RU2100304C1 - Raw mixture for extra strength and heavy concrete making - Google Patents

Abstract

FIELD: building industry. SUBSTANCE: raw mixture for making heavy concrete (class B80-B105) has cement (sort is M500, not below), large and small filling agents made of preliminary treated scale, water and superplasticizer based on Na-salts of condensation product of naphthalene sulfoacid with formaldehyde. Component consumption, kg/$$$ concrete: cement (sort - M500, not below) 610-650; large filling agent from the above indicated scale: fraction 10-20 mm 800-1000; fraction 5-10 mm 900-1200; small filling agent from the same scale: fraction 1.25-5 mm 400-500; fraction 0.63-1.25 mm 400-500; fraction 0.16-0.63 mm 500-650; water 165-180, and superplasticizer 0.5-1% of cement consumption. In alternative variant scale treated in ball mill for 20-40 s and enriched by removal of fractions below 0.31 mm is used. EFFECT: increased strength and density of concrete. 2 cl, 4 tbl

Description

 The invention relates to building materials, in particular to a raw material mixture for the preparation of extra strong and heavy concrete, mainly for a container for transporting or storing spent nuclear fuel (SNF).

 Known containers for the transportation and storage of spent nuclear fuel, the manufacturing method of which includes concreting the tank in the form of a glass (German patent N 3331892, class G 21 F 5/02, 1986, GDR patent N 235353, class G 21 F 5/00, 1986) .

In accordance with radiation safety standards and the requirements of the IAEA, such containers should provide high protective properties in emergency situations that are possible during the transportation and storage of spent nuclear fuel. For example, presented by the IAEA regulatory documents include the provision of:
radiation safety of personnel during transportation and storage of the container;
tightness in case of emergency fall from a height of 9 m and onto a rigid base or onto a pin with a diameter of 150 mm from a height of 1 m;
resistance to shock waves with a front pressure of 30 kPa;
safety when falling onto a container of an airplane weighing 20 tons at an airplane speed of 200 m / s;
resistance to thermal effects in case of fire at 800 ^o C for 30 minutes and when immersed in water to a depth of 15 m for 8 hours;
long-term operation at negative temperatures up to minus 40 ^o C.

 At the same time, it is advisable to have a container of relatively low mass and relatively large net volume. The mass of the container should not exceed the carrying capacity of the vehicles used.

 The listed requirements for the container force designers to seek and apply materials with very high mechanical, physical and protective properties.

Known heavy concrete for the manufacture of a container for transportation and storage of a radioactive substance, containing in 1 m ³ from 280 to 370 kg of cement, from 2800 to 3400 kg of filler; the water content is determined by the ratio of water to cement in the range of 0.40-0.60. From 650 to 800 kg of barite and from 2200 to 2400 kg of hematite are used as filler. Heavy concrete has a compressive strength of 40 to 60 MPa in 28 days, the density of the concrete mixture is up to 3800 kg / m ³ , and concrete in the dry state is 3500 kg / m ³ (EPO, 0264321, class C 04 B 20/00, 1988).

The disadvantages of this heavy concrete are:
low strength of concrete due to insufficient strength of barite aggregate and high water-cement ratio of concrete mix; the presence of barite aggregate in concrete with low resistance to fire and low frost resistance;
very high cost of aggregate.

 Closest to the proposed one is the raw material mixture for the manufacture of heavy concrete of class B 20 on the mill scale, intended for protective shields from radioactive radiation.

The composition of the raw mix is as follows, kg per m ^{3 of} concrete:
Coarse aggregate of scale 5-10 mm 1858
Fine aggregate of scale 0-5 mm 1380
Cement activity 48 MPa 401
Water 248
The density of the raw material (concrete) mixture is ρ 3.887 kg / m ³ , the density of concrete at 28 days of natural hardening r is 3820 kg / m ³ , the mobility of the mixture is 14 cm of precipitation of a standard cone, the strength at 28 days of age is 23.2 MPa (Construction of nuclear power plants / Under the direction of V. B. Dubrovsky, M. Energoatomizdat, 1987, p. 122, table 5.7).

The specified solution has the following disadvantages:
low concrete strength, which does not allow to create a container that meets the IAEA in terms of strength and carrying capacity of standard railway platforms;
manifestation of concrete shrinkage in the hardening process, which follows the loss of mass by 67 kg for 28 days of hardening; such mass loss eliminates tight contact of concrete due to the high water-cement ratio (W / C 0.62).

The proposed invention is aimed at creating extra-strong (R _compress. 1000-1200 kgf / cm ² ) and heavy concrete (r 4000-4100 kg / m ³ ), as a structural and protective element of a metal-concrete container for transportation and storage of spent nuclear waste.

This problem is solved due to the fact that the raw material mixture includes cement of a grade not lower than M 500, coarse and fine aggregate from mill scale of machine firing (for example, blooms, slabs and other workpieces) of fractions 10-20 mm, 5-10 mm, 1.25 -5 mm, 0.63-1.25 mm, 0.16-0.63 mm, water at the following component consumption per 1 m ^{3 of} concrete, kg:
Cement grade not lower than 500 610-650
Scale fractions 10-20 mm 800-1000
Scale fraction 5-10 mm 900-1100
Scale fraction 1.25-5 mm 350-450
Scale fraction 0.63-1.25 mm 400-500
Scale fraction 0.16-0.63 mm 500-650
Water 165-180
In addition, the raw material mixture additionally contains a Na-based superplasticizer of the condensation product of naphthalene sulfonic acid with formaldehyde in an amount of 0.5-1% by weight of cement.

The scale of machine fire stripping is preliminarily processed before being used in a ball mill for 20-40 seconds, then grains from 0 to 0.16 mm in size are removed from the treated mixture, and the remaining dross mass is dispersed into the fractions listed above. In the process of processing scale in a ball mill, weak inclusions and contacts of large grains, as well as impurities, are destroyed. During sieving, weak grains are removed along with grains of 0-0.16 mm. The total mass of aggregates is 3150-3300 kg / m ³ ; water-cement ratio is in the range of 0.27-0.30; the mobility of the concrete mix 8-14 cm precipitation cone.

The proposed technical solution allows you to:
several times increase the strength of concrete, achieve a very high density, ensure tight contact and reliable joint work of the metal structure and concrete of the container due to the formation of non-shrink concrete;
guarantee high uniformity of concrete in strength and density along the height of the container due to the increased density of the mortar part of the raw concrete mix;
create a container that meets the IAEA requirements for strength and degree of protection against radiation and the corresponding load capacity of standard railway platforms.

 Studies on the selection of compositions of extra-strong and heavy concrete were carried out by a multivariate experiment with varying ratios of components and their characteristics indicated in the claims.

 In the table. Figure 1 shows examples of compositions of extra-strong and heavy concrete based on enriched scale and cement M 500, their main mechanical and physical properties and technological parameters of the concrete mix depending on the ratio and properties of the components.

 The strength of concrete was determined by testing standard samples (GOST 10178 Concrete. Methods for determining compressive and tensile strength, mobility of concrete mixtures were determined in accordance with GOST 10181.1 Concrete mixtures. Methods for determining workability, concrete density in accordance with the requirements of GOST 12730.1 Concrete. Methods for determining density. Table C -3 - a superplasticizer based on a salt of the condensation product of naphthalenesulfonic acid with formaldehyde, TU 6-36-0204229-625-90; W / C - water-cement ratio).

A very high concrete strength was achieved through the use of the most durable of the varieties of dross of the scale of machine fire stripping (MOH) of blooms, slabs and other billets, a low water-cement ratio of the concrete mixture, and an optimal selection of the mass ratio of aggregates in concrete. From the variety of aggregates recommended for biological protection against ionizing radiation of radioactive substances, equipment, contaminated products, etc. dross (metallurgical waste) having a high true density (r _and 4.8-5.6) and strength was selected, and the latter was selected from the types of dross-sheet rolling production, crimping production, continuous casting of steel, and machine fire stripping (MOZ). Dross of MOH is the most durable, has a higher and stable density (ρ _and 5.3-5.6), contains grains with a grain size of 0.14 to 20 mm. It can be divided into fractions and make up the most dense mixture. In addition, the grain scale of the Ministry of Health is closer to the cubic form.

As aggregates for extra strong and heavy concrete, all types of scale were investigated, including the most complete scale used in the prototype. The scale of sheet-metal production used in the prototype is a plate of various sizes, less dense and stronger than the scale of MOZ (density less than 0.2-0.5 g / cm ³ ), mainly fine-grained. Using the innovations adopted in the present invention, it was possible to obtain concrete with a strength of 63 to 73 MPa, which is 30-60 MPa lower than the concrete strength at the MOH scale (see Table 2).

 The invention is fundamentally new is the use of enriched aggregate obtained by removing weak rocks and impurities in the scale and fragile contacts in large grains. This is achieved by partial grinding (processing) of the initial scale in a standard ball mill for 20-40 s, followed by removal of grains of 0-0.3 mm and sieving the remaining mass into standard fractions. The criterion for improving the properties of scale after partial grinding is to increase the true density of the corresponding fraction of the scale before and after partial grinding and to reduce the content of elutriated particles in it.

 The results of the processing of scale in a ball mill, are presented in table. 3, convincingly show an improvement in its properties as a filler: density increases, pollution decreases. In the table. 4 shows the results of the selection of concrete compositions on untreated scale. Comparing them with the properties of concrete obtained on processed scale (Table 1), it is clear that the proposed innovation in the mechanical processing of scale allows one to obtain more durable and dense concrete.

 The technical efficiency of the proposed extra-strong and heavy concrete as a structural and protective material for a metal-concrete container compared to the prototype is that the use of the proposed concrete allows you to create a container that meets the IAEA requirements for strength and protective properties and transportation conditions by standard means.

Claims (2)

1. The raw material mixture for the preparation of particularly strong and heavy concrete, including cement, coarse and fine aggregates from scale and water, characterized in that it contains cement grade not lower than M 500, coarse and fine aggregate fractions 10 20 mm, 5 10 mm, 1.25 5 mm, 0.63 1.25 mm, 0.16 0.63 mm from the scale of the machine firing stripping at the following component consumption, kg per m ^{3 of} concrete:
Cement grade not lower than M 500 610 650
Coarse aggregate from the mentioned scale fraction 10 20 mm 800 1000
fractions 5 10 mm 900 1200
Fine aggregate from the aforementioned mill scale 1.25 5 mm 400 500
fractions 0.63 1.25 mm 400 500
fractions 0.16 0.63 mm 500 650
Water 165 180
in addition, the feed mixture further comprises a superplasticizer based on Na-salts of the condensation product of naphthalenesulfonic acid with formaldehyde in an amount of 0.5 to 1% by weight of cement consumption. 2. The raw material mixture according to claim 1, characterized in that it contains coarse and fine aggregates of scale processed in a ball mill for 20
40 s and enriched by removing fractions smaller than 0.16 mm containing weak inclusions and impurities.

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