Imperial Chemical Industries Limited

Edmund J West

Desmond W Osmond

Maurice W Skinner

David G Dawson

Stephen Barry Downing

Cementitious compositions having a modulus of rupture greater than 20 MN/m.sup.2 are prepared by subjecting a mixture of hydraulic cement, fine aggregate, a selected water-dispersible polymer and water to a homogenization process (in order to very substantially reduce voidage in the product) and by thereafter curing and drying the product. The aggregate improves the modulus of rupture and resists any loss in this strength property due to moisture uptake and loss.

Cementitious compositions

In U.S. Pat. No. 4,070,199 we have described cured polymer-containing cementitious compositions of high modulus of rupture. The cured compositions are made by curing the product of subjecting to a homogenization process comprising high shear mixing (e.g. extrusion or calendering) the ingredients hydraulic cement, water and a selected water-dispersible polymer. The polymer is selected by a test which determines thermally its effect on the cement hydration reaction. The present invention describes the use in similar compositions of a class of water-dispersible acidic polymer, not selected by the above-mentioned test, which contains a specified proportion of carboxyl groups. Shaped products comprised of the new cured compositions of high modulus of rupture are useful, for example, in building applications where previously it was necessary to employ asbestos in admixture with the cement.

Cured cementitious compositions having a modulus of rupture of greater than 15 MN/m.sup.2 are prepared by curing and drying a homogeneous uncured cementitious composition which comprises in defined proportions hydraulic cement, water and a selected water-dispersible polymer.

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High Wycombe, United Kingdom

Edmund J West