CN113800866A

CN113800866A - Multifunctional lightweight concrete and preparation method thereof

Info

Publication number: CN113800866A
Application number: CN202111019315.7A
Authority: CN
Inventors: 阳黎; 夏艳晴; 王宁; 林燕; 腾银见; 张雨晴
Original assignee: Jiahua Special Cement Co ltd
Current assignee: Jiahua Special Cement Co ltd
Priority date: 2021-09-01
Filing date: 2021-09-01
Publication date: 2021-12-17
Anticipated expiration: 2041-09-01
Also published as: CN113800866B

Abstract

The invention discloses multifunctional lightweight concrete and a preparation method thereof, and relates to the technical field of building materials. The invention comprises 92-97% of component A and 3-8% of component B; wherein the component A comprises 2500-3000 parts of cement, 2000-2500 parts of quicklime, 100-300 parts of gypsum, 4700-4900 parts of fly ash, 5-15 parts of aluminum paste and 4500-5500 parts of water; the component B comprises 300-700 parts of unfired natural magnesite powder, 50-150 parts of expandable graphite and 5-10 parts of sodium hydroxide or potassium hydroxide. The lightweight concrete can prevent collapse in early maintenance, absorb heat in case of fire, reduce temperature, generate compact result after being heated to increase concrete strength, release flame retardant gas to reduce oxygen concentration and prevent fire from spreading, adsorb particulate matters to reduce dense smoke concentration and increase escape opportunity.

Description

Multifunctional lightweight concrete and preparation method thereof

Technical Field

The invention relates to the technical field of building materials, in particular to multifunctional lightweight concrete and a preparation method thereof.

Background

Along with the development of society, people have higher and higher requirements on safety and performance of building engineering, and the quality and performance of lightweight concrete as a heat-insulating and heat-resisting material frequently used in the building engineering play a decisive role in the safety, functionality and durability of buildings. The light concrete may be dried and shrunk due to the factors of high humidity, temperature, porosity and the like in the curing and service processes, so that the service function of the light concrete is influenced and the durability of the light concrete is reduced.

In 2016, 5 and 18, an invention patent with the publication number of CN105585330A and the name of 'an energy-saving and heat-preservation aerated concrete block and a preparation method thereof' is disclosed, which is prepared from the following components in parts by weight: 86-96 parts of ordinary portland cement, 2-3 parts of pentaerythritol stearate, 3-4 parts of poly dimethyl diallyl ammonium chloride, 6-7 parts of a polycarboxylic acid water reducing agent, 56-63 parts of water, 12-15 parts of metakaolin, 8-10 parts of zirconium boride, 5-7 parts of maghemite, 16-18 parts of oil shale waste residues, 6-8 parts of brucite fibers, 4-6 parts of chopped carbon fibers, 2-3 parts of hydrogenated rosin, 2-3 parts of magnesium oxide, 3-4 parts of alkyl polyglucoside, 3-4 parts of sodium carboxymethylcellulose and 1-1.2 parts of hydrogen peroxide. The energy-saving heat-preservation aerated concrete block is prepared by adopting a special formula and process, has the characteristics of simple process, energy conservation and emission reduction, and is a regeneration product of the energy-saving building concrete at present. However, because of the existence of a large amount of oil shale waste residues and organic groups, a large amount of toxic and harmful gases are released when the oil shale waste residues and the organic groups are heated; in addition, due to the existence of hydrogen peroxide, oxygen generated by heating can accelerate the spread of fire. As a building material, when a fire disaster is faced, certain potential safety hazards exist.

12.6.2019, an invention patent with publication number CN110540397A and name "an anti-cracking energy-saving heat-insulating aerated concrete block and a preparation method thereof" is disclosed, which comprises the following components in parts by weight: 16-25 parts of flotation steel slag tail mud, 22-34 parts of calcined municipal sludge, 30-38 parts of fly ash, 7-11 parts of cement, 14-21 parts of lime, 1-3 parts of gypsum, 5-8 parts of lignin fiber, 1.2-1.6 parts of air entraining agent, 0.1-0.4 part of foam stabilizer and 0.06-0.1 part of aluminum paste, and then mixing and stirring, slurry injection molding, standing and maintaining, demolding and cutting, and autoclaving and maintaining. The flotation steel slag tail mud and calcined municipal sludge are used as partial siliceous raw materials and calcareous raw materials, so that the green energy-saving aerated concrete building wall material is prepared by recycling solid wastes, and the purposes of saving energy, reducing emission and protecting the environment are achieved. However, a large amount of flotation reagents are generally remained in the flotation steel slag tailing slurry, most of the flotation reagents are organic substances and slowly volatilize into the air, and certain damage is caused to human bodies when the flotation reagents are in the environment for a long time; in addition, the existence of heavy metals and other harmful substances in the municipal sludge causes certain damage to human bodies.

In order to expand the application of the lightweight heat-insulating concrete under high-temperature conditions, the flame-retardant lightweight concrete has become a research hotspot at present. The main technical means is to mix inorganic or organic flame retardant materials into the cement-based cementing materials. However, these technical means have single function, harsh process, high cost and poor flame retardant effect.

Disclosure of Invention

The invention provides multifunctional lightweight concrete for overcoming the defects and shortcomings in the prior art, and aims to solve the problems that the lightweight thermal insulation concrete in the prior art is high in cost and poor in flame retardant effect. The multifunctional lightweight concrete provided by the invention can effectively prevent collapse in early maintenance, can effectively absorb heat when a fire breaks out, reduce the temperature, generate a compact result after being heated to increase the strength of the concrete, release flame-retardant gas to reduce the oxygen concentration and prevent the fire from spreading, and can adsorb particles to reduce the concentration of dense smoke and increase the escape chance. The multifunctional lightweight concrete provided by the invention enhances the functions and effects of the lightweight concrete in the case of fire, and has lower cost and good flame retardant effect compared with the existing lightweight concrete.

In order to solve the problems in the prior art, the invention is realized by the following technical scheme:

the multifunctional lightweight concrete comprises, by mass, 92-97% of a component A and 3-8% of a component B; wherein the component A comprises 2500 to 3000 parts of cement, 2000 to 2500 parts of quicklime, 100 to 300 parts of gypsum, 4700 to 4900 parts of fly ash, 5 to 15 parts of aluminum powder paste and 4500 to 5500 parts of water by mass; the component B comprises, by mass, 300 to 700 parts of unfired natural magnesite powder, 50 to 150 parts of expandable graphite and 5 to 10 parts of sodium hydroxide or potassium hydroxide.

The cement in the component A is ordinary PO42.5 cement, and the granularity is 3-65 mu m.

The quicklime in the component A is common quicklime with the granularity of 30-80 mu m.

The granularity of the gypsum in the component A is 30-80 mu m.

The fly ash in the component A is second-grade fly ash, and the granularity is 50-80 mu m.

The aluminum powder paste in the component A is aerated aluminum powder paste.

The granularity of the natural magnesite powder in the component B is 3-32 mu m.

The granularity of the expandable graphite in the component B is 0.05mm-0.2 mm.

The preparation method of the component B comprises the following steps:

the preparation method of the expandable graphite comprises the following steps: screening the purified flake graphite concentrate to obtain flake graphite concentrate with the granularity of 0.05-0.2 mm; adding a solid oxidant with the mass of 0.08-0.15 time of that of graphite and a liquid oxidant with the mass of 2-5 times of that of graphite into the screened crystalline flake graphite concentrate to carry out oxidation intercalation; after the intercalation is oxidized for 30min to 90min, the prepared expandable graphite is washed to be neutral by water; drying the expandable graphite obtained by washing with water for later use;

crushing the natural magnesite: firstly, smashing primary blocky natural magnesite into small blocks of 3-5 cm, then placing the small blocks into a jaw crusher for primary crushing, crushing the natural magnesite primarily crushed by the jaw crusher by a crusher, and screening the crushed natural magnesite to 3-32 mu m for later use;

mixing: taking out 300-700 parts of unfired natural magnesite powder and 50-150 parts of expandable graphite, adding 5-10 parts of sodium hydroxide or potassium hydroxide, and uniformly mixing in a mixer to obtain the component B.

The solid oxidant is potassium permanganate and/or potassium dichromate.

The liquid oxidant is one or the combination of more of concentrated nitric acid, concentrated hydrochloric acid, concentrated sulfuric acid, concentrated perchloric acid, boric acid, phosphoric acid and glacial acetic acid.

The invention also provides a preparation method of the multifunctional lightweight concrete, and the method has the advantages of simple process, easy operation and low preparation cost.

A preparation method of multifunctional lightweight concrete comprises the following steps:

the preparation step of the component A is as follows: taking 2500-3000 parts of cement, 2000-2500 parts of quicklime, 100-300 parts of gypsum, 4700-4900 parts of fly ash, 5-15 parts of aluminum powder paste and 4500-5500 parts of water by mass, and adding into a mortar stirrer to be uniformly mixed to obtain a component A;

the preparation step of the component B is as follows: taking out 300-700 parts by mass of unfired natural magnesite powder and 50-150 parts by mass of expandable graphite, adding 5-10 parts by mass of sodium hydroxide or potassium hydroxide, and uniformly mixing in a mixer to obtain a component B;

mixing and pouring the component A and the component B: respectively taking 92-97% of the component A and 3-8% of the component B according to the mass percentage, fully and uniformly mixing, and then filling into a mold;

and (3) maintenance: placing into a mold, placing into a steam curing box, steaming at 40-70 deg.C for 40-80min, and taking out; cutting bread with saw blade, continuously placing the light concrete with bread removed into steam curing box, steaming at 40-70 deg.C for 5-7 hr, taking out, and curing at normal temperature; and demolding after the age of the lightweight concrete reaches 1d, and continuously curing at normal temperature for 27d after demolding to obtain the multifunctional lightweight concrete.

Compared with the prior art, the beneficial technical effects brought by the invention are as follows:

1. the flame-retardant heat-insulating material comprises 92% -97% of the component A and 3% -8% of the component B, the strength and the heat-insulating capacity are derived from the component A, the flame-retardant function is derived from the component B, and the two components can make up for the deficiencies of each other.

Firstly, the aluminum powder paste in the component A reacts under alkaline conditions to generate micro-bubbles, the cement and the fly ash react under alkaline conditions to hydrate, the bubbles are locked in the concrete, and a compact pore structure is formed in the concrete, so that the heat transmission can be effectively blocked; the magnesite in the component B can be decomposed to generate water and carbon dioxide when being heated, the evaporation energy of the water can absorb a large amount of heat, meanwhile, the carbon dioxide can isolate oxygen to play a flame retardant effect, the volume of the expandable graphite in the component B can be increased sharply when being heated, and the expanded carbon layer formed by pyrolysis has good high temperature resistance, so that a good heat insulation and oxygen insulation layer is formed.

Furthermore, MgO, a main product generated by the thermal decomposition of the component B, is a heat-resistant material, and can form a compact ceramic protective layer on the surface of the combustible material, so that the speed of transferring heat from the surface to the combustible material is reduced, and the effect of isolating oxygen in the air from continuing to contact with the combustible material is achieved. The generation of smoke can be effectively suppressed while the continuation of combustion is prevented.

Finally, the expanded graphite generated by the expansion of the expandable graphite in the component B can also adsorb the pyrolysis products of the polymer, so that the secondary combustion of the polymer is prevented, and the generated flame-retardant gas can isolate oxygen. Meanwhile, the expandable graphite can block the air hole, so that air convection is prevented from being formed, and a heat source is isolated.

2. In the prior art, calcined or lightly calcined magnesite powder is used for preparing concrete, but the calcined or lightly calcined magnesite powder utilizes the flame retardant property of calcined or lightly calcined magnesia, the main component of magnesite is magnesium carbonate, and the calcined magnesite is magnesium oxide, and the calcined magnesite loses the capability of thermal decomposition. And this application directly adopts the natural magnesite that does not fire, and after the maintenance shaping, partial natural magnesite powder does not take place chemical change, exists in the concrete, when the conflagration breaing out, is heated and can decompose and produce water and carbon dioxide, and the evaporation of water can absorb a large amount of heats, and carbon dioxide can insulate off oxygen simultaneously and play flame retardant efficiency. The present application primarily makes use of the decomposition reaction of calcined magnesite when heated. The magnesite is heated and decomposed in the concrete at high temperature to generate compact magnesium oxide which is attached to pores, so that the sudden drop of the strength of the concrete after high temperature is prevented.

3. In the invention, magnesite is used as a flame retardant, magnesium carbonate in the magnesite and sodium hydroxide or potassium hydroxide equivalent alkali can generate alkali-carbonate reaction, weak volume expansion is shown in the reaction process, and the volume stability of concrete is improved to a certain extent. Avoiding early collapse of concrete. Meanwhile, the alkali-carbonate reaction is carried out in a concrete pore solution, reaction products of magnesium hydroxide and calcium carbonate are insoluble substances and are precipitated in gaps, sodium carbonate or potassium carbonate is crystallized along with the gradual reduction of moisture, and the crystals are retained in the pores of the precipitates, so that the strength and the durability of the concrete can be effectively improved. In the process of preparing concrete, part of magnesite reacts with added sodium hydroxide or potassium hydroxide to generate micro-swelling, the rest magnesite still exists in the concrete in an original state, and the magnesite is heated and decomposed when meeting high-temperature conditions such as fire and the like.

4. The invention specifically controls the granularity of the natural magnesite within 3-32 mu m, so that the natural magnesite can be inserted between expanded graphite layers, and the expansion of the expandable graphite can be accelerated when the natural magnesite is heated, thereby blocking the heat transmission more quickly.

5. In the invention, expandable graphite is selected as another flame retardant, and the expandable graphite can absorb part of heat in the expansion process and also has a certain flame retardant effect.

6. The particle sizes of the magnesite and the expandable graphite are limited, the magnesite has small particle size, the expandable graphite has large particle size, the magnesite with small particle size can enter the interlayer of the expandable graphite, and the expansion of the expandable graphite is accelerated by gas generated when the expandable graphite is heated, so that the formation of flame-retardant heat-insulating capability is accelerated.

Drawings

FIG. 1 is an electron micrograph of expandable graphite of the present invention prior to a fire;

FIG. 2 is an electron micrograph of the expandable graphite of the present invention after it has been subjected to a fire;

FIG. 3 is a comparison analysis chart of XRD before and after fire of natural magnesite at different temperatures;

FIG. 4 is an electron microscope image of the lightweight concrete of the present invention before the fire occurs;

FIG. 5 is an electron microscope image of the lightweight concrete of the present invention after the fire.

Detailed Description

The technical solution of the present invention is further elaborated below with reference to specific examples. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As an embodiment of this example, the compounding ratio in each example is given with reference to the following table.

Table 1 shows four example proportioning schemes for component A

Table 2 shows four example proportioning schemes for component B

	Expandable graphite	Non-calcined natural magnesite powder	Sodium hydroxide	Potassium hydroxide
					Example 1	150	300	5	-
Example 2	50	700	8	2
					Example 3	100	450	-	6
Example 4	200	400	4	4

The preparation ratios of the expandable graphite in each example of the component B are shown in the following Table 3.

Table 3 shows the compounding ratio of expandable graphite in each example of component B

	Graphite	KMnO₄	K₂Cr₂O₇	HNO₃	H₃PO₄	HCL	H₂SO₄	CH₃COOH
									Example 1	100	13	-	300	100	-	-	-
Example 2	100	-	15	200	50	100	50	-
									Example 3	100	7	8	-	-	300	200	100
Example 4	100	12	-	200	-	-	-	200

Specific descriptions of the examples in the above tables 1, 2 and 3 are as follows:

example 1

As can be seen from Table 1 above, the preparation of component A was carried out: taking 2500 parts by mass of cement with the particle size of 3-65 mu m, 2500 parts by mass of quicklime with the particle size of 30-80 mu m, 100 parts by mass of gypsum with the particle size of 30-80 mu m, 4900 parts by mass of fly ash with the particle size of 50-80 mu m, 5 parts by mass of aluminum paste and 5500 parts by mass of water, and adding the mixture into a mortar mixer to be uniformly mixed to obtain a component A;

as can be seen from Table 2 above, the preparation of component B was carried out: taking out 300 parts by mass of unfired natural magnesite powder and 150 parts by mass of expandable graphite, adding 5 parts by mass of sodium hydroxide, and uniformly mixing in a mixer to obtain a component B;

mixing and pouring the component A and the component B: according to the mass percentage, respectively taking 97 percent of the component A and 3 percent of the component B, fully and uniformly mixing, and then filling into a mold;

and (3) maintenance: placing into a mold, placing into a steam curing box, steaming at 40-70 deg.C for 40-80min, and taking out; cutting bread with saw blade, continuously placing the light concrete with bread removed into steam curing box, steaming at 40-70 deg.C for 5-7 hr, taking out, and curing at normal temperature; and demolding after the age of the lightweight concrete reaches 1d, and continuing curing at normal temperature for 27d after demolding to obtain the multifunctional lightweight concrete test piece 1.

As can be seen from Table 3 above, the expandable graphite in component B is prepared from graphite having a particle size of 0.1mm-0.2mm and KMnO in a ratio₄：HNO₃：H₃PO₄: graphite =13:300: 100: 100, taking out 150 parts of the prepared expandable graphite, and uniformly mixing the expandable graphite with 300 parts of magnesite powder with the fineness of 3-32 mu m to obtain a component B.

Example 2

As can be seen from Table 1 above, the preparation of component A was carried out: taking 3000 parts by mass of cement with the particle size of 3-65 mu m, 2000 parts by mass of quicklime with the particle size of 30-80 mu m, 300 parts by mass of gypsum with the particle size of 30-80 mu m, 4700 parts by mass of fly ash with the particle size of 50-80 mu m, 15 parts by mass of aluminum paste and 4500 parts by mass of water, and adding the mixture into a mortar mixer to mix uniformly to obtain a component A;

as can be seen from Table 2 above, the preparation of component B was carried out: taking out 700 parts by mass of unfired natural magnesite powder and 50 parts by mass of expandable graphite, adding 8 parts by mass of sodium hydroxide and 2 parts by mass of potassium hydroxide, and uniformly mixing in a mixer to obtain a component B;

mixing and pouring the component A and the component B: respectively taking 92% of the component A and 8% of the component B according to the mass percentage, fully and uniformly mixing, and then filling into a mold;

and (3) maintenance: placing into a mold, placing into a steam curing box, steaming at 40-70 deg.C for 40-80min, and taking out; cutting bread with saw blade, continuously placing the light concrete with bread removed into steam curing box, steaming at 40-70 deg.C for 5-7 hr, taking out, and curing at normal temperature; and demolding after the age of the lightweight concrete reaches 1d, and continuing curing at normal temperature for 27d after demolding to obtain the multifunctional lightweight concrete sample 2.

As can be seen from Table 3 above, the expandable graphite in component B is prepared from graphite having a particle size of 0.05mm to 0.2mm and a ratio K₂Cr₂O₇：HNO₃：H₃PO₄：HCl:H₂SO₄Graphite =15:200: 50: the component B is prepared by acid oxidation intercalation of 100:50:100, and 50 parts of the prepared expandable graphite are taken out and mixed evenly with 700 parts of magnesite powder with the fineness of 3-15 mu m to obtain the component B.

Example 3

As can be seen from Table 1 above, the preparation of component A was carried out: taking 2800 parts by mass of cement with the particle size of 3-65 mu m, 2200 parts by mass of quicklime with the particle size of 30-80 mu m, 200 parts by mass of gypsum with the particle size of 30-80 mu m, 4800 parts by mass of fly ash with the particle size of 50-80 mu m, 5 parts by mass of aluminum paste and 5000 parts by mass of water, adding the mixture into a mortar mixer, and uniformly mixing to obtain a component A;

as can be seen from Table 2 above, the preparation of component B was carried out: taking out 450 parts by mass of unfired natural magnesite powder and 100 parts by mass of expandable graphite, adding 6 parts by mass of potassium hydroxide, and uniformly mixing in a mixer to obtain a component B;

mixing and pouring the component A and the component B: respectively taking 95% of the component A and 5% of the component B according to the mass percentage, fully and uniformly mixing, and then filling into a mold;

and (3) maintenance: placing into a mold, placing into a steam curing box, steaming at 40-70 deg.C for 40-80min, and taking out; cutting bread with saw blade, continuously placing the light concrete with bread removed into steam curing box, steaming at 40-70 deg.C for 5-7 hr, taking out, and curing at normal temperature; and demolding after the age of the lightweight concrete reaches 1d, and continuing curing at normal temperature for 27d after demolding to obtain the multifunctional lightweight concrete test piece 3.

As can be seen from Table 3 above, the expandable graphite in component B is prepared from graphite having a particle size of 0.1mm-0.2mm and KMnO in a ratio₄：K₂Cr₂O₇: HCl:H₂SO₄Graphite =7:8:300: 200: 100 parts of expandable graphite is taken out and is uniformly mixed with 450 parts of magnesite powder with the fineness of 3-15 mu m to obtain a component B.

Example 4

As can be seen from Table 1 above, the preparation of component A was carried out: taking 2900 parts by mass of cement with the particle size of 3-65 mu m, 2100 parts by mass of quicklime with the particle size of 30-80 mu m, 150 parts by mass of gypsum with the particle size of 30-80 mu m, 4850 parts by mass of fly ash with the particle size of 50-80 mu m, 8 parts by mass of aluminum powder paste and 5400 parts by mass of water, and adding the mixture into a mortar mixer to mix uniformly to obtain a component A;

as can be seen from Table 2 above, the preparation of component B was carried out: taking out 400 parts by mass of unfired natural magnesite powder and 200 parts by mass of expandable graphite, adding 4 parts by mass of sodium hydroxide and 4 parts by mass of potassium hydroxide, and uniformly mixing in a mixer to obtain a component B;

mixing and pouring the component A and the component B: respectively taking 94% of the component A and 6% of the component B according to the mass percentage, fully and uniformly mixing, and then filling into a mold;

and (3) maintenance: placing into a mold, placing into a steam curing box, steaming at 40-70 deg.C for 40-80min, and taking out; cutting bread with saw blade, continuously placing the light concrete with bread removed into steam curing box, steaming at 40-70 deg.C for 5-7 hr, taking out, and curing at normal temperature; and demolding after the age of the lightweight concrete reaches 1d, and continuing curing at normal temperature for 27d after demolding to obtain the multifunctional lightweight concrete test piece 4.

As can be seen from Table 3 above, the expandable graphite in component B is prepared from graphite having a particle size of 0.05mm-0.2mm and KMnO in a ratio₄：HNO₃：CH₃COOH: graphite =12:200: 100, taking out 150 parts of the prepared expandable graphite, and uniformly mixing the expandable graphite with 300 parts of magnesite powder with the fineness of 3-15 mu m to obtain a component B.

Example 5

The lightweight concrete samples 1, 2, 3 and 4 prepared in the above examples 1, 2, 3 and 4 were subjected to tests:

(1) molding the lightweight concrete, and molding and maintaining the test piece according to national standard GB/T11971-1997;

(2) after the test piece is cured at normal temperature for 3d, 7d and 28d, the compressive strength is detected according to the standard;

(3) after the test piece is maintained for 28d, the dry density is detected according to the standard;

(4) after the test piece is maintained for 28 days, testing the heat conductivity coefficient according to the test method for the heat conductivity coefficient of lightweight concrete JC 275-; the test results are shown in table 4 below.

Table 4 shows the performance of the lightweight concrete samples 1 to 4

From the above test results, referring to the attached fig. 1-5 of the specification, fig. 1 shows the electron microscope images of the expandable graphite prepared in example 2 before being fired, fig. 2 shows the electron microscope images of the expandable graphite prepared in example 2 after being fired, and as can be seen from fig. 1 and fig. 2, the volume of the expandable graphite is increased sharply when being heated, and the expanded carbon layer formed by pyrolysis has good high temperature resistance and forms a good heat insulation and oxygen insulation layer.

FIG. 3 is a comparative XRD analysis chart of natural magnesite before and after different temperature fire in example 2; from the test results shown in fig. 1, fig. 2, fig. 3 and the above test results, it can be seen that the magnesite and the expandable graphite have smaller particle sizes, the expandable graphite has larger particle sizes, the magnesite with smaller particle sizes can enter the interlayer of the expandable graphite, and the gas generated when the expandable graphite is heated accelerates the expansion of the expandable graphite and accelerates the formation of the flame retardant and heat insulation capability.

Fig. 4 is an electron microscope image of the test piece 2 prepared in example 2 before the fire, fig. 5 is an electron microscope image of the test piece 2 prepared in example 2 after the fire, and it can be seen from fig. 4 and fig. 5 that magnesium carbonate in magnesite and equivalent alkali of sodium hydroxide or potassium hydroxide can generate alkali-carbonate reaction, and shows weak volume expansion in the reaction process, thereby improving the volume stability of concrete to a certain extent. Avoiding early collapse of concrete. Meanwhile, the alkali-carbonate reaction is carried out in a concrete pore solution, reaction products of magnesium hydroxide and calcium carbonate are insoluble substances and are precipitated in gaps, sodium carbonate or potassium carbonate is crystallized along with the gradual reduction of moisture, and the crystals are retained in the pores of the precipitates, so that the strength and the durability of the concrete can be effectively improved. Fig. 4 and 5 illustrate in comparison: the volume of the expandable graphite is increased sharply when the expandable graphite is heated, and an expanded carbon layer formed by pyrolysis has good high-temperature resistance and forms a good heat insulation and oxygen insulation layer.

Claims

1. The multifunctional lightweight concrete is characterized in that: comprises 92-97 percent of component A and 3-8 percent of component B by mass percentage; wherein the component A comprises 2500 to 3000 parts of cement, 2000 to 2500 parts of quicklime, 100 to 300 parts of gypsum, 4700 to 4900 parts of fly ash, 5 to 15 parts of aluminum powder paste and 4500 to 5500 parts of water by mass; the component B comprises, by mass, 300 to 700 parts of unfired natural magnesite powder, 50 to 150 parts of expandable graphite and 5 to 10 parts of sodium hydroxide or potassium hydroxide.

2. The multifunctional lightweight concrete according to claim 1, wherein: the cement in the component A is ordinary PO42.5 cement, and the granularity is 3-65 mu m.

3. The multifunctional lightweight concrete according to claim 1, wherein: the quicklime in the component A is common quicklime with the granularity of 30-80 mu m.

4. The multifunctional lightweight concrete according to claim 1, wherein: the granularity of the gypsum in the component A is 30-80 mu m.

5. The multifunctional lightweight concrete according to claim 1, wherein: the fly ash in the component A is second-grade fly ash, and the granularity is 50-80 mu m.

6. The multifunctional lightweight concrete according to claim 1, wherein: the aluminum powder paste in the component A is aerated aluminum powder paste.

7. The multifunctional lightweight concrete according to claim 1, wherein: the granularity of the natural magnesite powder in the component B is 3-32 mu m.

8. The multifunctional lightweight concrete according to claim 1, wherein: the granularity of the expandable graphite in the component B is 0.05mm-0.2 mm.

9. The multifunctional lightweight concrete according to claim 1, wherein: the preparation method of the component B comprises the following steps:

10. The preparation method of the multifunctional lightweight concrete is characterized by comprising the following steps: the method comprises the following steps: