RU2728023C1 - Antifreeze additive for concrete mixture - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to construction materials and can be used in making concrete and mortar hardening at low temperatures. Antifreeze additive for concrete mixture contains, wt. %: silica gel 79.43–87.49, polycarboxylate-based superplasticiser Melflux 2651F 2.75–4.92, antifoaming agent Troykyd D128 0.03–0.05, sodium thiosulphate 9.73–15.6.

EFFECT: technical result is high strength of concrete during compression at age 28 days during hardening at negative temperatures.

1 cl, 1 tbl

Description

The invention relates to compositions of antifreeze additives based on industrial by-products and can be used in underground, transport and civil engineering for the manufacture of cement concrete, hardening at negative ambient temperatures.

Known complex additive for concrete (patent RU No. 2307099, publ. 09/27/2007), including superplasticizer S-3 or Polyplast SP-1, technical lignosulfonates - LST, potash and sodium formate with the following ratio of components, wt.% (On dry matter ): superplasticizer 5-40, LST 0.5-10, potash 10-40, sodium formate - the rest.

The disadvantage of this composition is insufficient compressive strength at the age of 28 days at negative hardening temperatures, due to the retarding effect of the superplasticizer S-3 or Polyplast SP-1 on the hydration of Portland cement in the first hours of hardening of the mixture and lengthening the time of the start of setting of the cement paste.

Known chemical additive in concrete mixtures and mortars (patent RU No. 2359935, publ. 27.06.2009), which contains, by weight. %: sodium thiosulfate - 10-77.7, sodium thiocyanate - 10-77.7, sodium sulfate - 12.3-80.

The disadvantage of this composition is insufficient compressive strength at the age of 28 days at negative temperatures of hardening, due to the absence of a water-reducing component - a superplasticizer.

Known additive for concrete (patent RU No. 2247092, publ. 27.02.2005), including organic silicon defoamer, superplasticizer C-3 - sodium polynaphthalene methyl sulfonate, sodium thiosulfate, superplasticizer-lignopan, sodium carbonate in the following ratio of components, wt. %: organic silicon defoamer 0.02-0.06, superplasticizer C-3 - sodium polynaphthalene methyl sulfonate 0-40, sodium thiosulfate 40-55, superplasticizer-lignopan 10-20, sodium carbonate 1-2.

The disadvantage of this composition is insufficient compressive strength at the age of 28 days at negative hardening temperatures, due to the retarding effect of the superplasticizer C-3 on the hydration of Portland cement for the first time, hours of hardening of the mixture and lengthening the time of the beginning of the setting of the cement paste.

Known complex additive (patent RU No. 2360879, publ. 10.07.2009), containing in its composition, wt. %: superplasticizer - sodium polynaphthalene methyl sulfonate - 30-45, antifoam Troykyd D128 - 0.25-0.50, sodium thiosulfate - the rest.

The disadvantage of this composition is insufficient compressive strength at the age of 28 days at negative hardening temperatures, due to the retarding effect of a superplasticizer based on sodium polynaphthalene methyl sulfonate on the hydration of Portland cement for the first time, hours of hardening of the mixture and lengthening the time of the onset of setting of the cement paste.

Known complex additive (patent RU No. 2552565, publ. 06/10/2015), taken as a prototype, including components at the following ratio, wt.%: Superplasticizer on a polycarboxylate base Melflux 2651F - 15.00-29.00, antifoam Troykyd D128 - 0 , 12-0.33 and sodium thiosulfate - the rest.

The disadvantage of this composition is insufficient compressive strength at the age of 28 days at negative temperatures of hardening, due to insufficient structure formation for the first time hours and days of hardening of the mixture.

The technical result is the creation of an antifreeze additive for a concrete mixture that provides increased concrete strength in compression at the age of 28 days when hardening at low temperatures by reducing the time of the beginning and end of the setting of the cement paste when using silica gel.

The technical result is achieved by the fact that it additionally contains silica gel with the following ratio of components, wt%:

silica gel 79.43-87.49 polycarboxylate-based superplasticizer Melflux 2.75-4.92 defoamer Troykyd D128 0.03-0.05 sodium thiosulfate 9.73-15.6

The claimed composition of the antifreeze additive for concrete mix includes the following reagents and commercial products containing them:

- silica gel obtained in the production of aluminum fluoride by the interaction of fluorosilicic acid with aluminum hydroxide. The silica gel corresponded to TU 2123-009-70864601-2009,

- superplasticizer MELFLUX 2651F in dry form in accordance with GOST 24211-2008 “Additives for concrete and mortars. General technical conditions "

- sodium thiosulfate in accordance with GOST 27068-86,

- antifoam Troykyd D128 based on vegetable oils (US 5685898, 11.11.1997).

Sodium thiosulfate was crushed and mixed with the remaining components in the claimed percentage.

To study the properties of the inventive additive, mortar mixtures were prepared with a ratio by weight of cement to sand of 1: 3, containing Portland cement PC500D0N CJSC "Maltsovsky Portlandcement", river sand with a fineness module of 2.3. The sand was in accordance with GOST 8736-2014 “Sand for construction works. Technical conditions ". Grade according to the workability of the mortar mixture P _to 2. The amount of additive was calculated in% of the mass of Portland cement (for dry products).

The inventive additive was introduced in the following way. The additive, sand and cement were mixed and mixed with the accepted amount of mixing water. The mortar mixture was mixed in a forced mixer for 8 minutes.

Samples were prepared from the mixtures and tested in accordance with GOST 5802. The samples hardened at a temperature of -10 ° C, -15 ° C, -20 ° C according to the mode of paragraph 10.1.2.6 of GOST 30459-2008 and at the age of 28 days the samples were tested for strength.

Tests of the solution made using the prototype additive were also carried out.

The test results are presented in the table. The claimed composition of the antifreeze additive allows increasing the compressive strength of concrete at the age of 28 days when hardening at negative temperatures.

The proposed antifreeze additive allows you to obtain concrete with a higher compressive strength at negative temperatures of hardening. Compared to the prototype, the compressive strength increases up to 50%. The addition of silica gel shortens the time for the beginning and end of the setting of the cement paste, increases the strength and density of the cement stone, which is associated with the chemical reaction between the silica gel and calcium and magnesium hydroxide. The reaction products fill the pores and also strengthen the contact zones in the cement concrete. The formed structure of cement concrete is less susceptible to destruction when the pore fluid passes into ice. Sodium thiosulfate, due to the intensification of hydration processes, contributes to an increase in the solubility of cement minerals and an increase in the concentration of Ca ^{2+ ions} in the suspension, which contributes to the chemical reaction between silica gel and calcium hydroxide. This reduces the time of the beginning and end of the setting of the mixture, changes the ratio between the gel and capillary porosity of concrete towards an increase in the gel porosity, as a result of which the processes of structure formation of concrete are accelerated, and the early strength of concrete increases.

Claims (2)

Antifreeze additive for concrete mix, including superplasticizer on a polycarboxylate base Melflux 2651F, antifoam Troykyd D128 and sodium thiosulfate, characterized in that it additionally contains silica gel in the following ratio of components, wt%: silica gel 79.43-87.49 superplasticizer on Melflux polycarboxylate base 2.75-4.92 defoamer Troykyd D128 0.03-0.05 sodium thiosulfate 9.73-15.6