CN114349446A - Papermaking white mud aerated concrete and preparation method thereof - Google Patents
Papermaking white mud aerated concrete and preparation method thereof Download PDFInfo
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- CN114349446A CN114349446A CN202210145006.2A CN202210145006A CN114349446A CN 114349446 A CN114349446 A CN 114349446A CN 202210145006 A CN202210145006 A CN 202210145006A CN 114349446 A CN114349446 A CN 114349446A
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- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Abstract
The invention discloses a papermaking white mud aerated concrete and a preparation method thereof, and research and analysis on mechanics and micro performance of the papermaking white mud aerated concrete show that the optimum mix proportion of the aerated concrete is the following concrete material dosage per cubic meter: 70kg of cement, 112kg of lime, 21kg of gypsum, 469kg of fly ash, 385kg of water and 209g of aluminum powder, and 28kg of papermaking white mud after calcination treatment at 1000 ℃ or 1200 ℃.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of concrete preparation, in particular to papermaking white mud aerated concrete and a preparation method thereof.
[ background of the invention ]
The yield of commercial concrete in China is increased year by year. The yield of the aerated concrete is also increased year by year while the yield of the concrete is increased year by year. The aerated concrete production industry belongs to the high-energy-consumption and high-pollution industry due to the limitation of the production process.
Paper making enterprises can produce a secondary pollutant which is harmful to the environment in the alkali recovery process of paper pulp production and is called papermaking white mud. The papermaking white mud is a byproduct harmful to the environment generated in the alkali recovery link in the papermaking production process, and is prepared by extracting, evaporating and concentrating pulping black liquor raw materials, calcining the raw materials by an alkali recovery furnace to obtain molten substances, adding water to dissolve the molten substances to form green liquor, adding lime to perform causticization treatment, washing and filtering the generated precipitate to recover residual alkaline waste residue precipitate, namely the papermaking white mud. Statistically, the production of 1 ton of pulp stock results in about 0.5 ton of papermaking white mud byproduct.
At present, the treatment of the papermaking white mud in China is mainly extensive. The statistics of the State statistical office show that the papermaking yield in 2019 of China exceeds 1.25 hundred million tons and increases by 3.5 percent cumulatively. The subject group is obtained by visiting Guangxi Liujiang paper mills, about 3 tons of paper pulp are needed for producing 1 ton of paper, and 0.5 ton of papermaking white mud is produced for 1 ton of paper pulp, so that the yield of the papermaking white mud in China is very large according to the calculation. The resource recycling of the papermaking white mud is urgent.
[ summary of the invention ]
The invention provides a papermaking white mud aerated concrete and a preparation method thereof, wherein the papermaking white mud is utilized in the production process of the aerated concrete, so that the problem of environmental pollution caused by the papermaking white mud can be solved, and the production cost of the aerated concrete can be reduced.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of papermaking white mud aerated concrete comprises the following steps:
1) calcining the primary papermaking white mud material at 800-;
2) preparing raw materials: preparing the concrete material dosage per cubic meter according to the mixing ratio: 70kg of cement, 112kg of lime, 21kg of gypsum, 469kg of fly ash, 385kg of water, 0.209kg of aluminum powder and 28kg of papermaking white mud raw material;
3) pouring the papermaking white mud raw material, cement, lime, gypsum and fly ash into a stirrer for pre-stirring, fully mixing, adding water and aluminum powder into the stirrer, and continuously stirring uniformly;
4) pouring the slurry uniformly stirred in the step into a mold at the height of 1/2, standing for 30min to allow the gas to fill the mold, scraping the surface of the mold by using a scraper, demolding the test piece after 24h, feeding the demolded test piece into an autoclave for autoclaving and curing for 10.5h, and taking the test piece out of the autoclave to obtain the papermaking white mud aerated concrete.
In the invention:
in the step 1), calcination at 1000-1200 ℃ is preferably carried out for 20-24 h.
The invention also relates to the papermaking white mud aerated concrete prepared by the preparation method of the papermaking white mud aerated concrete, and the characterization and microscopic performance analysis of the material of the papermaking white mud aerated concrete sample through XRD and SEM tests show that the hydration products mainly comprise tobermorite, hydrated calcium silicate (C-S-H) gel, hydrated garnet and silicon dioxide (SiO)2) The tobermorite is mainly plate-shaped and acicular, and the pore structure consists of bubbles, capillary pores and gel pores. The physical and mechanical properties of the papermaking white mud aerated concrete are researched, and the findings are as follows: each test group is greater than the blank control group in density; in the aspect of water absorption, the water absorption rate is reduced along with the increase of the substitution rate of the papermaking white mud, and is gradually increased along with the increase of the calcining temperature of the papermaking white mud. In the aspect of mechanical property, the cubic compressive strength is higher than that of a blank control group and can reach 6.86 MPa; the axial compression strength is improved along with the increase of the substitution rate of the papermaking white mud raw material, and when the substitution rate of the papermaking white mud raw material is 20%, the maximum increase is 14.11%; splitting deviceAnd the cracking resistance is high, when the substitution rate of the papermaking white mud raw material is 5%, the cracking tensile data of each calcining temperature group is not changed greatly, and when the substitution rate of the papermaking white mud raw material is increased to 10% and 20%, the cracking tensile strength value of the calcining temperature group at 800 ℃ is higher than that of the calcining temperature groups at 1000 ℃ and 1200 ℃.
Compared with the prior art, the invention has the following advantages:
according to the papermaking white mud aerated concrete, the design idea of producing the aerated concrete by partially replacing lime with the treated papermaking white mud raw material is combined with aerated concrete mix proportion design, a papermaking white mud calcination temperature and the substitution rate of the papermaking white mud are used as variables to design a test, and a common aerated concrete standard mix proportion test block with A5.0-grade strength is used as a blank control group to carry out test design. According to the relevant standard of China on autoclaved aerated concrete blocks, preparing an autoclaved aerated concrete standard test piece, carrying out tests on physical, mechanical and microscopic properties, recording relevant data, comparing test data of the autoclaved aerated concrete test piece prepared by papermaking white mud at different calcination temperatures and different substitution rates with test data of a blank control group autoclaved aerated concrete test piece by analyzing test data and results, and determining reasonable calcination temperature and substitution rate of equal mass substituted lime of papermaking white mud waste in the process of producing aerated concrete. The relation between the paper making white mud raw material and the physical mechanics and microscopic properties of the aerated concrete is established, and a foundation is laid for subsequent research.
[ description of the drawings ]
FIG. 1 is a process flow chart of a preparation method of a papermaking white mud aerated concrete according to the invention;
FIG. 2 is an XRD diffraction pattern of the papermaking white mud in the experimental example;
FIG. 3 is a scanning electron micrograph of the papermaking white mud of 12000 times in the experimental example;
FIG. 4 is a drawing of the preparation of a test piece of aerated concrete of paper white clay in the experimental example (FIG. 4 a: slurry injection molding; FIG. 4 b: test piece formation; FIG. 4 c: test piece);
FIG. 5 is a line graph of the water absorption test value of the paper white clay aerated concrete in the experimental example.
FIG. 6 is a graph of the calcination temperature test of the aerated concrete of the paper white clay in the experimental example (FIG. 6 a: same calcination temperature and different substitution rate strength values; FIG. 6b same substitution rate and different calcination temperature strength values; FIG. 6c a cube compression strength broken line graph);
FIG. 7 is a graph of the compressive strength test of the aerated concrete of the paper mill white clay in the experimental example (FIG. 7a shows the axial compressive strength values at the same calcination temperature and different substitution rates; FIG. 7b shows the axial compressive strength values at the same substitution rate and different calcination temperatures; FIG. 7c shows the axial compressive strength line graph);
FIG. 8 is a graph of an axial compressive test of aerated concrete of papermaking white clay in an experimental example (FIG. 8 a: axial compressive strength values of same calcination temperature and different substitution rates; FIG. 8 b: axial compressive strength values of same substitution rate and different calcination temperatures; FIG. 8 c: a line graph of axial compressive strength values of same calcination temperature and different substitution rates);
FIG. 9 is a comparison of XRD tests of paper making white clay and aerated concrete in experimental examples (FIG. 9 a: X-ray diffraction spectrum of ordinary aerated concrete; FIG. 9 b: X-ray diffraction spectrum of paper making white clay and aerated concrete at different calcination temperatures);
FIG. 10 is a drawing of SEM test of paper mill white clay aerated concrete and ordinary aerated concrete in the experimental example (FIG. 10a is a scanning electron microscope drawing of paper mill white clay calcination temperature group aerated concrete at 800 deg.C; FIG. 10b is a scanning electron microscope drawing of paper mill white clay calcination temperature group aerated concrete at 1000 deg.C; FIG. 10c is a scanning electron microscope drawing of paper mill white clay calcination temperature group aerated concrete at 1200 deg.C; FIG. 10d is a scanning electron microscope drawing of ordinary aerated concrete);
FIG. 11 is a SEM (scanning electron microscope) image of the pore structure of the paper-making white clay aerated concrete and the common aerated concrete in the experimental example (FIG. 11a is a scanning electron microscope image of the paper-making white clay aerated concrete and FIG. 11b is a scanning electron microscope image of the common aerated concrete).
[ detailed description ] embodiments
The following examples are provided to further illustrate the embodiments of the present invention.
Before the embodiments are described in detail, it is necessary to provide some remarks for explanation: experiments were carried out with different substitution rates of papermaking white mud.
Example 1:
a preparation method of papermaking white mud aerated concrete comprises the following steps:
1) calcining the primary papermaking white mud material at 1000 ℃ for 20 hours, and screening to obtain a papermaking white mud raw material with the fineness of 0.075 mm;
2) preparing raw materials: preparing the concrete material dosage per cubic meter according to the mixing ratio: 70kg of cement, 112kg of lime, 21kg of gypsum, 469kg of fly ash, 385kg of water, 0.209kg of aluminum powder and 28kg of papermaking white mud raw material;
3) pouring the papermaking white mud raw material, cement, lime, gypsum and fly ash into a stirrer for pre-stirring, fully mixing, adding water and aluminum powder into the stirrer, and continuously stirring uniformly;
4) pouring the slurry uniformly stirred in the step into a mold at the height of 1/2, standing for 30min to allow the gas to fill the mold, scraping the surface of the mold by using a scraper, demolding the test piece after 24h, feeding the demolded test piece into an autoclave for autoclaving and curing for 10.5h, and taking the test piece out of the autoclave to obtain the papermaking white mud aerated concrete.
Example 2:
a preparation method of papermaking white mud aerated concrete, which is characterized in that in the step 1), calcination is carried out for 20 hours at 1200 ℃, and the rest is the same as that in the example 1.
Example 3:
a preparation method of papermaking white mud aerated concrete, which is characterized in that the papermaking white mud aerated concrete is calcined at 800 ℃ for 24 hours in the step 1), and the rest is the same as the step 1.
Experimental example:
according to the invention, a papermaking white mud raw material with the fineness of 0.075mm is calcined and screened at the temperature of 800 ℃, 1000 ℃ and 1200 ℃, a test piece is prepared according to the lime substitution rate with equal mass of 5%, 10% and 20%, an orthogonal test is designed by taking the calcination temperature and the substitution rate as variables, a common aerated concrete with the strength grade of A5.0B07 as a blank control test group, the physical mechanics and the microscopic properties of the aerated concrete are mainly researched by replacing the lime raw material with the papermaking white mud, and the physical mechanical property determination, the material characterization and the microscopic property analysis determination of the papermaking white mud aerated concrete test piece prepared by the test are carried out.
1. Measurement of physical and mechanical Properties of test specimens
According to the requirements of national specification of autoclaved aerated concrete performance test method (GB/T11969-Buchner 2020) and autoclaved aerated concrete block (GB 11968-Buchner 2020) on an aerated concrete test block, a water absorption test, a cubic compressive strength test, an axial compressive strength test and a splitting tensile strength test are selected from the specification, and the important physical and mechanical performance indexes are measured.
2.1 Material characterization and microscopic Property analysis
And obtaining diffraction patterns of the papermaking white mud and lime raw materials before and after calcination by using an X-ray diffraction analyzer, and performing qualitative analysis and comparative analysis on the diffraction patterns of the papermaking white mud and lime raw materials and the lime raw materials.
The microscopic hydration products and the crystal structure changes of the paper-making white mud aerated concrete prepared by different test groups are analyzed by using a scanning electron microscope, and the influence of the paper-making white mud on the hydration products and the crystal structure of the aerated concrete is analyzed by comparing the microscopic hydration products and the crystal structure of the common reinforced concrete prepared by lime raw materials.
2.2 preparation of papermaking white mud raw material
2.2.1 preparation of papermaking white mud raw material
The papermaking white mud produced by Yangtze river paper mill in Liuzhou city, Guangxi province is selected. The papermaking white mud is big when just producing, at first put into NT-4A type intelligence electric heat constant temperature oven with the papermaking white mud for the experiment, set up the temperature to 105 ℃ and carry out drying process, when papermaking white mud quality is not changing, carry out grinding process in putting into the ball mill, put into box resistance furnace and set up 800 ℃, 1000 ℃ and 1200 ℃ three grades of temperatures respectively and carry out 1 h's post-calcination mark group number with papermaking white mud after drying grinding, put into standard sieving machine with three groups of post-calcination papermaking white mud at last and carry out screening process, select the powder that the fineness is 0.075mm as raw materials for subsequent use.
2.3 testing basic Properties of the raw materials
2.3.1 analysis of physical Properties and Water content of papermaking white mud
The papermaking white mud is a fine white granular object which is grey white and about 1-3 millimeters in nature, basically has no pungent smell, and has the average water content of 26.13 percent measured in a laboratory.
2.3.2 chemical composition analysis, XRD test and microscopic analysis research of papermaking white mud
TABLE 1 chemical composition analysis table of papermaking white mud
The XRD diffraction pattern of the papermaking white mud obtained after the analysis by the XRD test is shown in figure 2.
FIG. 2: XRD diffraction pattern of papermaking white mud.
As can be seen from Table 1, the main oxide of the white paper-making mud is calcium oxide (CaO), the content of the main oxide is more than 50 percent of the total content of all the oxides of the white paper-making mud, and the main diffraction peak of the white paper-making mud is calcium carbonate (CaCO) after XRD diffraction pattern analysis3) Other than CaCO3No other diffraction peaks were evident beyond the diffraction peak. The XRF and XRD test results of the papermaking white mud are combined for comprehensive analysis, and the papermaking white mud is a typical calcareous raw material.
And (3) carrying out microstructure analysis on the papermaking white mud by using a scanning electron microscope, wherein a scanning electron microscope photo of the papermaking white mud is shown in figure 3. The white mud for paper making is magnified by 12000 times, and the grains of the white mud are mainly calcium carbonate grains which present irregular polygonal clumping and stacking shapes.
FIG. 3: scanning electron micrograph of papermaking white mud x12000 times.
3 study on mix proportion design and forming influence of paper making white clay aerated concrete
3.1 design scheme of mix proportion of paper making white mud aerated concrete
3.1.1 raw material proportioning principle
The inventor utilizes the quality of the papermaking white mud to replace lime to prepare the aerated concrete, because the content of activated CaO obtained by the papermaking white mud at different calcining temperatures is different from that of the lime, and simultaneously, the change of the substitution rate of the papermaking white mud can also influence some physical, mechanical and durability performances of the aerated concrete, the invention researches and carries out orthogonal tests by respectively setting the calcining temperature of the papermaking white mud to 800 ℃, 1000 ℃ and 1200 ℃ and setting the substitution rates to 5%, 10% and 20%, and finds out reasonable calcining temperature and substitution rate of the papermaking white mud by observing the change of each group of performances so as to determine the reasonable mixing ratio of the papermaking white mud aerated concrete.
3.1.2 design of mix proportion of paper making white mud aerated concrete
1. Blank control group aerated concrete mix proportion design
The invention researches that the treated paper making white clay powder raw material replaces lime raw material to produce aerated concrete, so that a control group selects the strength grade of A5.0 dry density B07 according to the specification of autoclaved aerated concrete building blocks, and the dosage per cubic meter is as follows according to the measurement and batching of the autoclaved aerated concrete raw material provided by Liuzhou Huashen novel building materials Limited responsibility company: 70kg of cement, 140kg of lime, 21kg of gypsum, 469kg of fly ash, 385kg of water and 0.209kg of aluminum powder.
2. The raw material dosage of the paper-making white mud aerated concrete under different substitution rates
The research idea of the invention is to use the calcination temperature of the papermaking white mud and the lime substitution rate of the calcined papermaking white mud as variables, use the fineness of the papermaking white mud of 0.075mm as a quantification and research the influence of the calcination temperature and the substitution rate of the papermaking white mud on the performance of the aerated concrete. The calcined papermaking white mud is used for replacing lime according to the mass of 5%, 10% and 20% substitution rate, and the mixing proportion is calculated by combining a blank control group under different substitution rates to obtain the following raw material dosage:
when the substitution rate of the papermaking white mud is 5%, the dosage per cubic meter is as follows: 70kg of cement, 133kg of lime, 21kg of gypsum, 469kg of fly ash, 385kg of water and 209g of aluminum powder, and 7kg of calcined papermaking white mud.
When the substitution rate of the papermaking white mud is 10%, the dosage per cubic meter is as follows: 70kg of cement, 126kg of lime, 21kg of gypsum, 469kg of fly ash, 385kg of water and 209g of aluminum powder, and 14kg of calcined papermaking white mud.
When the substitution rate of the papermaking white mud is 20%, the dosage per cubic meter is as follows: 70kg of cement, 112kg of lime, 21kg of gypsum, 469kg of fly ash, 385kg of water and 209g of aluminum powder, and 28kg of calcined papermaking white mud.
3. Test group numbering
Test group number details table 2.
TABLE 2 test Block numbering and grouping
3.2 influence of calcination temperature and substitution rate of papermaking white mud on aerated concrete formation
3.2.1 influence of calcination temperature of papermaking white mud on aerated concrete formation
The method is characterized in that based on the test design mix proportion in section 3.1.2 of the invention, a papermaking white mud raw material with fineness of 0.075mm after being treated at different calcination temperatures is selected, a test group with the ratio of mass of papermaking white mud to lime being 10% is selected, a calcination temperature single variable test is carried out, a blank control group without papermaking white mud is designed for test, the raw materials are weighed, mixed and stirred, a 100mm x 100mm mould is selected, the stirred and mixed slurry is injected into the mould for forming, the aerated concrete is prepared, 9 test blocks are prepared in each calcination temperature interval test group, the gas generation condition of the test blocks is observed and recorded, the mass of each test block group is measured, and the average value of the density is calculated. The test results are detailed in table 3.
TABLE 3 influence of calcination temperature of papermaking white mud on aerated concrete formation
As can be seen from Table 3, the density of the test pieces decreased with the increase of the calcination temperature of the papermaking white clay, mainly due to CaCO of the papermaking white clay when the calcination temperature was increased3The conversion rate is improved, the activity of the obtained CaO is relatively high, the CaO can better react with aluminum powder to release hydrogen, and the porosity of the test block is improved. Meanwhile, the gas forming condition is observed, the gas forming condition of the test piece is poor when the papermaking white mud is calcined at 800 ℃, the gas forming condition of the test piece is normal when the papermaking white mud is calcined at 1000 ℃ and 1200 ℃, and the forming of the test piece is basically not influenced. In conclusion, under the condition that the substitution rate and the fineness are fixed, the calcination temperature of the papermaking white mud is preferably controlled to be 1000-1200 ℃, the gas evolution of the test piece is normal, the forming of the test piece is not influenced, and the density of the test piece is similar to that of a blank control group.
3.2.2 Effect of substitution rate of papermaking white mud on aerated concrete formation
In the subsection, papermaking white mud with the calcination temperature of 1000 ℃ and the fineness of 0.075mm is selected, and the influence of the substitution rate of the papermaking white mud on the forming of the aerated concrete is researched by changing the substitution rate of the papermaking white mud and comparing with a blank control group. Preparing aerated concrete slurry according to the design mixing proportion in section 3.1.2, injecting the prepared aerated concrete slurry into a 100mm multiplied by 100mm mould for forming, preparing 9 test blocks in each group, observing and recording the gas forming condition, and weighing each test block to calculate the average density. The results of the tests are detailed in table 4.
TABLE 4 influence of the amount of the papermaking white mud on the formation of aerated concrete
Table 4 influence of blending amount of papermaking white mud on aerated concrete forming
As can be seen from table 4, the average density measured when the substitution rate of the papermaking white mud is only 5% is equivalent to that of the blank control group, when the substitution rate of the papermaking white mud is 10%, the average density of the test block is slightly increased compared with that of the blank control group, and when the substitution rate of the papermaking white mud is further increased to 20%, the average density is the largest compared with that of the other substitution rate test groups, but the gas generation condition is normal, and the influence on the forming of the aerated concrete is small. After comprehensive consideration, when the calcination temperature and the fineness of the primary papermaking white mud are fixed, the substitution rate of the papermaking white mud raw material is controlled to be 10-20%, the air-forming of the aerated concrete can be normally formed without influencing the air-forming of the aerated concrete.
4 research on influence of papermaking white mud on mechanics and microscopic performance of aerated concrete
4.1 preparation of test pieces
The theoretical basis of the test piece preparation is the current national standard related to the autoclaved aerated concrete. Firstly, weighing papermaking white mud raw materials obtained by calcination treatment, cement, lime, gypsum and fly ash according to a result calculated by a designed mixing ratio, then putting the raw materials into a stirrer for pre-stirring, wherein the purpose of the process is to eliminate the influence on the performance of aerated concrete caused by uneven material distribution, after the materials are fully mixed, putting the weighed water and aluminum powder into the stirrer for continuous stirring, after uniform stirring, pouring slurry into a mold at the height of 1/2, standing for 30min to ensure that the slurry is aerated to fill the mold, scraping the surface of the mold by a scraper, demoulding a test piece after 24h, sending the demoulded test piece into an autoclave for autoclave curing, wherein the autoclaving process comprises the steps of firstly boosting the pressure for 2.5h, naturally reducing the temperature to 170-175 ℃ at constant temperature and constant pressure for 8h when the pressure reaches 0.8MPa, and then discharging the test piece out of the autoclave after naturally reducing the temperature to room pressure, and obtaining the test piece required by the test.
FIG. 4: preparation of paper white clay aerated concrete test pieces (figure 4 a: slurry injection molding; figure 4 b: test piece forming; figure 4 c: test piece).
4.2 aerated concrete Water absorption test
According to the relevant requirements of the water absorption test in the autoclaved aerated concrete performance test method (GB/T11969-2020). 10 test groups were designed, and a total of 30 test pieces were prepared from 3 test pieces of each group, and the average water absorption of each group is reported in detail table 5.
TABLE 5 aerated concrete Water absorption test values
FIG. 5: and (4) a line graph of the aerated concrete water absorption test value.
4.2.3 assay analysis
The research shows that when the calcination temperature of the papermaking white mud is fixed, the water absorption of the test piece is reduced along with the increase of the substitution rate of the papermaking white mud. The reason is that the active CaO content in the papermaking white mud is less than that in the lime, so that the hydrogen released after the reaction of the papermaking white mud and Al is less than that of the lime, and further, the air holes are reduced, and the water absorption rate is reduced. When the substitution rate of the papermaking white mud is constant, the water absorption rate increases along with the increase of the calcining temperature of the papermaking white mud. The CaO conversion amount and activity of the papermaking white mud obtained at the calcining temperature of 1200 ℃ are better than those of the papermaking white mud obtained at the calcining temperature of 800 ℃ and 1000 ℃, so that the reaction activity of the papermaking white mud and Al is promoted, the gas forming amount and porosity are improved, and the water absorption rate is increased.
4.3 cubic compression strength test of aerated concrete
A cubic aerated concrete compression test specimen of 100mm multiplied by 100mm is prepared according to the requirements of an autoclaved aerated concrete performance test method (GB/T11969-2020) for testing.
4.3.1. Test data
The aerated concrete cubic compression test is designed into 10 groups according to a design scheme, the number of each group of test pieces is 3, and the total number of the test pieces is 30. The specific data obtained in the test are shown in Table 6.
TABLE 6 cubic compression strength test data of aerated concrete
4.3.2. Assay analysis
The analysis data can show that when the calcination temperature of the papermaking white mud is 1200 ℃, the average density and the average cube compressive strength of the two groups of the substitution rate of 5 percent and the substitution rate of 10 percent are equivalent to those of a blank control. When the substitution rate is increased to 20%, the test values of the average density and the average cubic compressive strength are higher than those of a blank control group, and the gas is normal, so that the scheme that the papermaking white mud is calcined at 1200 ℃ and then lime is replaced by 5%, 10%, 20% and the like is feasible, and the cubic compressive strength meets the requirements of national standards on qualified products.
When the calcination temperature of the papermaking white mud is 1000 ℃, the gas generation rate of two groups of 5% and 10% is normal, and the average density and the average cube compressive strength are equivalent to those of a blank control. The scheme that the substitution rate of the papermaking white mud is 5% and 10% at the calcination temperature of 1000 ℃ is proved to be feasible, when the substitution rate of the papermaking white mud is improved to 20% at the calcination temperature, although the average density is increased more than that of a blank control group, the cubic compressive strength meets the requirements of the national standard on A5.0B07 strength and dry density for qualified products, and therefore, the scheme that the papermaking white mud replaces lime by 5%, 10%, 20% and the like after being calcined at the calcination temperature of 1000 ℃ is also feasible.
When the calcination temperature of the papermaking white mud is set at 800 ℃ and the substitution rate is 10 percent and 20 percent, the gas forming condition of a test piece is poor, the average density and the average cubic compressive strength are higher than the corresponding values of a blank control group due to poor gas forming, the dry density at the substitution rate of 20 percent does not meet the requirement of B07 on the dry density of a qualified product, and when the substitution rate is 5 percent, the gas forming condition is normal, but the substitution rate of the papermaking white mud is low, the waste utilization rate is low, so that the 800 ℃ calcination temperature test group is not recommended.
FIG. 6: graph of calcination temperature experiment of paper white clay aerated concrete (figure 6 a: same calcination temperature different substitution rate strength value; figure 6b same substitution rate different calcination temperature strength value; figure 6c cube compression strength line graph).
4.4 axial compressive strength test of aerated concrete
According to the study on the compressive strength test of the axle center of the paper white clay aerated concrete, a prism test piece with the thickness of 100mm multiplied by 300mm is prepared according to the requirement of an autoclaved aerated concrete performance test method (GB/T11969-2020).
4.4.1. Test data
The axial compression test of the aerated concrete is designed into 10 groups according to a design scheme, the number of each group of test pieces is 3, and the total number of the test pieces is 30. The specific data obtained in the test are shown in Table 7.
TABLE 7 axial compressive strength test data of aerated concrete
4.4.2. Assay analysis
The analysis data can obtain that when the substitution rate of the papermaking white mud in each calcining temperature group is 5%, the axial compression resistance value is close to that of the blank control group. Under the condition of a certain calcination temperature, the axial compressive strength is increased along with the increase of the substitution rate of the papermaking white mud, and when the substitution rate is 20%, compared with the axial compressive strength of a blank control group, the axial compressive strength increases of three groups of the calcination temperature of 800 ℃, 1000 ℃ and 1200 ℃ are 14.11%, 6.05% and 8.06%, respectively, so that the influence of the papermaking white mud on the axial compressive strength at the calcination temperature of 1000 ℃ and the substitution rate of 20% is small.
FIG. 7: graph of the compression resistance test of the paper white clay aerated concrete (figure 7a shows axial compression strength values with the same calcination temperature and different substitution rates, figure 7b shows axial compression strength values with the same substitution rate and different calcination temperatures, and figure 7c shows a line graph of the axial compression strength).
4.5 aerated concrete splitting tensile strength test
According to the splitting tensile strength test of the invention, according to the relevant requirements of the autoclaved aerated concrete performance test method (GB/T11969-2020), a cubic aerated concrete test piece of 100mm multiplied by 100mm is prepared, and the splitting tensile strength test is carried out on the cubic aerated concrete test piece.
4.5.1. Test data
The aerated concrete splitting tensile strength test is designed into 10 groups according to a design scheme, the number of each group of test pieces is 3, and the total number of the test pieces is 30 in total. The specific data obtained in the test are shown in Table 8.
Table 8 aerated concrete splitting tensile strength test data
4.5.2. Assay analysis
Analysis data shows that when the substitution rate of the papermaking white mud in each calcination temperature group is less than 5%, the splitting tensile strength value of the test piece is not changed greatly compared with that of a blank control group, and the influence on the splitting tensile property of the aerated concrete is not obvious when the substitution rate is less. When the substitution rate of the papermaking white mud is increased to 10% and 20%, the splitting tensile strength of each calcining temperature group is improved due to the reduction of air holes released by reaction with Al. When the substitution rate of the papermaking white mud is 20%, the cracking tensile strength is higher than that of the calcination temperature groups of 1000 ℃ and 1200 ℃ due to the poor gas generation, less air holes, large mass and high compressive strength of the test piece at the calcination temperature group of 800 ℃.
FIG. 8: graph of axial compressive test of paper making white clay aerated concrete (figure 8 a: axial compressive strength values with same calcining temperature and different substitution rates; figure 8 b: axial compressive strength values with same substitution rates and different calcining temperatures; figure 8 c: axial compressive strength broken line graph with same calcining temperature and different substitution rates).
4.6 micro analysis of aerated concrete of papermaking white mud
4.6.1 XRD test
4.6.1.1. XRD test of ordinary aerated concrete
The XRD test is carried out on the common aerated concrete by using a DX-2700X-ray diffraction analyzer, and the X-ray diffraction spectrum is shown in figure 9 a: x-ray diffraction spectrum of ordinary aerated concrete. As shown in FIG. 9a, the hydration product of ordinary aerated concrete is relatively single, and the hydration product is mainly silicon dioxide (SiO)2) And calcium silicate hydrate (C-S-H) gel.
4.6.1.2. XRD (X-ray diffraction) test comparison of papermaking white mud aerated concrete at different calcination temperatures
The papermaking white mud is calcined at the temperature of 800 ℃, 1000 ℃ and 1200 ℃ to respectively carry out XRD (X-ray diffraction) tests on the aerated concrete prepared according to the substitution rate of 20%, and the X-ray diffraction spectrum is shown in figure 9 b: x-ray diffraction spectra of the paper-making white mud aerated concrete at different calcination temperatures.
As can be seen from FIG. 9b, the hydration products of the aerated concrete prepared by the papermaking white mud are basically consistent with those of the common aerated concrete, and the main hydration product is silicon dioxide (SiO)2) And calcium silicate hydrate (C-S-H) gel, but the aerated concrete prepared by using the papermaking white mud also contains a small amount of unconverted calcium carbonate (CaCO)3) Calcium carbonate (CaCO) in the papermaking white mud as the calcination temperature of the papermaking white mud is increased3) The X diffraction wave peak is less and less obvious, which indicates that calcium carbonate (CaCO) is contained in the papermaking white mud3) The conversion rate is gradually improved along with the increase of the calcination temperature, and the content of calcium silicate hydrate (C-S-H) gel can be effectively increased by preparing the aerated concrete by using the papermaking white mud calcined at higher temperature, so that the contribution to the strength of the aerated concrete is provided.
FIG. 9: papermaking white clay aerated concrete XRD test comparison graph (figure 9 a: X-ray diffraction spectrum of common aerated concrete; figure 9 b: X-ray diffraction spectrum of papermaking white clay aerated concrete at different calcination temperatures).
4.6.2 SEM test
The invention researches preparation of aerated concrete by papermaking white mud, uses an American FEI FEG-250 microscope scanner to perform SEM test, analyzes differences of hydration products and pore structures of the aerated concrete prepared by the papermaking white mud after autoclaved curing and common aerated concrete, and selects three groups of papermaking white mud aerated concrete test groups prepared by treating the papermaking white mud at the calcining temperature of 800 ℃, 1000 ℃ and 1200 ℃ and respectively comparing the substitution rate of 20% with the common aerated concrete.
4.6.2.1. Hydration product analysis
SEM tests are respectively carried out on the three groups of paper making white mud aerated concrete and the common aerated concrete, and an SEM test picture is shown in figure 10. FIG. 10: the paper-making white clay aerated concrete and the common aerated concrete are subjected to SEM tests (figure 10a is a scanning electron microscope image of the paper-making white clay at the calcination temperature of 800 ℃ for the aerated concrete, figure 10b is a scanning electron microscope image of the paper-making white clay at the calcination temperature of 1000 ℃ for the aerated concrete, figure 10c is a scanning electron microscope image of the paper-making white clay at the calcination temperature of 1200 ℃ for the aerated concrete, and figure 10d is a scanning electron microscope image of the common aerated concrete).
After the analysis of fig. 10 a-10 d, the hydration products of the aerated concrete prepared by the calcined papermaking white mud are basically consistent with the hydration products of the ordinary aerated concrete after autoclaved curing, namely tobermorite, calcium silicate hydrate (C-S-H) gel, hydrated garnet and silicon dioxide (SiO)2) Mainly, however, the tobermorite in fig. 10a is substantially platy, the tobermorite in fig. 10b is coexistent with platy and acicular, the tobermorite in fig. 10c is mainly acicular with a small amount of platy, and the tobermorite in the ordinary aerated concrete in fig. 10d is substantially acicular, which means that the aerated concrete prepared by using the tobermorite is more fully hydrated after the calcination temperature of the papermaking white mud is gradually increased. The tobermorite is mainly calcium silicate hydrate, and the microporous structure formed by the tobermorite has the main effects of adsorbing free water and crystal water in the aerated concrete, so that the heat preservation and heat insulation performance of the aerated concrete is improved. Therefore, when the calcination temperature of the papermaking white mud is 1200 ℃, the thermal insulation performance of the prepared aerated concrete is the best in each group of the test from the view of the microscopic hydration products.
4.6.2.2. Air hole structure
The SEM test pattern of the pore structure is shown in FIG. 11: the paper making white clay aerated concrete and the common aerated concrete have SEM test images (fig. 11a is a scanning electron microscope image of the paper making white clay aerated concrete, and fig. 11b is a scanning electron microscope image of the common aerated concrete).
As can be seen from FIGS. 11a and 11b, the air pore structure of the paper white clay aerated concrete is substantially the same as that of the common aerated concrete, and the paper white clay aerated concrete is composed of air bubbles, capillary pores and gel pores, wherein the majority of the air pores have the pore diameter of 0.2-2mm, the average pore diameter is about 1mm, and part of the air pores can be communicated with each other to form communicating pores. The free water which is not hydrated is left in pores after evaporation, namely capillary pores, the shapes of the pores are irregular slender type, and the pore diameters are different from 5nm to dozens of micrometers. The micropores formed by the hydration product are gel pores which are mainly positioned in the hydrated silicate, the volume of the gel pores is generally small, and the pore diameter is between 1 and 5 nm.
To summarize:
the physical and mechanical properties of the papermaking white mud aerated concrete are researched, and the findings are as follows: each test group is greater than the blank control group in density; in the aspect of water absorption, the water absorption rate is reduced along with the increase of the substitution rate of the papermaking white mud, and is gradually increased along with the increase of the calcining temperature of the papermaking white mud. In the aspect of mechanical property, the cubic compressive strength is higher than that of a blank control group and can reach 6.86 MPa; the axial compression strength is improved along with the increase of the substitution rate of the papermaking white mud raw material, and when the substitution rate of the papermaking white mud raw material is 20%, the maximum increase is 14.11%; the splitting anti-cracking strength is high, when the substitution rate of the papermaking white mud raw material is 5%, the splitting tensile data of each calcining temperature group is not changed greatly, and when the substitution rate of the papermaking white mud raw material is increased to 10% and 20%, the splitting tensile strength value of the calcining temperature group at 800 ℃ is higher than that of the calcining temperature groups at 1000 ℃ and 1200 ℃.
After characterization and microscopic performance analysis of the material of the paper white mud aerated concrete sample through XRD and SEM tests, the hydration products are mainly tobermorite, calcium silicate hydrate (C-S-H) gel, hydrated garnet and silicon dioxide (SiO)2) The tobermorite is mainly plate-shaped and acicular, and the pore structure consists of bubbles, capillary pores and gel pores.
According to the invention, through research and analysis on mechanical and microscopic performances of the paper-making white clay aerated concrete, the optimum mix proportion of the aerated concrete is that the concrete material dosage per cubic meter is as follows: 70kg of cement, 112kg of lime, 21kg of gypsum, 469kg of fly ash, 385kg of water and 209g of aluminum powder, and 28kg of papermaking white mud after calcination treatment at 1000 ℃ or 1200 ℃.
5 conclusion
After experimental research on the paper-making white clay aerated concrete designed by the invention, the findings are as follows:
(1) the papermaking white mud calcined at 800 ℃, 1000 ℃ and 1200 ℃ is obtained by XRD test, and CaCO in the papermaking white mud at the calcination temperature of 800 DEG C3When the calcining temperature is raised to 1000 ℃ and 1200 ℃, the conversion in the papermaking white mud is obtained by X-ray diffraction pattern analysisCaCO3The conversion is complete, and the main wave peak of the map is Ca (OH)2And CaO.
(2) When the substitution rate of the papermaking white mud is fixed and the fineness is 0.075mm, the density of the prepared aerated concrete cubic test block is reduced along with the increase of the calcining temperature of the papermaking white mud, the papermaking white mud is calcined at the temperature of 800 ℃, the gas forming condition of the prepared aerated concrete is poor, the forming of the test block is influenced, and when the calcining temperature is increased to 1000 ℃ and 1200 ℃, the gas forming condition and the forming of the aerated concrete are not greatly influenced by the papermaking white mud.
(3) The gas generation condition is normal when the fineness of the papermaking white mud is 0.075mm and the substitution rate is 5%, 10% and 20% at the calcining temperature of 1000 ℃, but the average density is increased along with the increase of the substitution rate. From the angle of gas forming and waste utilization rate analysis, the substitution rate of the papermaking white mud after calcination treatment is preferably 10-20%.
(4) When the calcination temperature of the papermaking white mud is fixed, the water absorption of the prepared aerated concrete test piece is gradually reduced along with the increase of the substitution rate of the white mud. When the substitution rate of the papermaking white mud is constant, the water absorption rate increases along with the increase of the calcining temperature of the papermaking white mud. The analysis reason is that when the calcination temperature is constant and the substitution rate of the papermaking white mud is changed, the CaO content in the papermaking white mud is lower than that in the lime, and the hydrogen released by the reaction of the papermaking white mud and the Al is less than that released by the reaction of the lime and the Al, so that the water absorption of the formed pores is reduced, and when the substitution rate is constant and the calcination temperature is changed, the CaO conversion amount and the obtained activity of the papermaking white mud are better than those at 800 ℃ and 1000 ℃ at the calcination temperature of 1200 ℃, so that the reaction activity of the papermaking white mud and the Al is promoted, more pores are formed, and the water absorption is increased.
(5) Under the condition that the calcination temperature of the papermaking white mud is the same, the average density and the cubic compressive strength of the test piece are increased along with the increase of the substitution rate of the papermaking white mud, and under the condition that the substitution rate of the papermaking white mud is the same, the cubic compressive strength of the test piece is increased along with the increase of the calcination temperature of the papermaking white mud raw material, but the average density is in a descending trend.
(6) When the calcination temperature of the papermaking white mud is the same and only the substitution rate is changed, the axial compressive strength of the aerated concrete of the papermaking white mud is improved along with the increase of the substitution rate of the papermaking white mud, and when the substitution rate is the same as 20%, compared with the axial compressive strength of a blank control group, the axial compressive strength of the aerated concrete of the papermaking white mud is increased by 14.11% at the calcination temperature of 800 ℃, 6.05% at 1000 ℃, 8.06% at 1200 ℃ and 20% at the calcination temperature of 1000 ℃, the axial compressive strength of the aerated concrete of the papermaking white mud is less increased than that of the blank control group.
(7) After the splitting anti-cracking test, it is found that when the substitution rate of the papermaking white mud is only 5%, splitting tensile data of each calcining temperature group is not changed greatly, which indicates that when the substitution rate of the papermaking white mud is 5%, the splitting tensile property of the aerated concrete is not influenced obviously, and when the substitution rate of the papermaking white mud is increased to 10% and 20%, the splitting tensile strength value of the calcining temperature group at 800 ℃ is higher than that of the calcining temperature groups at 1000 ℃ and 1200 ℃.
(8) After XRD and SEM tests of ordinary aerated concrete and papermaking white mud aerated concrete, the hydration products are mainly tobermorite, hydrated calcium silicate (C-S-H) gel, hydrated garnet and silicon dioxide (SiO)2) However, the aerated concrete prepared by the papermaking white mud also contains a small amount of calcium carbonate (CaCO)3). And the beige mullite form of the paper-making white mud aerated concrete is gradually changed from a platy form to an acicular structure along with the rise of the calcining temperature of the paper-making white mud, and the beige mullite of the common aerated concrete is basically acicular, which shows that the heat preservation and insulation performance of the common aerated concrete is better than that of the paper-making white mud reinforced concrete.
The above description is intended to describe in detail the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the claims of the present invention, and all equivalent changes and modifications made within the technical spirit of the present invention should fall within the scope of the claims of the present invention.
Claims (3)
1. A preparation method of papermaking white mud aerated concrete is characterized by comprising the following steps: the method comprises the following steps:
1) calcining the primary papermaking white mud material at 800-;
2) preparing raw materials: preparing the concrete material dosage per cubic meter according to the mixing ratio: 70kg of cement, 112kg of lime, 21kg of gypsum, 469kg of fly ash, 385kg of water, 0.209kg of aluminum powder and 28kg of papermaking white mud raw material;
3) pouring the papermaking white mud raw material, cement, lime, gypsum and fly ash into a stirrer for pre-stirring, fully mixing, adding water and aluminum powder into the stirrer, and continuously stirring uniformly;
4) pouring the slurry uniformly stirred in the step into a mold at the height of 1/2, standing for 30min to allow the gas to fill the mold, scraping the surface of the mold by using a scraper, demolding the test piece after 24h, feeding the demolded test piece into an autoclave for autoclaving and curing for 10.5h, and taking the test piece out of the autoclave to obtain the papermaking white mud aerated concrete.
2. The preparation method of the paper white clay aerated concrete according to claim 1, which is characterized by comprising the following steps: in the step 1), calcining at 1000-1200 ℃ for 20-24 h.
3. The papermaking white mud aerated concrete is characterized in that: the paper-making white clay aerated concrete is prepared by the method of claim 1 or 2.
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| CN115611580A (en) * | 2022-10-21 | 2023-01-17 | 广西大学 | High-strength sound-insulation heat-insulation prefabricated inner partition plate based on papermaking white mud and preparation method thereof |
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