CN114965032A - Method for testing performance of ecological concrete with highland barley fibers - Google Patents
Method for testing performance of ecological concrete with highland barley fibers Download PDFInfo
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Abstract
The invention discloses a method for testing the performance of ecological concrete of highland barley fibers, which comprises the following steps: (1) modifying the highland barley fibers; (2) determining the mixing amount of the highland barley fibers; (3) testing the mechanical property of the highland barley fiber concrete; (4) testing the frost resistance of the highland barley fiber concrete; (5) and (3) carrying out frost resistance result and analysis on the ecological concrete with the highland barley fibers. The invention can obtain the highland barley fiber added with modification treatment in the ecological concrete by testing the performance of the ecological concrete of the highland barley fiber, greatly enhances the frost resistance effect of the mechanical property of the concrete, and can be widely popularized and applied in Tibet plateau areas.
Description
Technical Field
The invention belongs to the technical field of concrete testing, and particularly relates to a method for testing the performance of ecological concrete with highland barley fibers.
Background
The Tibet region is in the Qinghai-Tibet plateau, the average altitude is more than 4000 meters, the climate is cold and dry, the temperature difference between day and night is large, the ecological self-regulation capability is fragile, and if traditional slope protection materials such as grouted stone, dry stone and common concrete are adopted, the damage to the local ecological system can be caused, so that the biodiversity is sharply reduced. Compared with the prior art, the ecological concrete is applied to slope protection in high and cold high-altitude areas, so that the problem of protecting the bank and preventing erosion can be solved, the bank slope can be afforested, the heat island effect is reduced, the hardening and the afforestation of the concrete are perfectly combined, and the concrete and the natural ecology are harmonious.
Based on the natural conditions of the Tibet region, the performance of the ecological concrete in the alpine and high-altitude regions and the application of the ecological concrete in slope protection engineering are researched, the ecological concrete is a novel material with the performance between that of common concrete and plowed and planted soil, the ecological concrete is a concrete structure with cellular pores formed by taking large-particle-size coarse aggregate as a framework and cementing cement paste and an additive, and has the characteristics of air permeability and water permeability.
The production place of the highland barley fiber is in the region of Tibet Ali, the highland barley fiber is brown yellow, the diameter is generally 100-500 mu m, the length is 20-80 cm, the density is 1.12g/m, the highland barley fiber is thin and long in cross section, and the highland barley fiber has the characteristic of elongation, so that the highland barley fiber can play a role in toughening in concrete. Therefore, the highland barley fiber is doped into the ecological concrete to be a channel for improving the toughness of the concrete, and the performance of the ecological concrete with the highland barley fiber needs to be tested before the concrete is implemented.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for testing the performance of ecological concrete with highland barley fibers.
In order to solve the technical problem, the invention adopts the following technical scheme: the method for testing the performance of the ecological concrete with the highland barley fibers comprises the following steps:
(1) modifying the highland barley fibers;
(2) determining the mixing amount of the highland barley fibers;
(3) testing the mechanical property of the highland barley fiber concrete;
(4) testing the frost resistance of the highland barley fiber concrete;
(5) and (3) carrying out frost resistance result and analysis on the ecological concrete with the highland barley fibers.
The specific process of the step (1) is as follows: mixing highland barley fiber at 50 deg.C with 3% glacial acetic acid and 1.5% NaClO 2 The mixed solution is soaked for 4 hours and then dried in an oven with the temperature of 80 ℃.
The mixing amount of the highland barley fibers in the step (2) is divided into a high mixing amount and a low mixing amount; the anti-cracking performance of the low-dosage highland barley fiber concrete is obviously improved, and when a large amount of highland barley fiber is added into the concrete, the compressive strength of the concrete is mainly influenced; design 1Kg/m 3 、2Kg/m 3 、3Kg/m 3 、4Kg/m 3 、5Kg/m 3 The mechanical properties of the highland barley fiber concrete are comprehensively analyzed by five different highland barley fiber mixing amounts, and the optimal mixing amount is selected.
The specific process of the step (3) is as follows:
carrying out X-ray diffraction analysis and scanning electron microscope analysis on the modified highland barley fibers in the step (1) to research the microscopic mechanism of fiber modification;
secondly, adopting a single-factor test, doping highland barley fibers with different quantities into concrete according to the quantity change, wherein the water-cement ratio of the concrete is 0.3, the porosity is 25%, filling the mold after mixing, putting the filled mold in a cool place to avoid water evaporation, taking out the concrete test block from the mold after 24 hours until the concrete test block has certain strength, then moving the concrete test block into a more stable and constant-humidity curing room for curing, taking out the concrete test block after 28 days, and measuring the mechanical properties of the highland barley fiber concrete by using a Hualong mechanical property tester after taking out, wherein the mechanical properties comprise compressive strength, splitting strength and bending strength;
thirdly, the highland barley fiber concrete mechanical property data obtained in the second step are sorted and drawn, and the improvement condition of the highland barley fiber on the concrete mechanical property is obtained by analyzing the image and the data; the 5 groups of highland barley fiber concrete mechanical property data with different mixing amounts are imported into the software Origin, and the analysis is carried out after the drawing, so as to obtain how the concrete mechanical property changes along with the different mixing amounts of the highland barley fibers.
The specific process of the step (4) is as follows:
A) taking out the cured concrete test block in the curing chamber, observing the regular condition of the surface of the concrete test block, then putting the concrete test block into normal-temperature water for soaking for at least 4 days, taking out the concrete test block, dry-mixing the residual moisture on the surface of the concrete test block, and weighing the mass of the concrete to obtain the initial mass of the concrete;
B) firstly, setting a control panel of a freezing and thawing box, setting the temperature between-15 ℃ and-20 ℃, controlling the temperature not to be higher than 15 ℃ all the time, and setting three freezing and thawing cycle gradients which are 20 times, 40 times and 50 times respectively; 1Kg/m is added according to the different mixing amounts of the highland barley fibers 3 、2Kg/m 3 、3Kg/m 3 、4Kg/m 3 、5Kg/m 3 Placing 5 groups of highland barley fiber concrete test blocks into a freeze thawing box;
C) when the test reaches 20 times of freeze-thaw cycles, firstly stopping the freeze-thaw box to wait for the concrete test block to be completely thawed, taking out one third of the concrete test block, firstly weighing the mass of the concrete test block, then measuring the compressive strength of the concrete test block, after the test is finished, setting 20 times of cycles to continue operating the freeze-thaw box, after the operation is finished, taking out the required concrete test block, weighing and measuring the compressive strength of the concrete test block, then continuing setting 10 times of cycles, and after the cycle is finished, measuring the weight and the compressive strength; and if the quality of the concrete test block after a certain circulation is reduced to be below 95 percent of the original quality or the compressive strength is reduced to be below 75 percent of the original quality, the concrete test block is considered to be damaged, and after the experiment is finished, the frost resistance grade of the concrete is recorded as D + freeze-thaw cycle times.
And the step (5) comprises the steps of antifreeze data processing, appearance analysis, quality loss rate analysis and compressive strength loss rate analysis.
By adopting the technical scheme, the highland barley fiber is modified, the processed highland barley fiber is added into ecological concrete, the mechanical property test and the freezing resistance test are carried out on the performance of the highland barley fiber concrete, the test result is analyzed, and the final conclusion is as follows:
1. the highland barley fiber is bonded with the cement paste in the concrete, so that stones, the cement paste and the highland barley fiber in the concrete are bonded into a firm net, the external impact force is fully dispersed by the net structure, the deformation resistance of the concrete is improved, and the mechanical property is greatly improved; however, when the proportion of the highland barley fibers in the concrete is too much, the specific surface area of the fibers is increased, and the fibers are increased, so that the highland barley fibers absorb a lot of water when the concrete is mixed, the water-saturated highland barley fibers are difficult to combine with the cement slurry, the amount of the highland barley fibers wrapped by the cement slurry in the concrete is rapidly reduced, if the proportion of the highland barley fibers in the concrete is continuously increased, the highland barley fibers absorb a lot of water to cause the cement slurry to be completely disconnected with the highland barley fibers, the compactness of the concrete is rapidly reduced, the concrete framework is also completely collapsed, and the mechanical strength of the concrete is also greatly reduced.
2. The frost resistance of the concrete is improved due to the existence of the highland barley fiber.
3. The freezing resistance of the concrete is not greatly influenced by the addition of the highland barley fibers in the early stage of the freezing and thawing cycle, and the strength loss of the concrete can be effectively reduced by the highland barley fibers in the later stage of the freezing and thawing cycle.
4. The freezing resistance of the concrete is not greatly influenced by the doping of the highland barley fibers at the early stage of the freezing and thawing cycle, and the compressive strength loss of the concrete can be effectively reduced by the highland barley fibers at the later stage of the freezing and thawing cycle.
In conclusion, the invention can obtain the highland barley fiber added with modification treatment in the ecological concrete by testing the performance of the ecological concrete of the highland barley fiber, greatly enhances the frost resistance effect of the mechanical property of the concrete, and can be widely popularized and applied in Tibet plateau areas.
Drawings
FIG. 1 is a scanning electron microscope image of the pretreated barley fiber, which is 50 times amplified;
FIG. 2 is a scanning electron microscope image of the highland barley fiber after pretreatment, which is 10000 times amplified;
FIG. 3 is a plot of XRD patterns under different modification treatment conditions;
FIG. 4 is a scanning electron microscope image of the modified highland barley fiber at 50 times magnification;
FIG. 5 is a scanning electron microscope image of 10000 times magnified highland barley fiber after modification treatment;
FIG. 6 is a schematic diagram of thermogravimetric image analysis of unmodified barley fiber;
FIG. 7 is a schematic diagram of thermogravimetric image analysis of No. 8 modified barley fiber;
FIG. 8 is a comparison of IR spectra of modified highland barley fibers No. 0 and No. 1;
FIG. 9 is a comparative schematic of the IR spectroscopy analysis of modified highland barley fibers No. 0 and No. 6;
FIG. 10 is a comparison of IR spectra of modified highland barley fibers No. 0 and No. 8;
FIG. 11 is a graph showing the variation of mechanical properties of the barley fiber concrete with the amount of the fiber;
FIG. 12 is a graph showing the results of mass loss of barley fiber concrete;
FIG. 13 is a graph showing the result of the loss rate of compressive strength of barley fiber concrete.
Detailed Description
The invention discloses a method for testing the performance of ecological concrete with highland barley fibers, which comprises the following steps:
(1) modifying the highland barley fibers;
(2) determining the mixing amount of the highland barley fibers;
(3) testing the mechanical property of the highland barley fiber concrete;
(4) testing the frost resistance of the highland barley fiber concrete;
(5) and (3) carrying out frost resistance result and analysis on the ecological concrete with the highland barley fibers.
The specific process of the step (1) is as follows: firstly, washing the highland barley fibers with distilled water to remove impurities on the surfaces of the highland barley fibers, and then drying the washed highland barley fibers for 2 hours at the temperature of 80 ℃ to prepare pretreated highland barley fibers; as shown in fig. 1 (scanning electron microscope image obtained by amplifying the pretreated highland barley fiber by 50 times) and fig. 2 (scanning electron microscope image obtained by amplifying the pretreated highland barley fiber by 10000 times), the scanning electron microscope image of the pretreated highland barley fiber shows that the untreated highland barley fiber has a smooth surface and uniform thickness through fig. 1, and only a few pits and ravines are formed on the surface through fig. 2, and the defects on the surface can ensure that the highland barley fiber and the concrete are better combined and are not easy to pull out, so that the mechanical property of the ecological concrete can be improved.
The test reagents and test instruments for modifying the pretreated highland barley fibers are respectively shown in tables 1 and 2:
TABLE 1 test reagents
TABLE 2 test apparatus
The specific process of the modification treatment comprises the following steps: and (3) cutting the pretreated highland barley fibers into small sections of 10-25 mm, and performing orthogonal test design in the table 3 through three factors and three levels.
TABLE 3 orthogonal factor Table
As can be seen from the above orthogonal experimental design, there are 9 modification schemes for the highland barley fiber, and the scheme of pretreatment according to different conditions is shown in Table 4.
TABLE 4 orthogonal experimental design Table
In the above test, 9 groups of highland barley fibers were soaked at 50 ℃ for 2h in the respective treatment solutions, and then the treated highland barley fibers were washed with distilled water until the pH of the last cleaning solution was 7, and then the 9 groups of solutions were treated at different heat treatment temperatures for different times.
During the heating pretreatment process of the highland barley fiber, a series of physical and chemical reactions occur, the chemical composition of the highland barley fiber changes, and in the treatment process, the color of the fiber gradually turns yellow and the color of the solution gradually turns dark.
Then, the method for characterizing the highland barley fiber and analyzing the result comprises the following specific processes:
an X-ray diffractometer is an electromagnetic wave which can penetrate a certain thickness of a substance, and X-ray diffraction can be used for analyzing and researching the structure of a crystal, because each substance has a unique crystal structure, when a sample is irradiated by high-energy X-rays, an object in the sample is excited, and identification X-rays are generated, the crystal face reflection activity of the crystal follows bragg law, the qualitative analysis of a compound can be performed by measuring the position of a diffraction peak, and the quantitative analysis can be performed by measuring the intensity of the diffraction peak of a spectral line. In the test, an X-ray diffractometer is mainly used for analyzing the crystallization performance of the modified highland barley fiber.
Preparation of samples of ethylene oxide
Generally, a sample having a small particle size, stable properties, and a uniform spherical size distribution is relatively desirable. During the sample pressing process, the entire sample well is typically covered with the powder sample. It should be noted that if the samples are in the same series and the force difference is large, the density of the samples is easy to change, and therefore the diffraction intensity of the samples may be affected. In the test, the dried highland barley fiber is cut into sections, put into a sample tank, then put into an X-ray diffractometer, and a computer system connected with the X-ray diffractometer is operated to analyze the X-ray diffraction image of the sample.
Analysis of capsule wall
One of the test methods is an orthogonal analysis method, which passes a treatment solution (6% NaOH, 6% NaOH + 10% H) 2 O 2 3% glacial acetic acid +1.5% NaClO 2 ) Orthogonal design is carried out on three levels of three factors, namely treatment time (2 h, 4h and 6 h) and heat treatment temperature (80 ℃, 100 ℃ and 120 ℃), XRD analysis is carried out on the modified fiber, and the crystallinity is calculated.
The second test method is a comparative analysis method, which mainly studies the influence of different treatment conditions on the crystallinity of the highland barley fiber. The comparative analysis method usually compares several test data with common characteristics, so as to make certain comments, and finally obtain some experimental result. In the test, the XRD curves of the highland barley fibers under the treatment condition are compared, or the XRD curves of the highland barley fibers under the treatment condition and the XRD curves of the highland barley fibers under the non-treatment condition are compared, and the crystallization properties of the highland barley fibers under different conditions are analyzed; comparing the shapes of the highland barley fibers under different pretreatment conditions, and researching the influence of pretreatment on the fiber structure.
⒊ XRD image analysis of highland barley fiber
When the highland barley fibers were modified with the reagents of numbers 1 to 9 in Table 5 and the crystal structure of cellulose was examined with an X-ray diffractometer, the crystallinity of the cellulose fibers was measured from the intensity and position of the diffraction points.
TABLE 5 crystallinity index of fiber under various conditions
XRD pattern curves under different modification conditions were obtained corresponding to the experimental numbers in Table 5, as shown in FIG. 3. The test analyzes the relationship between different treatment conditions and crystallinity by an orthogonal test method. The calculation shows that the crystallinity of No. 8 is better.
⒋ SEM image analysis of highland barley fiber
The scanning electron microscope adopts a point-by-point imaging image decomposition method, sequentially and proportionally converts the image into a video signal, and the video signal is amplified through a network and subjected to data processing of control signals, so that the video signal can be transmitted to a grid electrode of a fluorescent screen which is synchronously scanned by an electron beam and is used for modulating the intensity of the electron beam of a cathode ray tube. Because the sample scanning and the scanning of the SEM equipment are completely synchronous, the sample scanning and the scanning of the SEM equipment can be magnified images of the sample.
The characteristics of a scanning electron microscope:
1) the sample preparation process is simple;
2) the freedom in the sample chamber is very large;
3) the image is rich in stereoscopic impression;
4) the magnification range is large, and the resolution is high;
5) the damage and the pollution of the electron beam to the sample are small.
In the sample preparation of a scanning electron microscope, for a powder sample, the powder sample is adhered on a sample seat by conductive adhesive (or collodion or double-sided adhesive), a conductive film is plated, or the powder is subjected to sample material to prepare cell suspension, the cell suspension is dripped on the sample seat, and the conductive film is plated after the solution is volatilized. In the test, the highland barley fiber is adhered to the sample seat, and because the highland barley fiber is a non-conductive material, carbon spraying or gold spraying treatment needs to be carried out on the surface of the highland barley fiber, so that the influence on the image quality caused by the accumulation of charges under the irradiation of an electron beam is avoided.
For the modified highland barley fiber scanning electron microscope image, as shown in fig. 4 (scanning electron microscope image of 50 times of the modified highland barley fiber) and fig. 5 (scanning electron microscope image of 10000 times of the modified highland barley fiber), the fiber surface becomes rough, and many scratches can be seen on the fiber surface, which is favorable for the adhesion of the highland barley fiber and the ecological concrete. Furthermore, the fiber surface was seen to have a number of flocs, since the treated barley fiber lignin and hemicellulose were removed and floated on the fiber surface, leaving the cellulose fully exposed and smooth. By removing lignin and hemicellulose, the mechanical property of the highland barley fiber is improved, and subsequent research is convenient
⒌ thermogravimetric image analysis of highland barley fiber
As shown in FIG. 6 (schematic diagram of thermogravimetric image analysis of unmodified highland barley fiber) and FIG. 7 (schematic diagram of thermogravimetric image analysis of No. 8 modified highland barley fiber), it can be seen from FIG. 6 and FIG. 7 that the mass change at this stage is mainly water loss on the surface of straw at 0-200 deg.C, and DSC curve shows that it is an endothermic process. At 280-380 ℃, the mass reduction at this time is mainly the pyrolysis of hemicellulose and cellulose. In this process, curve 0 drops sharply and curve 8 drops uniformly. The modification shows that partial hemicellulose of the highland barley fiber is removed. This portion is an exothermic process. At the temperature of 380-600 ℃, the quality reduction of the process is mainly to lose the water which is the component of the straw (the component is sugar), and only carbon is left at the temperature of 600 ℃. The DSC curve indicates that it is an exothermic process.
⒍ Infrared Spectrum image analysis of highland barley fiber
Comparing the change of the infrared spectrum image of the modified highland barley fiber in different solution environments, and comparing the treatment effect. Comparing the untreated No. 0 sample with the No. 1 sample treated with the alkali solution to obtain an infrared spectrum image as shown in FIG. 8 (a comparison schematic diagram of infrared spectrum analysis of No. 0 and No. 1 modified highland barley fibers). As can be seen in FIG. 8, in the absorption peak of hemicellulose with respect to No. 0, No. 1 is at 1255.35cm -1 The C-O stretching peak at position disappears, 1735 cm -1 C = O expansion peak disappeared; absorption peaks of lignin are 1600, 1514 and 1462cm -1 The absorption peak disappears, which shows that the modification result of the treatment by the sodium hydroxide solution is good, and the removal rate of the hemicellulose and the lignin is higher.
Comparing the infrared spectra of the untreated No. 0 highland barley fiber and the No. 6 highland barley fiber treated by the alkaline hydrogen peroxide solution, FIG. 9 (a comparison schematic diagram of infrared spectroscopic analysis of the No. 0 and No. 6 modified highland barley fibers) can be obtained, and it can be seen from FIG. 9 that the infrared spectrum of the No. 6 highland barley fiber has no obvious change.
Comparing the IR spectra of untreated No. 0 highland barley fiber and No. 8 highland barley fiber treated with sodium chlorite and glacial acetic acid solution, FIG. 10 (comparative IR spectra analysis of No. 0 and No. 8 modified highland barley fiber) can be obtained, and from FIG. 10, the result of No. 8 sample treatment is good, and at 1600cm -1 The vibration peak of aromatic skeleton is removed, 1514cm -1 C = C stretching vibration peak in the aromatic ring is removed, which shows that the lignin contained in the highland barley fiber is mainly removed by No. 8 modification.
The morphological structure of the highland barley fiber is researched on the crystallinity and the apparent morphology of the highland barley fiber under the 9 groups of different treatment conditions, and the result proves that the crystallinity of the highland barley fiber can be improved by the modification treatment, and the apparent morphology of the highland barley fiber can be changed. The influence of different pretreatment factors on the crystallinity index of the highland barley fiber is obtained through an orthogonal test design method and a comparison method, so that the optimal level combination is found out.
Through the macroscopic morphology analysis and SEM microstructure analysis of the untreated fiber, the surface of the untreated highland barley fiber is quite smooth, and the highland barley straw is relatively hard due to the existence of cellulose, hemicellulose, lignin and the like in the fiber.
Through three-factor three-level orthogonal design test, the highland barley fiber is modified, and the experimental phenomenon shows that the highland barley fiber is modified by 3 percent of glacial acetic acid and 1.5 percent of NaClO 2 When the solution is treated at the temperature of +4h +80 ℃, the color of the solution gradually turns yellow, and then the solution becomes darker and is brown or dark brown.
The crystallinity index under different treatment conditions can be obtained by XRD and infrared spectrum image analysis, and the result shows that the crystallinity index of the 8 th group of the test number is 55.55 percent, and the crystallinity is the best. This gave 3% glacial acetic acid +1.5% NaClO 2 +4h +80 ℃ is the optimal level combination.
The morphology structure of the modified highland barley fiber is analyzed through SEM, so that lignin, hemicellulose, fructose and the like of the processed highland barley fiber are partially removed, and the fiber surface presents a plurality of ordered and clear gullies and pits, and the structure is favorable for improving the interface adhesion of the highland barley fiber and ecological concrete.
After the modification is obtained through thermogravimetric image analysis, part of hemicellulose is removed from the highland barley fiber, so that the remained highland barley straw is mainly cellulose.
The analysis after modification shows that the No. 8 surface modification treatment scheme has better effect theoretically, and can be considered to be doped into concrete to improve the mechanical property and frost resistance of the concrete.
Because the ecological concrete is formed by mixing cement, stones with larger particle sizes and a water reducing agent in a water adding manner, the strength of the hardened concrete is ensured by a connecting body formed by cement paste and the stones, but because the particle sizes of the stones used in the test are larger, a large gap is formed between the stones, the concrete with the structure is easy to crack once subjected to the action of external force in the actual working environment, and the whole structure of the concrete after crack propagation is completely collapsed. Therefore, when the concrete is mixed, the highland barley fibers with certain length and certain volume are added, so that gaps in the concrete can be filled, and the highland barley fibers and the cement paste are connected with each other, so that the whole concrete is more stable and can resist greater stress concentration, and the strength of the concrete is improved. The mixing amount of the highland barley fiber is a very critical factor.
The mixing amount of the highland barley fiber in the step (2) can be divided into a high mixing amount and a low mixing amount. The anti-cracking performance of the fiber concrete with low addition amount is obviously improved, and when a large amount of fibers are added into the concrete, the compression strength of the concrete is mainly influenced. The experimental design is 1Kg/m 3 、2Kg/m 3 、3Kg/m 3 、4Kg/m 3 、5Kg/m 3 The mechanical properties of the fiber concrete are comprehensively analyzed by five different fiber mixing amounts, and the optimal mixing amount is selected.
Compared with the untreated No. 0 highland barley fiber, the treated No. 8 highland barley fiber has very rough fiber surface, and the treated fiber surface has the appearance similar to scratches, so the structure is favorable for the adhesion of the highland barley fiber and cement mortar. And we can also see that a plurality of floccules appear on the surface of the fiber, because the impurities such as lignin, hemicellulose and the like in the highland barley fiber after the highland barley fiber is subjected to acid-base treatment are removed and float on the surface of the fiber, the remained cellulose is fully exposed and becomes smooth and regularly arranged, and the mechanical property of the highland barley fiber is improved by the structure after the modification treatment.
The specific process of the step (3) is as follows:
carrying out X-ray diffraction analysis and scanning electron microscope analysis on the modified highland barley fibers in the step (1) to research the microscopic mechanism of fiber modification;
secondly, adopting a single-factor test, doping highland barley fibers with different quantities into concrete according to the quantity change, wherein the water-cement ratio of the concrete is 0.3, the porosity is 25%, filling the mold after mixing, putting the filled mold in a cool place to avoid water evaporation, taking out the concrete test block from the mold after 24 hours until the concrete test block has certain strength, then moving the concrete test block into a more stable and constant-humidity curing room for curing, taking out the concrete test block after 28 days, and measuring the mechanical properties of the highland barley fiber concrete by using a Hualong mechanical property tester after taking out, wherein the mechanical properties comprise compressive strength, splitting strength and bending strength;
thirdly, the highland barley fiber concrete mechanical property data obtained in the second step are sorted and drawn, and the improvement condition of the highland barley fiber on the concrete mechanical property is obtained by analyzing the image and the data; the 5 groups of highland barley fiber concrete mechanical property data with different mixing amounts are imported into the software Origin, and the analysis is carried out after the drawing, so as to obtain how the concrete mechanical property changes along with the different mixing amounts of the highland barley fibers.
Mixing the highland barley fiber concrete with the optimal mixing ratio (the water-cement ratio is 0.30 and the porosity is 25 percent), and testing the mechanical property after curing for 28 days. And (3) drawing a graph of the 28-day mechanical property of the highland barley fiber concrete along with the fiber content, as shown in fig. 11 (a graph of the mechanical property of the highland barley fiber concrete along with the fiber content).
The contrast group is the common concrete which is mixed by the optimal mixing ratio of No. 8 and is not added with the highland barley fiber, and the average strength of the common concrete is 14.64Mpa of compressive strength, 3.01Mpa of cleavage strength and 1.36Mpa of rupture strength.
It can be seen that the compressive strength, the splitting strength and the breaking strength of the concrete are obviously changed after the highland barley fibers are doped into the concrete. The mixing amount of the highland barley fiber is 1Kg/m 3 ～3Kg/m 3 Meanwhile, the mechanical property of the concrete is obviously improved, wherein the mixing amount of the highland barley fiber is 1Kg/m 3 ～3Kg/m 3 The change of the concrete is that the compressive strength of the concrete is respectively increased by 7.8 percent, 15.0 percent and 20.8 percent, the splitting strength is respectively increased by 5.3 percent, 39.8 percent and 75 percent, and the breaking strength is respectively increased by 22.5 percent, 47.8 percent and 63.8 percent; but when the mixing amount of the highland barley fiber is continuously increased, the mechanical property of the concrete begins to be reduced.
The reason may be that the ecological concrete adopted in the test is macroporous concrete, a plurality of pores exist in the middle of the concrete, and when external impact force acts on the concrete, stress concentration in the concrete is very strong, so that the concrete structure is damaged. After a certain amount of highland barley fibers are doped into the concrete, the highland barley fibers enter gaps in the concrete to fill holes in the concrete, so that the internal structure of the concrete is more compact.
In addition, the highland barley fiber is bonded with the cement paste in the concrete, so that stones, the cement paste and the highland barley fiber in the concrete are bonded into a firm net, the external impact force is fully dispersed by the net structure, the deformation resistance of the concrete is improved, and the mechanical property is greatly improved; however, when the proportion of the highland barley fibers in the concrete is too much, the specific surface area of the fibers is increased, and the fibers are increased, so that the highland barley fibers absorb a lot of water when the concrete is mixed, the water-saturated highland barley fibers are difficult to combine with the cement slurry, the amount of the highland barley fibers wrapped by the cement slurry in the concrete is rapidly reduced, if the proportion of the highland barley fibers in the concrete is continuously increased, the highland barley fibers absorb a lot of water to cause the cement slurry to be completely disconnected with the highland barley fibers, the compactness of the concrete is rapidly reduced, the concrete framework is also completely collapsed, and the mechanical strength of the concrete is also greatly reduced.
The specific process of the step (4) is as follows:
A) taking out the cured concrete test block in the curing chamber, observing the regular condition of the surface of the concrete test block, then putting the concrete test block into normal-temperature water for soaking for at least 4 days, taking out the concrete test block, dry-mixing the residual moisture on the surface of the concrete test block, and weighing the mass of the concrete to obtain the initial mass of the concrete;
B) firstly, setting a control panel of a freezing and thawing box, setting the temperature between-15 ℃ and-20 ℃, controlling the temperature not to be higher than 15 ℃ all the time, and setting three freezing and thawing cycle gradients which are 20 times, 40 times and 50 times respectively; 1Kg/m is added according to the different mixing amount of the highland barley fiber 3 、2Kg/m 3 、3Kg/m 3 、4Kg/m 3 、5Kg/m 3 Placing 5 groups of highland barley fiber concrete test blocks into a freeze thawing box;
C) when the test reaches 20 times of freeze-thaw cycles, stopping the freeze-thaw box, waiting for the concrete test block to be completely thawed, taking out one third of the concrete test block, weighing the mass of the concrete test block, then testing the compressive strength of the concrete test block, setting the freeze-thaw box to continue to operate for 20 times of cycles after the test is finished, taking out the required concrete test block after the operation is finished, weighing and testing the compressive strength of the concrete test block, then continuing to set for 10 cycles, and measuring the weight and the compressive strength after the cycle is finished; and if the mass of the concrete test block after a certain circulation is reduced to below 95 percent of the original mass or the compressive strength is reduced to below 75 percent of the original mass, the concrete test block is considered to be damaged, and the frost resistance grade of the concrete is recorded as D + freeze-thaw cycle times after the experiment is finished.
And (5) carrying out anti-freezing data processing, appearance analysis, quality loss rate analysis and compressive strength loss rate analysis.
1. Freeze resistance data processing as shown in tables 6, 7 and 8.
Table 620 freeze thaw cycle results
Table 740 freeze thaw cycle results
Table 850 freeze thaw cycles results
2. Appearance analysis
(a) Through observing the concrete test block processed by different freezing and thawing times, the surface stones of the concrete test block become loose and easily fall off after the freezing and thawing test, the surface of the concrete test block has the tendency of forming carved strips, deformed holes can be seen on the surface of the concrete, and the phenomena are more and more obvious along with the increase of the freezing and thawing cycle times.
(b) The surface damage of the common concrete after the frost resistance test is more serious than that of the highland barley fiber concrete, which shows that the frost resistance of the concrete is improved due to the existence of the highland barley fiber.
3. The mass loss rate analysis is performed, and the mass loss rate is plotted as shown in fig. 12 (a highland barley fiber concrete mass loss rate result chart):
the following can be found from fig. 12:
(1) the increase of the number of freeze-thaw cycles continuously reduces the quality of the concrete, and the quality loss of the concrete is continuously accelerated.
(2) The mass loss rate of the concrete without the highland barley fibers is very high, and the mass loss rate of the highland barley fiber concrete is very low, which indicates that the highland barley fibers slow down the mass loss of the concrete, namely the highland barley fibers have positive significance on the frost resistance of the concrete.
(3) Along with the increase of the freezing and thawing times, when the freezing and thawing cycle times are less than 40, the change rate of the quality loss rate of the highland barley fiber concrete is not much different from that of the common concrete, but when the freezing and thawing cycle times are more than 40, the increase speed of the quality loss rate of the highland barley fiber concrete is much slower than that of the common concrete. The result shows that the freezing resistance of the concrete is not greatly influenced by the doping of the highland barley fibers at the early stage of the freeze-thaw cycle, and the strength loss of the concrete can be effectively reduced by the highland barley fibers at the later stage of the freeze-thaw cycle.
4. Analysis of compressive strength loss rate, the compressive strength loss rate is plotted as shown in fig. 13 (the result graph of the compressive strength loss rate of highland barley fiber concrete), and the following conclusions can be found from fig. 13:
(1) the loss rate of the compressive strength of the concrete is in an increasing trend.
(2) The loss rate of the compressive strength of the common concrete is much higher than that of the highland barley fiber concrete. This shows that the highland barley fiber has the function of enhancing the frost resistance of the concrete.
(3) Along with the increase of the freezing and thawing times, when the freezing and thawing cycle times are less than 40, the change rate of the compressive strength loss rate of the highland barley fiber concrete is not much different from that of the common concrete, but when the freezing and thawing cycle times are more than 40, the increase rate of the compressive strength loss rate of the highland barley fiber concrete is much slower than that of the common concrete. The result shows that the freezing resistance of the concrete is not greatly influenced by the doping of the highland barley fibers at the early stage of the freeze-thaw cycle, and the compressive strength loss of the concrete can be effectively reduced by the highland barley fibers at the later stage of the freeze-thaw cycle.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described above, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (6)
1. The method for testing the performance of the ecological concrete of the highland barley fiber is characterized by comprising the following steps: the method comprises the following steps:
(1) modifying the highland barley fibers;
(2) determining the mixing amount of the highland barley fibers;
(3) testing the mechanical property of the highland barley fiber concrete;
(4) testing the frost resistance of the highland barley fiber concrete;
(5) and (3) carrying out anti-freezing result and analysis on the ecological concrete with the highland barley fibers.
2. The method for testing the performance of the ecological concrete with highland barley fibers according to claim 1, which is characterized in that: the specific process of the step (1) is as follows: firstly, washing the highland barley fibers with distilled water to remove impurities on the surfaces of the highland barley fibers, and then drying the washed highland barley fibers for 2 hours at the temperature of 80 ℃ to prepare pretreated highland barley fibers; then the pretreated highland barley fiber is treated with 3 percent glacial acetic acid and 1.5 percent NaClO at the temperature of 50 DEG C 2 The mixed solution is soaked for 4 hours and then dried in an oven with the temperature of 80 ℃.
3. The method for testing the performance of the ecological concrete with highland barley fibers as claimed in claim 2, wherein the method comprises the following steps: the mixing amount of the highland barley fibers in the step (2) is highThe doping amount and the low doping amount are two; the anti-cracking performance of the low-dosage highland barley fiber concrete is obviously improved, and when a large amount of highland barley fiber is added into the concrete, the compressive strength of the concrete is mainly influenced; design 1Kg/m 3 、2Kg/m 3 、3Kg/m 3 、4Kg/m 3 、5Kg/m 3 The mechanical properties of the highland barley fiber concrete are comprehensively analyzed by five different highland barley fiber mixing amounts, and the optimal mixing amount is selected.
4. The method for testing the performance of the ecological concrete with highland barley fibers according to claim 3, which is characterized in that: the specific process of the step (3) is as follows:
carrying out X-ray diffraction analysis and scanning electron microscope analysis on the modified highland barley fibers in the step (1) to research the microscopic mechanism of fiber modification;
secondly, adopting a single-factor test, doping highland barley fibers with different quantities into concrete according to the quantity change, wherein the water-cement ratio of the concrete is 0.3, the porosity is 25%, filling the mold after mixing, putting the filled mold in a cool place to avoid water evaporation, taking out the concrete test block from the mold after 24 hours until the concrete test block has certain strength, then moving the concrete test block into a more stable and constant-humidity curing room for curing, taking out the concrete test block after 28 days, and measuring the mechanical properties of the highland barley fiber concrete by using a Hualong mechanical property tester after taking out, wherein the mechanical properties comprise compressive strength, splitting strength and bending strength;
thirdly, the highland barley fiber concrete mechanical property data obtained in the second step are sorted and drawn, and the improvement condition of the highland barley fiber on the concrete mechanical property is obtained by analyzing the image and the data; the 5 groups of highland barley fiber concrete mechanical property data with different mixing amounts are imported into the software Origin, and the analysis is carried out after the drawing, so as to obtain how the concrete mechanical property changes along with the different mixing amounts of the highland barley fibers.
5. The method for testing the performance of the ecological concrete with highland barley fibers according to claim 4, which is characterized in that: the specific process of the step (3) is as follows:
A) taking out the cured concrete test block in a curing room, observing the regular condition of the surface of the concrete test block, then putting the concrete test block into normal-temperature water, soaking for at least 4 days, taking out the concrete test block, wiping the residual moisture on the surface of the concrete test block, and weighing the mass of the concrete to obtain the initial mass of the concrete;
B) firstly, setting a control panel of a freezing and thawing box, setting the temperature between-15 ℃ and-20 ℃, controlling the temperature not to be higher than 15 ℃ all the time, and setting three freezing and thawing cycle gradients which are 20 times, 40 times and 50 times respectively; 1Kg/m is added according to the different mixing amounts of the highland barley fibers 3 、2Kg/m 3 、3Kg/m 3 、4Kg/m 3 、5Kg/m 3 5 groups of highland barley fiber concrete test blocks with the doping amount are placed in a freeze-thawing box;
C) when the test reaches 20 times of freeze-thaw cycles, stopping the freeze-thaw box, waiting for the concrete test block to be completely thawed, taking out one third of the concrete test block, weighing the mass of the concrete test block, then testing the compressive strength of the concrete test block, setting the freeze-thaw box to continue to operate for 20 times of cycles after the test is finished, taking out the required concrete test block after the operation is finished, weighing and testing the compressive strength of the concrete test block, then continuing to set for 10 cycles, and measuring the weight and the compressive strength after the cycle is finished; and if the mass of the concrete test block after a certain circulation is reduced to below 95 percent of the original mass or the compressive strength is reduced to below 75 percent of the original mass, the concrete test block is considered to be damaged, and the frost resistance grade of the concrete is recorded as D + freeze-thaw cycle times after the experiment is finished.
6. The method for testing the performance of the ecological concrete with highland barley fibers according to claim 5, which is characterized in that: and the step (5) comprises the steps of antifreeze data processing, appearance analysis, quality loss rate analysis and compressive strength loss rate analysis.
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