CS203258B1 - Method of producing mixtures of silicate concrete - Google Patents

Abstract

Prod. of a dense silicate concrete for large building elements from quartz sand, lime and water is improved in that, already in the first grinding stage, surfactants (pref. carboxylic acids, amino alcohols or other cpds. contg. OH gps.) and/or synthetic tanning agents are added. Alternatively, these additives can be introduced into the lime during its grinding or slaking; or in the mixing stage. The prods. are then autoclaved. The early stages of the concrete prepn. are facilitated and accelerated by introduction of surfactants or synthetic tanning agents.; the lime-slaking conditions are improved; the workability of the fresh concrete is improved; the strength of the prod. is increased.

Description

The invention relates to a process for the production of mixtures of silicate concrete, in particular dense silicate concrete for large-scale building elements.

From the German Patent Specification WP 106 621 on page 2, it is known to produce dense silicate concrete mixtures composed of:

6.0 to 12.5 ° / o quicklime with a CaO content of> 80%,

6.7 to 14.0% of quartz sand ground with an S ^: Ch content of> 90%,

73.5 to 87.3% of quartz sand 0-4 mm, 13 5 to 18.0% water.

An equal amount of lime hydrate may be used instead of quicklime. The mixing of all the components may be carried out either simultaneously or consecutively in a suitable order. This mixture is then formed in the usual manner, compacted by vibration, and then cured in a certain way by steam in the autoclave. The following composition is also known, also described in NDR WP 106 621 on page 9:

0.5 to 2.0% anhydrite,

6.7 to 37.5% ground quartz sand, 4T5 ⁷ to _8; 3% quartz sand 0-4 mm,

1.3.0 to 18.0% water.

The additional cement and / or quicklime and anhydrite improves the flowability of the mixture and binds the excess water required after compaction. According to the proposed method, the flowability of generally easily compactable silicate concrete mixtures can be increased by the addition of plasticizing agents and / or air pore-forming additives, without the need to work with excess water. The proportion of cement and / or quicklime as well as anhydrite are retained as a flow aid.

It is further known that high strength silicate concrete is obtained by mixing, shaping and curing quartz flour with lime hydrate in a weight ratio of 45:55 with up to 65% of the ingredients. For high strength silicate concrete, the quartz flour according to the GDR dependent patent No. 58,465 should have a fineness of 5 to 90 ₍ am, the maximum fineness being limited by the following granularity as the Z residue on the mesh in percent:

4.0 to 8.5 ° / o lime hydrate,

1.5 to 4.5% cement and / or quicklime,

0 3 2 59

Grain size in μΠΙ Residue on Z networks in% 5 70.5 10 59.5 20 May 40.2 40 15.7 63 3.5 90 0

Accordingly, the mixing and compacting of the fresh concrete mixture is carried out with more than 15% by weight of free water. Excess water allows compaction without the use of presses. Even in a simple vibration compaction, compacts without a structure are to be achieved. The excess water resulting from the compaction is drained off by absorbent pads, sieves or drains during this process.

The shortcoming of these known methods is that, although the individual measures in the individual operations achieve an improvement on the one hand, they must, on the other hand, be redeemed by other technical and economic victims. In the process of grinding, slaking of quicklime and compaction, they lead to disproportions in the control of fabric processes, which ultimately weighs down on the technologically necessary time and continuity of the process.

The object of the invention is to provide a process for the production of mixtures of silicate concrete, in particular dense silicate concrete for large-scale building elements, while avoiding the above-mentioned drawbacks which can safely handle the industrial process by complex application of one measure.

The invention is based on the object of design! a method of production of mixtures of silicate concrete, in which the fineness of grinding is improved in the initial operation or the grinding time is reduced by the addition of surfactants at the same fineness and the delay and uniformity of slaked lime is improved; even with a reduced proportion of ground quartz sand.

This object is achieved according to the invention in that the first grinding operation is carried out with an addition of 0.005 to 0.15% by weight, in particular 0.02 to 0.10% by weight, of surfactants and / or tanning agents, based on the dry weight of the mixture. in particular carboxylic acids, aminoalcohols, hydroxyl group compounds and synthetic tannins, to silicate concrete components - quartz sand and / or lime.

The above surfactants and / or tannins are added in the mixing operation.

According to another feature, one surfactant or tanning agent or a mixture of at least two surfactants and / or tanning agent is used.

By using the finest grinding apparatus, such as a vibrating mill, and using the surfactants and / or tanning agents described herein, as a milling aid for quartz sand, a very fine quartz sand is obtained as a binder component. The fineness of quartz sand must lie within the fineness range between grain size 1 and 2, as the remainder Z of the mesh, according to the following table 1:

Table 1

Grain size Grain Grain v μΐη 1 ') 5 69.0 42.5 10 57.0 25.5 20 May 37.0 9.0 40 15.5 0.7 63 5.5 0 90 0 0

The advantage of this measure is that the proportion of ground quartz sand in the concrete mixture can be reduced to 3.0 to 6.0 weight percent without loss of strength, since the SiOh of very fine quartz sand, reflecting on the solidifying OSH-phases, is not reduced. If the conversion of SiO 2 of ground quartz sand is usually 20 to 30 percent by weight, the conversion of SiO 2 by using very fine quartz sand is between 70 and 80 wt.% Of ground quartz sand. Reducing the proportion of ground quartz sand reduces the susceptibility to formation. cracks in the cured concrete element. Despite decreasing the proportion of ground quartz sand to 3.0 to 6.0 weight percent, the flowability of surfactants or tannins will improve the flowability of these mixtures

The object according to the invention is also solved according to the following principle: The viscosity minimum of conventional mixtures of silicate concrete under mixed water is achieved when the quartz sand is ground to a specific surface of 3,000 to 5,000 cm2 / g. without the addition of surfactants. Surprisingly, it has been found that the stated fineness of quartz sand always leads to a viscosity minimum, irrespective of the proportion of quartz sand and lime in the fresh concrete mixture. Thus, the amount of lime in the silicate concrete mixture may be 5.0 to 13.0 weight percent and the amount of quartz sand 7.0 to 20.0 weight percent. The advantage of this measure consists in improving the formability of large-dimensioned concrete elements, i.e. in a more uniform vibration compaction throughout. surface of the building element without additional load. In addition, greater concrete strength is achieved.

If, as part of the further development of the surfactant or tanning agent is added to the silicate concrete mixture in the stated concentration range, the viscosity minimum moves the fresh concrete mixture towards the even lower viscosities due to the liquefaction effect, so that even the sum of the effects can be said.

The processing of quicklime during the production process of the silicate concrete mixture is also carried out with the addition of surfactants or tanning agents until the use of quicklime in the silicate concrete mixture. The grinding of quicklime with the usual fineness of 10% of the residue to nets below 90 is substantially accelerated by the addition of surfactants or tanning agents with the same grinding fineness, or the grinding fineness increases with the same mill performance.

During the slaking of quicklime, the finest particles are extinguished very quickly in the first slaking phase, while the slaking rate of larger bodies decreases with increasing slaking time. Surfactants or tanning agents already added during grinding retard the high slaking speed of the finest particles, on the other hand they have only a minor effect on the slaking rate of larger grains due to their smaller surface, so that even slaking of quicklime or partially slaked quicklime can be achieved. Mixing a mixture of silicate concrete with water has a significant advantage, as it increases the pot life of the fresh concrete mixture.

The preparation of fresh concrete involves mixing the solid silica components with the mixing water. Surfactants or tannins found in ground quartz sand, optionally ground milled lime component or added during mixing of fresh concrete at the concentration described, reduce the water requirement. In addition to the flowability of the fresh silicate concrete mixture, the flowability of the mixture is improved. Differences in strength through the formation of layers and inhomogeneity in the structure of the concrete are thereby avoided.

It is also an effective measure to add surfactants and / or tannins while maintaining the stated concentration range, partly in the milling operation and partly during mixing at any ratio. Further, it is successful if the mixture is prepared from at least two surfactants and / or tannins and this is used. The strength of the concrete of the autoclave-cured concrete elements is improved when the quartz sand is ground in the fine grinding apparatus with said surfactants and / or tanning agents at concentrations of 0.005 to 0.10 weight percent. The effect of these substances as grinding aids results in finer quartz flour than in conventional grinding. This greater fineness of the quartz flour causes better formation of the CSH-phases in the autoclave and the greater the strength of the concrete in the silicate concrete elements.

If surfactants and / or tanning agents are added only when mixing the silicate concrete mixture, the liquefaction effect leads to a known reduction in water demand in the fresh concrete mixture, which allows for better compaction, and this again results in an increase in the strength of the concrete.

The proposed measures, i.e. the effect of surfactants and / or tanning agents at all stages of the production of silicate concrete mixtures, prove their technical and economic efficiency.

The process according to the invention is illustrated by the following examples.

Example 1

The use of surfactants and / or tanning agents in the grinding of quartz sand below

3.5 mm in a ball mill as well as in the mass of silicate concrete (compaction and curing) as compared to materials without surfactants and / or tannins (in percent increase).

The following surfactants and tanning agents are used:

From the group of carboxylic acids a mixture of synthetic fatty acids with a chain length of Cd to Cs, from the group of aminoalcohol triethanolamine, from the group of compounds with hydroxyl groups dodecyl alcohol. Synthetic Dabrogan tannins are chosen from tannins. The concentration of the additive is in each case 0.05% by weight based on dry matter.

The degree of march

Percentage increase over materials without additives triethanol-dodecyl-Dabrogan fatty acid

Cd-C 5 amine alcohol

Grinding begin. value 2000 cm ² / g Compaction of fresh concrete + 15.0 + 25.0 + 20.0 + 10,0 - Flowability (degree of spillage) Curing of silicate concrete - Compressive strength + 65.0 + 43.0 + 35.0 + 50.0 the beginning. value 30 MPa + 12.0 + 14.0 + 10,0 + 7.0

livo Dabrogan in works on concentration always

0.03 weight percent, based on dry matter, during grinding and mixing. The quartz sand is ground with triethanolamine,

Example 2

Based on Example 1, the triethanolamine surfactant and synthetic tanning agent 203258 are added as the most effective grinding aid to achieve the improvement of Example 1. When mixing the silicate concrete mass, the same amount of Dabrogan is added with the mixing water. The improvement in flowability and pressure strength (curing) is at the same level as in Example 1 of the Dabrogan values

Example 3

According to Example 1, instead of one surfactant, a mixture of two surfactants of 50% C 1 to C 50 fatty acid and 50% triethanolamine in a concentration of 0.05% by weight on dry weight basis is added to the ground quartz sand. The grinding improvement at an initial grinding fineness of 2000 cm ² / g in this case is 21.0%, a flowability of 52.0% and for a compressive strength at an initial value of 30.0 MPa 5.0%. _TO

Example 4

In a continuously operating vibratory mill, 3.15 mm quartz sand is ground with the addition of 0.05% triethanolamine to the following fineness (as residue on the mesh Zj:

Grain size in μΐη Granularity in% 5 62.0 10 43.0 20 May 25.5 40 6.7 63 0.9 90 0

5.0 weight percent of this fine quartz sand is added to the silicate concrete mass instead of 12.0 weight percent of the commonly used quartz sand of 1520 to 1200 cm ² / g. The flowability of fresh concrete is, in spite of the reduced proportion of quartz sand, of the order of magnitude equal to that of fresh concrete with quartz sand with a fineness of 1500 to 2000 cm ² / g. Non-cracked concrete elements have the same compressive strength of 30.0 MPa as elements with lower fineness of quartz sand.

Example 5

Quartz sand with a grain size below 3.15 mm is ground in a ball mill to a fineness of 3700 cm ² / g. The mixture of silicate concrete consists of:

5.0 weight percent CaO,

0.7% by weight of quartz sand of the above fineness,

84.7% by weight of quartz sand 0-3.15 mm,

9.2 weight percent water.

This silicate concrete mixture has a significant viscosity minimum compared to mixtures with a quartz sand fineness of 1700 cm ² / g or 6300 cm ² / g, so that the complete reinforcement of the steel reinforcement during vibration compaction is achieved. In addition, the compressive strength of silicone concrete with quartz sand of 1700 cm ² / g can be increased from 30.0 MPa to 41.0 MPa. '' ·

To the silicate concrete mixture described, 0.05% by weight of C 1 to C 7 fatty acid, based on the solid mass of the mixture, is mixed with the mixing water. The viscosity minimum of fresh concrete or its flowability is reduced by the same value as in Example 1.

Example 6

0.10 wt.% Of C 1 to C 8 fatty acid, based on solids, is added to quicklime and ground in a ball mill to 6000 cm ² / g. In the same test without surfactants, a surface of 5100 cm ² / g was obtained at the same grinding time.

The rate of slaking of quicklime according to the P'ev method is reduced by using 010% fatty acid Ci to Cs as compared to the slaked lime sample as follows:

Burnt lime Extinguishing rate in ° C / min after the extinguishing time: 5 min. 10 min. 30 min 60 nn i. without additive 0.10% fatty acid 1.19 1.26 -0.23 0.00 0.70 1.11 0.48 0.08

Claims (4)

OBJECT OF THE INVENTION 1. A method for producing silica sand, lime and water silicate concrete mixtures for large-dimensional dense silicate concrete building blocks in successive operations of grinding quartz sand, quenching burnt lime ground alone or mixed with sand and mixing ground quartz sand with slaked or curve ^F EcNo slaked quicklime and the mixing water, characterized in that already the first grinding operation is performed with the addition of 0.005 to 0.15% by weight, in particular 0.002 to 0.10% by weight of surfactants and / or tanning, based on the dry matter of the mixture, in particular of carboxylic acids, aminoalcohols, compounds with hydroxyl groups and synthetic tannins, to the components of silicate concrete - quartz sand and / or lime. Method according to claim 1, characterized in that a part of the surfactants and / or tannins is added in the mixing operation. 3. Method according to claim 1 or 2, characterized in that very fine quartz sand is added to the silicate concrete mixture as one binder component with a fineness between grain size 1 and 2, such as grain size 5 with a sieve residue of between 69.0 and 42.5%, in an amount of 3.0 to 6.0% by weight, containing surfactants and / or sober. 4. A process according to claim 1, characterized in that ground quartz sand having a specific surface area of 3000 to 5000 cm @ ² / g is added in an amount of 7.0 to 20.0% by weight and with a proportion of 5.0 to 13.0% by weight of lime. dry matter of silicate concrete mixture.