Non-efflorescing cementitious bodies
AssigneeLafarge Aluminates
InventorsAnastasia George Constantinou, Colin Dow, Charles Hubert Fentiman, Mary Ruth Hoy, Karen Louise Scrivener
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Abstract
A non-efflorescing cementitious body is formed from sources of calcium aluminate, calcium silicate, calcium sulphate and reactive silica, these ingredients being present in such relative proportions that, upon hydration, both monosulphate (C3A.CŜ.12H) and hydrated alumina (AH3) are formed. Also disclosed is a hydraulic binder and a paste from which such bodies can be formed and a method for forming such bodies. In addition to exhibiting low efflorescence, these bodies retain satisfactory physical properties, especially good durability to natural weathering conditions.
Claims23
A non-efflorescing cementitious body being formed upon curing of an aqueous paste formed by the addition of water to a pre-mixed dry binder comprising from 10% to 49% by weight of a first ingredient comprising a source of active silica, and a remainder including:
- (i) from 40% to 90% by weight of a second ingredient comprising a source of calcium aluminate selected from calcium alumiate cement or clinker and calcium sulpho aluminate cement or clinker, said source of calcium aluminate having at least 25% alumina or a C/A ratio of less than 3;
- (ii) from 5% to 55% by weight of a third ingredient comprising Portland cement or clinker as a source of calcium silicate;
- and
- (iii) from 3% to 50% by weight of a fourth ingredient comprising a source of sulphate at least 25% being SO3;
- said ingredients being present in such relative proportions that, upon hydration, both mono-sulphate (C3A.Cŝ.12H) and hydrated alumina (AH3) are formed.
A method of forming a non-efflorescing cementitious body as a coating on a concrete article, said body being formed upon curing of an aqueous paste formed by the addition of water to a pre-mixed dry binder comprising from 10% to 49% by weight of a first ingredient comprising a source of active silica, the remainder including:
- (i) from 40% to 90% by weight of a second ingredient comprising a source of calcium aluminate selected from calcium aluminate cement or clinker and calcium sulpho aluminate cement or clinker, said source of calcium aluminate having at least 25% alumina or a C/A ratio of less than 3;
- (ii) from 5% to 55% by weight of a third ingredient comprising Portland cement or clinker as a source of calcium silicate;
- and (iii) from 3% to 50% by weight of a fourth ingredient comprising a source of sulphate at least 25% being SO3;
- said ingredients being present in such relative proportions that, upon hydration, both mono-sulphate (C3A.Cŝ.12H) and hydrated alumina (AH3) are formed, wherein said body is constituted by a coating on a concrete article, the method comprising coating an exterior surface of a hardened or fresh concrete article with said paste and curing the article and the coating together at a relative humidity of from 75% RH to 100% RH at a temperature of from 0° C. to 50° C. for a period of from 30 minutes to 24 hours.
A hydraulic binder for forming a non-efflorescing cementitious body, comprising from 10% to 49% by weight of a first ingredient comprising a source of active silica, and a remainder including:
- (i) from 40% to 90% by weight of a second ingredient comprising a source of calcium aluminate selected from calcium aluminate cement or clinker and calcium sulpho aluminate cement or clinker, said source of calcium aluminate having at least 25% alumina or a C/A ratio of less than 3;
- (ii) from 5% to 55% by weight of a third ingredient comprising Portland cement or clinker as a source of calcium silicate;
- and
- (iii) from 3% to 50% by weight of a fourth ingredient comprising a source of sulphate at least 25% being SO3.
An aqueous paste for forming a non-efflorescing cementitious body, formed by the addition of water to a pre-mixed dry binder comprising from 10% to 49% by weight of a first ingredient comprising a source of active silica, and a remainder including:
- (i) from 40% to 90% by weight of a second ingredient comprising a source of calcium aluminate selected from calcium aluminate cement or clinker and calcium sulpho aluminate cement or clinker, said source of calcium aluminate having at least 25% alumina or a C/A ratio of less than 3;
- (ii) from 5% to 55% by weight of a third ingredient comprising Portland cement or clinker as a source of calcium silicate;
- and
- (iii) from 3% to 50% by weight of a fourth ingredient comprising a source of sulphate at least 25% being SO3, said ingredients being present in such relative proportions that, upon hydration, both mono-sulphate (C3A.Cŝ.12H) and hydrated alumina (AH3) are formed.
Dependencies are inferred from the claim text.