RU2386599C1 - Fibre-concrete mixture - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the industry of construction materials and more specifically to compositions of fibre-concrete mixtures used in making precast and monolithic reinforced concrete structures. The fibre-concrete mixture which contains cement, filler and steel wire reinforcing agent, contains portland cement in amount of 1.0-2.0 % of the volume of the mixture, Mixarm steel wire with diametre 1 mm and length 54 mm with anchors at the ends and additionally a complex additive in amount of 0.75-1.5 wt % of portland cement, consisting of D-11 plasticising agent and technical carbon-soot in mass ratio equal to 1:1.

EFFECT: increased strength during early hardening stages, starting with the first day.

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Description

The claimed invention relates to the construction materials industry, namely, the composition of concrete mixtures used in the manufacture of precast and monolithic reinforced concrete products and structures.

Known concrete mixture, including cement, aggregate and a complex additive containing calcium chloride, ammonium nitrate and bischofite [RF Patent No. 21489850, 2000 - analogue].

The disadvantage of the concrete mixture is the low rate of curing in the early stages of hardening, starting from 1 day, and a significant content of chloride compounds in the complex additive, negatively affecting the corrosion of reinforcement in reinforced concrete products.

Known fiber-reinforced concrete mixture, including cement, aggregate and hardener - steel wire [RF Patent No. 2188804, 09/10/2002 - prototype].

The disadvantage of fiber-reinforced concrete mix is a small increase in strength both in the early and in the final stages of hardening with an increased consumption of an expensive hardener - steel fiber.

The technical task of the invention is to increase strength, including early hardening of fiber-reinforced concrete mix, through the use of complex additives with a minimum amount of chloride compounds and reduce the consumption of hardener - steel fiber.

The technical result obtained in the process of solving the problem is achieved by the fact that the fiber-reinforced concrete mixture, including cement, aggregate and hardener - steel wire, contains Portland cement as cement, in the amount of 1.0-2.0% of the mix volume steel wire Mixarm "With a diameter of 1 mm and a length of 54 mm with anchors at the ends and additionally an integrated additive in the amount of 0.75-1.5 wt.% Of cement, consisting of a plasticizing additive" D-11 "and carbon black in a mass ratio of 1: one.

Concrete, being a heterogeneous material, is characterized by the microstructure of the cement gel, as well as the macrostructure due to the interaction of binder and aggregates. The formation of the microstructure of cement stone, on which the basic physicomechanical properties of concrete depend, begins with a supramolecular level of dispersion of particles measuring 3-5 · 10 ^-9 m (3-5 nm). Calcium hydrosilicates formed as a result of the interaction of a binder with water in the initial period of cement hydration at a supramolecular level have a size of elementary nuclei of a new crystalline phase up to 3 nm. Structural defects in the form of a dislocation, having similar dimensions, also begin to form at this stage of cement stone formation.

To increase the strength of concrete at the macro level, “Mixarm” steel fibers were introduced, made of wire with a diameter of 1 mm and a length of 54 mm with anchors at the ends, blocking the development of macrocracks and being centers for the accelerated formation of large solid tumors in the structure of fiber concrete.

The use of a complex additive based on the plasticizing additive “D-11” and carbon black made it possible to modify the gel microstructure of fiber concrete at the nanoscale due to faster and more complete binding of hydrosilicates and calcium hydroxides, which significantly reduces their solubility and increases the rate of increase in strength.

Multifunctional plasticizing additive "D-11", developed in LLC NPP Irstroyprogress in accordance with TU 574325-004-44628610-2006. In accordance with TU "D-11" contains superplasticizer in an amount of not more than 35 wt.%, Hardening accelerator and mineral composition sealant, wt.%; SiO ₂ 18-30, SO ₃ 25-35, Na ₂ O 8-15, CaO 3-8, Cl no more than 0.15, pp no more than 30. Adsorption of additive particles on the surface of cement grains increases the wettability of the solution and reduces its water demand, which leads to an accelerated increase in the strength of hardened concrete.

Fine powder of carbon black soot with a particle size of not more than 5 μm when introduced into the concrete mix increases its mobility, which reduces the amount of mixing water by 10-15%, reduces the water-cement ratio of the mixture and thereby increase the strength starting from the early stages of hardening.

Thus, the complex introduction of Mixarm metal fibers into the raw mix made of wire with a diameter of 1 mm and a length of 54 mm, as well as the use of a complex additive including the plasticizing additive D-11 and carbon black, increases the strength fiber-reinforced concrete in the early stages of hardening, starting from 1 day, which is a new technical property of the inventive fiber-reinforced concrete mixture.

Fiber-concrete mixture is prepared from the calculation of the consumption of materials per 1 m ³ mixture, kg:

Portland cement Sebrjakowski cement plant brand 400 300 sand of the Oryol quarry Volgograd region 620 granite crushed stone of Bystrorechensky career of two fractions (5-10 mm) and (10-20 mm) in the ratio 1: 2 1230 water 140

A complex additive, including D-11 plasticizer and carbon black in a ratio of 1: 1, in the amount of 0.75-1.5% by weight of cement, is pre-dissolved in a small amount of mixing water until a homogeneous solution is obtained and uniformly introduced into the concrete mix with the rest of the water. Fiber hardener “Mixarm” with a diameter of 1 mm and a length of 54 mm in the amount of 1.0-2.0% of the mixture volume is introduced into the concrete mixer after preliminary mixing of cement, aggregates, a solution of a complex additive and the remaining mixing water.

To determine the mechanical properties of the fiber-reinforced concrete mixture, sample cubes of 15 × 15 × 15 cm in size, hardening in natural conditions, are prepared according to the standard method and tested for compressive strength in the early, starting from 1 day, hardening periods.

For experimental verification of the claimed fiber-reinforced concrete mixture, several mixtures of mixtures were prepared, differing in the different contents of the components of the complex additive as a percentage by weight, three of which showed optimal results.

The quantitative compositions of the complex additive and hardener in the fiber-reinforced concrete mixture are presented in Table 1.

Table 1 The compositions of the claimed complex additives The content of the components of the complex additives,% by weight of cement one 2 3 Plasticizer "D-11" 0.375 0.5 0.75 Carbon black 0.375 0.5 0.75 Fiber "Mixarm" with a diameter of 1 mm and a length of 54 mm,% of the volume of the mixture 1,0 1,5 2.0

The influence of the complex additive and hardener in the form of “Mixarm” fiber on the increase in the strength of fiber concrete under natural hardening conditions is presented in table 2. To determine the compressive strength and compare the test results, samples of the fiber concrete mixture were made according to the prototype (see table 2).

table 2 The compositions of the claimed fiber-reinforced concrete mixture The limit of compressive strength, MPa Fiber Concrete Age 1 day 3 days 7 days 28 days one 14.3 31,2 45.7 53,4 2 18.5 34.6 49.8 55.8 3 21.6 38,2 51,2 57.4 Concrete mix similar 13.8-16.4 23.5-27.9 32.1-37.2 38.2-43.8 Fiber-concrete mix according to the prototype 15.7 28.3 41.8 52,5

An analysis of the data presented in table 2 shows that the introduction of the mixed fiber-fiber mixture “Mixarm” into the claimed fiber-reinforced concrete mixture, as well as a complex additive including the “D-11” plasticizer and carbon black, contributes, according to the specified ratios of its constituent components, according to compositions No. 1-3, an increase in compressive strength at the age of 28 days compared with the analogue by 31-40%, and compared with the prototype by 2-9%. The increase in strength of the claimed fiber-reinforced concrete mix (composition No. 3) during hardening at the age of 1, 3 and 7 days compared to the analogue is 31-38%, and compared to the prototype - 22-37%.

An increase in the strength of the claimed fiber-reinforced concrete mixture compared to the prototype is achieved by reducing the cost of an expensive hardener - steel wire by 20% (2.0% of the volume of the claimed fiber-reinforced concrete mixture versus 2.4% - according to the prototype).

The use of soot waste (carbon black) from heat-generating plants will increase the rheological properties of mixtures while increasing the strength of fiber concrete, improve the environmental situation and reduce costs through the use of non-utilized production waste and reduce the consumption of steel wire.

Claims (1)

Fiber-concrete mix, including cement, aggregate and hardener - steel wire, characterized in that it contains Portland cement in the amount of 1.0-2.0% of the mixture volume as cement, Mixarm steel wire with a diameter of 1 mm and a length of 54 mm with anchors at the ends and additionally a complex additive in an amount of 0.75-1.5 wt.% from cement, consisting of a plasticizing additive "D-11" and carbon black in a mass ratio of 1: 1.