How Long Does Screed Take To Dry

All screed mixes contain more water in them than what is required to hydrate the cement. Just virtually twoscore-50% of the water added to a screed mix is used to hydrate the cement, whilst the remaining l-threescore% takes up the part of making information technology workable. In one case the screed is installed, this 'excess' construction water is no longer required in the screed and has to be ousted completely before laying the concluding floor end. If left to stay inside the screed, this residue water tin be the cause of serious moisture problems and screed failure.

The Drying process

When a screeded surface is exposed to the atmosphere, its full general tendency is to attain equilibrium with the atmosphere. The moisture in the screed moves from the base of operations layers to the height past capillary activeness and diffusion, and escapes to the atmosphere through evaporation, if the atmospheric air is dry (non excessively humid).

At this stage, it is quite easy to mistake the screed to exist dry, as the exposed acme surface looks dry and even coloured, when the screed could still exist harbouring moisture in the layers below. As it is often difficult to make a visual judgement, the best way to ensure the screed is dry throughout is to acquit out a reliable moisture exam such as the Calcium Carbide Examination at the terminate of the prescribed drying period.

According to industry guidelines a 75mm traditional screed would require up to 110 days to dry at xx˚C and l%RH at the rate of 1mm per twenty-four hours for the showtime 40mm and 0.5 mm thereafter. However, it is much shorter for modified screeds which apply water reducing and additives and admixtures to reduce the water/cement ratio in the screed mix. Only, no matter what the screed blazon is, information technology is important to brand sure that all screeds are immune to dry for the specified fourth dimension prescribed past the manufacturer, even if the screed appears to be dry from the surface.

External factors affecting screed drying time:

Relative Humidity:

The wet content or relative humidity of the atmosphere plays is a major factor that affects the drying fourth dimension of the screed. By definition, Relative Humidity (RH) is a measure of the corporeality of water vapour present in the atmosphere relative to the amount of water vapour it can concur at that given temperature. For case, a Relative Humidity of 50% would mean the atmosphere is capable of property double that moisture before it reaches saturation.

The higher the RH, the lesser the amount of moisture the temper will be able to take up from the screeded surface, and college would exist the fourth dimension required for the screed to dry out out to the required level.

Temperature:

Air temperature is another important cistron that plays a major part in speeding up evaporation from the screed surface. Higher temperature (and lower humidity) will help to increase the rate of the drying by providing higher thermal energy to drive the evaporation process. Hence the rate of drying is higher in summer and is much slower on a common cold day.

Rate of air flow:

Higher rate of air flow helps the screed to dry out quickly as it prevents the wet laden air from stagnating in a higher place the screed surface. When the air is still, the air above the screeded surface becomes saturated with moisture, bringing the drying process to a stop. Providing good ventilation can speed up the drying. But remember not to leave the screed exposed to rain or external wet in the process.

Internal factors affecting screed drying times

Water/Cement Ratio:

The lower the initial water-cement ratio, the shorter the drying time required for the screed. But as reducing the h2o content tin can affect the workability of the screed and brand the screed friable, the best solution is to add a water-reducing additive or admixture to the screed which tin can assist to keep the water requirement to a minimum, while providing expert workability and strength to the screed mix.

Thickness of the Screed:

The thickness of the screed is some other major gene determining the drying time of the screed. Equally discussed earlier, for traditional screeds the general guideline is to allow 1 day per millimeter for the first 40mm, and 1 twenty-four hour period for every 0.5mm thereafter. Given below is a table showing a rough estimate of screed drying times of traditional screed depending on thickness.

Screed Thickness	Estimated Drying time
50mm	4-half-dozen weeks
75mm	6-eight weeks
50mm screed plus 100mm concrete with no DPM	6-12 months

However, for fast drying screeds the drying fourth dimension is much shorter (depending on the formulation used), and is also not more often than not as bound strictly by ambient humidity and temperature weather.

When on a strict timeline, it is mutual practice to resort to force drying to speed upwardly the drying process. But it has a major side effect – excessive drying shrinkage, which in plough can cause keen and crimper of the screed.

So if y'all are on a time bound projection, your best bet would exist to go for a proprietary screed which tin can requite yous a drying time that suits your project. But no matter what your screed blazon is, make certain y'all bear out a reliable moisture examination at the stop of the drying flow and make sure the screed is dry for the final floor finish, for a small error in judgment can be a plush mistake where moisture is concerned.