RU2344110C1 - Method of concrete mix production - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to construction materials. The method of concrete mix production includes mixing Portland cement, super softener C-3, micro-silica, fine-grained filling agent such as sand for construction works and coarse-grained filling agent of 5-20 mm fractions. Crushed stone of mainly cubic shape or gravel of mainly round shape is used as the above coarse-grained filling agent. The mixing process is performed at the following order of components supply to mixer: the above-mentioned coarse-grained filling agent, tempering water, super softener C-3 and microsilica. The mixture is stirred during 2-10 minutes and Portland cement and construction sand are introduced. Then mixture is stirred during 3 minutes under the following ratio of components, wt %: Portland cement - 11-17.6, coarse-grained filling agent - 52.8-54.1, super softener C-3 - 0.09-0.13, microsilica - 1.1-1.76, construction sand - 21.37-28.55, water is the remaining ingredient.

EFFECT: reduction of power consumption and labour efforts, simplification of technology at high concrete strength properties.

1 tbl, 1 ex

Description

The invention relates to methods for the preparation of concrete mixtures with the addition of silica fume.

A known method of preparing a concrete mixture, including the processing of coarse and fine aggregate with 80-90% mixing water containing 10 ^-4 -10 ^-2 % plasticizer with respect to the aggregate, then inject cement and the remaining 10-20% mixing water and carry out the final mixing [A.S. USSR No. 1754693 A1, IPC (5) С04В 40/00, publ. 08/15/92].

However, this method does not provide high concrete strength, the greatest compressive strength achieved in this method, 36.0 MPa (example 3) is insufficient for the construction of facilities using high-strength concrete. In addition, the operation of “steaming” concrete leads to additional energy and labor costs.

Closest to the proposed invention in technical essence and the achieved result is a method of preparing a building mixture, including preliminary joint grinding of Portland cement, quartz sand and superplasticizer to a specific surface of 4500-5500 cm ² / g and subsequent mixing of the grinding product with silica fume for 3-4 minutes and then with ordinary building sand or a mixture of it with crushed stone of a fraction of 5-20 mm in the following ratio of components, wt.%:

Portland cement 14.7-22.5 quartz sand 1.7-2.5 superplasticizer 0.22-0.34 silica fume 0.7-1.1 crushed stone fractions 5-20 mm 0-51.0 ordinary building sand 22.56-82.68.

[RF patent No. 2201412 C2]

This method provides high strength concrete. However, to achieve high concrete performance, additional operations were introduced: joint grinding of Portland cement, quartz sand, superplasticizer and mixing of the grinding product with silica fume, which complicates the technology and increases the energy and labor costs for obtaining 1 m ³ concrete mixes.

The aim of the invention is to reduce energy, labor, simplification of technology while ensuring high strength characteristics of concrete.

This goal is achieved by the fact that in the method of preparing a concrete mixture, including mixing Portland cement, S-3 superplasticizer, silica fume, fine aggregate - sand for construction work and coarse aggregate fraction 5-20 mm, crushed stone of predominantly cuboid form is used as said coarse aggregate or the gravel is predominantly round in shape, and the specified mixing is carried out in the following sequence of feeding the components to the mixer: the specified large aggregate, mixing water, super astifikator-3 and microsilica, the mixture was stirred 2-10 minutes, and then carried out the supply of Portland cement and sand for construction and agitated for 3 minutes in the following ratio, wt.%:

Portland cement 11-17.6 specified coarse aggregate 52.8-54.1 superplasticizer C-3 0.09-0.13 silica fume 1.1-1.76 sand for construction work 21.37-28.55 water rest.

The essence of the method lies in the fact that when mixing a large aggregate with mixing water, superplasticizer and silica fume for 2-10 minutes due to friction and collision of silica fume particles with a filler, silica fume is dispersed to sizes less than 1 μm and these dimensions are maintained as a result of coating them with plasticizer , excluding mutual adhesion of particles, followed by active interaction with the products of hydration of cement and ensuring high strength characteristics of concrete.

In addition, when dispersing silica fume, the aggregate surface is activated, which ensures the best adhesion of the aggregate with the mortar part of concrete and, accordingly, an increase in bending strength.

After Portland cement and fine aggregate sand is supplied to the mixer for construction work and all components are mixed for 3 minutes, the most uniform distribution of dispersed silica particles in the concrete mixture occurs.

The greatest effect on obtaining high strength characteristics of concrete (R _cr , R _arr ) is achieved when crushed stone is predominantly cuboid in shape or gravel is predominantly rounded.

Concrete implementation example

To implement the method using the following materials:

1. Portland cement M400 (GOST 10178-85).

2. Large aggregate: diabase gravel, gravel fraction 5-20 mm (GOST 82690-97). The content of diabase grains of a cuboid form is 80%. Round gravel content is 90%.

3. Fine aggregate: sand for construction work M _cr = 2.8 (GOST 8736-93).

4. Silica fume MK-85 (TU 7-249533-90).

5. Superplasticizer C-3 in the form of a liquid (TU 6-36-0204229-625-90).

Coarse aggregate of a fraction of 5-20 mm, mixing water, C-3 superplasticizer, silica fume are loaded into the mixer, and the mixture is stirred 1.8; 2; 10; 11 minutes Portland cement and sand are added to the resulting mixture for construction work and mixed for 3 minutes.

For objectivity of comparison, a building mixture is also prepared according to the prototype method: a joint grinding of quartz sand, superplasticizer and Portland cement is carried out in a ball laboratory mill to a specific surface of 5500 cm ² / g and then mixing the grinding product with silica fume for 4 minutes, and then with an ordinary mixture building sand and gravel.

Of the prepared mixtures, 10 × 10 × 10 cm cubic samples and 4 × 4 × 16 cm cubic samples are made and subjected to natural hardening, and physical and mechanical tests are performed after 28 days.

The compositions of concrete mixtures and concrete test results are shown in the table. Analyzing the tabular data (test results), we can conclude that the boundary limits for the mixing time of coarse aggregate, silica fume and superplasticizer with mixing water are 2-10 minutes. When mixed for less than 2 minutes, the compressive strength of concrete is reduced by 7.9-11.1%; bending by 12.7-17.1% (trains No. 7, 8, 9 compared with trains No. 1, 2, 3). When mixing for more than 10 min, the compressive and bending strength of concrete practically does not change (compositions 10, 11, 12 compared with compositions 4, 5, 6), therefore, a further increase in the mixing time is impractical.

Analyzing the test results shown in the table, we can conclude that the strength characteristics of concrete are increased using the proposed method.

Claims (1)

A method of preparing a concrete mixture, including mixing Portland cement, S-3 superplasticizer, silica fume, fine aggregate - sand for construction work and a coarse aggregate of 5-20 mm fraction, characterized in that crushed stone is predominantly cubical in shape or gravel is predominantly round forms, and the specified mixing is carried out in the following sequence of feeding the components to the mixer: the specified coarse aggregate, mixing water, C-3 superplasticizer and mi rokremnezem, the mixture was stirred 2-10 minutes, and then carried out the supply of Portland cement and sand for construction and agitated for 3 minutes, the following component ratio, wt.%:
Portland cement 11-17.6 Indicated coarse aggregate 52.8-54.1 Superplasticizer S-3 0.09-0.13 Silica fume 1.1-1.76 Sand for construction work 21.37-28.55 Water Rest