RU2844091C1 - Concrete mixture for making reinforced concrete drainage articles - Google Patents

Abstract

FIELD: construction materials.

SUBSTANCE: invention relates to production of construction materials and can be used for making reinforced concrete thin-wall drainage structures. Concrete mixture for making reinforced concrete drainage articles contains sulphate-resistant portland cement, a mixture of natural sand with crushed stone or gravel, a mineral additive, a structure-forming additive and water. Mineral additive used is condensed microsilica, natural sand with fineness modulus from 2.0 to 2.5, crushed stone or gravel of dense rocks – fractions from 5 to 10 mm, and structuring additive is additive containing, wt. %: polyplast type S 63-68 and SikaControl-95 Aer 32-37. Concrete mixture contains components in the following ratio, wt. %: sulphate-resistant portland cement 16.52-17.68, natural sand 29.12-32.98, crushed stone or gravel 41.29-43.47, condensed microsilica 0.1-2.62, structure-forming additive of said composition 0.16-0.25, water – balance.

EFFECT: obtaining a concrete mixture for reinforced concrete thin-walled drainage products operating in aggressive environments, ensuring increased strength and a long service life.

1 cl, 2 tbl, 1 ex

Description

The invention relates to the production of building materials and can be used for the manufacture of reinforced concrete thin-walled drainage products, such as an aeration tray for a concrete drainage system, a drainage tray for motorways operating in aggressive environments.

The most important technical characteristic of drainage products is their strength, because the risk of deformation during installation in a ditch and their possible depth of installation depend on it. If the strength is reduced, the pipeline will not bear the load and will not perform its original functions. The crack resistance of concrete and resistance to aggressive environments are also necessarily taken into account.

To give the concrete mixture the appropriate characteristics, various additives are introduced into it. Among the additives for concrete, Polyplast PK type S is known - a highly effective superplasticizer based on polycarboxylate esters https://polyplast-un.ru/catalog/promyshlennaya-khimiya/dobavki-dlya-sukhikh-smesey/poliplast_pk_tip_s/?ysclid=mamktc4lj934265476 (TU20.59.59-131-58042865-2021). Its characteristics ensure increased plasticity and fluidity of the solution, improvement of most characteristics of the hardened mixture, reduces the consumption of binder, increases resistance to cracking and stability of self-leveling systems, and also obtains a smooth surface without defects.

Characteristic features of POLYPLAST® PC type S superplasticizers in dry building mixtures and solutions: ensuring good flowability of the finished solution, obtaining a uniform consistency, short mixing time in screw pump mixers and environmental safety.

Also known is the surface-active additive SikaControl-95 Aer of complex composition, https://rus.sika.com/ru/stroitelstvo/dobavki-v-beton/tovarnyj-beton/51103/sikacontrol-95-aer.html#documents. SikaControl®-95 Aer is a new generation air-entraining additive for concrete and mortars. It is used to create a system of closed and uniformly distributed pores of a certain size in concrete, providing concrete structures with high frost resistance. Meets the requirements of TU 20.59.59-036-13613997-2019. This additive increases the frost resistance of concrete, including in salt solutions, the mobility and workability of the concrete mixture, as well as the segregation resistance of the concrete mixture.

The composition of fine-grained concrete is known from the state of the art (Bazhenov Yu.M. Concrete Technology. - M.: Higher School, 1987. Pp. 246-252), which contains water, sand, and Portland cement as a binder.

The disadvantages of known concrete include low flexural and compressive strength, as well as high water absorption.

A concrete mixture for the production of a ballast pipe is known (RU 2453515, class C04B 28/02, F16L 58/06, C04B 111/20, 2012), including sulfate-resistant Portland cement, barite ore, plasticizing additives based on polycarboxylate ether and water in the following ratio of components, wt.%:

sulfate-resistant Portland cement 12-17, water 4-10, plasticizing additive based on polycarboxylate ether 0.1-0.25, barite ore the rest.

With this content of barite ore fractions, wt.% is selected from the following ratio:

large fraction with grain size of 3 - 25 mm from 7 to 18%,

fine fraction with grain size of 0.16 - 3 mm from 75 to 85,

very fine fraction with particle size of 0.01-0.16 mm from 7 to 16.

In addition, the mixing water of the concrete mixture is pre-treated by passing it through a magnetic field in which the intensity is maintained at 120,000-140,000 A/m, with a passing speed of 0.5-3.0 m/s, while the water treatment time is at least 2 hours.

This concrete mix composition is difficult to manufacture, as it requires additional water treatment. In addition, barite ore is located in limited areas, and therefore requires its delivery, which is not economically viable.

A concrete mixture based on sulfide-resistant Portland cement is known (RU 2435094, class F16L 1/16, F16L 58/06, C04B 28/00, 2011), including components, wt.%:

Sulfate-resistant Portland cement m500 12-17% Water 5.5-9.5% Water to cement ratio 0.46-0.56 Superplasticizer 0.25-0.3% Water repellent 0.01-0.03% Barite ore rest

The manufacture of products based on the specified composition requires additional ballast coating, which complicates and increases the cost of manufacturing products. In addition, the presence of barite ore in the mixture requires its delivery to the production site, which is difficult if there is no mining of it on the territory of concrete product production.

A concrete mixture is known (RU 2771650, class C04B 28/04, 2022), consisting of Portland cement, crushed stone or gravel, construction sand, naphthalene-formaldehyde-based superplasticizer and water, amorphous nanomodified silicon dioxide, nanomodified tripoli or flask, sodium nitrate, saponified wood resin or neutralized resin, as well as an air-entraining additive in the following ratio of components, wt. %:

Portland cement 7.2-10.5 crushed stone or gravel fraction 20-40 mm 50.0-56.0 construction sand 34.0-26.0 naphthalene-formaldehyde based superplasticizer 0.04-0.08 amorphous nanomodified silicon dioxide 0.01-0.07 nanomodified tripoli or opoka 0.02-0.08 sodium nitrate 0.2-0.4 saponified wood resin or resin neutralized air entrainment 0.001-0.008 water rest

This concrete mixture is difficult to manufacture due to the presence of components that require specialized processing, as well as the insufficient strength of concrete products obtained from this concrete mixture.

The prototype of the invention is a concrete mixture (RU 2111188, cl. C04B 28/02, C04B 28/02, C04B 18/08, C04B 24/06, C04B 111/20, 1998), consisting of Portland cement, filler in the form of a mixture of crushed stone and sand, microsilica, water and a surface-active additive in the form of a mixture of alkylbenzyl dimethyl ammonium chloride and polyhexamethylene guanidine chloride. In this case, the ratio of components in wt.% is as follows:

Portland cement - 17.0 - 23.0

filler - 64.8 - 74.0

microsilica - 0.51 - 1.01

surface-active additive of the specified composition - 0.26 - 0.69

water - the rest

The known concrete mixture does not have sufficient strength required for concrete drainage trays operating in aggressive environments with increased loads. In addition, the production of products from the known concrete mixture is highly expensive, since it requires a long time for the curing process of products in order to give them the necessary physical and mechanical performance characteristics.

The problem of the invention is to eliminate the shortcomings of known concrete mixture compositions.

The technical result of the invention is an improvement in the composition of the concrete mixture for reinforced concrete thin-walled drainage products operating in aggressive environments, with improved performance characteristics, including increased strength and a long service life, as well as a simplification of the production technology with increased productivity, due to the possibility of hardening the product in natural conditions immediately after removing it from the mold.

The stated problem and the declared technical result are achieved due to the fact that the concrete mixture for the production of reinforced concrete drainage products includes Portland cement, a mixture of natural sand with crushed stone or gravel, a mineral additive, a structuring additive and water. According to the invention, sulfate-resistant Portland cement is used as Portland cement, condensed microsilica is used as a mineral additive, natural sand is used with a fineness modulus from 2.0 to 2.5, crushed stone or gravel of dense rocks is used with a fraction from 5 to 10 mm, and the following composition is used as a structuring additive, wt.%:

polyplast type S 63.0 - 68.0 SikaControl-95 Aer 32.0 - 37.0

with the following ratio of components, wt.%:

sulfate-resistant portland cement 16.52 - 17.68 natural sand 29.12 - 32.98 crushed stone or gravel 41.29 - 43.47 condensed microsilica 0.1 - 2.62 structuring additive of the specified composition 0.16 - 0.25 water the rest

The use of sulfate-resistant Portland cement as Portland cement in a ratio of 16.52 to 17.68 wt.% allows increasing the resistance of products to aggressive environments in which drainage channels are used. At the same time, reducing the content of sulfate-resistant Portland cement below 16.52 does not allow obtaining sufficient concrete strength and immediate stripping of products, and exceeding it above 17.68 leads to the production of "fat" concrete and sticking of products in the form, as well as the formation of shrinkage cracks.

The introduction of natural sand with a fineness modulus of 2.0 to 2.5 and crushed stone or gravel of dense rocks of fraction from 5 to 10 mm in the declared ratio and fractional composition into the concrete mixture provides the products with high density and low porosity. Due to this, high water resistance, protection from aggressive substances and durability are achieved. At the same time, the selected fineness modulus of the filler and fractional composition allows to obtain a high packing density of the components and adhesion of the cement-sand part with the large filler. With a fineness modulus of sand less than 2.0, the water demand of the sand increases, which leads to a decrease in the strength of the concrete. With a fineness modulus of sand more than 2.5, water separation of the mortar part increases, which leads to the formation of shrinkage cracks. When using crushed stone or gravel with the largest size of more than 10 mm, sufficient quality of the surface of the products is not ensured. In this case, an increased number of cavities with sizes above the permissible ones are observed on the products.

The use of crushed stone or gravel in a ratio of 41.29 to 43.47 wt.%, as well as natural sand from 29.12 to 32.98 wt.%, allows for a high packing density of inert components. Exceeding or decreasing these ranges leads to a decrease in the packing density of the components, which is manifested in increased water separation of the solution part, an increase in the porosity of concrete and a decrease in strength.

The use of condensed microsilica as a mineral additive in an amount from 0.1 to 2.62 wt.% ensures increased concrete strength (Tables 1, 2) due to increased adhesion of cement paste to sand, crushed stone and/or gravel, and also increases the packing density of grains of the mineral part and chemical interaction between silica and cement hydration products with the formation of high-strength calcium hydrosilicates. With a microsilica content of less than 0.1%, it does not actually lead to an increase in strength. Exceeding the microsilica content over 2.62% leads to an increase in the water requirement of the mixture and a decrease in strength.

The use of a structuring additive in a concrete mix containing a mixture of Polyplast type S with SikaControl-95 Aer in the specified ratio allows for concrete suitable for immediate stripping of the product (removal of the form immediately after molding), which increases the productivity of product manufacturing. In addition, concrete can harden under natural conditions without heating (heat and moisture treatment) or in a low-temperature mode due to self-heating, which also reduces the cost of heat carriers (after 24 hours, the product gains at least 50% of its strength without heat-moisture treatment). In this case, the ratio of Polyplast type S with SikaControl-95 Aer was selected experimentally and when the amount of Polyplast type S in the structuring additive is reduced to less than 63 wt.%, or exceeds 68 wt.%, additional heat treatment of the products will be required before stripping, which will lead to additional heat carrier costs and product hardening time, affecting productivity. The amount of SikaControl Aer in the structuring additive should also be between 32 and 37 wt.%. Exceeding or decreasing the amount of SikaControl-95 Aer in the structuring additive will also result in the impossibility of immediate stripping of the product immediately after its molding. The structuring additive in the specified ratio also increases the strength, water resistance and frost resistance of concrete by reducing capillary porosity and standardized air entrainment into the concrete mixture.

The production of concrete mixture for the production of reinforced concrete drainage products is illustrated by the following example.

Example

The raw materials were pre-prepared, including removal of contaminants from fillers (wood, paper, etc.), transportation to storage and consumption bins, heating of raw materials, water and chemical additives in winter. The structuring additive was made by dosing and mixing Polyplast type S in the amount of 3.4 kg and SikaControl-95 Aer in the amount of 1.6 kg. Mixing was carried out by bubbling until a homogeneous state was obtained.

Then, the raw materials were dosed and mixed until a homogeneous mass was obtained in a forced-action mixer in the following ratio, kg: sulfate-resistant Portland cement CEM I 42.5 H-SS - 397 kg (16.52 wt.%), natural sand with a fineness modulus of 2.3 - 737 kg (30.72 wt.%), crushed granite of fraction 5-10 mm - 1041 kg (43.37 wt.%), condensed microsilica mk-85 - 32 kg (1.33 wt.%), the specified structuring additive - 5 kg (0.21 wt.%) and water - 189 kg (7.85 wt.%).

After mixing, the resulting concrete mixture was delivered to the molding site, placed in a pre-cleaned and lubricated mold, vibratory compaction was performed, and the molds were transferred to the curing station, where the mold was immediately removed from the product (concrete drainage tray). The product hardens under natural conditions within 24 hours. The finished product was sent to the finished product warehouse.

Other examples of raw mix preparation were carried out similarly to example 1, the data for which are presented in Table 1.

Table 1

No.
p/p Composition, wt.% Portland cement sulphate-resistant Natural sand Crushed stone fraction 5-10 mm Aggregate Microsilica Structuring additive Surface-active additive Water RU 2111188 (prototype) 20.5 - - 68.7 1.0 - 0.26 9.54 1 16.52 30.72 43.37 - 1.33 0.21 - 7.85 2 17.00 32.98 41.29 - 1.5 0.16 - 7.07 3 17.36 29.12 43,47 - 2.50 0.25 - 7.30 4 17.68 32,33 42.7 - 0,1 0.23 - 6.96 5 17.36 29.12 43.47 - 2.62 0.25 - 7.18

Table 2

Concrete drainage channel test results

No.
p/p Properties Strength
for compression after heat treatment, MPa
(1 day) Strength
under compression, MPa
(28 days) Water absorption, % Water resistance, W Frost resistance, F ₂ RU 2111188 (prototype) - 32.5 - - - 1 41.9 70 3.8 12 300 2 32.5 55.6 4.1 10 300 3 39.4 66.1 3.2 14 300 4 43.8 64.3 4.4 10 300 5 35.6 72.8 1.9 16 300

The compressive strength of the concrete drainage channel obtained from the declared concrete mixture after 28 days (example No. 5) exceeds the strength values of a similar prototype product by 55%. Frost resistance grade F ₂ 300, water resistance grade W16, water absorption 1.9%, which indicates low porosity of concrete and high corrosion resistance of this composition.

Currently, the concrete mixture is at the stage of industrial implementation in production for the manufacture of reinforced concrete drainage products.

Claims (4)

A concrete mixture for the production of reinforced concrete drainage products, including Portland cement, a mixture of natural sand with crushed stone or gravel, a mineral additive, a structuring additive and water, characterized in that sulfate-resistant Portland cement is used as Portland cement, condensed microsilica is used as a mineral additive, natural sand is used with a fineness modulus from 2.0 to 2.5, crushed stone or gravel of dense rocks is used with a fraction from 5 to 10 mm, and an additive of the following composition is used as a structuring additive, wt.%: polyplast type S 63.0-68.0 SikaControl-95 Aer 32.0-37.0 with the following ratio of components, wt.%: sulfate-resistant portland cement 16.52-17.68 natural sand 29.12-32.98 crushed stone or gravel 41.29-43.47 condensed microsilica 0.1-2.62 structuring additive of the specified composition 0.16-0.25 water rest