The history of polymers in construction
Sour milk mixed with zinc powder produced an early version of today’s water soluble polymer paints. The word “latex” comes from the Latin for milk. Modern day polymer solutions used for mortar modification or as bonding agents are emulsions of acrylics or poly vinyl acetates (PVA) and have the appearance of milk. Technologies have developed and the benefits of polymers in cement based products are now well known and utilized on most construction sites. However, a lack of understanding of the practical use of polymers has led to site failures.
The do’s and don’ts of using polymers in construction
Viewed under a powerful microscope it can be seen that polymers added to cementitious mortars produce a clear film like “shrink wrap” around each developing crystal as the cement hydrates. If kept wet the film does not form and the polymers are ineffective and this is why you should never water cure polymer modified cementitious products.
Polymers act as slight retarders of the set of cement. If polymer modified products are used in dry, windy conditions a film will form on the outside whilst the mortar underneath is still plastic. Always protect polymer modified mortars against evaporative surface set. Wetting a trowel with a dilute polymer solution will help prevent trowel drag. The application of a dry trowel onto this surface will produce dragging cracks in the product.
Technology has led to the development of a wide range of polymers with different effects. Mild acid resistance and water-proofing can be induced into floors and cement based slurries by the use of polymers.
For further technical guidance consult Samson for selecting of the appropriate polymer.