Screeds for Quick Construction from MAPEI

The durability and functionality of any type of flooring, whether the material used is ceramic, stone, textile, resilient or wood, is highly dependent on the physical and elastic-mechanical characteristics of the substrate on which it is installed.

The screed is a layer of cementitious mortar installed directly on a substrate. Its purpose is to bring the installation surface for the flooring to the designed height and provide a surface suitable for installing the specified flooring. Screeds are usually made up of cement, sand/aggregates and water. When a screed is laid, it must guarantee the following characteristics:

• Sufficient thickness for the type of flooring to be installed and the intensity of traffic acting on it
• Mechanically resistant
• Compact and homogeneous
• Cured and dimensionally stable before installing any type of flooring

The importance of cured and dimensionally stable screed

It is absolutely essential that the screed is cured and that most of the shrinkage is completed before installing any type of flooring. During the curing cycle, screeds are prone to “hygrometric shrinkage”, a phenomenon in which water evaporates or dry out causing the screed to shrink and reduce in volume. Adding too much water to the mix leads to higher shrinkage and longer time to dry out. There are two risks involved when that happens:

• When floor covering is bonded to the screed before the excess water has evaporated off, stresses and tension in the substrate will be transferred to the flooring and may cause the floor covering to be detached.
• As the water evaporates, it will seep through the joints between the tiles in the form of vapour, consequently forming an unsightly saline efflorescence. An even greater risk is that the vapour could stagnate under the flooring, especially in the case of materials that are particularly sensitive or even permeable (wood, PVC) and cause the flooring to detach.

Reduced curing time for screeds with MAPEI’s Topcem Pronto

The curing time for screed made from traditional cementitious mortar is around 28 days, which is rather long. However, this curing time may be reduced considerably by using pre-blended, controlled-shrinkage, rapid-drying screed mortar ― Topcem Pronto.

Topcem Pronto by MAPEI

Topcem Pronto is able to form screed that is trafficable in 12 hours and completely dry in 4 days (less than 2% residual moisture content). With Topcem Pronto, screeds are able to receive ceramic tiles after 24 hours and natural stone flooring after 2 days. Self-levelling compound can be applied after 4 days to receive resilient covering.

Levelling of Topcem Pronto after application

The product is easy to use (just mix with water) and pre-blended (fast to prepare). Furthermore, it sets in the same amount of time as conventional cement-based mortars but dries much more quickly. It is ideal for repairing screeds in areas where it is required to lay floorings in a short time (e.g. supermarkets, shops, residences, offices, etc).

The steps at the State Chancellery in Düsseldorf were installed upon quick-drying screed, Topcem Pronto

Enquiries: email to [email protected] or visit www.mapei.com.sg and MAPEI's profile on Archify.