RU2804940C1 - Geopolymer composite - Google Patents

Abstract

FIELD: construction materials.

SUBSTANCE: production of facing material in the form of building bricks, which allows for efficient disposal of large volumes of waste, both iron ore and ash and slag waste, with subsequent use to obtain useful products. The geopolymer composite includes components in the following ratio, wt.%: iron ore enrichment waste – 54.55-54.84, solid fuel combustion ash – 17.58-18.18, sodium silicate solution – 27.27-27.58.

EFFECT: creation of a composition with high strength properties and recycling of production waste.

1 cl, 3 tbl

Description

The invention relates to the production of building materials, in particular to the production of facing material in the form of building bricks, which allows for the efficient disposal of large volumes of waste, both iron ore and ash waste, with subsequent use to obtain useful products.

A geopolymer binder system for heat-resistant concrete is known (patent No. 2664723, published on August 22, 2018) containing at least one finely dispersed amorphous aluminosilicate, where this finely dispersed aluminosilicate is in the form of metakaolin, annealed clay, brick flour, coal fly ash, blast furnace slag; lime-sand stone flour and/or amorphous silica, wherein the activator contains a combination of at least two magnesium components (Mg-components), which react with water according to an alkaline mechanism, and at the same time react differently with time binder with the formation of a geopolymer, and the magnesium components exhibit different chemical activity in relation to air moisture and in relation to the binder.

The disadvantage of this mixture is its insufficient strength for the production of facing material.

A water-curing geopolymer composite binder is known (patent No. 2780901, published April 10, 2022), containing thermally activated polymineral montmorillonite-kaolinite clay as an aluminosilicate component, dolomite and thermally activated limestone as mineral fillers, and sodium metasilicate pentahydrate as an alkaline activator, with the following ratio wearing components , wt.%: thermally activated montmorillonite-kaolinite clay - 25.6-35.7; thermally activated limestone - 25.6-35.7; dolomite - 14-34.2; sodium metasilicate pentahydrate Na ₂ SiO ₃ 5H ₂ O - 14.6.

The disadvantage of this composition is the need for thermal activation of the mixture components at high temperatures to obtain the feedstock.

Geopolymer aggregates are known (patent No. 2701954, published on December 17, 2015), including: porous aggregates containing aluminosilicate nanoparticles, wherein: the average size of aluminosilicate nanoparticles ranges from about 5 nm to about 60 nm, most of the porous aggregates are characterized by a size of about 50 nm to about 1 μm, and most of the pores between the aluminosilicate nanoparticles in the porous aggregates have pore widths ranging from about 2 nm to about 100 nm, with the porous aggregates containing up to about 0.5 wt%. conjugate acid anions, including sulfates, nitrates, chlorides and acetates.

The disadvantage of this product is the need for additional large-scale preparation for grinding/receiving the fine fraction waste required for this composition.

Geopolymer composite binders with specified characteristics for cement and concrete are known (patent No. 2517729, published on May 27, 2014) containing: (i) at least one fly ash containing calcium oxide in an amount less than or equal to 15 wt.%; (ii) at least one gelling accelerator; and (iii) at least one hardening accelerator having a composition different from the composition of the at least one fly ash.

The disadvantage of this composition is the use of additional components in the form of hardening accelerators, which may contain substances that are highly toxic.

A geopolymer composite for ultra-high quality concrete is known (patent No. 2599742, published on October 10, 2016) containing: a binder containing at least one reactive aluminosilicate and at least one reactive alkaline earth aluminosilicate; an alkaline activator containing an aqueous solution of at least one of sodium hydroxide and potassium hydroxide, and at least one of silica fume, sodium silicate glass, potassium silicate glass, sodium silicate solution and potassium silicate solution; and one or more fillers.

The disadvantage of this mixture is the use of aqueous solutions in the material, which negatively affect the strength characteristics of the final product.

There is a known method for producing a geopolymer with controlled porosity (patent No. 2503617 , published on April 23, 2009), taken as a prototype, containing the stage of dissolution/polycondensation of aluminosilicate raw materials in an activating solution, which, if necessary, may contain silicate components, and contains the following sequential stages, in which : specify the characteristics of the overall porosity of the resulting geopolymer; determining a value for at least one parameter selected from the group that includes the total amount of water and the particle size distribution of optional silicate components, which allows to obtain the specified characteristic of the total porosity; select the specified predetermined value.

The disadvantage of this composition is the use of highly alkaline activators, which can complicate the production process of finished products.

The technical result is the creation of a composition with high strength properties and recycling of production waste.

The technical result is achieved by additionally introducing solid fuel combustion ash, and iron ore enrichment waste is used as an aluminosilicate component, with the following component ratio, wt.%:

iron ore processing waste 54.55 - 54.84, solid fuel combustion ash 18.18 - 17.58, sodium silicate solution 27.27 - 27.58.

The inventive geopolymer composite includes the following reagents and commercial products containing them:

- iron ore enrichment waste 48.35 - 47.81%, FKKO code 22130000000;

- solid fuel combustion ash 16.12-16.38%, FKKO code 61100000000;

- sodium silicate 27.27 - 27.58% in the form of a solution, produced in accordance with GOST 13078-81.

Waste from iron ore processing is the main component of the geopolymer composite, which accumulates in the tailings of processing plants. The chemical composition of this waste was determined by X-ray fluorescence spectroscopy and is presented in Table 1:

Table 1 – Chemical composition of iron ore processing waste Substance Mass. % _SiO2 71.4 _{Fe2O3 _} 18.0 MgO 4.17 CaO 3.38 _{Al2O3 _} 2.03 _K2O 0.74 _Na2O 0.62 _{P2O5 _} 0.206 MnO 0.092 _TiO2 0.055

The use of iron ore enrichment waste increases the strength of the final product.

Solid fuel combustion ash is an additional component in the geopolymer composite. The chemical composition of this waste was also determined by X-ray fluorescence spectroscopy and is presented in Table 2:

Table 2 – Chemical composition of solid fuel combustion ash Substance Mass. % _SiO2 41.8 _{Fe2O3 _} 8.3 MgO 4.8 CaO 12.0 _{Al2O3 _} 11.0 _K2O 1.3 _Na2O 0.9 _{P2O5 _} 0.5 MnO 0.1 _TiO2 0.7 SO ₃ 2.0 WITH 14.5 N 1.7 N 0.4

The use of solid fuel combustion ash serves to increase the strength characteristics due to the aluminosilicate compounds contained in its composition.

The use of sodium silicate, in the form of a solution, is sufficient to become an alkaline activator and have the necessary properties for the geopolymerization reaction to occur.

Obtaining a geopolymer composite with stable characteristics is as follows:

The size of ash particles from the combustion of solid fuels and iron ore enrichment waste should not exceed 200 microns for the most complete occurrence of the geopolymerization reaction. To do this, the samples, previously dried to an air-dry state, were crushed using a laboratory rotary mill to the required grain size.

Several solutions with different ash contents and different temperature treatment regimes were prepared in different proportions. The solutions were poured into a closed container and dried naturally within 24 hours. To prepare the solution, a laboratory mixer with a top drive is used. Mixing is done on a non-absorbent mixing plate. Initially, iron ore enrichment waste and solid fuel combustion ash are mixed in accordance with the specified proportion for about two minutes, followed by gradual addition of an alkaline solution. Once the mortar is ready, it is poured into the appropriate molds in three layers, carefully compacting each layer using a tamping rod to achieve complete compaction. All finished samples are stored under standard conditions. Temperature treatment of all samples was carried out after the final setting of the solution at 50°C for 24 hours.

6 geopolymer composite compositions were produced in laboratory conditions. Each composition is explained by the following examples, and the results are presented in Table 3.

Example No. 1.

This sample contains exclusively iron ore enrichment waste and sodium silicate in the form of a solution. Sodium silicate in a volume of 80 ml is poured into a non-absorbent container, and then iron ore enrichment waste in an amount of 240 grams is added in small quantities. The solution is thoroughly mixed using a top-drive laboratory stirrer. After the solution becomes a homogeneous mass, it is poured into the mold and left under standard conditions for 24 hours. After 24 hours, the composition has not hardened, which is not a positive result. This is due to the absence of additional components with a high content of aluminum and iron.

Example No. 2.

This composition includes iron ore enrichment waste, ash from burning solid fuels and sodium silicate. Sodium silicate in a volume of 85 ml is poured into a non-absorbent container, and then a mixture of iron ore enrichment waste weighing 180 g and solid fuel combustion ash weighing 80 g is added in small quantities. The solution is thoroughly mixed using a laboratory mixer with a top drive. After the solution becomes a homogeneous mass, it is poured into the mold and left under standard conditions for 24 hours. During the preparation process, the consistency of the sample was loose and porous; the finished sample also had a large number of cracks and pores. This sample did not undergo additional temperature treatment at 50°C and the compressive strength was 5 MPa. This building material meets the criteria of GOST 7484-78 and GOST 530-95 “Ceramic bricks and stones. Technical specifications" and can be assigned the M50 grade.

Example No. 3

This composition includes iron ore enrichment waste, ash from burning solid fuels and sodium silicate. Sodium silicate in a volume of 85 ml is poured into a non-absorbent container, and then a mixture of iron ore enrichment waste weighing 180 g and solid fuel combustion ash weighing 80 g is added in small quantities. The solution is thoroughly mixed using a laboratory mixer with a top drive. After the solution becomes a homogeneous mass, it is poured into the mold and left under standard conditions for 24 hours. During the preparation process, the consistency of the sample was also loose and porous, as in example No. 2. This sample underwent additional temperature treatment at 50°C in a drying oven for 24 hours and the compressive strength was 5.5 MPa. This building material meets the criteria of GOST 7484-78 and GOST 530-95 “Ceramic bricks and stones. Technical specifications" and can be assigned the M50 grade.

Example No. 4.

This composition includes iron ore enrichment waste, ash from burning solid fuels and sodium silicate. Sodium silicate in a volume of 90 ml is poured into a non-absorbent container, and then a mixture of iron ore enrichment waste weighing 180 g and solid fuel combustion ash weighing 60 g is added in small quantities. The solution is thoroughly mixed using a laboratory mixer with a top drive. After the solution becomes a homogeneous mass, it is poured into the mold and left under standard conditions for 24 hours. During the preparation of the solution, the consistency of the sample was less porous and more plastic, which has a beneficial effect on the strength characteristics of the finished sample. This sample did not undergo additional temperature treatment at 50°C and the compressive strength was 7.4 MPa. This building material meets the criteria of GOST 7484-78 and GOST 530-95 “Ceramic bricks and stones. Technical specifications" and can be assigned the M75 grade.

Example No. 5.

This composition includes iron ore enrichment waste, ash from burning solid fuels and sodium silicate. Sodium silicate in a volume of 90 ml is poured into a non-absorbent container, and then a mixture of iron ore enrichment waste weighing 180 g and solid fuel combustion ash weighing 60 g is added in small quantities. The solution is thoroughly mixed using a laboratory mixer with a top drive. After the solution becomes a homogeneous mass, it is poured into the mold and left under standard conditions for 24 hours. During the preparation of the solution, the consistency of the sample was less porous and more plastic, which has a beneficial effect on the strength characteristics of the finished sample. This sample underwent additional temperature treatment at 50°C in a drying oven for 24 hours and the compressive strength was 11.2 MPa. This building material meets the criteria of GOST 7484-78 and GOST 530-95 “Ceramic bricks and stones. Technical specifications" and can be assigned the M100 grade.

Example No. 6.

This composition includes iron ore enrichment waste, ash from burning solid fuels and sodium silicate. Sodium silicate in a volume of 90 ml is poured into a non-absorbent container, and then a mixture of iron ore enrichment waste weighing 180 g and solid fuel combustion ash weighing 60 g is added in small quantities. The solution is thoroughly mixed using a laboratory mixer with a top drive. After the solution becomes a homogeneous mass, it is poured into the mold and left under standard conditions for 24 hours. During the preparation of the solution, the consistency of the sample was less porous and more plastic, which has a beneficial effect on the strength characteristics of the finished sample. This sample underwent additional temperature treatment at 100°C in a drying oven for 24 hours and the compressive strength was 5 MPa. This is explained by the fact that when the sample is quickly heated to a temperature exceeding 50°C, the material begins to crack and excess moisture escapes through the pores, which leads to destruction of the sample.

The described stages of manufacturing a geopolymer composite provide a clear structure of the final product, and the aluminosilicate components of the mixture are activated at low temperature and alkaline pH of a sodium silicate solution. The compressive strength test results are presented in Table 3.

Table 3 - Compressive strength test results No. Iron ore processing waste Solid fuel combustion ash Sodium silicate Temperature Setting time Compressive strength G Mass. % G Mass. % ml Mass. % °C h MPa 1 240 75 0 - 80 25 20 More than 48 <1 2 180 52.17 80 23.19 85 24.64 20 5 5 3 180 52.17 80 23.19 85 24.64 50 5 5.5 4 180 54.55 60 18.18 90 27.27 20 3 7.4 5 180 54.55 60 18.18 90 27.27 50 3 11.2 6 180 54.55 60 18.18 90 27.27 100 3 <1

* Compressive strength tests were carried out on three parallel samples using a laboratory press. The table shows average values for three tests of each composition.

The data presented in Table 3 indicate the effectiveness of using a composition based on iron ore enrichment waste, ash from burning solid fuels and a sodium silicate solution with an activation temperature of 50°C for 24 hours.

The proposed geopolymer composite for the production of facing material in the form of bricks has resource-saving characteristics due to the use of iron ore enrichment waste and solid fuel combustion ash. Based on the test results, geopolymer composite samples were assigned a grade based on compressive strength in accordance with GOST 530-2012. Finished sample grade B7.5; M100.

Claims (2)

A geopolymer composite comprising aluminosilicate components and a sodium silicate solution, characterized in that solid fuel combustion ash is additionally introduced, and iron ore enrichment waste is used as an aluminosilicate component in the following component ratio, wt.%: iron ore processing waste 54.55-54.84 solid fuel combustion ash 17.58-18.18 sodium silicate solution 27.27-27.58