RU2230048C2 - Concrete mix preparation method - Google Patents

Abstract

FIELD: manufacture of building materials. SUBSTANCE: in a method of preparing concrete mix comprising stirring of cement, sand, broken stone, tempering water, and plasticizer-microsilica slurry, order of components fed into concrete mixer is the following: cement, sand, broken stone, and tempering water, after which above components are stirred for 0.5-0.9 min and then supplemented by plasticizer-microsilica slurry and additional water to achieve required workability followed by final stirring. Weight ratio of plasticizer (superplasticizer S-3) to microsilica in their slurry is 1:10 and that of dry components to water (1.0-1.2):(2.8-3.0). EFFECT: improved quality of mix and reduced preparation expenses. 4 cl, 1 tbl

Description

The invention relates to building materials, in particular to methods for the preparation of concrete mixtures used for the manufacture of building structures.

A known method of preparing concrete mixtures, including mixing cement, sand, gravel, water, plasticizer (Mchedlov-Petrosyan, O.P. and others. Prospects for the use of PHPF in precast concrete technology // Concrete and reinforced concrete, 1986, No. 8, p.32- 33.).

The disadvantage of this technical solution is the insufficient strength of the resulting concrete.

The closest in its technical essence is a method of preparing a concrete mixture, including mixing cement, sand, gravel, mixing water, a suspension of plasticizer with silica fume (AS USSR No. 1525126, class. 04 V 22/00).

The disadvantage of this method is that its implementation requires a long time for aging the suspension, and in addition, the suspension is first fed into the sand, as a result of which sand grains sticking together from the effects of plasticizer and silica fume are formed, which, when mixed, are difficult to separate to obtain a homogeneous mixture with cement even in the presence of additional water. This process requires additional energy and time to obtain high-quality concrete mix.

The objective of the present invention is to improve the quality of the concrete mixture and at the same time reduce the cost of its preparation.

The present problem is solved in that in a method for preparing a concrete mixture, including mixing cement, sand, crushed stone, mixing water, a suspension of plasticizer with silica fume, they are fed into a concrete mixer in the sequence: cement, sand, crushed stone, mixing water, mixing 0.5- 0.9 min, then a plasticizer suspension with silica fume and an additional amount of water to obtain the necessary workability and final mixing.

As a plasticizer, C-3 superplasticizer is used.

The ratio in suspension of superplasticizer C-3 and silica fume is 1:10.

The ratio in the suspension of dry components (C-3 + silica fume) and water is (1.0-1.2) :( 2.8-3.0).

The method is as follows. Concrete mixture for the production of concrete and reinforced concrete products is prepared in a forced-action mixer.

As a plasticizer, S-3 superplasticizer is used. Superplasticizer and silica fume are fed through the path of supplying liquid additives in the form of a suspension. The suspension is prepared in a container for liquid additives with mechanical stirring. In this case, the suspension should have the following characteristics:

- the ratio of superplasticizer S-3 and silica fume 1:10;

- the amount of dry components of the suspension of 27.5%;

- amount of water 72.5%;

- density 1.15 g / cm ³ .

A decrease in the amount of water in relation to the dry components of the suspension reduces its mobility, complicates its supply to concrete and leads to higher cost of production.

An increase in the amount of water relative to dry components leads to a decrease in the quality of concrete.

The dosed components of the concrete mixture enter the concrete mixer in the following sequence: cement, sand, gravel, water, mixing for 0.5-0.9 minutes, a solution of a suspension of plasticizer with silica fume, additional water to obtain the necessary workability, final mixing. The completeness of the mixing process is determined visually by the uniformity of the concrete mixture.

If the mixing time is insufficient, the uniformity of the concrete deteriorates and its strength decreases.

At a shorter time for mixing a mixture of cement, sand and crushed stone with mixing water, before a solution of a suspension of plasticizer with silica fume is fed into it, incomplete wetting of the particles of the prepared concrete occurs, as a result of which hydrate formation in the presence of silica does not begin simultaneously over its entire mass, which leads to a decrease durability.

An increase in the duration of mixing reduces the performance of the concrete mixer and increases the cost of production per unit.

The results of testing concrete of the design class for strength of 22.5 are shown in the table.

The total time for preparing the concrete mixture is reduced by 7-29 s.

The prepared concrete mixture is delivered to the molding workshop, where, using the concrete-dispensing equipment, it is placed in pre-prepared forms, no later than 2 hours after preparation. The compaction of the concrete mixture is carried out by vibration.

Claims (4)

1. A method of preparing a concrete mixture, including mixing cement, sand, crushed stone, mixing water, a suspension of plasticizer with silica fume, characterized in that the cement, sand, crushed stone, mixing water are fed into the concrete mixer, mixing 0.5-0, 9 min, then feeding a suspension of plasticizer with silica fume and an additional amount of water to obtain the necessary workability and final mixing. 2. The method according to claim 1, characterized in that C-3 superplasticizer is used as a plasticizer. 3. The method according to claim 2, characterized in that the ratio in suspension of superplasticizer C-3 and silica fume is 1:10. 4. The method according to claim 1, characterized in that the ratio in the suspension of dry components and water is (1.0-1.2) :( 2.8-3.0).

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