RU2681720C2 - Method of producing building materials with high physical-mechanical and water-frost-resistant properties - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: mixing of the binder powder in the form of Portland cement or caustic magnesite with a surfactant additive based on polyethylene glycol, followed by ultra-fine grinding of the mixture in an electromagnetic apparatus to a particle size of 60-100 nm by introducing into the mixture a polydisperse fine-grained silica of 50-100 microns in the binder: SiO₂=1:2 and mixing the produced mixture with water using Portland cement or an aqueous solution of magnesium chloride using caustic magnesite.

EFFECT: increasing the speed of hardening the hardened material at an early stage, increasing the normalized strength while simultaneous increasing the wear resistance, water and frost resistance of the material.

2 tbl, 1 dwg

Description

 The invention relates to the building materials industry and can be used in the production of materials, products and structures from them, having high physical, mechanical, waterproofing and frost-resistant properties.

In the technology for producing special-purpose building materials with high mechanical strength, water and frost resistance, high-quality cements and a large arsenal of various methods and technological methods are used: organo-mineral additives (super- and hyperplasticizers together with a high-strength mineral component) are introduced into cements, water-repellent additives and highly active substances, finely dispersed active substances (silica fume, ground slurry, are introduced into the materials as fillers ki, sludge from blast furnaces, fly ash), produce a cement grinding joint with organomineral additives, increasing the specific surface of particles and their chemical activity, magnetize water during mixing of the cement mixture. A known method of preparation of a binder (cement) [1], including joint grinding in two stages: at the first stage, a mixture of Portland cement clinker, gypsum, superplasticizer C-3 and a siliceous mineral additive is ground to a specific surface of 2500-3000 cm ² / g, and in the second stage carry out a milling to a specific surface of 4500-6000 cm ² / g with the remaining mineral additive and structuring additive.

The implementation of this method allowed to obtain cements with a high content of mineral additives or fillers (49-70 wt.%) While maintaining the brand of binder at the level of M400, M500.

The disadvantages of the method are:

- at the indicated degree of dispersion of particles (4500 ... 6000 cm ² / g), this composition of the product caused difficult to control acceleration of the "setting" of the mass and strong shrinkage phenomena;

- dispersing a mixture of up to 6000 cm ² / g in a ball mill requires significant energy costs.

A known method for the production of cement with a mineral additive [2], including grinding Portland cement clinker with gypsum, superplasticizer C-3, a siliceous mineral additive, followed by grinding with a siliceous mineral additive, characterized in that it is ground to a specific surface of 4000 ... 6000 cm ² / g and siliceous mineral additive is used in an amount of 5-28 wt. % of these components, milled to a specific surface of 3000-3900 cm ² / g, using siliceous mineral additives in an amount of 30-70 wt. % of cement. This method achieves a more efficient grinding up to 6000 cm ² / g and mechanochemical activation of clinker grains with minimization of energy consumption and wear of grinding bodies, since clinker grains of an active mineral additive, when combined with cement clinker, play the role of micronizing bodies. In addition, the proposed technical solution allows you to enter a significant amount of mineral additives and to provide high construction and technical properties of cement stone. The disadvantages of the invention include:

- lack of data on the effect of dispersion on the rate of curing of the mass, water and frost resistance of cement stone;

- changes in the normalized strength indicate that the dispersion and activation of cement by this method is not effective enough.

A well-known complex additive for concrete and closed mixtures, including a finely ground mineral component is a waste product of the production of ferrosilicon based on SiO ₂ - silica fume, additives C-3 and sodium nitrite in the following ratio of components, mass. %: silica fume - 10-21, C-3 - 14-32, sodium nitrite - 47-75 [3]

Silica fume is an ultrafine powder with a specific surface of 7000 ... 11000 cm ² / g. The additive was introduced into Portland cement M-500DO in an amount of 0.5% by weight of cement. Concretes with the indicated admixture are actively gaining strength both in the early and subsequent curing periods. The rate of curing (compared to concrete without additives) is 160 ... 170% early and 140 ... 150% at the age of 28 ... 56 days.

The disadvantages of this invention include:

- limited amount of information about the effect of directly complex additives on the properties of the material;

- from the data presented it is impossible to identify the role of ultrafine silica fume in the kinetic process, which is responsible for the fast rate of material strength gain.

The methods for producing materials on a magnesian binder (Sorel cement), which have high mechanical strength, water resistance, and frost resistance, are mainly based on the introduction of modifying surfactants and various highly dispersed mineral additives with a high content of active silicon dioxide. The latter include: slag, acid ash, dust collection products of furnaces, etc.

Known raw mix [4], including, by weight. %: caustic magnesite - 15.0-21.5; ground basic granulated slag - 24.0-28.5; ground blast furnace dust or blast furnace gas treatment slurry - 9.0-30.0; bischofite solution with a density of 1.3 g / cm ³ - 9.30-11.16; aluminosilicate additive (waste from mechanical cutting of decorative sections on the surface of crystal products) - 1.0-5.0.

This raw material mixture in the closed state has increased mobility and vitality, and upon curing it forms a material with high water resistance and compressive strength.

At the same time, the mixture proposed in the invention has significant disadvantages:

- long viability time in a highly mobile state and a slow set of strength (time before setting, at 20 ° C is from 21 to 28 hours). This limits the use of the mixture, the composition additionally requires long-term monitoring and care before commissioning;

- a high content in the mixture of slag and blast furnace dust or sludge from blast furnaces increases the compressive strength of materials, their water and frost resistance, but brittle materials are obtained;

- the use as components of a mixture of granular slag, blast furnace dust, gas treatment sludge, waste from mechanical cutting of thin sections imposes severe restrictions on the production of materials due to the instability of the compositions of these wastes.

A known method of manufacturing products on a magnesian binder [5] by mixing a caustic magnesite powder with a mineral additive, C-3 superplasticizer, an aqueous solution of magnesium chloride, aggregate and the subsequent formation and curing of the resulting mixture. The proposed method allows to increase the strength of the magnesian material, but the increase in strength is low. In addition, the invention does not have data on water and frost resistance of the obtained materials and products from them. A known method of manufacturing building materials on a magnesian binder [6], comprising mixing a caustic magnesite powder, mineral additive, superplasticizer, an aqueous solution of magnesium chloride and aggregate, followed by the formation and curing of the mixture, characterized in that at least at least part of the caustic magnesite powder is activated by joint grinding with a superplasticizer and mineral additive to a specific surface area of particles of 6000-10000 cm ² / g, and then mixed with the rest of the specified composition ntami and additionally introduced methyl cellulose, moreover, an aqueous solution of magnesium chloride is used with a density of 1.1 ... 1.31 g / cm ³ , while the ratio of the components during joint grinding is, mass. %: caustic magnesite powder - 60-90; superplasticizer - 0.5-1.50; mineral additive - the rest, and the ratio of components in the total mixture, wt. %: the specified aqueous solution of magnesium chloride - 10-35; methyl cellulose - 0.02-0.10; caustic magnesite powder 0-10; placeholder - the rest. Fiber in an amount of 0.025-0.15 wt. % over 100%.

Fine dispersion of the binder together with a mineral additive and superplasticizer (up to a specific surface of 6000-10000 cm ² / g) made it possible to significantly increase the normalized compressive strength of the obtained building material (by 25-40%) and increase the strength at an early stage (1 day) by 25 -60% compared to the analogue.

This invention in its technical essence is the closest to the proposed and taken as a prototype.

The disadvantages of the invention include:

- lack of data on the effect of fine dispersion on the water and frost resistance of the materials obtained;

- the use of drum ball mills when grinding is a long-term, energy-consuming and environmentally unattractive way of fine grinding of substances. In addition, with prolonged grinding, severe abrasion of the balls occurs and abrasion products are adsorbed on the surface of the finely dispersed mixture, reducing its quality;

- a rather complex composition of building material, including expensive additives produced by foreign firms.

The aim of the invention is to develop a method for producing building materials on cement binders, providing increased physical and mechanical properties (speed curing at the early stage of curing, normalized strength, wear resistance), water and frost resistance.

This goal is achieved by the fact that the method of obtaining building materials with improved physicomechanical and water-and-cold resistant properties, comprising mixing a binder powder in the form of Portland cement or caustic magnesite with a surface-active additive based on polyethylene glycol, followed by ultrafine grinding of the mixture in an electromagnetic apparatus to particle size 60-100 nm, the introduction of a mixture of polydisperse fine-grained silicon dioxide with a particle size of 50-100 microns in the ratio of binder: SiO ₂ = 1: 2 and mixing the floor learned mixture with water when using Portland cement or an aqueous solution of magnesium chloride when using caustic magnesite.

To obtain building materials as cement binders used: Portland cement M-500 GOST 10178, magnesia caustic powder M-350 GOST 1216-87.

Magnesia binder was shut on a solution of magnesium chloride, an aqueous solution of a density of 1.19-1.26 g / cm ^{3 was used} ; magnesium chloride - hexahydrate crystalline hydrate MgCl ₂ * 6H ₂ O, GOST 7759-73 produced by PA Kaustik (Volgograd).

Fine-grained polydisperse (fractions of 50 ... 100 microns) silicon dioxide of the Ramensky GOK (Moscow Region) was used as a filler.

As a modifying additive, surfactants based on polyethylene glycol were taken in an amount of 2 wt. % by weight of cement.

Ultrafine grinding and activation of cement binders was carried out in a laboratory electromagnetic apparatus (EMA-1), where in one device the effect of alternating electromagnetic field, constant magnetic field and mechanical effect of permanent magnets on cement is combined. Electromagnetic grinding and activation of cements were carried out with the same experimentally selected optimal operating mode of the apparatus. In experiments on the effectiveness of ultrafine grinding, the parameters of the electromagnetic field varied within:

- field strength - from 35 to 60 kA / m;

- frequency - from 50 to 100 Hz.

The grinding intensity increased with increasing electromagnetic field strength, which is caused by an increase in the rotation speed of the magnetic granules. For the optimal field parameters at which grinding was carried out, the following were taken: tension 60 kA / m, frequency 50 Hz. The cement processing time varied from 5 to 30 minutes in increments of 5 minutes. After each electromagnetic treatment, the cement was mixed with a filler (silicon dioxide), the mixture was closed, cured at room temperature, and the properties of the obtained material were studied. Depending on the processing time of the cement binder, the degree of its grinding can be changed over a wide range - from thin (2-10 μm) to ultrafine with particle sizes of sub- (tenths of microns) and nanoscale (50-100 nm).

Portland cement base

Processing a Portland cement binder in an electromagnetic field causes changes in the properties of both the mass closed on its basis and the properties of the cured material. The maximum change in properties was observed after processing Portland cement in an electromagnetic field for 13 minutes. A further increase in processing time practically did not entail noticeable changes.

Portland cement powders with a high content of calcium and aluminum oxides are relatively easy to break down to the nanoscale particle size. Electron microscopic images of samples treated in an EMA for 13-15 minutes did not contain micro-range particles, the average particle size was 60 nm (0.06 μm).

Table 1 shows the effect of the electromagnetic treatment of Portland cement (13 minutes) on the properties of the solidified mass and cement stone.

Electromagnetic processing causes quite dramatic changes in the properties of both the cement paste and the resulting cement stone:

- the value of the water-solid ratio drops from V / T = 0.24 to V / T = 0.1 upon receipt of a workable mass (OK 10 cm);

- shortens the viability of the mass;

- the density of the mass increases;

- 4 times the speed of curing at an early stage (1 day) and ~ 2 times the normalized strength while a sharp decrease in the abrasion of the material;

- repeatedly increases frost resistance and water resistance.

Magnesia base

In the electromagnetic apparatus, caustic magnesite of the M-350 brand was processed, containing a modifying surfactant additive based on polyethylene glycol (2 wt.%).

Processing magnesia binder was carried out at the optimal operating mode of the apparatus. Processing time varied from 10 to 30 minutes; after processing, the binder was mixed with silicon dioxide in the ratio of binder / SiO ₂ = 1: 2 and the resulting mixture was closed on an aqueous solution of magnesium chloride with a density of 1.17 ... 1.26 g / cm ³ . Next, the sealed mass was placed in molds to obtain samples of various sizes, intended for the study of properties, and solidified at room temperature.

Ultrathin dispersion and activation of a magnesian binder in an electromagnetic field cause, as in the case of Portland cement, strong changes in the properties of both the closed mass and cement stone. The processing time at which the maximum change in the properties of the material on a magnesian basis is achieved (30 min) is more than 2 times the processing time of Portland cement (13 min).

Magnesium oxide is more durable than calcium oxide, and its destruction is more difficult. According to a study using a laser particle size analyzer, even after prolonged treatment of magnesia cement in the EMA, particles of both nano and micro ranges are present in it (Fig. 1). The study of the distribution of particles after prolonged treatment (20-30 minutes) is very difficult due to aggregation of particles.

Properties of the obtained magnesian materials are presented in table 2.

Changes in the properties of materials on magnesian and Portland cement binders obey the same regularity. With an increase in the time of processing cement in an electromagnetic field and an increase in the degree of dispersion of the binder particles, the viability of a workable sealed mass is shortened and the water-solid ratio for its creation decreases. The rate of set strength of the cured mass increases at an early stage, the normalized material strength, wear resistance, water and frost resistance increase. At maximum cement processing time, the normalized strength of the material almost doubles, wear resistance, water and frost resistance increase many times.

Ultrafine grinding and activation of cements in high-intensity magnetic fields not only sharply increase the specific surface and cause the active particles to pass from the cement binder to the surface, but also generate free-radical particles (as a result of the destruction of chemical bonds) and excite the electronic atom subsystem. As a result, almost all chemical and physicochemical processes are transformed, both during mixing of the cement mass and during its curing: the processes of dissolution, particle hydration, the formation of coagulation neoplasms, the formation of crystallization nuclei, and processes of interphase interactions. Processing in electromagnetic fields dramatically changes the kinetics of processes, the sequence and completeness of many of them, and also provokes processes that cannot be carried out without the participation of particles arising from electromagnetic grinding and activation.

Portland cement and magnesia cement stones have fundamentally different compositions, structures and mechanisms of transition of closed masses into a solid state. The basis of Portland cement stone, as is known, is made up of calcium hydrosilicates, in the voids of which there are filler particles, various neoplasms of a globular shape, and grains of incompletely reacted cement. The formation of cement stone is based on hydration processes.

The basis of the magnesia stone is crystalline hydrates of 5MgO * MgCl ₂ * 15H ₂ O and 3MgO * MgCl ₂ * 11H ₂ O hydroxo salts, the voids between which are filled with filler grains, magnesium hydroxide Mg (OH) ₂ , particles of incompletely reacted cement and various neoplasms. The main role in the formation of a magnesian stone is played by interphase interactions in the MgO - MgCl ₂ - H ₂ O system.

Ultrathin dispersion and activation of particles of Portland cement or magnesia cement cause, first of all, their more complete interaction in the closed mass, acceleration of the curing process and an increase in the strength of the obtained material. The presence of highly active particles dramatically enhances chemisorption processes, increases the rate of hydration and the completeness of the formation of calcium hydrosilicates (Portland cement base). Fine particles with the sizes of subnano and nanoscale densify the cement stone, sharply reduce microporosity, fill capillary channels, thereby providing low permeability and high frost resistance of the resulting material.

An important role in the course of chemical and physicochemical processes is played by a modifying superplasticizing surfactant additive based on polyethylene glycol. It causes not only an increase in the mobility of the closed mass and reduces the water-solid ratio, but also initiates an additional dispersing effect of cement and filler particles, reducing the surface tension at the solid – liquid interface. The dispersing effect accelerates the formation of neoplasms and subsequent crystallization.

The research results showed that by additional electromagnetic processing of cements, it is possible to almost double the grade of material: M-350 in M-700, M-500 in M-1000 while increasing their waterproofing and frost-resistant properties. This opens up new possibilities for obtaining special-purpose building materials (underground construction, construction of hydraulic structures, airfields, etc.) with enhanced physical, mechanical, water and frost-resistant properties by additional electromagnetic treatment of high-quality cements. In construction work, there is also the opportunity to significantly reduce the consumption of cement binder.

The claimed method of producing building materials, which is based on ultrafine grinding and activation of cement binder in electromagnetic fields, and the properties of the materials are interconnected by a single inventive concept, leading to the achievement of the results and allowing the creation of materials with enhanced physical, mechanical, water and frost resistant properties . Such a possibility for the prototype and analogues is extremely limited due to insufficient knowledge of the properties of materials and fragmentary information presented in general. A comparative analysis of the results of the claimed invention and the obtained data of the prototype and analogues shows that traditional methods of grinding and activation of cements are not effective enough and significantly inferior to the method of processing them in intense electromagnetic fields.

Information sources

1. RF patent No. 2167114,2001. Method for the production of binder (cement).

2. RF patent No. 2371402, 2007. Method for the production of cement with a mineral additive.

3. RF patent №2308429, 2006. Complex additive for concrete and dissolved mixtures.

4. RF patent №2130437, 1998. Raw mix.

5. RF patent №2121987, 1988. A method of manufacturing products on a magnesian binder.

6. RF patent №2222508, 2002. A method of manufacturing building materials on a magnesian basis (prototype).

Claims (1)

A method of obtaining building materials with improved physicomechanical and water-frost-resistant properties, comprising mixing a binder powder in the form of Portland cement or caustic magnesite with a surface-active additive based on polyethylene glycol, followed by ultrafine grinding of the mixture in an electromagnetic apparatus to a particle size of 60-100 nm by introducing polydisperse mixture of fine silica particle size of 50-100 microns in a ratio of binder: SiO ₂ = 1: 2 and mixing the resulting mixture with water using n rtlandtsementa or an aqueous solution of magnesium chloride using caustic magnesite.

Images