CS264724B1 - Building material - Google Patents

Abstract

The solution deals with a cement-based building material with increased strength increase, especially for hardening temperatures lower than 0 °C. Its essence is that in addition to cement, water and possibly aggregate, it contains, based on the weight of cement, 0.05 to 2% of a dispersant, such as sulfonated melamine formaldehyde resin or a condensation product of alpha-naphthalene sulfonic acid with formaldehyde, and 0.5 to 10% of a mixture of nitrous acid salt and/or nitric acid with formic acid salt in a ratio of 5:100 to 100:5. The building material according to the solution is suitable wherever it is necessary to ensure an increase in the strength of cement mortars and concretes at hardening temperatures lower than 0 °C.

Description

264724 2

The invention relates to a cement-based building material with an increased strength increase, a curing temperature map below 0 ° C. In construction practice, plasticizing additives are often used to reduce the content of the downcomer in cement mortars and concretes. However, the use of plasticizers alone does not impose the desirable increase in strengths at the negative hardening temperatures of cement mortars and concretes since they generally slow down the initial stages of cement hydration.

Anti-freeze additives are known from the Soviet literature (eg SA Mironov: Theory and methods of zimnego betonirovanija, Moscow, Strojizdat, 1975, or VB Ratinov and TI Rosenberg: Dobavki in Concrete, Moscow, 1973) to ensure the strength of mortars and concretes and lower hardening temperatures. as 0 ° C. Such additives include, for example, mixtures of nitrate and calcium nitrate, a further mixture of nitrate and calcium nitrite and calcium chloride and / or urea (carboxyldiamide, however, the recommended dosage of ingredients is high (Ruko- vodstvo after priming of chimicides in concrete, Moscow, Strojizdat, 1980), depending on the type of additive and the hardening temperature of the concrete are as follows:

The hardening temperature of the concrete, The dosage range of the additive% by weight of the cement ° C 0 to - 5 3 to 6 - 6 to -10 5 to 9 -11 to -15 7 to 10 The anti-freezing agent, consisting of a combination of soluble formate and nitrate. Its optimum dose for the initial increase in strength is 4% of the weight of the cement. By further increasing this dose, for example to 6 to 8% by weight of cement, the increase in initial strengths at hardening temperatures below 0 ° C is not accelerated (see S. Slaniček's article: Basic Selection and Verification of Antifreeze Agents. (1987).

Surprisingly, it has been found that the above-mentioned drawbacks are eliminated by building material based on cement. The essence of this is that, in addition to Portland clinker cement and possibly water, it contains a synergistic mixture consisting of a 0.05 to 2% dispersant, based on the weight of the cement, such as a sulfonated melamine formaldehyde resin or a beta-naphthalenesulfonic acid condensation product with formaldehyde. and 0.5 to 10% of a mixture of a nitrous acid salt and / or a buffing salt with a formic acid salt in a ratio of from 5: 100 to 100: 5. The advantages of the invention are illustrated by the following example of use: White Portland cement from the Rohožník site, the following chemical composition shown in Table 1, was used for the tests. 1:

Table 1

Component Component content,% wt. CaO 67.04 MgO '2.00 sieve2 22.68 ai2o3 4.52 ^ θ2θ3 0.19 SO3 1.90 loss on ignition 1.32 alkali unspecified residue not determined I-1

Said cement had a specific surface area according to Blaina (CSN 72 2114) 382 m ..kg, and C ^ A content calculated by Bogua (CSN 72 2125) 11.65%. Its standard strengths according to ČSN 72 2117 are given in Tab. 3 264724

Table 2

Trial term 1 day 3 days 7 days 28 days Flexural strength. MPa 2,7 6,3 7,5 8,7 Compressive strength, MPa 18,4 27,0 32,4 42,5 Test mortar specimens were produced from the mentioned cement according to ČSN 72 2117. However, unlike CSN 72 2117, a constant water coefficient of 0.5, but a constant processability of 160 ± 5 mm, measured as plasticity according to CSN 72 2441, was not observed. The test specimens were immediately stored for 14 days in an air-conditioned room with a temperature of -10 ° C. The strengths of the known masses were compared with the strengths of the mass containing the synergistic compositions of the invention. The first part of the strengths was measured immediately after thawing of the test samples, the next part of the test samples after thawing was tested after 1, 3, 7 and 28 days of further hardening under standard conditions according to ČSN 72 2117 (first 24 hours at 20 ° C with relative humidity of 90 %, then in water at the same temperature). The results obtained are shown in Tab. 3. Table 3 Mixture containing additives% by weight of cement Water coefficient / c Freezing strength MPa Compressive strength for 20 after further hardening ° C for 1 day 3 7 28 days Comparison without additives 0,50 1,6 6,8 11,1 21 , 31.0 Known mixtures with 2% Ca (HCOO) 22i NaNO3 + 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 t disperser 1) + 2% Ca (HCOO) 2 + 2% According to NaNC> 2 0.43 8.5 19.8 28.0 35.5 42.8 with 0.5% dispersant 2) + 2% Ca (HCOO) 2 + 2% NaNO3 0.44 10.5 20.0 29.8 36.4 44.5

Note: 1. Water-soluble sulfonated melamine formaldehyde resin, commercially designated Melment L 10; said 0.5% dose refers to the dry substance. 2. The condensation product of beta-naphthalenesulfonic acid with formaldehyde with the commercial designation Kortamol NNO was used as a dispersant.

As shown in the data in Tab. 3, the building material according to the invention has substantial strengths as known in the art. The action of a mixture of a dispersant and a mixture of formic acid and / or nitric acid salts on the release strength immediately upon thawing of the test samples is substantially greater than the additive effect of the dispersant itself and the salt mixture itself. This effect on the strength increase is maintained even at a further hardening at 20 ° C.

The building material according to the invention can be produced in a number of ways, for example by preparing a mixture of salts and a powder disperser, optionally with the addition of a small amount of inorganic powder substance as an anti-sticking agent such as

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.