Mixing two-component flexible cementitious sealing slurries on-site immediately before use may soon become a thing of the past. A redispersible polymer powder has been developed that enables the formulation of one-component products. Polymer powders of this type can also be used successfully, in other ‘elastic' applications, such as highly flexible tile adhesives
The effects of polymer dispersions on the physical and chemical properties of flexible cementitious sealing slurries are well known.1 The resulting products have been used for many years as surface-protection systems.2 Second-generation sealing slurries of this type are characterized by their high polymer fraction with the polymer-cement (p/c) ratio being typically 0.8 or more. The polymer, which ensures that the membrane remains flexible down to low temperatures, must have a very low glass-transition temperature (Tg) (typically in the region -5 to -60°C). The technical properties of this type of building material are described elsewhere.1-2
The aim of this article is twofold: to explain the difficulties in producing a redispersible powder with adequate low-temperature flexibility, and to present a new solution to this problem, including a description of the associated physical and chemical characteristics. The use of powdered products of this kind in other "elastic" applications, such as flexible tile adhesives, will also be discussed.