RU2348598C2 - Method of preparation of concrete "flint stone -granite" - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: according to the method of preparation of concrete, dry components of concrete mixture are preliminary blended in bladeless mixer: portland cement, road metal and sand, there after water with dissolved therein plasticizing agent MDF 0.003 at 0.15 - 0.2 water - cement ratio with formation of pellets, hard core whereof is formed by road metal, cover consists of damped mixture of Portland cement and sand. There after received concrete mixture from the mixer is discharged into the form with application of vibration load being intermixed simultaneously, and gets consolidated. Pellets been formed coloring agent is loaded into the concrete mixture.

EFFECT: enhanced strength and density of concrete, getting high quality glazed surface.

2 cl, 2 ex

Description

The invention relates to the production of concrete from mixtures used for molding products for various purposes.

A known method of preparing a concrete mixture (US Pat. RF No. 2147017, С04В 28/00, publ. 03/27/2000), according to which water is poured into a concrete mixer with previously dissolved superplasticizer S-3 and specially prepared binder, sand, is added, crushed stone and mix. An astringent is obtained by co-grinding Portland cement, C-3 superplasticizer and silica additives in the form of quartz sand with traces of zirconium compounds.

The composition of the mixture is as follows (%):

astringent 20,0 placeholders 73.0 water 6 plasticizer C-3 0.04

Characteristics of concrete:

strength 600-800 MPa frost resistance no less than 200 cycles abrasion 0.7 g / cm ² water absorption less than 2%

However, for this concrete, it is necessary to specially prepare the binder, which is laborious and associated with significant costs of electricity and additional components, an expensive plasticizer is used.

A known method of preparing a concrete mixture according to the patent of Russian Federation No. 2042653, С04В 28/02, С04В 24/20, publ. 08/27/1995, the Method includes the preliminary processing of cement with S-3 superplasticizer and mixing with mechanical action of 30-120 W per 1 kg of the mixture to be treated, subsequent mixing with aggregates and water, and this is first treated with 3.45-46.15 wt. cement of its total amount and the remaining amount of cement is introduced with stirring with the remaining components of the concrete mixture. The following materials are used: Portland cement M 400, washed granite crushed stone. 5-10 mm, lake sand with a micron density of 2.2 cm, drinking water, S-3 superplasticizer based on sodium salt - a condensation product of naphthalenesulfonic acid and formaldehyde. The processing of cement with a plasticizer is carried out in a mill. The concrete mixture is prepared in a concrete mixer SB-101.

Process parameters:

processing time, sec 3,4.10 ⁴ energy consumption, j 11.46.10 ³

Characteristics of concrete:

workability of concrete mix OKcm 0,5

compressive strength MPa - 28.4 after 24 hours;

62.6 in 28 days

water-cement ratio W / C 0.40.

(The indicators are taken as in example 3 of the patent specification.)

However, the concrete preparation scheme is quite complex and lengthy, characterized by a significant consumption of components, in particular, rather expensive S-3 plasticizer and electricity, and with a water-cement ratio of 0.40, water can remain in the concrete, which will affect its strength characteristics. The compressive strength of hardened concrete is low.

As a prototype, a method of concrete preparation was adopted, including mixing in a mixer the components of the concrete mixture: Portland cement, mineral filler, sand, plasticizer, water, unloading the resulting concrete mixture into a mold with a vibration load, subsequent solidification (see Bazhenov Yu.M. Concrete technology Moscow, Higher School, 1978, p. 48, 183-185, 202-203, 205). Crushed stone is mainly used as a mineral filler, SSB, S-3, etc. additives are used as a surfactant. Water is not given special attention to the process of introducing water. Various pigments may be used that are introduced together with the components of the mixture. Thus, the proposed solution coincides in the amount of features and for the intended purpose with the prototype. The quality indicators of concrete according to the prototype with the addition of S-3:

Water cement ratio W / c 0.75-1.0 Compressive Strength MPa 100-125 Frost resistance cycles 100-130 Permeability% 1-3

(According to the book of Bazhenov, Yu.M. Concrete technology, Moscow, Higher school, 1978, table 3 of the appendix). It turns out concrete with a rough surface. With a water-cement ratio of 0.75-1.0, the density of concrete decreases, water can remain in it, its strength characteristics decrease. In addition to toga, S-3 plasticizer is quite expensive.

These shortcomings are eliminated by the proposed solution.

The problem to be solved is the improvement of the method for producing concrete when it is cheapened by eliminating expensive plasticizer.

The technical result is an increase in the density and strength of concrete, providing its glossy surface for the manufacture of, for example, decorative products.

This technical result is achieved by the fact that in the method of preparing concrete, comprising mixing in the mixer the components of the concrete mixture of Portland cement, mineral filler, sand, plasticizer, water, unloading from the mixer into a mold with a vibration load, subsequent solidification, dry components are pre-mixed in a bladeless mixer mixture, after which water is gradually added with the MDF plasticizer dissolved in it - 0.003 at a water-cement ratio of 0.15-0.2 with the formation of pellets, the core oryh is a mineral filler and the shell consists of a hydrated mixture of Portland cement and sand; unloading from the mixer is carried out without stopping mixing,

pigment is added to the concrete mixture after the formation of pellets,

crushed stone is used as a mineral filler.

The gradual introduction of water with a plasticizer after mixing the dry components in a bladeless mixer creates the conditions for the formation of pellets. In addition, the plasticizer MDF - 0.003 cheaper than S-3, 10 times, available and has high plasticizing properties. The water-cement number of 0.15-0.20, along with the shape of the pellets, allows you to remove air from concrete as much as possible when pouring it into the mold.

The use of a bladeless mixer and continued mixing when unloading concrete from the mixer contributes to the formation of pellets and their compaction to the complete exclusion of air gaps. Adding pigment to the concrete mixture after the formation of pellets allows them to be dyed to the desired depth and to save pigment.

The method is as follows. The components of the dry mixture are prepared: Portland cement, mineral filler, sand, and the total mass is determined by the Fuller formula:

Σ _m = 30% A _m + 30% V _m + 40% C _m , where

And _m is the mass of the mineral filler, such as crushed stone, with a particle diameter equal to (1 / 3H) / 3; H is the thickness of the cast concrete product;

C _m is the mass of sand with a particle diameter of 0.5 to 1.0 mm;

Σ _m = 2.3 P _m , where P _m is the mass of Portland cement;

In _m is the mass of crushed stone particles with a diameter equal to (1 / 3H) or 1/3 A _m .

Accordingly, the mass of the concrete mixture Σ _b is expressed by the following formula:

E _b = Σ _m + P _m + M _modif. + M _water + M _pigm , where

M _modif = P _m · 0.007;

M _water = P _m · 0.15;

M _pigm = P _m · 0.015, and M _pigm , for example, is titanium dioxide or its mixture with other pigments in a ratio of 1: 1, respectively.

The dry components are mixed in a bladeless mixer for about three minutes. If necessary, a strength accelerator, for example technical calcium chloride, and reinforcing additives in the form of fibers, for example fibropropylene, can be added. At the same time, a solution of plasticizer (alkaline modifier) MDF - 0.003 in water is prepared and gradually added to the dry mixture while stirring is continued. Under these conditions, pellets form, the core of which is a mineral filler (for example, gravel), and the shell consists of a moistened mixture of Portland cement and sand. After the formation of the pellets, a pigment, for example titanium dioxide, can be added. The staining depth is controlled by the mixing time. When pellets with pigment are found for 10-15 sec, the staining depth is up to 1.0 mm, 20-30 sec - up to 3 mm, 30-60 sec - up to 5 mm.

The preparation time for the finished concrete mixture is 3-5 minutes. A rigid concrete mixture is obtained with a water-cement ratio of 0.15-0.20, which, however, is well formed.

The finished concrete mixture is discharged from the mixer with continuous stirring and poured into a mold on which a horizontal circular vibration load is applied to the vibrating table. Superdense castings with a glossy surface are obtained due to the low water-cement ratio and maximum air removal during the pouring process.

Example 1 of the method.

Provided that the mass of Portland cement was taken as a unit, the ratio of components in the concrete mixture was as follows:

Portland cement 1,0 crushed stone 2,3 sand 1,2 plasticizer MDF 0.003 - 0.005 water 0.15

The plasticizer MDF - polyether acrylate - an unsaturated polyester formed during the polymerization of allyl ethers of polybasic acids in the presence of peroxides, azo compounds and other initiators. Various grades of polyester acrylates and compositions based on them are produced in industry (MDF - 0.003 was used in the experiments). They are mainly used as binders for the manufacture (modification) of reinforced plastics (see Korshak V.V. Plastics Technology, Moscow, Chemistry, 1972, p. 394-396).

The dry components were mixed in a bladeless mixer for three minutes, after which water was gradually added with the plasticizer MDF 0.003 dissolved in it to obtain a water-cement ratio of 0.15. An increase in this number of more than 0.2 already introduces excess fluid into the concrete, which may be the cause of the appearance of microchannels in the product, and consequently, a decrease in density and strength. A decrease in water-cement number less than 0.15 does not provide sufficient moisture and, accordingly, the formability of the concrete mixture. Round pellets with a diameter of 1.0-5.0 cm were formed.

After mixing for 5 minutes, the finished concrete mixture was poured into the molds without stopping mixing, and their compaction on the vibrating table immediately began.

Received products with a glossy gray surface.

In the finished concrete product after its hardening, there is no residual water at all.

Tests give the following characteristics of the resulting concrete:

compressive strength MPa 800-950 frost resistance cycles 1000 abrasion, g / cm ² 0.3 water permeability% less than 1.0

Example 2

Carried out, as example 1, using the same components in the same quantities. Moreover, after the formation of round pellets with a diameter of 1.0-5.0 cm was completed, titanium dioxide pigment was added in an amount of 0.015 weight of Portland cement. The residence time of the pellets with pigment was varied from 10 to 30 seconds. The staining depth was 1.0-3.0 mm, respectively. Products had a white glossy surface.

These characteristics significantly exceed the characteristics of the prototype. As a result of the claimed method for preparing concrete due to the new simple technology of mixing concrete mixture, high-quality products with increased strength characteristics and low water-cement ratio were obtained.

The increased density of the product (the absence of pores in concrete) provides a high-quality glossy surface of the products, which allows etching any patterns on the front surface and producing products of any size and shape that can be used for decorative cladding and decoration of buildings both inside and outside, paving sidewalks and road routes with the provision of any given pattern on the front surfaces of the finished product.

Claims (2)

1. A method of preparing concrete, comprising mixing in the mixer the components of the concrete mixture: Portland cement, mineral filler - crushed stone, sand, plasticizer, water, unloading the resulting concrete mixture from the mixer into a mold with a vibration load, subsequent solidification, characterized in that it is pre-mixed in a bladeless mixer of dry components of the concrete mixture, after which water is gradually added with the plasticizer MDF 0.003 previously dissolved in it at a water-cement ratio 0.15-0.2 with the formation of pellets, the core of which is crushed stone, the shell consists of a moistened mixture of Portland cement and sand, and the indicated discharge from the mixer is carried out without stopping mixing. 2. The method according to claim 1, characterized in that pigment is added to the concrete mixture after the formation of pellets.