RU2392246C1 - Dry mortar - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: dry mortar contains the following components, wt %: ash 50-85, caustic magnesite powder 10-30, natural mineral schungite of III type 0.1-10, modifying additives 0.1-1.5, construction sand - the rest.

EFFECT: improved efficiency of hazardous substances neutralisation in process of ash recycling and improved quality of construction materials due to application of ash in dry mortars.

6 cl, 1 tbl, 3 ex

Description

The invention relates to the production of building materials, and in particular to methods for manufacturing dry building mixtures using ashes filler from the burning of waste wastewater treatment. The invention allows to create cheap dry building mixtures, replacing cement and gypsum building materials, with the simultaneous disposal of toxic and radiation hazardous waste that remains after wastewater treatment.

At present, the final product of multi-stage processing of urban wastewater at the city water supply facilities is ash, which is formed by burning wastewater treatment waste at a specialized plant. The annual volume of ash produced by only one plant is several tens of thousands of tons.

The ash contains substances classified as I-III hazard class according to GOST 12.1.007-76. Among them, lead, mercury, arsenic, cadmium, cobalt, etc., the mineral residue in the ash is about 80%. The effective specific activity of natural radionuclides (A _eff. ) In the ash is 230-500 Bq / kg, calculated on the dry weight of the ash. The presence of gamma-emitting technogenic radionuclides was detected in ash samples. The specific activity of ¹³⁷ Cs in individual ash samples reaches 30–40 Bq / kg; in some samples, the presence of ⁶⁰ Co and ⁵⁹ Fe was detected at the level of the first units of Bq / kg.

Ash is currently being disposed of at a special landfill requiring additional protective equipment; the need to expand such landfills is constantly growing.

Other methods for utilizing ash are known. For example, in the RF patent for invention No. 2037476 dated November 20, 1991 (prototype), a method for using shale fly ash as a cementitious component in building blocks that can be used for mass industrial construction is proposed. Shale fly ash is formed during the combustion of oil shale in shaft mill furnaces of power plants and is captured in cyclones and electrostatic precipitators. This ash, which has astringent properties, is then mixed with aggregates in the form of sand or various construction waste, for example, coal slag, foundry foundry ground, brick bricks, etc. The resulting mixture is filled into metal molds, resulting in building briquettes, similar to traditional concrete.

However, for the manufacture of concrete by this method, steaming of the concrete mixture in strong metal forms is required at an elevated pressure and temperature of 90-95 ° C with a holding time of 24 hours, which leads to the complexity of the process and the cost of finished products. At the same time, concrete is obtained with high porosity and strength of finished products of only 7-16 MPa, which significantly limits its scope.

The ash from the combustion of sewage sludge, in contrast to the ash specified in the prototype, contains a significantly larger amount of harmful, including radioactive substances. In addition, it does not have astringent properties, so in building blocks it can only be used as a filler. Adding such ash to concrete based on a binder - Portland cement allows only partially reduce the toxicity of harmful components. The issue of strength, crack resistance and dust formation of finished products for use as building materials of residential and public buildings is also not being addressed. In addition, Portland cement concrete with filler in the form of ash obtained by burning wastewater treatment waste does not reduce the activity of radionuclides to sanitary standards.

For materials used in constructed and reconstructed residential and public buildings, the effective specific activity of natural radionuclides should be: A _eff. ≤370 Bq / kg. As indicated above, in ash from the incineration of wastewater treatment wastes this figure is much higher, and in addition to radionuclides in ash there are many other dangerous and harmful substances.

The objective of the proposed solution is to increase the efficiency of neutralization of harmful substances in the disposal of ash and improve the quality of building materials through the use of ash in dry building mixtures with specially selected components.

To solve the problem in a dry building mixture containing ash and building sand, the natural mineral shungite, caustic magnesite powder and modifying additives were additionally introduced, in the following ratio of components, wt.%:

Ash 50-85 Caustic Magnesite Powder 10-30 Natural Shungite Mineral 0,1-10 Modifying additives 0.1-1.5 Building sand rest

Ashes can be used ash from the burning of waste water from sewage treatment plants, ash from thermal power plants and metallurgical slag. Ash in the proposed mixture is a filler.

Caustic magnesite powder grade PMK-87 is used in the proposed mixture as an astringent component, it contains a mass fraction of active magnesium oxide from 0.75 to 0.95. (GOST 1216-87). Caustic magnesite powder is obtained by trapping dust generated during the production of sintered periclase powder. Caustic magnesite powder of the PMK-87, PMK-83 or PMK-75 grades can be used in the proposed mixture.

As an adsorbent in the proposed mixture, shungite of the III variety of the Zazhoginsky deposit was used, which consists of 30% shungite carbon and 68% silicates and is a nanostructured natural composite. One of the specific properties of such a breed is its ability to sorb many substances, both organic - oil products, benzene, phenol, pesticides, and mineral - iron, manganese, phosphorus, arsenic, etc. (Kalinin Yu.K. Shungity and human life safety. Materials of the first All-Russian scientific-practical conference. Petrozavodsk, 2007).

Modifying additives can be set and hardening regulators, water-absorbing, plasticizing, densifying and increasing adhesion substances.

The bischofite solution can serve as a substitute in the proposed mixture.

As a filler, ash can be supplemented with barite concentrate or screening of crushed granite (dolomite, marble, etc.).

The proposed composition of the components of the dry building mixture ensures the binding and neutralization of organic, mineral and radioactive substances present in the ash, including ash from the burning of waste water. In addition, this composition due to the interaction of its constituents provides high-quality building materials.

The manufacturing technology of dry building mixes includes the following operations: preparation, dosing and mixing of ash, caustic magnesite powder, shungite and modifying additives in a mechanical mixer, followed by packing in 20-25 kg paper bags. Mixtures are made in the factory (at the place of ash formation) or at the landfill. Ready dry mixes are delivered to construction sites in dry form and mixed in a certain proportion immediately before use with natural bischofite - saline solution of magnesium chloride MgCl _{2 with a} density of 1.1-1.25 kg / l. The solution mixture crystallizes and gradually passes into the final stable phase - the magnesian stone of a tangled-fibrous structure.

Products cured by this method from the ash-magnesia-shungite composition (ZMSh) do not emit harmful substances into the water and air in quantities exceeding the MPC and ODE and comply with the requirements of sanitary rules and norms.

With the estimated ratio of components of the product from ZMSh guaranteed to meet the requirements of NRB-99 for the content of natural radionuclides established for building materials of class I with A _eff. ≤370 Bq / kg (production, storage, transportation and use) without restrictions on the radiation factor.

The compressive strength of ZMSh in finished products for a given proportion of the main ingredients (Table 1) is about 20 MPa, which makes it possible to widely use this material in the construction of municipal housing facilities, warehouses, manufacturing, entertainment, sports, domestic, administrative and other premises. The strength of the proposed compounds due to its texture, characterized by the mutual germination of spiral tubular filamentous aggregates.

The proposed building material can be applied in the form of floor screeds, wall blocks, partitions and other products.

The floor screed and wall blocks made according to the invention, according to the tests carried out, have a bulk density of 1800-1900 kg / m ³ .

The technology for obtaining the proposed dry building mix is illustrated by the following examples.

Example 1

A mixture is made up of the following components, wt.%:

Ash 85 Caustic Magnesite Powder 10 Modifying additives 0.1 Natural Shungite Mineral 0.1 Building sand rest

This composition is the most economical, has a minimum strength (1-2 MPa), but allows you to make large blocks and prevent dusting of ash during disposal at the landfill.

Example 2

A mixture is made up of the following components, wt.%:

Ash fifty Caustic Magnesite Powder twenty Natural Shungite Mineral 10 Modifying additives 0.5 Building sand rest

This composition has a maximum strength (18-22 MPa) and meets sanitary rules and standards for use in construction without restriction on the radiation factor. The mixture is well molded and suitable for the manufacture of, for example, wall blocks for internal partitions.

Example 3

A mixture is made up of the following components, wt.%:

Ash 65 Caustic Magnesite Powder 25 Natural Shungite Mineral 8.0 Modifying additives 1,0 Building sand rest

This composition has a strength (15-20 MPa), sufficient for the manufacture of screeds for laying floor coverings, binds the maximum amount of ash and complies with sanitary rules and standards for use in construction without restrictions on the radiation factor. When compiling this mixture, dosimetric monitoring of the ash of each batch should be carried out.

After dosing, the components in dry form are mixed in a mixer and packaged in paper bags with a capacity of 20-25 kg. The finished mixture is already at a construction site mixed with saline bischofite with a density of 1.2 kg / l.

The composition of the dry construction mixture may include barite concentrate or screening of granite crushed stone (dolomite, marble, etc.) as an addition or replacement of part of the ash.

Thus, in the present invention, the problem of creating dry building mixtures that bind and neutralize harmful waste and have optimal construction characteristics is solved. At the same time, the problem of waste disposal is being solved. The above characteristics include: high strength, fast hardening rate, lack of pores, crack resistance, good adhesion to concrete substrates, incombustibility, and the absence of harmful emissions into indoor air and water. The mixture is laid on a concrete base, leveled and smoothed to the end of hardening. In 7-10 days after laying, the flooring of the final floors (linoleum, parquet, laminate, tile, etc.) is made or coated with a polymer composition.

The table shows the average results of strength tests of the proposed mixture ZMSh for various ratios of binder / ash after 28 days.

Table №№ The ratio of the main components of the binder / ash Compression / bending strength, after 28 days, MPa one 1/2 25/8 2 1/3 15/5 3 1/4 10/3 four 1/5 5/1 5 1/10 one/-

As can be seen from the table, compounds No. 1, 2 are suitable for construction purposes, and No. 3-5 for binding ash before disposal.

An undeniable advantage over conventional building materials on Portland cement is the conversion of hazardous waste into an environmentally friendly building material.

Claims (6)

1. A dry building mixture containing ash and building sand, characterized in that it additionally contains caustic magnesite powder, a natural mineral of schungite III variety and a modifying additive in the following ratio of components, wt.%:
ash 50-85 caustic magnesite powder 10-30 natural mineral shungite 0,1-10 modifying additive 0.1-1.5 building sand rest 2. The dry building mixture according to claim 1, characterized in that it uses ash from the burning of wastewater treatment waste. 3. The dry building mixture according to claim 1, characterized in that it uses the ash of thermal power plants. 4. The dry building mixture according to claim 1, characterized in that metallurgical slag is used as ash. 5. The dry building mix according to claim 1, characterized in that the barite concentrate is used as a filler. 6. The dry building mix according to claim 1, characterized in that the granite screening (dolomite, marble, etc.) is used as a filler.