RU2120926C1 - Raw mix for manufacturing non-autoclave cellular concrete of natural hardening, and method of manufacturing products from cellular concrete - Google Patents

Abstract

FIELD: building materials industry. SUBSTANCE: claimed mix comprises, wt. pts: cement, 1; sodium or calcium chloride, 0.008-0.01; nitrosilica, 0.04-0.1; plasticizer C-3, 0.002-0.01; gas producer, 0.0016-0.002; water, 0.3-0.4. Mix comprises 0.05-0.1 wt.pt of unslaked lime or gypsum of the weight of cement. Method of preparing building structures from non-autoclave cellular concrete by molding said structures naturally from highly viscous mixes and subsequently hardening them. The claimed method comprises using raw mixes according to any of claims 1-4. EFFECT: greater strength and accelerated hardening of cellular concrete and reduced density, shrinkage and lower energy consumption and cost. 7 cl

Description

 The invention relates to building materials and technology and relates to a raw material mixture for the manufacture of non-autoclaved cellular concrete and a method for manufacturing products from it.

 Known raw mix for the manufacture of cellular concrete containing Portland cement, lime, aluminum powder, calcium chloride and water (ed. St. USSR N 1491857, class C 04 B 38/02. Published in BI in 1989).

 A known method of manufacturing building products from non-autoclaved aerated concrete by forming them from highly viscous vibrated mixtures (ed. St. USSR N 365339, M. cl. C 04 B 15/02 B 28 B 1/08. Published in B. I. in 1973 )

 The known raw material mixture for the manufacture of non-autoclaved aerated concrete has a molten consistency and contains a large amount of water - 56 ... 84% by weight of cement, which does not allow to achieve high strength non-autoclaved aerated concrete with a decrease in density, lengthens the acquisition time of tempering strength and transportability of molded products during natural hardening, despite the presence of an increased amount of hardening accelerator - sodium chloride in an amount of 2 ... 3.6% by weight of cement. Corrosion of the reinforcement and the possibility of efflorescence on the products in this case become inevitable, which limits the use of the known mixture. In addition, cast mixtures give greater shrinkage (more than 3 mm / m) when hardening non-autoclaved aerated concrete, especially in vivo.

A known method of manufacturing products from non-autoclaved aerated concrete provides for the acceleration of hardening using highly viscous vibrated mixtures and heat treatment of molded products at a temperature of 80 ... 100 ^o C for 5 ... 8 hours. However, with known compositions of raw mixes, this method does not allow to accelerate hardening non-autoclaved aerated concrete in the early stages without heat treatment and significantly increase its strength, reduce shrinkage and process humidity.

 The objective of the invention is to increase the strength and accelerate the hardening of non-autoclaved aerated concrete natural hardening while reducing density, shrinkage, energy consumption and cost.

 The solution to the problem is achieved by the fact that the raw material mixture for the manufacture of non-autoclaved cellular concrete of natural hardening contains the following components in wt. parts in relation to cement: cement - 1; sodium chloride or calcium - 0.005 ... 0.01; silica fume - 0.04 ... 0.1; superplasticizer C-3 - 0.002 ... 0.01; gas blowing agent - 0.0016 ... 0.002; water - 0.3 ... 0.4. In this case, Portland cement or non-shrink Portland cement or tensile cement is used as cement. In addition, the mixture may contain quicklime - 0.05 ... 0.1 parts and / or gypsum - 0.05 ... 0.1 parts by weight of cement. Silica fume and C-3 superplasticizer can be used as a finished product - concrete modifier MB-01. As a blowing agent, aluminum metal powders and ferrosilicon are used.

 In the method of manufacturing building products from non-autoclaved aerated concrete by forming them from highly viscous vibrated mixtures followed by natural hardening, the above raw mixes are used. In the method of manufacturing building products after natural hardening, they are cut into building elements of the required size.

 Silica fume introduced into the raw material mixture interacts physically and chemically with lime released during the hydrolysis of alite and belite in cement, as well as with lime added to the raw material mixture, forming an additional amount of high-strength low-basic calcium hydrosilicates, strengthening the structure of cement stone and cellular concrete in general.

The introduction of an additional quantity of lime and gypsum into the raw mix is based on the calculation of the maximum binding of cement aluminates and aluminoferrites of calcium to ettringite and its stabilization over time. To prevent the breakdown of ettringite at an early stage of hardening of non-autoclaved aerated concrete, the ambient temperature should not be higher than 60 ^o C. The resulting ettringite causes expansion of the forming cement stone, compensating for shrinkage.

Condensed silica fume is obtained by selection from bag or electric filters of gas treatment systems for furnaces smelting silicon-containing alloys, in particular ferrosilicon. The main component of silica fume is silica of amorphous modification, the content of which reaches 85 percent or more. In small quantities, condensed silica fume contains oxides of alkali, Na ₂ O and K ₂ O (not more than 2%), calcium oxide, CaO (not more than 3%) and sulfur dioxide, SO ₂ (not more than 0.6%). Condensed silica fume for use in mortars and concrete was developed and agreed with the Moscow City Center of the State Sanitary and Epidemiological Surveillance TU 5743-048-02495332-96. There is also a Hygienic certificate N 19. MC. 03.225.T.05691.36 dated 03/07/96. The C-3 superplasticizer meets the requirements of TU 6-36-0204229-625.

The concrete modifier MB-01 meets the requirements of the technical conditions for its production and use in construction, TU 5743-049-02495332-96, also agreed with the Moscow City Center for State Sanitary and Epidemiological Surveillance. Hygienic certificate N 19. MC. 03.225.T. 16925.16 from 06/13/96. The MB-01 modifier is produced in four grades: MB-8-01, MB-10-01, MB-12-01 and MB-14-01. The numbers in parentheses indicate the content of the C-3 superplasticizer in the modifier as a percentage based on dry matter. The complex nature of the concrete modifier MB-01 greatly simplifies the technology. There is no need for additional lines for separate acceptance, storage, transportation, preparation and dosage of silica fume and superplasticizer. The acceptance, storage, transportation and dosing of the MB-01 modifier is carried out according to a scheme similar to cement. The concrete modifier MB-01 has an increased bulk density (700 ... 800 kg / m ³ ) compared with conventional silica fume (150 ... 500 kg / m ³ depending on the compaction); does not hang, unlike the latter in silos and bins and has a high fluidity, facilitating its transportation and dosing.

 Superplasticizer C-3, along with a lower temperature of the mixture and vibration, can further reduce the amount of mixing water without reducing the mobility of the mixture, which together provides a significant increase in the strength of non-autoclaved cellular concrete and an improvement in all its other properties.

 As a binder, non-shrink Portland cement of grades ПЦ 400, 500 БУ is used, which meets the requirements of TU 212613-90, straining cement of grades НЦ-2 (4) and Portland cement of grades ПЦ 400, 500 ДО. In the latter case, as indicated above, an additional amount of lime and gypsum must be added to the raw mix. Their introduction, along with sodium chloride or calcium, allows you to: increase the temperature and pH of the raw mixture, closed with unheated water; accelerate its expansion and hardening; stimulate the formation of an increased amount of needle ettringite, providing accelerated hardening of aerated concrete and reduce shrinkage.

 The use of highly viscous vibrating mixtures, characterized by accelerated hardening, allows a 2 ... 3.5 times reduction in the amount of hardening accelerator introduced - sodium chloride compared to its amount in the known raw material mixture, which eliminates the possibility of corrosion of the reinforcement and the appearance of efflorescence.

The raw material mixture for the manufacture of cellular concrete is prepared by mixing the components in the following sequence when they are introduced into the gas concrete mixer: water, sodium chloride or calcium, cement, lime, gypsum, silica fume, superplasticizer, or concrete modifier MB-01, gasifier. The water-solid ratio in the raw mix is 0.3 ... 0.4 with an average density of aerated concrete of 500 ... 400 kg / m ³ ; mixing water temperature 20 ± 5 ^o C. Mixing time of mixture components in high-speed mixers 3.. .5 minutes before the introduction of the blowing agent and 1.5 ... 2 minutes with the blowing agent after its introduction. The swelling of the mixture is carried out with vibration for 8 ... 12 minutes After the expansion has completed, the molded products and arrays harden under natural conditions in a humid environment in insulated chambers at a temperature not exceeding 60 ^o C, which is maintained in the chamber and products for 10 ... 12 hours only due to the heat of hydration of cement, lime and gypsum with limited heat loss due to the low thermal conductivity of aerated concrete of reduced density and increased thermal protection of the chamber. After such hardening, cellular concrete from the proposed compositions of the raw mix acquires 50 ... 70% of the design strength.

 The proposed raw mix and method of manufacturing building products from non-autoclaved aerated concrete based on it allow you to: increase strength to the level of the best samples of autoclaved aerated concrete of domestic and foreign production; reduce the average density, minimize and even eliminate moisture and carbonization shrinkage and significantly improve performance due to a sharp decrease in capillary porosity. Comparative data on the known and proposed raw mixes for the manufacture of cellular concrete and its properties are given in the table.

 A significant advantage of non-autoclave aerated concrete made by the proposed method from a raw mixture is the reduced energy and metal consumption of its production due to the complete elimination of traditional (heating) heat and moisture treatment (autoclave, steaming, electric heating, irradiation and other types); the absence of sand and associated equipment conversions and energy costs for these conversions and reduction of production space. This provides, along with the specific composition of the mixture, a reduction in energy consumption and the cost of non-autoclaved cellular concrete by 1.5 ... 2 times compared with autoclaved and the prospect of expanding its production and use in construction.

Claims (5)

1. The raw material mixture for the manufacture of non-autoclaved cellular concrete of natural hardening, containing cement, a blowing agent and water, characterized in that the cement as a raw material mixture contains Portland cement, or non-shrink Portland cement, or tensile cement and additionally silica fume, superplasticizer C-3 and sodium chloride or calcium in the ratio of these components wt. hours in relation to cement:
Cement - 1
Sodium chloride or calcium - 0.005 - 0.01
Silica fume - 0.04 - 0.1
Superplasticizer S-3 - 0.002 - 0.01
Gas blower - 0.0016 - 0.002
Water - 0.3 - 0.4
2. The mixture according to p. 1, characterized in that it additionally contains quicklime 0.05 - 0.1 hours and / or gypsum - 0.05-0.1 parts by weight of cement.  3. The mixture according to p. 1, characterized in that it contains silica fume and superplasticizer C-3 in the form of a finished product - concrete modifier MB-01.  4. The mixture according to claim 1, characterized in that it contains aluminum metal powders or ferrosilicon as a blowing agent.  5. A method of manufacturing building products from non-autoclaved aerated concrete by molding them from highly viscous vibrated mixtures followed by natural hardening, characterized in that for the production of aerated concrete using raw mixes according to any one of paragraphs. 1-4.  6. The method according to p. 5, characterized in that after natural hardening is carried out cutting products into building elements of the required size.

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