RU2272013C1 - Concrete mix - Google Patents

Abstract

FIELD: manufacture of building materials.

SUBSTANCE: object of invention are special refractory concretes based on Portland cement and slag aggregates, which concretes can be used in manufacture of heat assemblies operated under prolonged high-temperature and sharp temperature gradient conditions. Concrete mix contains 16-22% Portland cement, 10-20% alumina hydrate in the form of production waste, 28-36% sand slag-pumice fraction up to 5-20 mm, broken slag fraction 5-20 mm, 0.5-1.5% super-plasticizer S-3, and water, said alumina hydrate being waste coming from synthetic rubber production or from radio component plant, namely from manufacture of electrolytic condensers in the form of aluminum foil etching waste.

EFFECT: increased density due to filled hollows in porous aggregate with alumina hydrate or reaction product thereof with lime releasing on hydration of clinker minerals, increased residual strength after firing at 800°C, and increased heat resistance.

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Description

The invention relates to heat-resistant concrete on Portland cement and slag aggregates and can be used for the manufacture of thermal objects operating under conditions of prolonged exposure to high temperatures and sudden changes in these temperatures.

At present, heat-resistant concrete is used on different types of aggregates and additives, which, under the conditions of sharp temperature changes, crack and quickly fail, which requires a complete replacement of concrete insulation. Known shotcrete mass [1], including in wt.%: Portland cement - 27 ... 35, slag pumice aggregate FR <5 mm - 45 ... 64, chrysotile asbestos - 3 ... 10, the etching waste of aluminum foil - 3 ... 10.

The disadvantages of this mass are: increased shrinkage during hardening due to the use of fine-grained aggregates and increased energy consumption for fine grinding, as well as reduced residual strength after firing at 800 ° C: 41 ... 46% and reduced heat resistance at 800 ° C: 8 .. .10 water heat exchangers.

The concrete mixture closest in technical essence is also known [2], including, wt.%: Portland cement - 14 ... 22, slag sand - 14 ... 25, crushed stone from cast slag - 32 ... 45, andesite powder - 7 ... 14, production waste of synthetic rubbers based on alumina hydrate - 1 ... 10, superplasticizer C-3 based on sodium salt - the condensation product of naphthalenesulfonic acid and formaldehyde - 0.1 ... 0.25, water - 7, 9 ... 10.75. The disadvantages of this mixture are also reduced residual strength and heat resistance due to the use of fillers heterogeneous in chemical and mineralogical nature (andesite and synthetic rubber production waste) and aggregates (slag pumice sand containing at least 50% glass phase and cast slag crushed stone containing not more than 10% glass phases, i.e., almost completely crystallized). In addition, cast slag crushed stone contains inclusions of magnesium compounds, causing cracking of this aggregate and heat-resistant concrete based on it even at temperatures of 400 ... 600 ° C.

The essence of the invention lies in the fact that sand and gravel from slag pumice, the same in chemical and mineralogical composition and glass phase content, are introduced into the composition of the concrete mixture as fine and coarse aggregates. Alumina hydrate is introduced as a filler from the etching waste of foil or synthetic rubbers, which increases the thermal properties of concrete, and at the same time as a plasticizer, C-3 superplasticizer is used with the following optimal ratio of components, wt.%:

Portland cement 16 ... 22 alumina hydrate 10 ... 20 sand slag pumice fr. up to 5 mm 28 ... 36 crushed stone slag pumice fr. 5 ... 20 mm 15 ... 29 superplasticizer C-3 0.5 ... 1.5 water rest

Slag pumice aggregates have a chemical and mineralogical composition close to Portland cement, and due to the sharp cooling of the slag melt during the hydro-screen method for the production of slag pumice, they do not have time to crystallize and remain more than 50% in a more active, amorphous glass phase. Magnesium silicates do not have time to crystallize in them, contributing to a decrease in the heat resistance of aggregates at sharp temperature changes in the service of heat-resistant concrete in thermal units. The increased content of amorphous alumina hydrate increases the refractoriness of refractory concrete on Portland cement, since, being in an active amorphous state, it binds calcium hydroxide released during the hydration of clinker minerals of Portland cement into insoluble calcium hydroaluminates (CaO · Al ₂ O ₃ · nH ₂ O), crystals which in the form of neoplasms clog pores in a cement stone, increasing its density, strength and heat resistance. Alumina hydrate mixes easily with cement paste when mixing concrete with water and, being finely dispersed, is evenly distributed on aggregate and binder grains. Therefore, this filler does not require additional energy consumption for grinding and dehydration and increases the indicated properties of heat-resistant concrete on Portland cement and slag aggregates. Alumina hydrate can be introduced both as synthetic rubber production waste and as aluminum foil pickling waste. The chemical rubber production waste by chemical composition includes up to 80% Al ₂ O ₃ , up to 10% CaO and pp - the rest. The aluminum foil etching waste is obtained in the production of electrolytic capacitors of radio component factories and, in terms of chemical composition, includes, in wt.%: Al ₂ O ₃ - 87.3; Na ₂ O - 6.75; CaO - 1.05; SiO ₂ 0.4; p.p.p. - 4.5.

The proposed compositions of heat-resistant concrete based on these components are summarized in table 1.

Table 1.
Compositions of heat-resistant concrete with filler from alumina hydrate. Name of materials Consumption of materials in the compositions Proposed Famous one 2 3 four 5 prototype analog Portland cement 16 19 22 fifteen 23 thirty 17 Sand slag pumice fr. 0 ... 5 mm 36 28 thirty 27 37 52 eighteen Crushed stone slag pumice fr. 5 ... 20 mm 25 28 fifteen 31 fourteen - - Synthetic rubber production waste (aluminum foil etching waste) 10 fifteen twenty 8 22 6 6 Superplasticizer S-3 0.5 1,0 1,5 0.4 1,6 - 0.18 Cast slag crushed stone - - - - - - 36 Water 8.5 9.0 11.5 8.6 12,4 12 8.82 Andesite powder - - - - - - 8 Asbestos chrysotile - - - - - - 6

Compositions 1 ... 3 were made according to the application, including the extreme values of the intervals of variation of the components of the concrete mix. Compositions 4 and 5 were investigated at costs exceeding the declared intervals, and for comparison, under the same conditions, averaged compositions of known concrete mixtures were manufactured and tested by analogy and prototype.

For the manufacture of concrete samples, the actual average density of the freshly compacted concrete mixture was previously determined. Then, the percentage of each component from table 1 was calculated from it and its consumption was found in kilograms per 1 m ^{3 of} concrete mixture, and then on the volume of the batch, which ensures the production of the required number of samples. Samples were made according to GOST 10180-90 to determine the compressive strength of concrete at the design age of hardening and residual strength in accordance with the requirements of GOST 20910-90. To determine the heat resistance from a concrete mixture of the same composition, the samples were made in the form of cubes of 7.07 × 7.07 × 7.07 mm, in accordance with the requirements of the above normative document for heat-resistant concrete. The hardening of the samples was also carried out in accordance with the requirements of the specified GOST (Appendix 2).

After calculating each composition, the components were weighed in weight and the concrete mixture was prepared in the following sequence: first, Portland cement and filler were mixed to homogeneity, then the mixture was mixed with water and C-3 plasticizer previously dissolved in it, and sand and crushed stone were introduced into them uniformly. by thoroughly mixing the mixture after the introduction of each component.

Compaction of the samples was carried out by vibration on a standard vibration platform for 2 ... 3 min until a cohesive state was reached and cement milk appeared on the surface of the samples. For low-cement compositions, a load was used. To determine each property, 3 ... 6 samples of each composition were prepared (6 pcs. For determining the strength characteristics and 3 pcs. For heat resistance). The hardening of the samples was carried out by steaming according to the mode 3 + 6 + 3 hours at a maximum temperature of 100 ... 110 ° C, followed by drying in an oven. After that, they were tested to determine the physical and mechanical properties.

The results of these tests are summarized in table 2.

Table 2.
Properties of heat-resistant concrete filled with alumina hydrate. Name of properties The values of the properties in the compositions Known (averaged) one 2 3 four 5 prototype analog The average density, kg / m ³ : - after drying 1900 2010 2060 1840 1960 1810 1780 - after firing at 800 ° C 1860 1940 1960 1780 1840 1680 1700 Compressive Strength, MPa: - after drying 29.5 34.8 37,4 27.1 30,4 27.5 23.6 - after firing at 800 ° C 14.75 19.8 24.7 12.5 14.6 10.0 9.9 Residual strength,%, after firing at 800 ° C fifty 57 66 46 48 36 42 Heat resistance at 800 ° С, number of water heat exchangers 12 fifteen 21 9 10 5 7

From this table it can be seen that the proposed compositions have a significantly higher density both after drying and after firing at a temperature of 800 ° C, which is explained by the filling of voids in concrete with alumina hydrate and the products of its interaction with lime released during hydration of clinker minerals, as well as available as a part of slag aggregates.

Significantly higher in the proposed compositions in comparison with known under the same conditions of manufacture and hardening, compressive strength both after drying and after firing. Moreover, the residual strength after firing at 800 ° C is much higher for the proposed compositions due to the increased content of alumina hydrate, and the heat resistance is 2 ... 3 times higher than that of the known compositions.

For compositions 4 and 5, containing prohibitive amounts of the main components, these indicators are reduced, which indicates the optimality of the declared limits of the content of the components of the concrete mixture.

References:

1. Auth. testimonial. No. 966068, publ. 10/15/1982.

2. Auth. testimonial. No. 1502517, publ. 08/23/1989.

Claims (1)

Concrete mixture, including Portland cement, filler - alumina hydrate in the form of production waste, sand slag pumice fractions up to 5 mm, crushed stone slag fractions 5-20 mm, superplasticizer C-3 and water, characterized in that it contains alumina hydrate in the form of synthetic production waste rubbers or electrolytic capacitors of the radio parts plant - waste etching of aluminum foil, as the specified crushed stone, it contains slag pumice crushed stone with the following optimal ratio of components, wt.%: Portland cement 16-22 Specified Alumina Hydrate 10-20 Indicated sand 28-36 Specified crushed stone 15 -29 S-3 0.5-1.5 Water Rest