is diﬀerent. The proportion of heavy duty screed is 1 part cement, 3 parts 0 to 4 mm sand, and 1 part of 6 to 10 mm single-sized aggregates. The density of heavy duty screed is more than the regular screed. It also can withstand more amount of load and is also used where the load coming on it is more.
Method Of Application
The application of concrete screed is as follows:
1. The materials i.e the cement, sand, and water are thoroughly mixed according to the requirements.
2. The mixture is poured on the hard concrete base. It is spread using a trowel evenly till the required thickness of the layer is achieved. This layer of concrete screed is usually thinner as compared to the concrete base present below.
3. The thickness of concrete screed varies from 25 mm to 35 mm, depending on its use.
4. Once it is evenly spread and the required thickness is achieved, the screed surface is given a finish. Generally, a smooth surface finish is given to the surface of the concrete screed. But it also depends on the intended use.
5. The layer of concrete screed is left to dry for some time, similar to the conventional concrete.
6. Once it is dried and matured, proper curing is done to the layer of screed to achieve the perfect strength.
Concrete Screed Finish
Screed in construction is referred to as a flat board using which the surface of concrete mix is smooth finished. The layer of concrete screed can be given various finishes.
Varying from an extremely smooth finish to a coarse finish, any kind of finish can be obtained on it. The surface finish of concrete screed depends on its intended use.
The concrete screed usually has a smooth finished surface but it is not intended for use as a finished flooring surface. It is used as a rigid layer under the final finished flooring surface.
Once the concrete screed is hardened after giving it the required finish, it is properly cured. If the screed is not treated properly, some defects like cracks, surface dust or bleeding, crumbly surface, and fractures around the pipework, can be observed.
Advantages Of Concrete Screed
The advantages of concrete screed are as follows:
1. Concrete screed provides a leveled surface for the flooring to rest upon.
2. The surface of concrete screed is rigid. So it provides strength to the flooring and it is capable to resist loads of footfall on the flooring surface.
3. The application of concrete screed is not so complex. Hence it is not necessary to hire highly skilled workers for it.
4. The materials required for concrete screed are cement, sand, and water. Sometimes additives and admixtures are also added if prescribed. They are easily and locally available.
5. Concrete screed provides a surface level and a certain suﬃcient height to the flooring.
6. It increases the lifespan of the flooring and also the concrete base, present below the flooring.
Disadvantages Of Concrete Screed
The disadvantages of concrete screed are as follows:
1. The consistency of the mixture should be kept accordingly to suit the requirements of the flooring. If the consistency is not maintained, the screed shall not resist the expected load.
2. All the ingredients of concrete screed should be given a thorough mix otherwise the strength of concrete may degrade.
3. The layer of concrete screed should be properly cured. If it is not cured properly, its strength and abrasive resistance are aﬀected.