Abstract:
A rapid setting cementitious composition useful for making cement boards employs an insoluble form of anhydrous calcium sulfate (anhydrite) to accelerate setting and to permit reducing the amount of high alumina cement usage.
Abstract:
The present invention relates to a hydraulic binder comprising: 25 to 60 % by mass of Portland clinker; 5 to 15 % by mass of a first mineral addition selected from: o mineral additions reacting with at least 400 mg/g of CaO according to the method at 90°C described in the NF P 18-513 Standard of December 30, 201 1, in Appendix A, and o latent hydraulic materials; a second mineral addition reacting with less than 400 mg/g of CaO according to the method described herein above; and either a third mineral addition with a base of calcium carbonate or calcium sulphate, or both; the hydraulic binder comprising at least 1 % by mass of reactive aluminium, which is to say that contributes to the development of strengths.
Abstract:
A high early-strength admixture for precast hydraulic cement comprises a calcium salt and a copolymer having a carbon-containing backbone to which are attached cement-anchoring members, such as carboxyl groups, and to which are also attached oxyalkylene pendant groups by linkages selected from the group consisting of amide and imide members. The copolymers used are preferably formed by reacting an acrylic polymer with ammonia or an alkoxylated amine. The calcium salt, preferably calcium nitrite, and the copolymer can added simultaneously as one admixture, or separately. The invention relates also to methods for enhancing high early strength in concrete, cement, masonry, and mortar mixtures generally, and to precast concrete particularly, and also pertains to such hydraulic mixtures containing the calcium salt and copolymer.
Abstract:
A hydraulic binder includes a Portland clinker having a Blaine specific surface of 4000 to 5500 cm2/g, from 2.5 to 8% of sulphate expressed by mass of SO3 relative to the mass of clinker, from 1.5 to 10% of calcium nitrite and/or calcium nitrate expressed as anhydrous mass relative to the mass of clinker and from 15 to 50% of a mineral addition including calcium carbonate by mass relative to the total mass of binder.
Abstract:
The present invention relates to a process to improve the mechanical strength 28 days after mixing of a hydraulic composition submitted to a thermal treatment, the hydraulic composition comprising a hydraulic binder and optionally a mineral addition, wherein the process comprises the addition of a calcium salt and an optimized quantity of sulphate to the hydraulic composition.
Abstract:
La présente invention concerne le secteur technique des suspensions de charges minérales broyées et notamment de carbonates de calcium broyés, et des additifs pour élaborer ces suspensions, notamment des agents d'aide au broyage, conférant à ces suspensions de charges la capacité d'améliorer très notablement les propriétés mécaniques et plus particulièrement les propriétés de « résistance aux jeunes âges » des matrices cimentaires ou liants hydrauliques, préparés avec ces suspensions.
Abstract:
The present invention provides an admixture composition comprising a liquid suspension of colloidal silica, siloxane, and polycarboxylate polymer cement dispersant for enhancing early age strength, finishability, and other properties in hydratable cementitious compositions such as concrete (e.g., shotcrete). An inventive method involves mixing the components together in a specific sequence, thereby to obtain a stable liquid suspension. This attainment of a stable liquid suspension is surprising and unexpected because (i) the polycarboxylate polymer cement dispersant and siloxane components are incompatible and immiscible with one another; and (ii) that colloidal silica and siloxane compound are incompatible and immiscible with one another. Yet, the present inventors achieved an additive in the form of a stable liquid suspension which can be conveniently dosed into concretes and shotcrete mixtures, to enhance early age strength, and to improve workability and rheology in terms of finishability of concrete surfaces and improved rebound performance in shotcrete applications.