RU2467972C1 - Mixture for producing fine-grained steel fibre concrete based on quartzite sandstone grinding screenings - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the construction industry and specifically to technologies of preparing a composition of fine-grained concrete mixtures used in making precast and monolithic reinforced concrete articles and structures. The mixture for producing fine-grained steel fibre concrete contains the following in kg/m³: low-water demand binder VNV-70 based on wet magnetic separation wastes -280-290, quartzite sandstone grinding screenings of with particle size not greater than 5 mm 860, Nizhne-Olshansky sand 540, steel fibre 60-65, superplasticiser S-3 1.6-1.7, water - the balance.

EFFECT: high compression and flexural strength, crack resistance and wear resistance.

1 ex, 4 tbl, 2 dwg

Description

The invention relates to the construction industry, and in particular to technologies for preparing the composition of fine-grained concrete mixtures used in the manufacture of precast and monolithic reinforced concrete products and structures.

Known concrete mixture, including Portland cement, steel fiber, aggregate, water, plasticizing additive "Polyplast SP-3", modifying the additive with the following ratios of the components of the mixture, kg / m ³ :

Portland cement 320-330 aggregate 1900-1920 steel fiber 70-80 superplasticizer 1.6-1.72 modifying additive 0.010-0.015 water rest

[RU 2397069, IPC B28C 5/40].

Its disadvantage is the low strength of the cement stone in compression and bending, as well as the high cost of the mixture through the use of granite crushed stone.

The aim of the invention is to increase the compressive strength and bending; shock and fatigue strength; crack resistance and viscous fracture; abrasion resistance of cement stone, reduction in the cost of concrete mix due to the use of composite binder and mining waste (screening of quartzite sandstone crushing) and wet magnetic separation waste (MMC waste).

A mixture for the production of fine-grained steel-fiber concrete, including a binder, aggregate, steel fiber, S-3 superplasticizer, water, is characterized in that a binder of low water demand VNV-70 based on wet magnetic separation waste is used as a binder, and quartzite sandstone crushing screening is used as a filler. fractions of no more than 5 mm and Lower Cholan sand with the following ratios of the components of the mixture, kg / m ³ :

astringent of low water demand VNV-70 280-290 quartzite sandstone crushing screening 860 sand lower kolkhansky 540 superplasticizer C-3 1.6-1.7 steel fiber 60-65 water rest.

A binder of low water demand VNV-70 is used on the basis of waste wet magnetic separation and silica obtained by mechanically activating the screening of crushing quartzite sandstone.

Screening crushing quartzite sandstone is formed by crushing crushed stone. It represents particles of a dusty fraction (not more than 5 mm) with a high silica content.

A feature of crushing screenings is the angular shape of grains with a highly developed surface, which contributes to increased adhesion of cement stone to them (Fig. 1).

The sand component determines the formation of the microstructure of the cement stone, determining the mesostructure of the material. When studying the processes occurring in the contact zone between the cement stone and the aggregate, the leading role of the mineralogical composition of the aggregate is noted.

The most structure-forming role of the aggregate is manifested in the formation of thin layers of cement stone between the aggregate grains. In this case, the increase in the microhardness of cement stone between the grains of the aggregate is attributed to the merging of contact zones, an increase in the density of cement stone in these zones.

The use of superplasticizer C-3 allows you to:

- increase the mobility of the concrete mixture from P1 to P5;

- reduce water demand during mixing of the binder by 20-28%;

- increase the final strength characteristics to 50%;

- adjust the setting time by changing the amount of added additive C-3;

- 1.5-1.6 times increase the adhesion of concrete with embedded reinforcement and hardware while inhibiting the metal surface;

- get "cast" concrete with increased moisture resistance, crack resistance, frost resistance - 350 cycles;

- reduce cement consumption by 20% (TU 5870-005-58042865-2005).

Superplasticizer C-3 acts as a retarder.

Based on the chemical composition of ferruginous quartzites of various deposits in Russia and neighboring countries, KMA deposits are characterized by an increased SiO ₂ content (from 31 to 42%), which leads to an increased content of quartz in MMC waste (Tables 1, 2). Hematite is noted as inclusions in diagenetic quartz grains. Amphiboles, carbonates, feldspars and mica are found as secondary. The quartz present in the MMC waste in crushed form can participate in the formation of neoplasms, and, therefore, the waste can be used in the production of airborne explosives.

Table 1 The chemical composition of the waste MMS,% Fe _commonly SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ FeO Cao MgO S P CO ₂ 10,2 77.72 0.57 6.58 7.12 1.48 2.26 0.128 0,023 3.63

table 2 Mineral composition of wastes of MMS Lebedinsky GOK,% Quartz Hematite Magnetite Silicates Carbonates 65-70 6-11 2-6 9-12 6-13

Example

VNV-70 based on wet magnetic separation was used as a binder. For the manufacture of prototypes used screening crushing quartzite sandstone and Lower Bolshan sand. To assess the quality of the used aggregates and fillers, their basic physical and mechanical properties were studied (Table 3).

Table 3 Physico-mechanical characteristics of the aggregate Name of indicator unit of measurement KVP dropout MMS waste Lower Bolshansk sand Fineness modulus M _cr 3,50 0.63 1.12 Unpacked bulk density ρ _us. kg / m ³ 1415 1300 1467 Bulk density in a compacted state ρ _{us. rep.} kg / m ³ 1490 1630 1648 True density ρ _ist. kg / m ³ 2710 3000 2630 Voidness V _m.p. ,% 47.8 59.3 44,2 Water demand B out _. % 5.5 25 eleven Cement requirement _Cpr. 0.530 1.95 0.63

Steel fiber milled using the VULKAN HAREX technology was adopted as fiber. The fiber has a characteristic bluish tint - an oxide layer that prevents the formation and development of corrosion during its storage. Fiber length - 32 mm, width - 3.8 mm.

Steel-fiber concrete mixture was prepared in two stages. Initially, a concrete mixture was prepared in a mortar mixer. Initially, the mixing of dry components was carried out, then water was mixed in small portions. Mixing lasted 5-10 minutes depending on the consistency of the mixture.

At the second stage, reinforcement was performed. To do this, experimentally determined the amount of concrete mixture required for molding one sample. Next, fiber was added to the prepared concrete mixture, previously measured according to the percentage of reinforcement.

After that, the mixture was mixed mechanically and manually placed in cleaned forms, carefully lubricated with oil. Compaction of the fiber-reinforced concrete mixture was carried out on a vibrating table until the appearance of cement milk.

Table 4 Mixture composition The composition of the mixture per 1 m ³ Composition 1 The limit of compressive strength, MPa Bending Strength, MPa Composition 2 The limit of compressive strength, MPa Bending Strength, MPa VNV-70 280 86.2 24.2 290 94.8 25.8 KVP dropout 860 860 sand 540 540 S-3 1,6 1.7 fiber 60 65 water 140 160

Testing of samples to determine compressive strength, tensile bending and elastic modulus was carried out on a universal machine UMM-10 according to the standard method for 28 days.

The developed composition of steel fiber concrete using a binder of low water demand (VNV-70) and screening crushing of quartz sandstone allowed us to obtain concrete with a compressive strength of 94.8 MPa, bending strength up to 25.8 MPa, which is 25% higher than in the prototype.

Steel-fiber concrete samples have high indicators of the above characteristics and can be widely used in the manufacture of steel-fiber concrete products of various assortments.

Claims (1)

A mixture for the production of fine-grained steel fiber concrete, including a binder, aggregate, steel fiber, S-3 superplasticizer, water, characterized in that a binder of low water requirement VNV-70 based on wet magnetic separation waste is used as a binder, and quartzite sand fraction is crushed no more than 5 mm and Nizhne-Olshansky sand with the following ratios of components, kg / m ³ mixture:
astringent of low water demand VNV-70 280-290 quartzite sandstone crushing screening 860 sand Lower Olshansky 540 superplasticizer C-3 1.6-1.7 steel fiber 60-65 water rest

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