Fabrication and Properties of Redispersible Polymer Powder-Modified Systems

The fabrication technique of redispersible polymer powder-modified mortar and concrete is about the same as that for latex-modified mortar and concrete. The materials and mix proportions used in this modified mortar and concrete are the same as those used in the latex-modified systems except that the addition of the redispersible polymer powders is involved.

The redispersible polymer powders are usually free-flowing powders and have ash contents of 5 to 15%, which primarily come from the anti-blocking aids. When the polymer powders are placed in water under agitation,

they redisperse or reemulsify easily and provide the polymer latexes with polymer particle sixes of 1 to 10 m. Generally, redispersible polymer powders are dry blended with cement and aggregate mixtures, followed by wet mixing with water. During the wet mixing, the redispersible polymer powders are redispersed or reemulsified.

If necessary, powder or liquid antifoaming agents are added to the wet mix. The curing of the modified systems is similar to that of latex-modified systems. The properties of redispersible polymer powder-modified systems are improved in comparison with ordinary cement mortar and concrete and these depend on the nature of polymer and polymer-cement ratio. The properties are improved with an increase in the polymer-cement ratio. This tendency is very similar to that of the latex-modified systems.

In general, the redispersible polymer powder-modified mortars are inferior to styrene-butadiene rubber-modified mortar in certain properties.

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