PL231221B1 - Cement for applications in low temperatures - Google Patents

Description

Description of the invention

The subject of the invention is cement for applications in low temperatures, which is used in winter construction.

In construction, many admixtures in concrete mixes are commonly used, enabling concreting at low temperatures. These include chloride-free chemical compounds (salts), air-entraining admixtures, plasticizing and fluidizing admixtures.

There is known from the Polish patent description No. PL 44998 a method for the production of high-speed Portland cement with high initial strengths, characterized in that potassium sulphate is added to the high-lithium clinker of Portland cement to be ground up to 3% in terms of SO3.

It is known from the Polish patent description No. PL 170947 as an anti-frost admixture to concrete, added to the concrete mix during its production, increasing the resistance of freshly made concrete to frost. The admixture consists of sodium or calcium formate in an amount of 40 to 60 parts by weight, sodium salt of beta-naphthalenesulfonic acid polycondensates with a degree of condensation of 7 to 10 in an amount of 25 to 40 parts by weight, urea in an amount of 5 to 20 parts by weight, nonylphenol ethoxylate = 8 to 10 in an amount of 0.1 to 1 part by weight and optionally ethylene glycol in an amount up to 3 parts by weight.

It is known from the Chinese patent description CN101386482 B frost-resistant cement containing calcium chloride, sodium chloride, sodium nitrite, sodium sulphate, gypsum, triethanolamine, alum.

Known from the Chinese patent application CN102485681 A, a frost-resistant cement containing calcium aluminate, sodium thiocyanate, hydrated calcium silicate, triethanolamine, alum and gypsum.

It is known from the international patent application WO1983004018 A1, a hydraulic cement mixture containing hydraulic cement, aggregate, the amount of water necessary to carry out cement hydration and an admixture containing one part by weight of a compound or mixture of two compounds belonging to the group of sulfonated melamine-formaldehyde plasticizers and one twentieth parts by weight of cement of the compound or a mixture of two or more compounds belonging to the group of water-soluble nitrates, nitrites and urethanes present in an amount up to 10% by weight of the cement to improve the maturation of the cement mix without side effects on the physical properties and strength of the cement mix.

The aim of the invention is to obtain a cement for applications at reduced temperatures, the high heat of hydration (485 J / g) and high initial strengths of which ensure the possibility of setting and hardening at negative temperatures. Cement for applications in low temperatures will be used in the production of binders, mortars, concrete used primarily for works requiring high strength in a short period of time, for example in "winter" construction for the repair of airport slabs and any repairs requiring rapid increase in strength with simultaneous occurrence of negative temperatures.

The cement according to the invention is obtained by mixing Portland cement with a tricalcium aluminate (C3A) content of less than 1% by weight. and strength class N, in an amount of 50% 80% by weight. and calcium aluminum ferrite (C6A2F) with a molar ratio of aluminum (III) oxide to iron (III) oxide (Al2O3 / Fe2O3), 0.36-2.23, in an amount of 20% -50% by weight, with a grain diameter of 0.090-0.056 mm and the content of accessory phase reactive additives such as monocalcium aluminate (CA) in the amount of 2% -6% by weight. calcium aluminoferrite (C6A2F) and majenite (C12A7) in an amount of 4% -15% by weight. Calcium aluminoferrite (C6A2F).

Preferably, the content of calcium aluminum ferrite (C6A2F) with a molar ratio of alumina (III) to iron (III) oxide (AbO3 / Fe2O3) of 2.2 is 39 wt.%.

Preferably the content of the calcium aluminoferrite (C6A2F), the monocalcium aluminate (CA) is 5 wt.%, The maenite (C12A7) 10 wt.%.

The advantage of the method according to the invention is that it is possible to obtain a cement for applications at sub-zero temperatures with high initial strengths. The end product is more resistant to corrosion without losing its strength parameters.

The subject of the invention is presented below in an embodiment.

P r z k ł a d

61 wt.% Was mixed. Portland cement of the strength class 42.5N with a content of tricalcium aluminate (C3A) below 1% by weight. with 39 wt.% Calcium aluminum ferrite (C6A2F) with a molar ratio of aluminum (III) oxide to iron (III) oxide (Al2O3 / Fe2O3) equal to 2.2 and grain diameter of 0.063 mm,

PL 231 221 Β1 containing accessory additives of reactive phases, such as monocalcium aluminate (CA) in the amount of 5% by weight, calcium aluminoferrite (C6A2F) and majenite (C12A7) in the amount of 10% by weight of calcium aluminoferrite (C ₆ A ₂ F).

In the process of hydration of Portland cement, in the first 3 hours of the process, ferrous aluminum ettringite (C3 (A, F) -3CaSO4-32H2O) was formed, as well as hydrated calcium aluminates and aluminates as well as hydrated calcium silicates [C2 (A, F) H6], [C3 ( A, F) H6j.

For the tests, a mortar was prepared in which the ratio of cement to standard sand was 1: 2.75 and the ratio of water to cement (W / C) was 0.45. The samples were kept at -15 ° C.

The results of the compressive strength tests of mortars made of the cement according to the invention and the cement "Chełm" 42.5N are presented in Table 1 below. Cement "Chełm", strength class 42.5 N, has a very low content of tricalcium aluminate (C3A) and is produced only in the Chełm Cement Plant in Poland.

Table 1

Compressive strength in MPa The number of days 1 3 7 28 90 Cement according to the invention 5.6 7.1 11.2 20.5 26.8 Cement Chełm 42.5N 0 0.5 2.9 5.4 9.3

Along with the development of the surface of calcium aluminoferrite (C6A2F) with the grain size indicated above, its activity towards water increased, and thus the heat of hydration and the degree of conversion increased. The greater the surface area of calcium aluminoferrite (C6A2F) that has been admixed to Portland cement, the higher its activity in the freezing-temperature cement and thus the better the cement.

Due to the presence of the hydrated aluminum ferrite and calcium aluminate phases C2 (AF) H6, C3 (AF) H6, which are products of calcium aluminoferrite hydration, the strength of the cement containing these hydrates has increased, which increases the product's resistance to any corrosion resulting from its exposure.

The tests show that the cement according to the invention achieves higher initial strength after 1 day, amounting to 5.6 MPa, compared to the cement without additives, which strength after 1 day is 0 MPa. After 28 days, the cement according to the invention achieves a compressive strength of 20.5 MPa, at a negative ambient temperature of -15 ° C.

Claims (3)

Patent claims A cement for low temperature applications containing an admixture for low temperature concreting, characterized in that it contains 50% -80% by weight of Portland cement of strength class N with a content of tricalcium aluminate (C3A) in the amount below 1% by weight. and 20% -50 wt.%. Calcium aluminoferrite (C6A2F) with the molar ratio of aluminum (III) oxide to iron (III) oxide (AbO3 / Fe2O3), 0.36-2.23, with a grain diameter of 0.090-0.056 mm and the content of accessory reactive phase additives, such as monocalcium aluminate (CA) in an amount of 2% -6% by weight. calcium aluminoferrite (C6A2F) and majenite (C12A7) in an amount of 4% -15% by weight. aluminum calcium ferrite (C6A2F). 2. Cement according to claim The method of claim 1, characterized in that the content of calcium aluminoferrite (C6A2F) with a molar ratio of aluminum (III) oxide to iron (III) oxide (Al2O3 / Fe2O3) equal to 2.2 is 39 wt.%. 3. Cement according to claim The process of claim 1, wherein the content of calcium aluminoferrite (C6A2F), monocalcium aluminate (CA) is 5 wt.% And that the maenite (C12A7) is 10 wt.%.