The Effectiveness of Polymer-Paraffin Emulsions to Reduce Moisture Loss from Hardening Concrete

Строительные материалы и изделия

The effectiveness of polymer-paraffin emulsions used for applying to the surface of hardening concrete to reduce moisture loss and reduce shrinkage was experimentally evaluated. Six types of moisture-proof coatings were tested in various temperature and humidity conditions, as well as in the presence of wind. Moisture losses from concrete were determined through a protective polymer-paraffin film of various thicknesses. The most effective of the tested ones was Emcoryl BFMK emulsion coating, which allows you to save up to 72-78% moisture from the amount lost by unprotected concrete for 72 hours at a temperature of 20 and 40 ℃ and the corresponding relative humidity of 60 and 30%. After the first 1-3 days of concrete hardening, the evaporation rate through the coatings, regardless of their type and thickness, becomes the same as with the open surface of the concrete. Therefore, coatings inhibit moisture evaporation only in the initial period, after which the evaporation rate is limited by diffusion in concrete. Studies have shown that in the first hours after applying the emulsion, while a solid film is not yet formed, the wind increases moisture loss, but contributes to the rapid drying of the film and a decrease in its vapor permeability. Therefore, an increase in wind speed leads to an overall reduction in moisture loss from concrete.