CS264724B1 - Building material - Google Patents

Abstract

The solution deals with building material cement-based, with increased strength, at least for hardening temperatures below as 0 ° C. Its essence is that, in addition to cement, water and aggregates, if any, contains on cement weight, 0.05 to 2% dispersant such as sulfonated melamine formaldehyde the resin or condensation product of the acid alpha-naphthalenesulfonic acid with formaldehyde, a 0.5 to 10% of a mixture of nitrous acid salt and / or / or nitric with a salt of formic acid from 5: 100 to 100: 5. Building material solutions are suitable wherever necessary to ensure an increase in cement strength mortars and concrete at hardening temperatures below 0 ° C.

Description

The present invention relates to a cementitious building material with an increased strength increase, in particular for curing temperatures below 0 ° C.

In construction practice, plasticizers are often used to reduce the mixing water content of cement mortars and concretes. Nevertheless, the use of plasticizers alone does not provide the desired increase in strength at negative cure temperatures of cementitious mortars and concretes, since they generally retard the initial phases of cement hydration.

From Soviet literature (eg S. A. Mironov: Teorija i metod zimnego betonirovanija, Moscow, Strojizdat, 1975, or V. B. Ratinov and I. I. Rosenberg: Dobavki v beton, Moscow,

(1973), antifreeze agents are known which provide an increase in the strength of mortars and concrete even at curing temperatures below 0 ° C. Such additives include, for example, mixtures of calcium nitrite and nitrate, further mixtures of nitrate and calcium nitrite and calcium chloride and / or urea (carboxy diaminamide, CO (NH ₂ ) ₂ ). However, the recommended additive dosages are high (Rukovodstvo po primeneniju chimicheskich dobavok v betonu, Moscow, Strojizdat, 1980), depending on the type of additive and the curing temperature of the concrete, as follows:

Concrete hardening temperature, Dosage range of ingredients % by weight of cement C 0 to - 5 3 to 6 - 6 to -10 5 to 9 -11 to -15 7 to 10

An anti-freezing agent consisting of a combination of soluble formate and nitrate is known from the author's certificate 235 584. Its optimal doses for the initial strength increase are in the region of 4% by weight of the cement. By further increasing this dose, for example to 6 to 8 weight of cement, the increase in initial strengths at curing temperatures below 0 ° C does not accelerate (see S. Slaničku article: Basic selection and verification of anti-freeze additives. Building Constructions, No. 10/1987) .

It has surprisingly been found that the above-mentioned deficiencies are eliminated by a cement-based building material. It is based on the fact that, in addition to Portland clinker cement and, where appropriate, water and aggregates, it contains a synergistic mixture consisting, based on the weight of the cement, of 0.05 to 2% dispersant, such as sulfonated melamine formaldehyde nutrients or condensation product of beta-naphthalenesulfonic acid with formaldehyde. and 0.5 to 10% of a mixture of a salt of nitric acid and / or nitric acid with a salt of formic acid in a ratio of 5: 100 to 100: 5.

The advantages of the invention are shown in the following example of use: White Portland cement from the Rohožník locality, of the following chemical composition, shown in Tab. 1:

Table 1

component Ingredient content,% by weight CaO 67.04 MgO 2,00 sieve ₂ 22.68 ai ₂ o ₃ 4.52 ^ θ2θ3 0.19 ^S0 3 1.90 loss on ignition 1.32 alkali not determined insoluble. Rest not determined

I —1

Said cement had a specific surface area according to Blain (CSN 72 2114) of 382 m < 3 > kg, and a C ^ A content by calculation according to Bogua (CSN 72 2125) of 11.65%. Its standard strengths according to ČSN 72 2117 are given in Tab. Second

Table 2

Trial term 1 day 3 days 7 days 28 days strength in bending tension. MPa 2,7 6.3 7.5 8.7 strength under pressure, MPa 18.4 27.0 32.4 42.5 Test mortar samples were made from the cement according to ČSN 72 2117. However, in contrast to ČSN 72 2117, a constant water coefficient of 0.5 was not observed, but a constant workability of 160 ± 5 mm, measured as plasticity according to ČSN 72 2441. Test specimens were stored for 14 days in an air-conditioned room at -10 C. In the tests, the strengths of the known masses were compared with those of the mass containing the synergistic mixture according to the invention. The first part of the strength was measured immediately after thawing of the specimens, the other part of the specimens was after thawing tested after 1, 3, 7 and 28 days of further hardening under standard conditions according to ČSN 72 2117 (the first 24 hours at 20 ° C and relative humidity) above 90%, then in water at the same temperature). The results are shown in Tab. Third Table 3 Mixture containing additives by weight of cement Water coefficient v / c Defrost strength MPa Compressive strength Dec 20 after hardening ° C after 1 days 3 7 28 days Comparative without additives 0.50 1.6 6.8 11.1 21.1 31.0 Known mixtures with 2% Ca (HCOO) ₂ 2% NaNOg + 0.49 4.5 10,0 18,2 27.2 34.2 with 0.5% dispersant 1) 0.44 1.8 7,5 10,1 20.0 31.0 with 0.5% dispersant 1) + 2% Ca (HCOO) ₂ + 2% NaNO ₂ 0.43 8.5 19,8 28,0 35.5 42.8 with 0.5% dispersant 2) + 2% Ca (HCOO) ₂ + 2% NaNO ₃ 0.44 10.5 20,0 29,8 36.4 44.5

Notes: 1. A water-soluble sulfonated melamine-formaldehyde resin, commercially designated Melment L 10, was used as dispersant; said dose of 0.5% refers to the dry weight of the resin.

2. The condensation product of formaldehyde beta-naphthalenesulfonic acid with the commercial designation Kortamol NNO was used as a dispersant.

As can be seen from the data in Tab. 3, the building material according to the invention has significantly higher strengths than the mixtures known. The effect of the dispersant mixture and the mixture of formic and nitric acid salts and / or nitrous acid on the demoulding strength immediately after thawing the test specimens is substantially higher than the additive effect of the dispersant itself and the salt mixture itself. Said effect on the increase in strength is maintained even after further curing at 20 ° C.

The building material according to the invention can be produced in a variety of ways, for example by preparing a mixture of salts and a powder dispersant, optionally adding a small amount of an inorganic powder substance as an anti-sticking and agglomerating agent, such as limestone; such a mixture is then added as a powder additive while mixing the mortar or concrete,

- a mixture of salts, powder dispersant and cement is prepared beforehand so that only aggregates and water are added in the production of the mass,

- a dry prefabricated mixture containing all the necessary ingredients except the mixing water is prepared in advance, which is added only with stirring at the place of use, and a mixed dispersant and salt solution is prepared, which is dosed together with the rest of the necessary mixing water for the building material

The building material according to the invention is suitable wherever it is necessary to provide an increase in the strength of cementitious mortars and concrete even at curing temperatures lower than 0 ° C.

Claims (1)

OBJECT OF THE INVENTION Building material, in particular for curing temperatures below 0 ° C, containing Portland cement clinker-based cement and, optionally, water and / or aggregate, characterized in that it comprises a mixture consisting of 0.05 to 2, based on cement weight % of a dispersant, such as sulfonated melamine-formaldehyde nutrients or a condensation product of beta-naphthalenesulfonic acid with formaldehyde, and 0.5 to 10% of a mixture of nitric and / or nitric acid with formic acid in a ratio of 5: 100 to 100: 5.