RU2425002C1 - Complex additive for concrete mixture - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to construction and specifically to composition of a complex additive for concrete mixture and can be used in producing concrete and reinforced concrete structures. The complex additive for concrete mixture contains the following in wt %: Mobet 2 hyper-plasticiser 30-38, Sika^® Rapid 2 curing agent 62-70.

EFFECT: high growth rate of strength of the concrete during early hardening stages with retention of high ultimate strength, high frost resistance and watertightness.

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Description

The invention relates to the field of construction, and in particular to compositions of concrete mixtures and additives for them, and can find application in the production of concrete and reinforced concrete products and structures.

Various additives are known to be introduced into concrete mixtures to improve the properties of hardened concrete. They differ in chemical and material composition, the effect on the properties of concrete mixtures and hardened concrete (RU 2096372 C1, 11.20.1997; RU 2270815 C1, 02.27.2006).

The use of synthetic superplasticizers based on sulfonated melamine and naphthalene formaldehyde resins as a part of a complex additive leads to a rapid loss of mobility of concrete mixtures; thus, the viability of cast concrete mixtures with C-3 superplasticizer usually does not exceed 45 minutes. Such an indicator is insufficient for ready-mixed concrete transported over considerable distances, which limits the use of these plasticizers in monolithic concrete.

Polycarboxylate type additives to a much lesser extent slow down the hydration of Portland cement and the structure formation of cement systems and practically do not involve additional air in the concrete mixture, which leads to higher mechanical characteristics of concrete.

Known complex additive (RU 2168478 C1, 12/20/1999), which is used in the manufacture of reinforced concrete products and structures.

This complex additive includes an accelerator and a plasticizer, and salts of hydrochloric and formic acids are used as an accelerator, and polyalcohols are used as a plasticizer in the following ratio of components, wt.%: Hydrochloric acid salts 30-90; polyalcohols 8-24; salts of formic acid 4-10.

The technical result is the acceleration of the set of strength in the early stages, maintaining the increase in strength after 23 days of hardening under normal conditions, however, the strength properties do not meet the requirements for them.

Another complex additive for concrete mix is known (RU 2278837, 06.27.2006), including technical lignosulfonate and trisodium phosphate, while trisodium phosphate is subjected to mechanical activation, as well as natural zeolite filler, or silica, or waste from the production of zeolite, or sodium dichromate, or potassium dichromate or sodium thiosulfate, which is also subjected to mechanical activation to a particle size of not more than 10 microns, preferably together with trisodium phosphate. The amount of additive is 0.4% by weight of cement.

However, this additive does not sufficiently provide high strength properties of concrete products.

The closest analogue is a complex additive for concrete mix, including, wt.%: Silica fume - 10-21, superplasticizer C-3 - 14-32, sodium nitrite - 47-75 (RU 2308429 C1, 04/10/2006).

The disadvantage of concrete with this complex additive is the insufficient rate of curing, low frost resistance and water resistance.

The objective of the present invention is to increase the growth rate of concrete strength in the early stages of hardening while maintaining their high final strength, increasing frost resistance and water resistance.

The result achieved by the fact that the complex admixture for concrete, containing a plasticizer and hardening accelerator according to the invention comprises, as plasticizer - giperplastifikator "Mobet grade 2", as an accelerator the curing - «Sika ^® Rapid 2", with the following component ratio, wt. %:

Hyperplasticizer "Mobet brand 2" - 30-38;

The hardening accelerator "Sika ^® Rapid 2" - 62-70.

The Mobet brand 2 hyperplasticizer according to TU 2600-003-54575429-2008, the hardening accelerator Sika ^® Rapid 2 meets the requirements of PN-EN 934-2.

The invention is illustrated by the following example.

To prepare the concrete mix of the production composition, we used cement M400 ПЦ Д20 of the Volsky plant, enriched sand of the Kama field with a particle size module of 2.7, crushed stone from gravel of the Kama field of a fraction of 5-20 mm, in the following ratio (parts by weight):

cement: crushed stone: sand = 1: 2.53: 1.32.

The complex additive was introduced into the concrete mixture in the form of an aqueous solution of working concentration with mixing water in the amount of 2.5-3.2% of the mass of cement in terms of dry matter.

Water was added to the concrete mixture until equal mobility (class P2) was achieved according to GOST 7473-94. The water-cement ratio of the composition without an additive was 0.46, with a complex additive - 0.33, with an additive analogous to 0.39.

Samples — cubes with dimensions of 10 × 10 × 10 cm — were made from concrete mixtures. After 1, 3, 7, 28 days of normal hardening, the samples were subjected to mechanical tests. The compressive strength of the samples was determined in accordance with GOST 18105-86.

Such indicators as frost resistance, water resistance, were determined at the age of 28 days of normal hardening according to relevant standards: water resistance according to GOST 12730.5-84, frost resistance according to GOST 10060.0-95.

The compositions of the complex additives and the results of mechanical testing of concrete are given in table 1. Concrete and concrete tests were also carried out with admixture according to the analogue and without admixture.

Table 1 No. p / p The content of components in the additive, wt.% Additive consumption,% by weight of cement Wed density bet. mixture, kg / m ³ Compressive strength (MPa)
concrete aged, days: one 3 7 28 one 2 3 four 5 6 7 8 9 one - - - 2370

2 Mobile brand 2 38 2.5 2475

Sika ^® Rapid 2 62 3 Mobile brand 2 36 2.7 2475

Sika ^® Rapid 2 64 four Mobile brand 2 33 2.9 2475

Sika ^® Rapid 2 67 5 Mobile brand 2 thirty 3.2 2475

Sika ^® Rapid 2 70 6 (analog) Superplasticizer - C3 fifteen 0.5 2470

Sodium nitrite 75 Silica fume 10 Note *: above the line is the average value of the indicator; below the line is the relative value of the indicator in% of the control

Based on the data obtained, it can be concluded that concrete using a complex additive in the first day has a compressive strength of 15-59% higher, on the 3rd day - 14-54%, on the 7th day - 8-29%, by 28 day - 4-12% compared with the analogue.

Table 2 shows the compositions of the complex additives and the test results of the samples for frost resistance and water tightness of concrete.

At the age of 28 days, frost resistance increases by 160-210 cycles, and water resistance - by 1-2 steps compared to the analogue.

The results obtained suggest that the complex additive increases the rate of curing of concrete in the early stages of hardening and allows to achieve high final strength, frost resistance and water resistance.

Claims (1)

Complex additive for concrete mix containing plasticizer and hardening accelerator, characterized in that it contains Mobet brand 2 hyperplasticizer as a plasticizer, Sika ^® Rapid 2 additive as a hardening accelerator in the following ratio, wt.%:
Hypermarket plasticizer "Mobet brand 2" 30-38
Curing accelerator "Sika® Rapid 2" 62-70