Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2000-06-26
2002-08-20
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S722000, C106S732000, C106S772000, C106S778000
Reexamination Certificate
active
06436184
ABSTRACT:
The present invention relates to a hydration modifier for mortar or concrete making it possible to obtain a limited shrinkage, to a Portland-type dry cement composition, to a ready-to-use concrete composition, to the process for preparing a mortar or concrete composition, to the use of the mortar or concrete compositions for the manufacture of construction works and to the self-leveling screeds manufactured from the mortar or concrete compositions.
In general, in order to compensate for the shrinkage of building works, it is common practice to use non-shrink admixtures which make it possible to obtain an expansive process for mortars or concretes. Among these admixtures, mention may be made, for example, of micronized aluminum powder, calcium carbide, quick lime, hydrogen peroxide, calcium sulfate, calcium aluminosulfate and iron powder. The swelling obtained with these non-shrink admixtures is of the order of 300 to 800 &mgr;m per meter after 28 days. The shrinkage of the cement/aggregate mix being of the same order of magnitude: 600 &mgr;m per meter for a mortar normalized after 28 days.
In theory, the shrinkage is therefore well compensated for, but in fact it is very difficult to control this expansion as well as the moment that it occurs.
It therefore appears important to develop a ready-to-use mortar or concrete composition which does not have these problems of controlling the expansion.
The applicant has surprisingly discovered, by turning toward a technology other than that normally employed in the field, that a mortar or concrete composition which comprises a Portland-type cement in combination with a hydration modifier produces a modified microstructure that does not lead to significant swelling during setting and limits the shrinkage during drying of the cementitious matrix of the mortar or of the concrete.
This is because the applicant noticed on the one hand that by combining at least one Portland-type cement with a modifier comprising at least three ingredients in proportions defined below, it obtained a mortar or concrete with limited shrinkage.
On the other hand, it noticed that the ingredients constituting the hydration modifier, in the proportions indicated, themselves have a synergistic action on the non-shrink effect of the Portland-type mortars or concrete.
A first subject according to the invention is a hydration modifier for mortar and concrete, comprising, in combination, from 30 to 80% of calcium sulfate, from 3 to 60% of ethylene oxide/propylene copolymer and from 0.5 to 6% of activator for the copolymer.
The calcium sulfate may be used in the form of gypsum or in anhydrous form, but in a preferred embodiment according to the invention it will be used in anhydrous form.
The ethylene oxide/propylene copolymer is a copolymer capable of being activated by the addition of an activator or catalyst. It will be possible to use copolymers differently substituted in terms of ethylene and propylene, but in a preferred embodiment copolymers consisting of 60 to 90% of ethylene oxide will be used.
The activator or catalyst makes it possible to activate the ethylene oxide/propylene copolymer used and may be any type of suitable activator. In a preferred embodiment, imidazole may be used as the activator for the ethylene/propylene [sic] copolymer.
In an even more preferred embodiment according to the invention, the hydration modifier comprises 51% of calcium sulfate, 46% of ethylene oxide/propylene copolymer and 3% of imidazole.
In another even more preferred embodiment according to the invention, the modifier comprises 80% of calcium sulfate, 18% of ethylene oxide/propylene copolymer and 2% of imidazole.
A second subject according to the invention is a ready-to-mix Portland-type dry cement composition comprising from 2to 10% by weight of a hydration modifier according to the first subject of the invention.
The Portland-type cement may be chosen from pure or compound cements.
In a preferred embodiment according to the invention, the cement composition comprises from 4 to 6% by weight of a hydration modifier.
A third subject according to the invention is a ready-to-use mortar or concrete composition comprising from 0.5 to 2.5% by weight of a hydration modifier, according to the first subject of the invention, in combination with a Portland-type cement.
In a preferred embodiment according to the invention, the mortar or concrete composition comprises from 0.8 to 1.3% by weight of a hydration modifier.
The mortar or concrete compositions according to the invention may include other admixtures, known per se in the art, of the type mentioned below.
For example, mention may be made of admixtures which act on the setting and hardening time, such as, especially, accelerators which shorten the time between hydration of the binders and their setting, and retarders which extend the time between the hydration of the particles of a binder and the onset of its setting. As accelerators, mention may be made, for example, of calcium or sodium chlorides, certain alkalis (soda, potash, ammonia) or their salts (potassium or sodium sulfate) . As retarders, mention may be made of carbohydrates (sugars, glucose, starch, cellulose), various acids or acid salts, or else zinc oxide or alkali phosphates.
Mention may also be made of admixtures which act on the plasticity and the compactness, such as plasticizers, thinning agents, called water reducers, air entrainers and thickeners. As plasticizers, bentonite, fat lime, ground limestone, flyash and keiselguhr may, for example, be incorporated. As thinning agents, naphthalene sulfonate, lignosulfates, sulfonated melanine [sic], resin soaps or synthetic detergents may be used. As air entrainers, sulfonates, sodium abietate or alkaline soaps of fatty acids may, for example, be used. As thickeners or antisedimentation stabilizers, methylcellulose, silica fume, stabilized casein and biopolymers may be mentioned.
Mention may also be made of admixtures which improve the resistance to external agents, such as antifreezing agents, which protect the material from the effects of frost until it has hardened; frost-preventing agents, which protect the hardened concretes from the effects of frost; waterproofing agents, which improve the impermeability of the concretes by reducing the possibilities of water penetrating by capillary effect; cure products, which prevent premature evaporation of the mixing water and maintain the necessary hydration. As antifreezing agents, calcium chloride or sodium aluminate may, for example, be used. As frost-preventing agents, air entrainers may be used. As waterproofing agents, silicones, fluosilicates, colloids or resins may be used. As cure products, emulsions of paraffins or waxes, oils, resins and various petroleum derivatives may, for example, be used.
The admixtures will be added in small proportions and must conform to the French standard NF P 18-103.
Depending on the season and/or the distance from the worksite to the place of manufacture, it will be possible, for example, to add superplasticizer-type rheology agents and antisedimentation agents to the mortar or concrete composition according to the invention.
The mortar or concrete compositions, so as to have a self-leveling character, may furthermore include one or more plasticizers, thinning agents, thickener and/or air entrainer.
This list is not exhaustive and the formulation of the mortar or concrete composition may be completed by adhesion promoters and antifoam agents.
In a preferred embodiment according to the invention, the mortar or concrete composition with a self-leveling character furthermore includes from 1 to 5% by weight of a thinning agent with respect to the weight of cement.
The mortar thus obtained may be pumped and spreads by itself. All that is required is to respect the levels to be attained and to carry out an outgassing operation. The building work thus constructed, such as a screed, presents the same ease of implementation as a self-leveling screed of the calcium-sulfate type, but with water insensitivity and the abili
Ceccaldi Jean-Dominique
Izoret Laurent
Marcantoni Paul
Oliff & Berridg,e PLC
Vicat
LandOfFree
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