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CONSTRUCTION MATERIALS. CONSTRUCTION COMPOSITIONS, MIXTURES AND COMPOSITIONS FOR MANUFACTURING BUILDING MATERIALS AND CONSTRUCTION OF CONSTRUCTION WORKS
INVENTION
Patent of the Russian Federation RU2285677

GYPSUM STRING

The name of the inventor: Gladus Maria Aleksandrovna (RU); Rzhanikova Alexandra Vladimirovna (RU); Ufimtsev Vladislav Mikhailovich (RU)
The name of the patent holder: State Educational Institution of Higher Professional Education "Ural State Technical University-UPI" (RU)
Address for correspondence: 620002, Yekaterinburg, ul. Mira, 19, SEI USTU-UPI, Intellectual Property Center
Date of commencement of the patent: 2005.04.08

The invention relates to compositions of waterproof gypsum binders containing active mineral additives including oxides of calcium, aluminum, silica. The technical result is an increase in the strength and water resistance of the binder, and a cheaper composition and utilization of a certain part of the solid emissions of heat power. In a gypsum binder based on calcium sulfate hemihydrate with a mineral additive in the form of high calcium ash and an organic additive, granular high calcium calcined ash from solid fuel combustion is used as the mineral admixture, not more than 5%, ground to a residue on a 008 sieve, and as organic - Plasticizer, with the following ratio of components, mass%: calcium sulfate hemihydrate - 73.9-90, plasticizer - 1.1-2.0, said high-calcium ash-residue - the rest.

DESCRIPTION OF THE INVENTION

The invention relates to compositions of composite gypsum binders characterized by high setting and curing speeds.

A gypsum composition is known comprising the following components, by weight : semi-aquatic gypsum or anhydrite 40-65, ground granulated slag of acidic composition 30-50, 5-8% Portland cement - so-called gypsum-cement cement binder (HSVC). Volzhensky AV, Burov Yu.S., Kolokolnikov BC Mineral binders. M., 1974, Stroizdat, p.464 / 1 / . This composition is characterized by a relatively slow hardening and has a relatively low strength, and the grinding of the acid granulated blast furnace slag is associated with increased energy consumption.

And the astringent is known based on calcium sulfate hemihydrate, mass%: shale (high calcium) fly ash 26.0-29.0, toluylene diisocyanate 0.2-1.05, calcium sulfate hemihydrate - the rest. A.S. USSR No. 1668330 A1, publ. 08/07/1991, 2 p . The binder can be used as a prototype. Compared to gypsum-cement cement, this binder does not require a special mill to produce, because the fly ash has a sufficiently high specific surface area. This astringent contains at least 69% calcium sulfate hemihydrate, which increases its cost. In addition, it has a relatively low water resistance.

The technical task to be solved in the invention is to increase the water resistance of the gypsum binder while simultaneously reducing the cost of the composition. This combination of properties can be obtained by eliminating the composition of toluene diisocyanate and incorporating into the mixture a mineral additive that is more effective than fly ash.

This technical problem is solved by using a semi-hydrated calcium sulfate binder with a mineral additive in the form of high-calcium ash and an organic additive as a mineral admixture of granulated high-calcium fly ash, ground to a residue on a 008 sieve of not more than 5%, and as an organic - plasticizer, with the following ratio of components, mass%:

Experimental testing of the claimed composition was made on the following materials: gypsum building G10A2 (GOST 125-79), fly ash of Berezovskaya GRES and toluene diisocyanate. All materials had the fineness of grinding in the range of 10-15% of the residue on a No. 008 sieve. Chemical composition of ash, wt.%: 27.8 SiO 2 ; 8.3 Al 2 O 3 ; 10.3 Fe 2 O 3 ; 39.2 CaO; 5.1 MgO; 4.2 SO.sub.3. As a plasticizing agent (plasticizer), superplasticizer C-3 was used.

In the course of the experiments, the original components of the mixture were thoroughly mixed and sealed with water. The mobility of the obtained test corresponded to a Suttard mobility index of 145-155 mm. Samples were produced from the dough-cylinders with a diameter and height of 28 mm, hardening of which occurred in air-moist conditions (in a desiccator, above the water surface). The water resistance of the formulations was evaluated by the softening factor, which was calculated as the ratio of the strength of the wet sample to the dry strength. The composition of the prototype contained an additive of toluene diisocyanate. In the other formulations this additive was eliminated.

Part of the high-calcium ash was subjected to granulation with 20% water addition. The ash pellets were obtained on a laboratory pellet granulator, dried and ground in a ball mill in the presence of a plasticiser additive.

GYPSUM STRING

From the materials of the table it follows:

- fly ash has relatively low astringent properties, which in the process of granulation on contact with water are reduced even more. Nevertheless, the replacement of fly ash with granular ash increases the strength of the combined binder. At the same time, there was no softening of the samples during their long storage, that is, for such compositions, there is no need for a pozzolanic additive. It follows that the high calcium ash in the composition with semi-aqueous calcium sulfate combines the functions performed by the combination of the clinker binding and the pusolanic additive in the composition of the GPC;

- in the case of a low content of granulated ash in the mixture, the composition has a shorter setting time, which complicates the technology of molding articles on such a binder;

- with a minimum ash content, the water resistance of the mixture is insufficient. In the case of increasing the proportion of ash to 26%, the rate of hardening and strength of the samples decreases. In this connection, it is not necessary to increase the amount of ash in the mixture by more than 25%;

- the introduction of a plasticizer lowers the water requirement of the composition, which is accompanied by an increase in strength and, at the same time, a shortening of the setting time. Use of a plasticizer additive of less than 1.1% is ineffective. An increase in its content in compositions with fly ash above 2.0% is not advisable, since the acceleration of setting the mixture with increasing the proportion of plasticizer in it above the specified limit makes its application more difficult. It follows that the plasticizer content interval of 1.1-2.0% for this composition is optimal.

The technical result obtained with the use of the invention consists in increasing the strength, water resistance of the gypsum binder, and its reduction in cost for both fly ash and ash granulated hammer. The noted improvement in construction and technical properties, in our opinion, is explained by a decrease in the alkaline index (pH) of the mixture on ash, in comparison with Portland cement. It is known that in gypsum binders this index is much lower than that of cement. This, according to many researchers, causes a certain incompatibility of gypsum and cement. Another confirmation of this assumption is the higher characteristics of the binder on the ground granulated ash in comparison with the astringent on fly ash. When granulating, during the process of moistening ash, some of the lime is bound to hydrate compounds, which reduces the pH-value with respect to the original ash. As a result, despite the decrease in the astringent potential of the ash constituent of the composition, the strength of the composition increases. In addition, the ground granulated ash has a particle size smaller than the original fly ash. In our experiments, the fineness of grinding of the ground granulated ash by the remainder on the 008 sieve was 5%, while at the initial value this value was 15%. It is known that attempts to grind the fly ash to a residue of less than 10% are accompanied by a significant increase in energy consumption for grinding due to the sticking of fly ash particles on grinding bodies and mill walls. When grinding dried ash granules, the cost of fine grinding of ash is significantly reduced because of the presence of hydrated free lime in the ash particles, which creates internal bursting stresses in the volume of the particle. As a result, the grinding efficiency is substantially increased. An additional increase in the strength of the binder based on granulated ash is probably due to the compacting effect on the stone structure of these small ash particles. The presence of the plasticizer in the mixture makes it possible to reduce the moisture content of the mixture, while simultaneously increasing its strength, but significantly shortening the setting time of the composition.

With the industrial use of the invention, it is possible to expect, in comparison with the prototype, for high calcium ash fly, the acceleration of hardening, increasing the strength and water resistance by 10-20%, and reducing the cost by 20-30%. For mixtures with the addition of ground granulated ash, we should expect an increase in strength and water resistance of 30-40% with a certain slowing of hardening in its initial stage. The estimated cost savings for the binder production should be 15-25%. An additional effect from the use of the invention consists in the utilization of a certain part of the solid emissions of the heat power industry, which is one of the most significant in terms of the negative impact on the natural environment.

CLAIM

A gypsum binder based on calcium sulfate hemihydrate with a mineral additive in the form of high calcium ash and an organic additive, characterized in that granular highly calcined fly ash from solid fuel combustion is used as a mineral additive, not more than 5%, ground to a residue on a 008 sieve, and As an organic - plasticizer, with the following ratio of components, mass%:

print version
Date of publication 15.12.2006гг