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Studies into the wetting behaviour of polymer-modified cement stones

• 1 Pores lined with polymer [1]

• 2 Schematic view, contact angle

• 3 Schematic structure of meas­uring apparatus,...

• 4 Measurement on cement stone powder

• 5 Schematic structure of measuring apparatus,...

• 6 Measurement of tile-shaped cement stone samples

• 7 Pore-radius distribution of cement stone...

• 8 Pore-radius distribution of cement stone...

• 9 Capillary water-absorption rates of cement...

• 10 Capillary water-absorption rates of cement...

• 11 Contact angle of powder and tile-shaped...

• 12 Contact angle of powder and tile-shaped...

• 13 Surface energies of the cement stones modified...

• 14 Surface energies of the cement stones modified...

• Polymer-modified cement stones

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Summary: Polymer modifications cause changes in the porosity of cement stones. The redispersible powder used here resulted in a rise in total porosity as the amount of powder added increased. The polymer dispersion used resulted, in particular, in a reduction in the proportion of capillary pores in the cement stones and in a more compact matrix. Despite these differing effects on the porosity of the cement stones, both types of modification achieved significantly lower rates of capillary water absorption compared to an unmodified sample. The hydrophobing action of polymers in polymer-modified cement stones was verified by means of measurement of the contact angle using the Washburn method.

Polymer-modified mortars and concretes are referred to both within Germany and internationally as polymer cement concretes (PCC). The input materials take the form of cement, aggregate, water, polymers and, where necessary, further additives. In an ideal case, the polymer particles are uniformly distributed in the structure and form a binder matrix together with the solidified cement (Fig. 1).

Modification with selected polymers makes it possible to systematically achieve specific PCC properties. These include, on the one hand, green-mortar and green-concrete properties; worthy...