RU2461524C1 - Concrete mixture - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to compositions of concrete mixtures and can be used in production of construction materials to make masonry blocks, walkway slabs and other concrete articles. The concrete mixture contains wt % mixed binder, containing portland cement, finely dispersed filler - blast-furnace screenings of the 0.14 mm fraction, dust from electric filters of the ferroalloy industry, a plasticiser with basic naphthenic sulphonic acid, ordinary water and water modified by electric current with pH=2.1-2.5, with the following ratio of components in wt %: mixed binder: portland cement 11.86-12.15, blast-furnace screenings with a fraction smaller than 0.14 mm 2.4-3.34, dust from smelting ferrosilicon 0.8-1.28, plasticiser with basic naphthenic sulphonic acid 0.03-0.04, hardening water: ordinary 6.6-6.8, modified with pH=2.1-2.5…0.35-0.56, aggregate…76.82-76.97, water/binder ratio 0.45.

EFFECT: preventing cracks during hardening and high compression strength at the age of 28 days of normal hardening.

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Description

The invention relates to compositions of concrete mixtures and may find application in the production of building materials for the manufacture of wall stones, paving slabs and other concrete products.

The composition of the fine-grained concrete mixture (mortar) is known. This composition is given in ed. testimonial. USSR No. 637357 M.Cl ² . С04В 13/00, published on December 15, 1978, in the following ratio, wt.%:

cement 5.05-5.2 ferrosilicon fly ash 1.0-1.49 lime 2.03-2.1 sulphite-alcohol bard 0.0075-0.0078 iron ore dressing waste 74.5-76,

having the following fractional composition, wt.%:

0.63-1.0 mm 5-15 0.31-0.63 mm 15-25 0.14-0.31 mm 30-40 less than 0.14 mm 30-40 - water rest

The advantages of the mixture include:

1) waste from metallurgical industries is disposed of;

2) increases the corrosion resistance of fine-grained concrete (mortar), because dust from smelting ferrosilicon is an amorphous silica-containing active mineral additive.

Along with the advantages, there are also disadvantages:

1) low compressive strength at the age of 28 days - 3.6 MPa;

2) low adhesion of the mixture with steel reinforcement, as iron ore wastes in the mixture have the same electric charge as steel - positive (“+” charge).

The closest composition of the concrete mixture for quality and technical solution is given in ed. testimonial. USSR No. 1346617 С04В 28/08 (СВВ 28/08 // 22/08, 24/20), published on 10.23.1987, with the following ratio of components, wt.%:

Portland cement 1-5 fine electric smelting slag 20-25 complex supplement 1-3

in addition:

magnesium sulfate 40-60 naphthenic sulfonic acids 40-60 water 8-15 aggregate rest

The advantages of the mixture include the disposal of fine slag.

Along with the advantages, there are also disadvantages:

1) low crack resistance during hardening of concrete due to the high content of fine slag in the composition of the mixture (20-25%), plugging capillaries, through which moisture diffuses to the surface for evaporation;

2) low compressive strength at the age of 28 days - 9.2 MPa.

The objective of the invention is to improve quality by eliminating cracking during hardening and to increase the compressive strength at the age of 28 days of normal hardening with a water-binder (V / Vyazh) ratio in the range of 0.4-0.5, and also to reduce the cost of concrete mix.

The concrete mixture includes Portland cement, a finely divided filler — slag and dust of electrostatic precipitators of ferroalloy production, a plasticizer with a base of naphthenic sulfonic acid, water with an acidic additive and aggregate. As a dispersed filler, screening of blast-furnace slag of 0.14 mm fraction and dust of electrostatic precipitators from smelting of ferrosilicon are introduced. additives. Due to the partial replacement of ordinary mixing water, water modified with electric current with pH 2.1-2.5 is introduced.

The ratio of all components, wt.%:

Mixed binder:

Portland cement 11.86-12.15 screening of blast furnace slag, fractions less than 0.14 mm 2.4-3.34 dust from smelting ferrosilicon 0.8-1.28 plasticizer with naphthenic sulfonic acid base 0.03-0.04

Mixing Water:

ordinary 6.6-6.8 modified with pH 2.1-2.5 0.35-0.56 aggregate 76.82-76.97 water binder ratio (W / Elm) 0.45.

Characteristics of concrete mix components:

1. Portland cement, grade M400 “PTs-DO” (GOST 10178-85, GOST 30515-97) (OAO Mikhailovcement, Ryazan Region, Mikhailovsky District, Oktyabrsky Village).

2. Screening of blast furnace waste slag fraction less than 0.14 mm (departure from crushed main blast furnace slag (dump)). The latter is crushed to obtain crushed stone and sand for lightweight concrete. Everything that passes through a 0.14 mm sieve is waste. In the present invention, this waste is proposed to be disposed of as a filler of a mixed binder and, accordingly, additive of a concrete mixture.

The chemical composition of the slag screenings includes, wt.%: CaO = (39-47)%; MgO = (5-10)%); SiO ₂ = (38-45)%; Al ₂ O ₃ = (5-10)%; FeO - up to 1%; MnO - up to 1%; S - up to 1.7%; TiO ₂ - up to 0.5%.

The specific surface area is 0.16-0.18 m ² / g, the basicity modulus is 1.1-1.15.

3. Pulverized waste (MK-85) of ferroalloy production of Kuznetsk Ferroalloys OJSC. This dust from electrostatic precipitators produced by ferrosilicon has a particle size of 1-1 microns. Under the action of high temperature, silica microparticles turn into vitreous amorphous dust. The specific surface area of microparticles is 14000-30000 m ² / kg, which is 3-10 times higher than the specific surface area of cement. The bulk density in the compacted state is 0.8 t / m ³ .

Chemical composition, wt.%: SiO ₂ = (91-97)%; Al ₂ O ₃ = (1.0-1.4)%; Fe ₂ O ₃ = (0.2-0.4)%; CaO = (0.2-0.4)%.

In the proposed composition of the concrete mixture, dust is accepted as an active mineral additive, because silica fume particles are amorphous and more reactive in comparison with flask, tuff and tripoli, and also as an additional plasticizing additive.

4. The plasticizer of the mixture. Two types of superplasticizers were obtained in the experiments, obtained by dissolving naphthalene in sulfuric acid with the addition of polymer resins and which are analogous to the C-3 superplasticizer. Those. Polyplast SP-1 and Relamix type 2 GOST 24211-2008 manufactured by Polyplast LLC, Novomoskovsk were adopted. Additives have a slightly alkaline medium pH 9 ± 1. Apply as a liquid or powder. The basis of the composition is naphthenic sulfonic acid in the form of a salt of Na ₂ SO ₃ and radicals - CH ₂ . In the invention adopted in combination with dust, silica fume in the role of plasticizer and neutralizer of the remaining acidic medium after mixing, because has an alkaline environment.

5. Modified by electric current ("dead") water with a pH in the range of 2.1-3. This type of water was obtained by electrolysis of spring water with an initial pH of 6.9. The electrolysis was carried out using the device "Zhivitsa" for 10 minutes. The device by electric current destroys water molecules into H ⁺ ions, i.e. "Dead" water with a pH of 2.1-3, and "living" enriched with OH ^- ions. In the experiments, water with a pH of 2.1-3 was used, i.e. "Dead" - sour.

6. Placeholders:

- small, i.e. quartz sand - Grade 1 meets the requirements of GOST 8736-93 (Atlantida LLC, Serpukhov.) The size module is 2.25.

- large - granite crushed stone of a fraction from 5 to 20 mm meets the requirements of GOST 8267-93 (Pavlovskgranit OJSC, Voronezh Region). Gravel of crushed stone according to crushing 1400.

7. Water for mixing corresponds to the technical conditions of GOST 23732-79.

Table 1 The compositions of the proposed concrete mixtures No. 2, No. 3, No. 4; compositions No. 1 and No. 5 - beyond, No. 6 - the composition of the known prototype Components
binder The number of mixtures and the content of components, mass% one 2 3 four 5 6 (prototype) 1. Portland cement M400 “PC-D0” 11.5 11.86 12.0 12.15 12,2 5,0 2. Filler:
- electric steelmaking slag
- pulverized waste ferroalloy production
- screening of blast furnace slag fr. less than 0.14 mm ---- ---- ---- ---- ---- 25.0 0.7 0.8 1,04 1.28 1,5 2.5 3.34 2.87 2,4 2,4 3. Plasticizer:
- magnesium sulfate
- naphthenic sulfonic acid ---- ---- ---- ---- ---- 1,5 0.01 0,03 0,035 0.04 0,045 1,5 4. Water
- usual pH 6.9
- modified: with a pH of 2.1
with pH 2.2
with pH 2.5
with pH 3.0 6.0 6.8 6.7 6.6 7.0 15.0 0.1 0.35 ---- ---- ---- ---- ---- ---- 0.46 ---- ---- ---- ---- ---- ----- 0.56 ---- ---- ---- ---- ---- ---- 0.6 ---- 5. Aggregates 78,2 76.82 76.9 76.97 76.26 52.0 6. Water binder ratio (W / Elm) 0.41 0.45 0.45 0.45 0.47 0.45

An example of the implementation of the task. A concrete mixture is prepared by dosing the components by weight, shown in table 1. Mix the mixture of fine aggregate (sand), macro- and micro-fillers (screening slag + dust from the production of ferrosilicon) with modified (acidic) and 1/2 part of ordinary water - 5 min, followed by the addition of a plasticizer with a base of naphthenic sulfocylates, crushed stone, Portland cement and the remainder of ordinary water and stirring is continued for another 5-6 minutes. Concrete samples are molded and hardened in accordance with the requirements of GOST 7473-94.

A concrete mixture of the composition of the prototype (. # 6) was prepared according to the methodology described in the example of ed. testimonial. USSR No. 1346617 C04B 28/08 (C04B 28/08 // 22: 08, 24:20), published on 10.23.1987. The presence of cracks was determined visually.

Table 2 shows the results of compression strength tests after 28 days of natural hardening and shows the presence of cracks in the samples.

The properties Concrete mixture numbers and parameter values one 2 3 four 5 6 (prototype) 1. The compressive strength at the age of the day (MPa) 36.0 43.5 41.3 40,4 36.7 9.2 2. Cracks there is no no no no there is

Analysis of the data shown in table 2 shows:

1) the strength of concrete has increased four times with the same V / Vyazh = 0.45, and Portland cement, fillers and plasticizer are included in the composition of mixed binders (proposed and known);

2) the composition of the concrete mixture No. 1 and No. 5 do not meet the task, because small cracks appeared on the surface of concrete samples of composition No. 1, and the compressive strength of concrete of mixture No. 5 was lower than compositions No. 2; No. 3 and No. 4.

The appearance of cracks (mixture No. 1) is justified by the lack of an acidic medium (water with a pH of 2.1) to prevent the belated process of quenching (hydration) of burnt particles of free lime contained in the slag plantings. The decrease in concrete strength in the composition of mixture No. 5 is explained by the excess of the optimum dust norm from smelting ferrosilicon, despite the highest consumption of Portland cement.

The chemical essence of the achievement (the task is the chemical interaction of the burnt free particles of calcium oxide (CaO) with acidic modified water and the transition to calcium hydroxide (Ca (OH) ₂ ), i.e. the delayed process of sawing of lime is prevented, and consequently, the formation of cracks hardening concrete.

The conversion of CaO to Ca (OH) _{2 also} contributes to an increase in the structure of concrete of calcium hydrosilicates, and, consequently, the strength of concrete.

As part of the prototype mixture, the burned-out particles of free calcium oxide, when interacting with the acidic environment formed by MgSO ₄ , go into CaSO ₄ gypsum, which also has a positive effect on crack resistance, but negatively on concrete strength, since gypsum (anhydrite) is an insoluble substance and does not form additional amount of calcium hydrosilicates in the concrete structure. However, cracks on the surface of the concrete of the prototype arise due to the increased content of finely dispersed steelmaking slag in the composition of the concrete mixture and the plugging of capillaries by which water diffuses to the surface for evaporation, which creates internal stresses leading to cracks.

The effect of increasing the strength lies in the chemical interaction of modified water with a pH of 2.1-2.5 with pulverized amorphous silica fume and its first transition to metasilicon (H ₂ SiO ₃ ), and then by polymerization of the latter into orthosilicon gel (H ₄ SiO ₄ )

The reliability of such a chemistry of conversion of amorphous silica into orthosilicic acid in an acidic medium is confirmed experimentally and is given in the work of Chukin GD (G.D. Chukin, reviewer: Doctor of Chemistry, Professor B.K. Nefedov, “Surface and Structure Chemistry of Dispersed Silica”, Ch. No. 8, Section 8.2. - The structure of a silica gel globule synthesized in an acidic medium - M .: Paladin Printing House, Printa LLC, 2008. - 172 p.).

As part of the concrete mixture, the gel of orthosilicic acid reacts with Ca (OH) ₄ , which is formed during the hydration of Portland cement clinker minerals by reaction (1):

Ca (OH) ₂ + 2H ₂ O + SiO ₂ = CaSiO ₃ · 3H ₂ O (1).

The molecular weight of Ca (OH) ₂ = 74 amu, and CaSiO ₃ · 3H ₂ O = 170 amu or the output of calcium hydrosilicate by reaction (1) is 70% of the total mass.

In the interaction of Ca (OH) ₂ with traditional active kamenzemsoderzhashchy mineral additives (flask, tripoli, etc.), the output of calcium hydrosilicate is less, i.e.

Ca (OH) ₂ + SiO ₂ + H ₂ O = CaSiO ₃ -2H ₂ O (2).

The molecular weight of CaSiO ₃ · 2H ₂ O = 160 am or the yield of calcium hydrosilicate by reaction (2) is 68% of the total mass, i.e., 2% less with respect to reaction (1).

Reaction equation (2) is written from the literature (Volzhensky A.V., Yu.S. Kolokolnikov et al. Mineral binders, 1979. - 472 s).

Thus, dust from smelting ferrosilicon together with “dead” water with a pH of 2.1-2.5 helps to eliminate concrete cracks during hardening and increase the products of hydration of calcium hydroslicates, and, accordingly, the strength of concrete.

Strength is enhanced by the lower water demand of the proposed concrete mixture due to the combined action of three components: a plasticizer with a base of naphthenic acid, dust from smelting ferrosilicon and modified acidic water pH 2.1-2.5, and the use of coarse aggregate (crushed granite).

The economic feasibility of the proposed concrete mixture in relation to the known (No. 6 prototype) is the following factors:

1) the consumption of mixed binder (in%) is reduced by 1% of aggregate, i.e.:

- for the known (48%: 52%) = 0.923;

- for the proposed (23, l% avg.: 76.9% avg.) = 0.3, i.e. the consumption is reduced three times;

2) the consumption of concrete mixture per unit of strength (MPa) of concrete at the age of 28 days of normal hardening is reduced, i.e.:

- for the known (100% b. mix: 9.2 MPa) = 10.87;

- for the proposed (100% b. mix: 39.3 medium) = 2.54 (4.28 times less, which had a positive effect on reducing the cost of the mixture).

The latter is also facilitated by the fact that sowing of slag is 10 times cheaper than finely dispersed steelmaking slag, and the cost of obtaining modified water is three times cheaper than magnesium sulfate. Thus, the cost of the proposed concrete mixture is 6-8% lower than the known one.

Claims (1)

Concrete mixture including Portland cement, finely divided filler — slag and dust of electrostatic precipitators of ferroalloy production, a plasticizer with a base of naphthenic sulfonic acid, water and aggregate, characterized in that screening of blast furnace slag of 0.14 mm fraction and dust of electrofilters from smelting are introduced as a finely divided filler, due to the partial replacement of ordinary mixing water, water modified with electric current is introduced with a pH of 2.1-2.5, in the following ratio of components, wt.%:
Mixed binder:
Portland cement 11.86-12.15 screening of blast furnace slag, fractions less than 0.14 mm 2.4-3.34 dust from smelting ferrosilicon 0.8-1.28 plasticizer with naphthenic sulfonic acid base 0.03-0.04
Mixing Water:
ordinary 6.6-6.8 modified with pH 2.1-2.5 0.35-0.56 aggregate 76.82-76.97 water binder ratio (W / Elm) 0.45