Efflorescence is the appearance of chalky stains on the surface of flooring like tiles and pavers. The crystalline deposits of mineral salts are a cosmetic issue that can be removed by pressure washing or chemical cleaning, but these have to be performed regularly as efflorescence can recur. Ultimately, efflorescence is an effect of the underlying issue that remains: water intrusion into the screed.
The efflorescence process
Efflorescence occurs due to the presence of two components, water and salts, that migrate from the screed to the flooring surface.
There are two ways water can enter the screed. Firstly, groundwater from the surrounding area below will be absorbed into the porous cement screed through capillary action, a process where water is transported upwards into areas of lower water concentration. Another way is where high volumes of rainwater on the surface infiltrate downwards into the screed where it will remain if undrained. In both cases, water that has entered the screed will begin to move up towards the drier surface.
Efflorescence is especially prevalent in floors with cement screeds due to cement’s high salt composition and porosity that facilitates capillary action. As water moves upwards via capillary action through the pores of the cement screed, it dissolves the soluble salts and carries them along. When the salt solution reaches the flooring surface, water evaporates and leaves behind salts which react with atmospheric carbon dioxide to form unsightly, powdery stains. This makes the surface dry again, drawing more water from below. The constant movement of water upwards creates a build-up of pressure in the screed and the flooring, causing them to crack in the long run.
How VersiDrain® P-Anchor® works
Water in the screed has to be properly managed to reduce the phenomenon of efflorescence. Capillary breaks, a barrier of hydrophobic material that has water impermeability to prevent capillary action, stops groundwater before it enters from below the screed. To address surface water infiltration, adequate drainage needs to be provided for the screed so that water will not collect and remain within.
VersiDrain® P-Anchor® under screed drainage sheet creates a separation gap between the structural concrete and the screed. Water that rises to the top of the structural concrete will not come into contact with the screed, and instead be guided by the drainage channels of VersiDrain® P-Anchor® into drainage outlets. Tiny perforations allow water in the screed to percolate through VersiDrain® P-Anchor® downwards into the separation gap the drainage sheet has created. The water then flows along the drainage channels into drainage outlets.
During installation, frusto-pyramidal openings allow the screed to flow through VersiDrain® P-Anchor® and bond with the structural concrete below. The bonds anchor the layers to each other with a pull out strength of more than 4 kN/m2. This increases stability of the floor layers and removes the “floating slab” effect of unintended movement between independent layers.
While we have explained efflorescence and VersiDrain® P-Anchor® using illustrations with simplified detailing of layers, the actual detailing can vary in complexity depending on the specific applications that a project requires.