Don't let the rains stop play

February 2014

Don't let the rains stop play
Rains are raging across the country, and the Met Office tells us to brace ourselves for more. As we pull out the tarpaulins to guard our screeds from the heavy downpours, remember not to leave the sand or cement bags soaking in the rain.
Keeping the sand protected from the rains is just as important as protecting the installed screed. Many of the fast drying screeds and admixtures are designed to bring down the water content in the screed mix and accelerate the drying time. But what if the sand is too wet in the first place?
Moisture in the sand can affect the consistency of the screed mix. If the screed mix fails the snow-ball test, it would render the screed mix unusable as screed laid using the mix could provide very poor quality surface regularity and show higher departure from datum.
When carrying out screeding in wet weather, it is advisable to load the sand on to the lorries the night before, as water can drain out of the sand overnight. To ensure this, good communication with the sand suppliers is crucial. Make necessary arrangements to bring the sand covered adequately with water tarpaulin or water proof material, and also ensure the sand is kept dry and protected once it is brought on site.
Also remember to make sure the moisture in the sand is taken into account while planning your job during wet conditions, as the screed is mixed according to pre-agreed mix designs, and alterations would be necessary depending on the moisture levels present in the sand.
Protecting cement from rain
Cement bags also need to be kept adequately protected from moisture and rain splashes during transport and storage. It is crucial that cement does not come in contact with water before the mixing process begins, because cement undergoes hydration as soon as it comes in contact with water. This can cause deterioration in the strength and quality of the cement.
It is ideal to stack the cement bags in pallets on the bed of the truck during transportation in wet weather. The cement bags should be covered with tarpaulin and canvas in such a way that the bags are completely protected from any water splashing up from the deck of the truck.
At the site, the cement bags should be stored in a protected area with a dry floor. It would be worthwhile to keep the cement bags elevated on pallets or planks and covered with tarpaulin to prevent the cement from hardening along the corners and edges. Remember, water-repellent cement bags are not fully water-proof. They have small perforations for air release, which can make them susceptible to moisture unless adequately covered during transport and storage.
The key again, a bit of care and planning to keep the material protected, and of course good communication with your cement and sand suppliers!