CN114890731A

CN114890731A - Coal gangue foam concrete for filling and preparation method thereof

Info

Publication number: CN114890731A
Application number: CN202210296739.6A
Authority: CN
Inventors: 冯源; 张鑫; 冯小平; 邹昀; 王振平; 简俊常; 骆伟
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2022-03-24
Filing date: 2022-03-24
Publication date: 2022-08-12

Abstract

The invention belongs to the field of building materials, and particularly relates to coal gangue foam concrete for filling and a preparation method thereof. The invention takes ordinary portland cement, coal gangue, fly ash and silica fume as cementing materials, adopts a plant source composite foaming agent for physical foaming, adds a foam stabilizer to improve the stability of a foam concrete bubble system, and adds polypropylene fibers to improve the foamThe flexibility of the foam concrete and the proportion relation of the raw materials are reasonably controlled, and the dry density grade of the prepared foam concrete is 400-900kg/m ³ The coal gangue has the characteristics of self-compaction, good fluidity, uniform pores and poor connectivity among the pores, can be used for closed filling treatment of working face void tunnels, goafs and other areas in mines, and simultaneously effectively reduces the cost of the foam concrete, the coal gangue can replace 10-40% of cement amount, reduces the cement amount, becomes a main raw material for preparing the foam concrete, and has strong competitiveness in actual engineering.

Description

Coal gangue foam concrete for filling and preparation method thereof

Technical Field

The invention belongs to the field of building materials, and particularly relates to coal gangue foam concrete for filling and a preparation method thereof.

Background

Spontaneous combustion and ignition of coal seams are a great disaster in coal mine safety production, and the main reason is that air entering a goaf directly contacts with coal, and the coal is oxidized and self-heated to cause spontaneous combustion. At present, methods such as building a closed partition wall and reducing air leakage entering a goaf are mainly adopted to prevent coal spontaneous combustion. The concrete measures are that two closed walls are built, and sand stone or clay is filled between the two closed walls, on one hand, the filling method has high labor intensity and complex working procedures, and on the other hand, the air tightness of the closed walls and the middle filling area is poor, so that air leakage is easily caused, and coal spontaneous combustion is formed. Coal gangue is used as an industrial waste generated in the processes of coal mine shaft building, mining tunneling, coal mining and coal washing, and a common treatment method in a mine field is to directly stack in the open air, so that air and underground water are polluted, and fire hazards are caused.

In the existing foam concrete, for example, in the patent of publication No. CN104478467 'a preparation method of coal gangue foam concrete', the disclosed components and proportions are as follows: 20 parts of cementing material PO42.5 cement, 55-65 parts of coal gangue, 15-20 parts of water and an additional early strength agent accounting for 3-5% of the mass of the cement; for example, in the patent of publication No. CN102285772A 'coal gangue treatment method, coal gangue foam concrete and roadway backfill method', the disclosed components and proportions are as follows: the weight percentage of the coal gangue powder or particle is 20 percent to 50 percent, the cement is 20 percent to 50 percent, and the water is 30 percent to 60 percent.

The existing filling material used in the mine sealing wall has the following defects: (1) the research on the tightness of the filling material mainly researches the compressive strength of the foam concrete, but the research on the performance of the filling material in the air tightness aspect is less; (2) in the actual use process, the fluidity of the foam concrete is an important performance index for the use of the foam concrete, and during the closed filling of a coal mine goaf, the foam concrete needs to be capable of automatically leveling and densely filling in a gap, but the research on the fluidity of the foam concrete is less.

Disclosure of Invention

In order to solve the pollution problems caused by natural ignition of coal and stacking and discharging of coal gangue in a coal mine due to air leakage in a goaf, a coal gangue foam concrete sealing wall filling material is developed, the material is light in weight, high in foaming multiple and excellent in mechanical property, the coal gangue is used as an aggregate, the resource recycling problem of the coal gangue is solved, and the pollution of the coal gangue in the mine area to the environment is effectively reduced.

The invention provides coal gangue foam concrete for filling, which comprises the following components in parts by weight:

308-617 parts of cement, 103-412 parts of coal gangue, 154-257 parts of fly ash, 51-103 parts of silica fume, 0.8-3.2 parts of polypropylene fiber, 520-860 parts of water, 1-1.3 parts of foaming agent and 1.7-2.1 parts of foam stabilizer; the foaming agent is a plant source composite foaming agent.

Preferably, the cement is 52.5 quick-hardening cement.

Furthermore, the specific surface area of the 52.5 quick hardening type cement is more than 300%, the loss on ignition is less than 5%, and the addition amount of gypsum is 7-9%.

Preferably, the fly ash is first-grade fly ash with the water content of 0.1-0.5%, the ignition loss of 1.5-2.5%, the water demand ratio of 70-90% and the fineness of 7-9%.

Preferably, the SiO of the silica fume ₂ 97.8 percent of total alkali, 0.5 to 1.5 percent of water content and 1 to 2 percent of loss on ignition.

Preferably, the plant source composite foaming agent is a surfactant composition with excellent foaming performance formed by performing hydrogenation-ethoxylation-sulfonation-neutralization and other reactions on rectified C8-12 fatty acid taking tropical plant palm kernels as a raw material.

Preferably, the specific gravity of the polypropylene fiber is 0.5-1, the tensile strength is more than 486MPa, and the fiber diameter is 18-48 mu m.

The invention also provides a preparation method of the coal gangue foam concrete for filling, which comprises the following steps:

(1) mixing cement, coal gangue, fly ash, silica fume and polypropylene fiber for 3-5min, adding water and mixing for 2-5min to obtain slurry;

simultaneously mixing the plant source composite foaming agent, the foam stabilizer and water, and obtaining foam by using a cement foaming machine;

(2) And adding the foam into the slurry, mixing, injecting into a mold for molding, standing for 12-36h, and then putting into a standard constant-temperature constant-humidity curing box for curing to obtain the coal gangue foam concrete.

Preferably, the water-to-gel ratio of the slurry is 0.6-0.75.

Preferably, in the step (2), the mixing time is 1-2 min.

Preferably, in the step (2), the curing temperature is 15-20 ℃ and the relative humidity is 95-99%.

In the invention, the silica fume and the polypropylene fiber are added, so that the aperture between the foam concrete can be effectively filled, the pore structure of the foam concrete is improved, and SiO in the silica fume ₂ The C-S-H gel can be used as a crystal nucleus in the production process of the C-S-H gel, so that hydration reaction of hydration products generated on the surface of cement particles is continued on the surface of the crystal nucleus, a film layer on the surface of the cement particles is broken, unreacted particles below the surface can be continuously contacted with water for hydration, secondary hydration of the cement is promoted, the hydration products are increased, pores are further filled, the combination of the particles is tighter, and the strength of the foam concrete is improved. The plant source composite foaming agent has good foaming performance, and the prepared foam has good toughness and is not easy to break, and can be preserved in concrete slurry Maintaining a stable shape.

Compared with the prior art, the technical scheme of the invention has the following advantages:

1. according to the invention, ordinary portland cement, coal gangue, fly ash and silica fume are used as cementing materials, a foaming agent is used for physical foaming, sodium stearate or calcium stearate is added as a foam stabilizer to improve the stability of a foam concrete bubble system, polypropylene fiber is added to improve the flexibility of the foam concrete and reasonably control the proportioning relation of the raw materials, and the prepared foam concrete has a dry density grade of 400-900 kg/m ³ The self-compacting porous filling material has the characteristics of self-compacting, good fluidity, low water absorption and uniform pores, and can be used for the closed filling of working face air leakage roadways, goafs and other areas in mines.

2. The foam concrete can be prepared at room temperature, the operation process is simple, the operation is easy in actual engineering, and the method has popularization.

3. The invention adopts the coal gangue to prepare the foam concrete, provides a method for treating and recycling the coal gangue, reduces the accumulation of the coal gangue, fully exerts the due effect of the land, slows down the pollution generated by the accumulation of the coal gangue, is comprehensively beneficial to the comprehensive utilization of the coal gangue, namely the solid waste on the coal mine, and changes waste into valuable.

4. The invention reduces the cost of the foam concrete, the coal gangue can replace 10-40% of the cement amount, the cement amount is reduced, the coal gangue becomes the main raw material for preparing the foam concrete, and the coal gangue has strong competitiveness in the actual engineering.

Drawings

FIG. 1 is a scanning electron micrograph of the product prepared in example 1;

FIG. 2 is a scanning electron micrograph of the product prepared in example 2;

FIG. 3 is a scanning electron micrograph of the product prepared in example 3.

Detailed Description

The present invention is further described with reference to the following drawings and specific examples so that those skilled in the art can better understand the present invention and can practice the present invention, but the examples are not intended to limit the present invention.

Example 1

Preparing according to the components and weight components: 518 parts of cement, 206 parts of coal gangue, 205 parts of fly ash, 103 parts of silica fume, 720 parts of water for cement paste, 2.4 parts of polypropylene fiber, 1.3 parts of plant source composite foaming agent, 78 parts of water for foaming agent and 2.0 parts of foam stabilizer.

The preparation method comprises the following specific steps:

(1) accurately weighing the components according to the parts by weight, and mixing and stirring the weighed cement, coal gangue, fly ash, silica fume and polypropylene fiber for 3 min.

(2) Adding water, and stirring for 5min to obtain uniform slurry.

(3) Uniformly mixing the plant source composite foaming agent and the foam stabilizer, adding water, stirring, and preparing foam by using a cement foaming machine.

(4) Adding foam into the slurry, stirring for 1min to prepare foam concrete slurry, injecting the prepared foam concrete slurry into a mold for molding, statically maintaining for 24h, and then putting the molded foam concrete slurry into a concrete standard constant-temperature constant-humidity curing box for curing to various ages, wherein the temperature of the concrete standard constant-temperature constant-humidity curing box is 22 ℃ and the relative humidity is 95%.

Example 2

Preparing according to the components and weight components: the material comprises 617 parts of cement, 103 parts of coal gangue, 205 parts of fly ash, 103 parts of silica fume, 772 parts of water for cement paste, 2.4 parts of polypropylene fiber, 1.2 parts of plant source composite foaming agent, 72 parts of water for foaming agent and 1.8 parts of foam stabilizer.

The preparation method comprises the following specific steps:

(2) Adding water, and stirring for 5min to obtain uniform slurry.

Example 3

Preparing according to the components and weight components: the material comprises 617 parts of cement, 206 parts of coal gangue, 154 parts of fly ash, 51 parts of silica fume, 670 parts of water for cement paste, 3.2 parts of polypropylene fiber, 1 part of plant source composite foaming agent, 60 parts of water for foaming agent and 1.7 parts of foam stabilizer.

The preparation method comprises the following specific steps:

(2) Adding water, and stirring for 5min to obtain uniform slurry.

Example 4

Preparing according to the components and weight components: in the material, 412 parts of cement, 308 parts of coal gangue, 205 parts of fly ash, 103 parts of silica fume, 617 parts of water for cement paste, 3.2 parts of polypropylene fiber, 1 part of plant source composite foaming agent, 60 parts of water for foaming agent and 1.7 parts of foam stabilizer.

The preparation method comprises the following specific steps:

(2) Adding water, and stirring for 5min to obtain uniform slurry.

Example 5

The preparation method comprises the following specific steps:

(1) accurately weighing the components in parts by weight, and mixing and stirring the weighed cement, coal gangue, fly ash, silica fume and polypropylene fiber for 5 min.

(2) Adding water, and stirring for 2min to obtain uniform slurry.

(4) Adding foam into the slurry, stirring for 2min to prepare foam concrete slurry, injecting the prepared foam concrete slurry into a mold for molding, statically maintaining for 24h, and then putting the molded foam concrete slurry into a concrete standard constant-temperature constant-humidity curing box for curing to various ages, wherein the temperature of the concrete standard constant-temperature constant-humidity curing box is 18 ℃ and the relative humidity is 99%.

Example 6

The preparation method comprises the following specific steps:

(2) Adding water, and stirring for 4min to obtain uniform slurry.

(4) Adding foam into the slurry, stirring for 2min to prepare foam concrete slurry, injecting the prepared foam concrete slurry into a mold for molding, statically maintaining for 24h, and then putting the molded foam concrete slurry into a concrete standard constant-temperature constant-humidity curing box for curing to various ages, wherein the temperature of the concrete standard constant-temperature constant-humidity curing box is 20 ℃ and the relative humidity is 97%.

Comparative example 1

The foam concrete material of the embodiment comprises 518 parts of cement, 206 parts of coal gangue, 205 parts of fly ash, 103 parts of silica fume, 720 parts of water for cement paste, 2.4 parts of polypropylene fiber, 1.3 parts of plant source composite foaming agent, 78 parts of water for foaming agent and 2.0 parts of foam stabilizer.

The preparation method comprises the following specific steps:

(2) Adding water, and stirring for 5min to obtain uniform slurry.

Comparative example 2

The preparation method comprises the following specific steps:

(2) Adding water, and stirring for 5min to obtain uniform slurry.

Comparative example 3

The foamed concrete of this example was different from example 1 only in that a commercially available K-12 type foaming agent was used as the foaming agent of this example, and the rest was the same as example 1.

Effect evaluation 1

The foam concrete prepared in the example was tested according to JGJ/T341-2014 foam concrete application technical Specification and JG/T266-2011 foam concrete according to examples 1-4 and comparative examples 1-3, and the test results are shown in Table 1.

TABLE 1 test results of examples 1 to 4 and comparative examples 1 to 3

From the above test results, it can be seen that the dry density of the foamed concrete of the present invention is controlled to 400kg/m ³ -900kg/m ³ And the density is low, the fluidity is good, and the water absorption is low. The water absorption rate can reflect the pore structure characteristics of the foam concrete to a certain extent, and the lower the water absorption rate is, the poorer the connectivity among air pores is. Foams made by the inventionCompared with the concrete prepared by the comparative example 1 and the comparative example 2 without silica fume and polypropylene fiber, the compressive strength and the fluidity of the concrete are obviously improved, the water absorption is obviously reduced compared with the comparative example 2, and the compressive strength, the fluidity and the water absorption of the concrete prepared by the plant source composite foaming agent are better than those of the concrete prepared by the comparative example 3 prepared by the commercial K-12 foaming agent.

The scanning electron micrographs of example 1, example 2 and example 3 are shown in FIGS. 1, 2 and 3. As can be seen from fig. 1, 2 and 3, the foam concrete has uniform pores, poor communication performance between pores and good air tightness. The method can be used for the closed filling treatment of working face air leakage laneways, goafs and other areas in mines.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.

Claims

1. The coal gangue foam concrete for filling is characterized by comprising the following components in parts by weight:

308-617 parts of cement, 103-412 parts of coal gangue, 154-257 parts of fly ash, 51-103 parts of silica fume, 0.8-3.2 parts of polypropylene fiber, 520-860 parts of water, 1-1.3 parts of foaming agent and 1.7-2.1 parts of foam stabilizer.

2. The coal gangue foam concrete for filling as claimed in claim 1, wherein the specific surface area of the cement is more than 300%, the loss on ignition is less than 5%, and the addition amount of gypsum is 7-9%.

3. The gangue foam concrete for filling according to claim 1, wherein SiO of the silica fume ₂ 97.8 percent of total alkali, 0.5 to 1.5 percent of water content and 1 to 2 percent of ignition loss.

4. The coal gangue foam concrete for filling as claimed in claim 1, wherein the foaming agent is a C8-12 fatty acid surfactant composite foaming agent using tropical plant palm kernel as a raw material.

5. The gangue foam concrete for filling as claimed in claim 1, wherein the polypropylene fiber has a specific gravity of 0.5 to 1, a tensile strength of more than 486MPa, and a fiber diameter of 18 to 48 μm.

6. A method for preparing the gangue foam concrete for filling as defined in any one of claims 1 to 5, comprising the steps of:

(1) mixing cement, coal gangue, fly ash, silica fume and polypropylene fiber, and adding part of water for mixing to obtain slurry;

simultaneously mixing the foaming agent, the foam stabilizer and the other part of water to obtain foam;

(2) and adding the foam into the slurry, mixing, forming and maintaining to obtain the coal gangue foam concrete.

7. The method of claim 6, wherein the slurry has a water-to-gel ratio of 0.6 to 0.75.

8. The method of claim 6, wherein in the step (2), the mixing time is 1-2 min.

9. The method according to claim 6, wherein in the step (2), the mixture is allowed to stand for 12 to 36 hours before curing.

10. The method according to claim 6, wherein in the step (2), the curing temperature is 15 to 20 ℃ and the relative humidity is 95 to 99%.