CS254246B1 - Modified high-performance and heavy-duty, cement - Google Patents

Abstract

The solution concerns the area of high-strength and expanding cements. The essence of the solution is a modified high-value and expanding cement, consisting of Portland cement, characterized by the fact that it contains, expressed in weight percentages of cement, 5 to 20% of amorphous silica, containing at least 30% of particles smaller than 3 jum -and at least 50% of particles smaller than 20 jum, 1 to 8% of calcium oxide, 0.01 to 2.0% sodium carbonate and 0.01 to 2.0% alkaline salt of lignosulfonic acid. The solution can be used wherever high concrete strengths, low concrete shrinkage values, high water resistance to aggressive waters, etc. are needed.

Description

254246

The present invention provides a modified high performance and expandable cement.

High-performance cements are those cements that have high final strengths, at a minimum pressure of 55 MPa per 28 days.

High-quality cements are most often produced by grinding portland clinker with a higher fineness, which is energy-intensive. Furthermore, they are produced by a certain modification of the mineralogical composition of conventionalportland clinkers, which in turn is a difficult raw material, energy at firing (high C3S content in sinter as well as technology discipline. (Bárta, R .: Cement Chemistry and Technology. 1961. J

Barbecue methods of obtaining high-quality cements based on conventional Portland clinkers have been proposed using additives. These additives either affect the hydration process and the formation of hydrated minerals (SEBOK, T .: Additives and Additions to Mortars and SNTL Praha, 1985) or bind the hydrated calcium hydroxide formed by crystallization. calcium silicates. (AO ZSSRč. 635 057, 637 358, 637 357.)

The drawback of these cements is the relatively difficult reproducibility of their properties and sometimes low resistance to sulphates as a high shrinkage value.

Expansion cement is considered to be a value that, when hydrated, increases its volume, restp. it does not shrink and ensures perfect filling of volume or volume increase during concreting.

Expansion cements, in particular, do not shrink substantially three components: base malt-vine, expander and rectifier, respectively. regulator. The basic mortar is aluminum or Portland cement. The expan- sion was cement-sulphate-aluminate, more recently a mixture of aluminous cement with calcium sulphate, or active magnesium oxide. A blast furnace basic slag is used as a rectifier (regulator, stabilizer). All these expansive, respectively. non-freezing cementitious expansions. Etringite crystals have a higher volume than the solids for high water content. By increasing, filling the cracks and pores. If this is not enough, they create in the hydrating cement an internal pressure which, when the material is cohesive, expands by expansion. In the expanded cements, there should be only a quantity of tetringite that will exert pressure to increase the volume without disruption, and in non-freezing cements it is sufficient to compensate for the shrinkage of Portland cement. (Bárta, R .: Cement Chemistry and Technology, NČSAVPraha, 1961, p. 776.) All expanding cements based on sulfoaluminates, eg AOZSSR No. 530 865, 366 164, have the same substance (formation of etringite).

The disadvantage of the above-mentioned expansion cements is their high sensitivity to mineralogical composition, water content, curing treatment, low expansion and sensitivity temperature during hydration as well as the presence of substances occurring in the underwater (NaOH, NaCl, Na2SO4, etc.), causing them to be upset. A further group of expandable mortars, cement resins, are mixtures where the increase in volume is based on the presence of swelling and gas generating substances, e.g., AO of CSSR No. 166 965, 187 901. porosity in a structure that results in a decrease in strength, low expansion and poor resistance to a-environment.

Also known are expandable cements composed of Portland cement containing free lime. The expansion process mechanism is based on increasing the volume of the calcium oxide to calcium hydroxide. The disadvantage of such expanding cementitious difficulty is to control the content of the free drum and the degree of expansion. In addition, lime hydration often occurs when cement is set and hardened, causing it to break. Concrete made from this cement is susceptible to leaching of calcium hydroxide and aggression by sulphate feeds.

The aforementioned drawbacks are eliminated by the solution of the modified high-performance and expandable cement consisting of Portland cement according to the invention, characterized in that the modified high-strength and expanding cement contains, expressed in weight percent of cement, 5 to 20% of amorphous silicon oxide containing at least 30% of particles smaller than 3 μΐη and not less than 50% of particles smaller than 20 μΐη, 1 to 8% of calcium oxide, 0,01 to 2,0% of carbonate and 0,01 to 2,0% of alkali metal salt of lithium sulphonic acid. An advantage of the modified high-performance cement of the present invention is that it can be produced from a conventional Portland clinker of unimpaired energy requirements. This cell has a high bending and compression strength. The concrete made from this cement has a high strength, high corrosion resistance and water-permeability. In addition, it has a low shrinkage value. The advantage of the modified expandable cement according to the invention is the high expansion strength of the high strength, which is due to the fact that the calcium oxide hydration is hydrated in such a composition of expandable cement so that the volume increases as the volume increases. it is in the plastic state, ie before the formation of the rigid structure.

In the hydration of the modified high-strength and expandable cement, a large number of "grains" of amorphous silicon oxide are inactivated and hence more intense chemical bonding of calcium hydroxide, 254246 5 6, formed during the hydration of the clinker minerals, resulting in an increase in strength. As the ammonium silicon dioxide, a fume generated by the production of ferro-silicon can be advantageously used. In addition to regulating the hydration processes (together with sodium carbonate), the alkali metal salt of lignosulphonic acid] is particularly suited to the perfectly homogeneous distribution of fine silica particles in cement and in the cement stone, thereby contributing to better binding of calcium hydroxide to calcium silicate hydrates.

The properties of the modified high-performance expandable cement according to the invention are documented by the following examples without any limitation (see Tables 1 and 2). Modified high-performance and expansible cement according to the invention with sand and water sub-standard CSN are mixed in the laboratory. Their strength as well as the composition are shown in Table 1. 1 and 2. For their preparation, Portland cement PC 400 was used from the Ladce cement plant, milled to a specific surface of 320 meters2. kg-1 by Blaina.

Modified high-performance and expandable cement can be used everywhere, where high concrete strength, low-shrinkage concrete, high resistance to a-greasy waters, etc. are required.

Composition of modified high-strength cement (w / w) 28-day strength (MPa) PC 400 Airborne S1O2 CaO Sodium lignosulfonate Na2CO3 bending pressure 100 0 0 0 0 7.63 46.62 85.94 10 3 1.03 0 , 03 8,19 75,50 75,55 20 4,5 0,045 0,045 10,80 75,00 80,92 15 4 0,04 0,04 8,6 73,26 84,94 10 3 2,00 0, 03 8.61 72.5 85.94 10 3 0.03 1.03 7.88 72.2 84.94 10 3 0.03 2.00 7.43 72.00 87.96 10 2 0.02 0 , 02 8.93 69.0 91.94 5 3 0.03 0.03 9.08 69.0 88.98 10 1 0.01 0.01 9.64 67.0 85.92 10 4 0.04 0.04 8.51 65.03 90.92 5 4 0.04 0.04 7.2 58.0 93.0 5 2 0 O 7.38 52.90 95.0 5 0 0 0 9.26 52 , 63 90.0 10 0 0 0 8.93 51.06 85.0 15 0 0 0 5.52 39.86 254 2 4 6 oa ta a Λo> fi

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Claims (1)

254246 7 PREDMET Modified high-performance and expanding cement, consisting of Portland cement, characterized in that it contains, by weight, from 5 to 20% amorphous silica containing at least 30% of the inventive particles of less than 3% by weight. not less than 50% of less than 30 μΐη, 1 to 8% of calcium oxide, 0,01 to 2% of sodium carbonate and 0,01 to 2% of lignosulphonic acid alkaline salt.