CS254244B1 - Portland cement with increased initial lands - Google Patents

Abstract

The solution concerns Portland cement with increased initial strengths. The essence of the solution is Portland cement made from clinker with a tricalcium sulfite content of over 56% by weight, a specific surface area of 250 to 1000 m2 kg-1 according to Blain, characterized in that it contains 0.1 to 7% by weight of aerated concrete with a content of 11% tobermorite with a particle size of less than 60 μm. Cement with increased initial strengths of the foundation can be used in prefabrication, for grouting, construction of chimneys and storage tanks with sliding formwork, in adverse weather conditions, in concrete technologies with cast concrete, and for reconstruction work during operation.

Description

The invention relates to Portland cement with increased early strengths.

Construction practice requires cements with increased early strengths for the production of concrete with increased early strengths, even for the production of concrete at normal temperatures, for accelerating the hardening of concrete by superheating and for winter concreting.

Cement with calcium chloride is suitable for all these purposes. However, calcium chloride cannot be used in reinforced concrete because it causes corrosion of steel reinforcement (SEBOK, T.: Additives and preparations for mortars and concretes, Prague SNTL 1985, p. 9).

Cement mixtures containing the additive aluminum sulfate are known from the literature (BECHYNĚ, L.: Technologie betonu, SNTL Praha 1954, p. 581). However, in the fresh state, cement mixtures with the additive aluminum sulfate have false setting (JISEL, A.: Admixtures for cement, published by author, Soisu, France 1973, p. 127), which practically makes their use to accelerate hardening and increase strength impossible.

Other methods of obtaining cements with increased initial strengths mainly consist in the changed mineralogical composition of the clinker compared to ordinary Portland clinker. They are based on obtaining active belite clinkers, sulfoaluminate belite clinkers, halogen-containing clinkers, etc. (HOROŠCÁK, T. and KOL.: Research into new types of silicate-based cements with programmable properties, VÚSH Brno 1982). The production of the above-mentioned clinkers or cements requires new expensive raw materials, their transportation and also the modification of the technological equipment or the production method, and often also the deterioration of the environment, which is their disadvantage.

The research of suitable additives with a similar effect as calcium chloride has brought many interesting results, e.g. sodium thiosulfate increases the rate of hydration of tricalcium silicate, although it is not as effective as calcium chloride, (ZLIELINSKA, E.: Chem. abstr., 92, 115 370, 1980), the addition of glycerol, triethanolamine and butyl alcohol increases the strength of crystalline neoplasms and their adhesions, (TAVLINOVA, T., DO VÝBOROVÁ, L.

N.: Chem. abstract 92, 46 339, 1980).

One of the most promising ways to increase the initial strength of cement is to add crystallization seeds to the cement, which then create conditions for faster nucleation of new forms, the formation of stronger adhesions between them, the overgrowth of the base material of the microstructure skeleton, as well as its subsequent filling with gel, and are also an active reagent in the formation of ettringite.

AO USSR 771 042 proposes the preparation of crystallization nuclei as an additive for increasing the strength of Portland cement. The crystallization nuclei are obtained by rapidly cooling Portland clinker in water from 1300 to 1500 °C to 50 to 100 °C, holding for 5 to 20 minutes in a wet state and subsequent drying. Under these almost hydrothermal conditions, xonolite and a hydrated form of tricalcium silicate are formed in the clinker grains. These are then suitable crystallization centers during the hydration of Portland cement, as proposed by AO USSR 765 227, which proposes the addition of 0.5 to 14% by weight of such an additive to Portland cement.

Lack of all the listed ingredients, or designs of cements with increased initial strengths are low efficiency, difficult to handle, demanding preparation, problems with dosing, high price and the like.

The above-mentioned shortcomings are eliminated by Portland cement with increased early strengths according to the invention, made from clinker with a tricalcium silicate content of over 56% by weight and a specific surface area of 250 to 1,000 m ² . kg ^-1 according to Blain, characterized in that it contains 0.1 to 7% by weight of aerated concrete with a content of 11 Å tobermorite with a particle fineness below 60 μΐη.

The advantage of the cement with increased strengths according to the invention is its high initial compressive and flexural strengths compared to Portland cement with the same mineralogical composition and the same fineness of grinding. All Portland clinkers can be used to produce the cement according to the invention — they do not require any special and expensive raw materials. The cement according to the invention can be produced without modifying the technological equipment and technological process. The additive is preferably added during cement grinding, which ensures complete homogenization of the cement components. For its preparation, breaks and waste from the production of aerated concrete, or aerated concrete from demolition machines, can be used. This additive does not have a corrosive effect on steel reinforcement, is hygienically harmless, easy to handle, can be dosed well and is affordable.

The properties of cement with increased early strengths according to the invention are shown by the following examples:

Example 1

In a laboratory mixer MCK 3, PC 400 from SC Banská Bystrica, kp, (tricalcium silicate content was 60% by weight, specific surface area of cement 310 m ² .kg ^_1 ), water and sand according to ČSN were mixed. Part of the cement was replaced with ground aerated concrete, which was ground to a particle size below 60 μΐη.

A relative comparison of their strengths after 1, 3, and 28 days is given in Table 1:

Table 1:

Final Relative strengths after 1, 3, 7 and 28 days % tration bending pressure

ingredients % 1 3 7 28 1 3 7 28 0 100 100 100 100 100 100 100 100 0.1 151 85 125 110 158 101 132 117 0.3 136 82 120 107 160 95 127 116 0.5 136 86 115 110 144 97 125 112 0.75 138 89 112 110 128 100 117 110 1.0 125 85 103 107 124 99 110 103 3.0 135 82 112 112 134 90 136 118 5.0 127 94 120 110 130 96 133 111 ' r í k 1 a d 2: water and sand according to CSN. Part of the cement bo

la replaced by ground post-concrete, which was ground to a particle size below 10 ^m. A relative comparison of their strengths after 1, 3 and 6 days is given in Table No. 2.

PC 400 from SC Banská Bystrica, kp, was mixed in a laboratory mixer MCK 3 (tricalcium silicate content was 60% by weight, specific surface area of cement 310 m ² .kg“ ¹ },

Table 2:

Ingredient concentration % Relative compressive strengths after 1, 3 and 7 days % 1 3 7 0 100 100 100 0.1 173 148 133 0.5 256 160 150 2.0 356 123 117

The cement with increased initial strengths according to the invention can be used in prefabrication, for assembly grouting, construction of chimneys and storage tanks using sliding formwork, in adverse weather conditions, in concrete technologies with cast concrete, or for reconstruction work during operation.

Claims (2)

254244 Table 1: End - Relative strength after 1, 3, 7 and 28 days% loss bending pressure additive% 1 3 7 28 1 3 7 28 0 100 100 100 100 100 100 100 100 0,1 151 85 125 110 158 101 132 117 0.3 136 82 120 107 160 95 127 116 0.5 136 86 115 110 144 97 125 112 0.75 138 89 112 110 128 100 117 110 1.0 125 85 103 107 124 99 110 103 3.0 135 82 112 112 134 90 136 118 5.0 127 94 120 110 130 96 133 111 'rik 1 ad 2: water and sand according to CSN. Part of the cement is replaced by ground concrete, which has been ground to a particle size below 10 µm. Relative compared to its strength after 1, 3 and 6 days is given in Table no. 2. In the MCK 3 laboratory mixer PC 400 from SC Banská Bystrica, kp (tricalcium silicate content 60% by weight, cement surface area 310 m2.kg -1 i, Table 2: Additive concentration% Relative compressive strength were mixed). after 1, 3 and 7 days% 1 3 7 0 100 100 100 0.1 173 148 133 0.5 256 160 150 2.0 356 123 117 Cement with increased initial strengths according to the invention can be used in pre-fabrication assembly cladding, buildingbukomies and storage tanks with sliding formwork, in unfavorable weather conditions, in concrete technology with liaison concrete, will be reconstructed during the operation OVER T Portland cement with increased initial strength made from clinker containing tricalcium silicate above 56% w / w of the invention according to Blaina, characterized in that it contains 0.1 to 7% by weight of 11 A tobermorite porous concrete with a particle size of less than 60 µm. !.