CN114804813B

CN114804813B - Bamboo ash-fly ash/magnesium oxychloride composite material and preparation method thereof

Info

Publication number: CN114804813B
Application number: CN202210461208.8A
Authority: CN
Inventors: 左迎峰; 盛国安; 李萍; 吴义强; 郑龙; 李新功
Original assignee: Central South University of Forestry and Technology
Current assignee: Central South University of Forestry and Technology
Priority date: 2022-04-28
Filing date: 2022-04-28
Publication date: 2023-04-07
Anticipated expiration: 2042-04-28
Also published as: CN114804813A

Abstract

The invention discloses a bamboo ash-fly ash/magnesium oxychloride composite material and a preparation method thereof. The preparation method of the composite material can improve the mechanical property and the water resistance of the composite material, compared with the traditional method, the added material belongs to a byproduct of future fuel energy, and belongs to waste utilization, and the preparation method of the composite material has the advantages of low cost, low emission, energy conservation and the like, is suitable for low-cost investment, and has good application prospect.

Description

Bamboo ash-fly ash/magnesium oxychloride composite material and preparation method thereof

Technical Field

The invention belongs to the technical field of low-carbon building materials, and particularly relates to a bamboo ash-fly ash/magnesium oxychloride composite material and a preparation method thereof.

Background

The application field of the foam magnesium oxychloride cement product is limited by the mechanical property and the water resistance, and the strength of the magnesium oxychloride cement product has a certain limit under the condition of no admixture, which depends on the main strength phase (5 MgO. MgCl) ₂ ·8H ₂ O) number and growth form, needle-like or fine rod-like five phases are easily hydrolyzed crystals, and are converted into magnesium hydroxide crystals with loose structure after being soaked in liquid.

In response to the above problems, the inventors of the present application have found that the addition of fly ash has an enhancing effect on the strength and water resistance of a magnesium oxychloride cement, which depends on the active oxides remaining after the combustion of coal as a high calorific value fuel to generate carbon dioxide, including about 45% silica, about 20% alumina, and about 10% iron oxide. These oxides are in particular SiO ₂ Has the characteristic of stimulating the germination and growth of the five-phase crystals in the hydration process of the magnesium oxychloride slurry. However, coal is an irrenewable resource, and with the increase of environmental awareness of people, the mining amount of coal is gradually reduced, the output of fly ash is reduced, and the cost is increased, so that a low-cost substitute of fly ash is urgently needed to be found as an admixture of magnesium oxychloride cement.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides the bamboo ash-coal ash/magnesium oxychloride composite material which has excellent mechanical property and water resistance, low carbon, energy conservation and environmental protection and good application prospect and the preparation method thereof.

In order to solve the technical problems, the invention adopts the following technical scheme.

A preparation method of a bamboo ash-fly ash/magnesium oxychloride composite material comprises the following steps:

s1, mixing magnesium chloride hexahydrate with water to prepare brine;

s2, adding the magnesium oxide, the bamboo ash, the fly ash, the foam stabilizer and the catalyst into the brine prepared in the step S1 after dry mixing to obtain mixed slurry A;

s3, adding a foaming agent into the mixed slurry A obtained in the step S2, and stirring to disperse the foaming agent to obtain expanded mixed slurry B;

s4, pouring the mixed slurry B prepared in the step S3 into a mold, maintaining, standing for curing, demolding, and continuously curing to obtain the bamboo ash-fly ash/magnesium oxychloride composite material;

the addition amount of each raw material is calculated by the mass portion, 406.6 to 609.9 portions of magnesium chloride hexahydrate, 396 to 618 portions of water, 928.3 to 974.5 portions of magnesium oxide, 51.6 to 123.7 portions of bamboo ash, 5.2 to 30.9 portions of fly ash, 54.0 to 61.9 portions of foam stabilizer, 10.6 to 20.8 portions of catalyst and 45.0 to 61.9 portions of foaming agent.

The preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material preferably comprises 609.9 parts of magnesium chloride hexahydrate, 396 parts of water, 928.3-974.5 parts of magnesium oxide, 51.6-123.7 parts of bamboo ash, 5.2-30.9 parts of fly ash, 54.0-61.9 parts of foam stabilizer, 10.6-20.8 parts of catalyst and 45.0-61.9 parts of foaming agent.

Preferably, in the preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material, the bamboo ash is the bamboo briquette burned by a thermal power station, the burning temperature is controlled at 500-800 ℃, the color of the bamboo ash is gray, and the fineness is more than 200 meshes.

In the preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material, preferably, the foam stabilizer is calcium stearate, the catalyst is manganese dioxide, and the foaming agent is a 30% hydrogen peroxide solution by mass.

Preferably, in the step S3, the stirring speed is 280r/min to 450r/min, and the stirring time is 7S to 15S.

In the above preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material, preferably, in step S4, the curing is performed under a constant temperature and humidity condition, the humidity is controlled to be 50% to 70%, the temperature is controlled to be 18 ℃ to 30 ℃, and the curing time is 24h to 36h.

Preferably, in the step S4, the standing solidification and the continuous solidification are both performed under normal temperature and normal pressure, the standing solidification time is 2 days to 3 days, and the continuous solidification time is 24 days to 25 days.

In the preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material, preferably, the magnesium oxide is light-burned magnesium oxide, the calcination temperature is 650-700 ℃, the heating energy consumption can be saved, and compared with the conventional dead-burned magnesium oxide (the calcination temperature is 800-1100 ℃), the hydration speed is higher after the magnesium oxide meets brine.

As a general technical concept, the invention also provides a bamboo ash-fly ash/magnesium oxychloride composite material prepared by the preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material.

In the invention, the mass of the bamboo ash is preferably 2.5-6% of the total mass of the magnesium oxide, the magnesium chloride hexahydrate and the water, and the mass of the fly ash is preferably 0.25-1.5% of the total mass of the magnesium oxide, the magnesium chloride hexahydrate and the water, based on the total mass of the magnesium oxide, the magnesium chloride hexahydrate and the water.

Compared with the prior art, the invention has the advantages that:

the invention provides a preparation method of a low-carbon, energy-saving and environment-friendly bamboo ash-fly ash/magnesium oxychloride composite material, wherein the bamboo ash has higher active SiO than the fly ash ₂ The content and the less content of metal oxide (as shown in an example table 1) enable the composite modified magnesium oxychloride cement to play the best activation role, and the bamboo ash, the 518 phase and the foam stabilizer construct a three-dimensional gel system at the foam pores, so that the mechanical property and the water resistance of the composite material are improved.

The combustion raw material of the bamboo ash is bamboo briquette, which belongs to waste compressed matter of bamboo processing, along with the gradual rise of biomass fuel, a thermal power plant generates a large amount of bamboo ash by combusting the bamboo briquette, the bamboo briquette is compounded with coal in a thermal power station for full combustion, the retained silicon oxide is bonded with 518 phase crystals, the growth of needle crystals to a platy or bonded rod shape is promoted, and the mechanical property and the water resistance of the bamboo briquette can be improved. The preparation of the traditional fly ash/magnesium oxychloride composite material puts higher requirements on working procedures of green and reasonable exploitation, clean and efficient combustion and the like of coal, and is not beneficial to long-term development of building materials. Compared with the prior art, the method has the characteristics of low carbon, energy conservation and environmental protection, the prepared building material, namely the bamboo ash-fly ash/magnesium oxychloride composite material has better mechanical property and water resistance, the raw materials required for preparation have low cost and no toxicity, the green production and the industrial application are facilitated, and the porous composite material can be applied to more fields, such as decorative partition boards, external walls and the like.

Drawings

Fig. 1 is an SEM image of bamboo ash particles in the preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material of examples 1 to 4 of the present invention, wherein the left image is × 2000 times, and the right image is × 20000 times.

FIG. 2 is a sectional SEM photograph of the bamboo ash-fly ash/magnesium oxychloride composite material prepared in example 3 of the invention.

Fig. 3 is a sectional SEM image of the magnesium oxychloride composite prepared in comparative example 1.

Detailed Description

The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention. The materials and equipment used in the following examples are commercially available.

The preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material comprises the following steps:

s1, mixing magnesium chloride hexahydrate with water to prepare brine;

Preferably, the bamboo ash is bamboo briquette fired by a thermal power station, the combustion temperature is controlled to be 500-800 ℃, the color is gray, and the ground fineness is more than 200 meshes.

Preferably, the foam stabilizer is calcium stearate, the catalyst is manganese dioxide, and the foaming agent is a 30% hydrogen peroxide solution in mass fraction.

Preferably, in step S3, the rotation speed of stirring is 280r/min to 450r/min, and the stirring time is 7S to 15S.

Preferably, in step S4, the curing is performed under the conditions of constant temperature and constant humidity, the humidity is controlled to be 50% -70%, the temperature is controlled to be 18-30 ℃, and the curing time is 24-36 h.

Preferably, in step S4, the standing solidification and the continuous solidification are both performed under normal temperature and pressure conditions, the standing solidification time is 2 days to 3 days, and the continuous solidification time is 24 days to 25 days.

Preferably, the magnesium oxide is light-burned magnesium oxide, and the calcination temperature is lower than 700 ℃.

The technical principle of the invention is as follows:

the invention adds the bamboo ash into the magnesium oxychloride composite material, the high-fineness bamboo ash can be uniformly mixed in the slurry, and the bamboo ash is high-content SiO ₂ Chemical components (which can be analyzed by using an X-ray fluorescence spectrum technology) exist in the mixed slurry, and the bamboo ash has volcanic ash reactivity and can promote the hydration product 518 of the magnesium oxychloride cement to be close to crystallization nucleation, and the hydration product is fused with the 518-phase crystals to form lath-shaped or bonded rod-shaped silicon-magnesium hydrogel (M-S-H). After the curing reaction is finished, the active SiO of the bamboo ash ₂ Mg-Cl of magnesium oxychloride cement and-COOCa in foam stabilizer ⁺ The three forms a chelate network structure, and a gel system with high hardness is formed, as shown in figure 2. When external force is applied, the structure enables the composite material to have stronger strain resistance; after the soaking treatment, the silicon-magnesium hydrogel layer is covered to protect 518 the phase from liquid erosion.

In the following examples, the bamboo ash is obtained from a combustion furnace of a bamboo processing plant, the fineness is more than 200 meshes, the particle morphology is shown in fig. 1, the chemical composition is shown in table 1, the fly ash is purchased from material limited in Henan, and the chemical composition is provided by a manufacturer, as shown in table 2.

TABLE 1 chemical composition Table of bamboo ash

	SiO ₂	Al ₂ O ₃	CaO	MgO	K ₂ O	Fe ₂ O ₃	Loss on ignition
								Bamboo ash	79.12	1.16	7.82	1.89	3.84	2.82	3.34

TABLE 2 chemical composition of fly ash

	SiO ₂	Al ₂ O ₃	CaO	SO ₃	Alkali content	CaCl ₂	Fe ₂ O ₃
								Fly ash	45.1	24.2	5.6	2.1	1.2	0.85	0.85

Example 1:

the invention relates to a preparation method of a bamboo ash-fly ash/magnesium oxychloride composite material, which comprises the following steps of:

s1, mixing 609.9 parts of magnesium chloride hexahydrate and 396 parts of water at normal temperature and normal pressure to prepare brine;

s2, uniformly mixing 974.5 parts of magnesium oxide, 51.6 parts of bamboo ash, 30.9 parts of fly ash, 61.9 parts of calcium stearate and 20.8 parts of manganese dioxide, adding the mixture into brine, and stirring the mixture for 8 minutes at the rotating speed of 350r/min by using a stirrer to obtain mixed slurry A;

s3, rapidly pouring 61.9 parts of 30% hydrogen peroxide solution into the uniformly mixed slurry A, and stirring for 10S at the rotating speed of 350r/min to obtain expanded mixed slurry B;

s4, when the liquid level of the mixed slurry B rises, pouring the mixed slurry B into a mold, placing the mold in a constant-temperature and constant-humidity box with the temperature of 25 ℃ and the humidity of 65 percent for curing for 30 hours, standing and curing for 2 days at normal temperature and normal pressure, and demolding to obtain a composite material;

and S5, continuously curing the composite material obtained in the step S4 for 25 days at normal temperature and normal pressure to obtain the bamboo ash-fly ash/magnesium oxychloride composite material. The composite material is a porous light composite material, and can be cut into building materials with standard specifications by using a sliding table saw.

In the embodiment, the magnesium oxide is light-burned magnesium oxide, and the calcination temperature is 650-700 ℃.

Example 2:

the preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material is basically the same as that of the embodiment 1, and the differences are that: in the step S2, 960.0 parts of magnesium oxide, 77.3 parts of bamboo ash and 20.6 parts of fly ash are added; in the step S3, stirring for 8S at the rotating speed of 370r/min of the stirrer; and in the step S4, maintaining in a constant temperature and humidity box for 36 hours.

Example 3:

the preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material is basically the same as that in the embodiment 1, and the difference is as follows: in the step S2, 943.6 parts of magnesium oxide, 103.1 parts of bamboo ash and 10.3 parts of fly ash are added; in the step S3, stirring for 8S at the rotating speed of 370r/min of the stirrer; and in the step S4, maintaining for 36 hours in a constant temperature and humidity box. The crystal form of the cross-sectional diagram of the composite material is shown in figure 2, and through adding the fly ash and the bamboo ash, the crystals are mutually bonded, the structure is changed into a gelatinous state, and the crystal retention rate is more excellent after the composite material is soaked in water.

Example 4:

the preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material is basically the same as that of the embodiment 1, and the differences are that: in the step S2, 928.3 parts of magnesium oxide, 123.7 parts of bamboo ash and 5.2 parts of fly ash are added; in the step S3, stirring for 8S at the rotating speed of 370r/min of the stirrer; and in the step S4, maintaining for 36 hours in a constant temperature and humidity box.

In the above examples 1, 2, 3 and 4, the amount of magnesium oxide was changed in that magnesium oxide was substituted for a part of magnesium oxide, bamboo ash and fly ash by controlling the total mass of the slurry (brine, magnesium oxide, bamboo ash and fly ash) to be almost unchanged, thereby demonstrating that bamboo ash has the ability to substitute magnesium oxide and fly ash for preparing a composite material.

Comparative example 1:

a preparation method of a magnesium oxychloride composite material comprises the following steps of raw materials in parts by mass:

s1, preparing 609.9 parts of magnesium chloride hexahydrate and 396 parts of water into brine at normal temperature and normal pressure;

s2, uniformly dry-mixing 974.52 parts of magnesium oxide, 61.9 parts of calcium stearate and 16.5 parts of manganese dioxide, adding the mixture into brine to obtain mixed slurry A, and stirring the mixed slurry A for 8 minutes at a rotation speed of 400r/min by using a stirrer;

s3, rapidly pouring 61.9 parts of 30% hydrogen peroxide solution into the mixed slurry A, and stirring at the rotating speed of 300r/min for 10S to obtain mixed slurry B;

s4, when the liquid level of the mixed slurry B rises, pouring the mixed slurry B into a mold, placing the mold in a constant-temperature constant-humidity box with the temperature of 25 ℃ and the humidity of 65% for curing for 24 hours, standing and curing for 2 days at normal temperature and normal pressure, and demolding to obtain a composite material;

and S5, continuously curing the composite material obtained in the step S4 for 25 days at normal temperature and normal pressure to obtain the magnesium oxychloride composite material, wherein the section diagram is shown in fig. 3, needle-shaped and rod-shaped five-phase crystals can be seen, the structures of the crystals are loose, the internal stress is large, and the mechanical properties of the composite material are adversely affected.

From the results of examples 1-4 and comparative example 1, the magnesium oxychloride light composite material in comparative example 1 has a softening coefficient of only 0.57, and within a certain range, as the content of bamboo ash in the composite material is increased, the mechanical strength and the water resistance performance tend to increase first and then decrease, and the performance of example 3 is the best in examples 1-4. The detection result shows that the performance of the composite material is obviously improved by adding the bamboo ash-fly ash.

TABLE 3 Performance tables for inventive examples 1-4 and comparative example 1

The foregoing is illustrative of the preferred embodiments of the present invention and is not to be construed as limiting the invention in any way. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make many variations and modifications to the disclosed embodiments, or equivalent variations, without departing from the spirit and scope of the invention, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention.

Claims

1. The preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material is characterized by comprising the following steps of:

s1, mixing magnesium chloride hexahydrate with water to prepare brine;

s2, after being dry-mixed and mixed, magnesium oxide, bamboo ash, fly ash, a foam stabilizer and a catalyst are added into the brine prepared in the step S1 to obtain mixed slurry A;

the addition amount of each raw material is calculated by mass parts, 609.9 parts of magnesium chloride hexahydrate, 396 parts of water, 928.3-974.5 parts of magnesium oxide, 51.6-123.7 parts of bamboo ash, 5.2-30.9 parts of fly ash, 54.0-61.9 parts of foam stabilizer, 10.6-20.8 parts of catalyst and 45.0-61.9 parts of foaming agent;

the bamboo ash comes from a combustion furnace of a bamboo processing plant, and the fineness of the bamboo ash is more than 200 meshes;

the foaming stabilizer is calcium stearate, the catalyst is manganese dioxide, and the foaming agent is a hydrogen peroxide solution with the mass fraction of 30%.

2. The preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material as claimed in claim 1, wherein in the step S3, the rotation speed of the stirring is 280r/min to 450r/min, and the stirring time is 7S to 15S.

3. The preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material according to claim 1, wherein in the step S4, the curing is performed under constant temperature and humidity conditions, the humidity is controlled to be 50-70%, the temperature is controlled to be 18-30 ℃, and the curing time is 24-36 h.

4. The preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material according to claim 1, wherein in step S4, the standing and curing and the continuous curing are both performed under normal temperature and pressure, the standing and curing time is 2 to 3 days, and the continuous curing time is 24 to 25 days.

5. The method for preparing the bamboo ash-fly ash/magnesium oxychloride composite material as claimed in claim 1, wherein the magnesium oxide is light-burned magnesium oxide, and the calcination temperature is 650-700 ℃.

6. A bamboo ash-fly ash/magnesium oxychloride composite material prepared by the preparation method of the bamboo ash-fly ash/magnesium oxychloride composite material as claimed in any one of claims 1 to 5.