CS276941B6 - A method for producing belite sulfoaluminate cement - Google Patents

Abstract

The production method relates to sulfoaluminate cement with controlled hydration. Its essence lies in the fact that sulfoaluminate clinker containing up to 3% by weight of anhydrite is ground separately. Anhydrite is ground separately, the fractions of which above 40 pm are mixed with sulfoaluminate clinker in an amount of 10 to 20% by weight

Description

/ Λ 1 CS 276941 B6 4

A method of producing belite sulfoaluminate cement

Technical field

The invention relates to a process for the production of belit sulphoaluminate cement with controlled hydration. State of the art

Hydration of Portland cement as the hitherto most thoroughly studied mortar (inorganic binder) is controlled by the fine grinding of the cement, the water coefficient, the hydration temperature, the content of impurities, which are the most common water-soluble polymers, or inorganic salts. In this way, the hydration and thus the formation of the binder stone structure and the development of its strength can also be controlled for other types of inorganic binders.

Cement itself is a composite material consisting of multiple mineralogical components. Cement production includes grinding cement with gypsum. Gypsum has the function of an internal solidification regulator. Troscortland cements are combined with blast furnace slag.

The granularity of the individual clinker minerals in the cement depends on their grindability (hardness) and the nature of the grinding equipment. The combined grinding of clinker and additives ensures good homogeneity of the resulting cement powder.

In addition to academic considerations, there has not been a serious incentive for a resolute synthesis of individual clinker minerals, their grinding and mixing into cements with adjustable granularity of individual minerals. There was also no incentive for separate grinding of gypsum and its additional admixture to ground clinker. Separate mletiesádrovca is possible, but not economic or practical. Gypsum is a light-weight mineral and accumulates in the fine fraction of the cement. The beneficial action of gypsum as a setting regulator depends on its high fineness. It is expected that the loss of homogeneity of the cement by additional admixture of more granularly suitable gypsum cannot be compensated for by the more favorable influence of hydration. For example, consider the gypsum content of cement (up to 50%) and the difficulty of additionally homogeneous dispersion of the particulate high-dispersion component in the high-dispersion system in which it is low. Too high fineness of the molar component on the other side of the coagulation effect in the preparation of the cement paste or mortar.

Different can be seen in the possibility of influencing the hydration of one of the mineralogical components of clinker with sulfoaluminate belite clinkers. These clinkers have a different mineralogical composition from the Portland clinker. They do not contain tricalcium silicate (C3S) and tricalciumaluminate (C3A) compounds. However, they contain tetra-calcium aluminate sulfate (C4A3S) and anhydrite (CS) compounds absent in Portland clinker.

The crystalline hydrate formed in the initial stage of hydration of the sulfoaluminate belite belite clinker (SAB), CS 276941 B6 2, is ettringite (Ca 2 Al 2 O 3 (SO 4) 3.32 H 2 O-C 3AS 3 H32). This may be different during the hydration period by different mechammarine - topomechanical, or by so-called solution through solution (homogeneous). In the first case, the primary product is excreted on the surface of the aluminate phase particles and the slower hydration is slowed. In this way, the gypsum and coarse regulator is used in the case of portlanine clinkers. Limiting the hydration of C3A - the mineral with the fastest hydration. However, such a mechanism of ettringite formation is undesirable for belite sulfoaluminate clinkers. In addition to retarding hydration, it also leads to expansion of the formed bodies and loss of mechanical strength. In the latter case, ettringite nucleates and precipitates in the liquid phase. There is no inhibition of hydration and the formation of a colloidal product layer on the surface of the aluminate phase solids by the expansion behavior of the materials.

So far, there are only limited possibilities of influencing the mechanics of ettringite formation and thus the control of the hydration process. free CaO content).

SUMMARY OF THE INVENTION

The principle of the process for the production of a controlled hydration of belite sulfoaluminate cement from a sulfoaluminate clinker with a low anhydrite content consists in the grinding of a sulfoaluminate clinker containing up to 3% by weight. anhydrite as clinker to a conventional surface area. Separately, anhydrite is milled, and fractions of less than 40 µm are removed and the fraction above 40 µm is mixed with ground sulfoaluminate clinker in an amount of 10 to 20% by weight.

The method of producing belite sulfoaluminate cement underlay invention is influenced by the ettringite formation mechanism without changing the chemical and phase composition of the system as a whole.

In contrast to the synthesis of belite clinker with the desired content of anhydrite (which can be as high as 20 to 30% by weight) and only synthesize clinker with a "threshold" content of anhydride (at 2 to 3% by weight). This threshold of andydrite practice (e.g. X-ray) can be checked to confirm the quality mineralogical composition of the clinker, and the required content of the clinker is additionally admixed to the clinker to be treated, or dosed in the preparation of the cement slurry.

In the presence of fine anhydrite in the hydrating system, such as in conventional clinker grinding, the liquid phase is rapidly saturated with SO 2 - 2, ettringite precipitation at the surface aluminate phases and hydration retardation. In the case of an anhydride with less fineness, which is the case for personal adjustment of its grain size, the saturation of the liquid phase is slower and the ettrinite precipitates in its volume.

Claims (1)

PATENT CLAIMS Process for the production of belite sulfoaluminate cement with controlled hydration from low anhydrite sulfoaluminate clinker, characterized in that sulfoaluminate clinker containing up to 3% by weight of anhydrite as a clinker mineral is ground to a common specific surface and the anhydrite is separately removed from it. fraction smaller than 40 [mu] m and subsequently the fraction above 40 [mu] m is mixed with ground sulfoaluminate clinker in an amount of 10 to 20% by weight. End of document