Preparation method of PS particle-doped high-performance fiber concrete

Abstract

The invention relates to the technical field of preparation of high-performance fiber concrete, and discloses preparation of PS particle-doped high-performance fiber concrete, which comprises the following steps: step 1, preparing a UHPC premix; 2, the UHPC premix is subjected to dry stirring and uniform mixing; step 3, keeping the stirrer running, adding water into the mixed and stirred powder, and continuously stirring; 4, dispersing the steel fibers, adding the dispersed steel fibers into the stirring pot, and continuously stirring; step 5, dispersing PS particles, putting the dispersed PS particles into the stirring pot, and continuously stirring for a preset time; 6, after stirring is completed, the mixture is added into the steel mold coated with the film coating agent; and 7, after pouring is completed, curing is conducted after the test piece is subjected to standing forming and demolding. According to the scheme, a proper amount of PS particles are doped, so that the cost of the steel fibers is reduced, meanwhile, the PS particles can serve as an artificial defect, increase the cracking tendency of a UHPC matrix when bearing tensile stress and also can serve as a micro stirrer to promote uniform dispersion of the steel fibers, and the mechanical property of the UHPC is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing high-performance fiber concrete, and particularly to a method for preparing high-performance fiber concrete doped with PS particles. Background Art

[0002] Ultra High Performance Concrete (UHPC) is a kind of concrete material with high strength and high durability, and is widely used in major structures such as bridges, tunnels, and high-rise buildings. Compared with traditional concrete, UHPC has achieved significant performance improvements and shows great application potential in the field of modern construction engineering. With its excellent tensile properties, UHPC has attracted the attention of many scholars. Especially strain-hardening UHPC, which can exhibit strain-hardening characteristics similar to metals under tensile stress. This strain-hardening process is usually accompanied by multi-crack cracking phenomena and high energy-consuming processes, thus endowing UHPC with excellent toughness and ductility.

[0003] So far, many studies have focused on enhancing the strain-hardening characteristics of UHPC under tensile stress by adjusting the fiber parameters in UHPC. For example, increasing the fiber content, increasing the aspect ratio of the fiber, using special-shaped fibers, and changing the surface characteristics of the fiber, etc. Although introducing steel fibers into UHPC can significantly improve its tensile strength and exhibit pseudo-strain-hardening phenomena similar to metals under tensile stress conditions, steel fibers usually account for more than 40% of the total cost of UHPC. Increasing the dosage of steel fibers will significantly increase the cost. In addition, too high steel fiber content and aspect ratio are prone to cause fiber aggregation, resulting in a decline in the mechanical properties of UHPC. Summary of the Invention

[0004] The present invention aims to provide a new method for preparing high-performance fiber concrete to solve the high-cost problem brought about by adjusting the tensile properties of UHPC by increasing steel fibers at present, as well as the fiber aggregation problem that affects the mechanical properties of UHPC.

[0005] To achieve the above object, the present invention adopts the following technical scheme: A method for preparing high-performance fiber concrete doped with PS particles, comprising:

[0006] Step 1: Prepare UHPC premix;

[0007] Step 2: Dry-mix the UHPC premix until evenly mixed;

[0008] Step 3: Keep the mixer running, add water to the mixed powder, and continue stirring;

[0009] Step 4: Disperse steel fibers, add the dispersed steel fibers to the mixing pot, and continue stirring;

[0010] Step 5: Disperse the PS particles, put the dispersed PS particles into a stirring pot, and continuously stir for a preset time;

[0011] Step 6: After the stirring is completed, add the mixture to a steel mold coated with a film-forming agent;

[0012] Step 7: After the pouring is completed, wait for the specimen to stand and form, demold, and then cure.

[0013] Preferably, the PS particles are surface-hydrophobic PS particles, the particle size of the PS particles is 3-4 mm, the particle density is 900-1100 kg / m³, the dosage of PS particles in the specimen is 1%-4%, and the particle size of the fine aggregate in the UHPC premix is 0.1-0.3 mm. Taking surface-hydrophobic PS particles as artificial defects and adding them to UHPC, appropriately incorporating PS particles can not only serve as artificial defects to increase the cracking tendency of the UHPC matrix under tensile stress, but also act as micro-agitators to promote the uniform dispersion of steel fibers. Specifically, in the mixing stage of UHPC, spherical PS particles can be evenly dispersed in the UHPC matrix, and the spherical structure can also help the steel fibers disperse better, reducing the possibility of fiber agglomeration. Thus, it helps the steel fibers disperse better, reduces the generation of agglomeration phenomena, and greatly improves the mechanical properties of UHPC.

[0014] Preferably, in Step 2, all the powders except quartz sand are first stirred and mixed, and then quartz sand is added for stirring and mixing. During the mixing process of the powders and quartz sand, powders such as cement may have started to absorb moisture or hydrate. If quartz sand is added too early, its particles may interfere with the bonding of the powder particles, resulting in uneven mixing. Adding quartz sand later helps to avoid this uneven distribution and ensures that the sand grains can be fully mixed with other components at the appropriate time.

[0015] Preferably, in Step 2, all the powders except quartz sand are first stirred and mixed for 1-3 min at a dry mixing speed of 90-110 rpm / min, and then quartz sand is added for stirring and mixing for 1-2 min.

[0016] Preferably, the quartz sand in Step 2 is processed into super-hydrophobic quartz sand by a mixing method. During the cement hydration process, by utilizing the water-repellent effect of the hydrophobic quartz sand, the surface energy of the hydrophobic sand is reduced, and the bonding force between the hydrophobic sand and the matrix decreases, which can reduce the cracking strength of UHPC.

[0017] Preferably, after adding steel fibers in Step 4, the stirring speed is adjusted to 190-210 rpm / min and stirred for 2-5 min.

[0018] Preferably, the steel fiber is an end-hooked copper-plated fine steel fiber, and the content of the end-hooked copper-plated fine steel fiber in the specimen is 1% to 2%.

[0019] Preferably, in step 7, the specimen is placed in a concrete curing chamber for curing, the curing temperature is 25 to 28 °C, and the humidity is 96% to 99%.

[0020] Preferably, after pouring in step 7, a plastic film is covered on the surface of the specimen. At the same time, covering the surface of the specimen with a plastic film can effectively reduce the evaporation of water, keep the concrete surface moist, promote the full hydration of cement, and thus improve the strength and durability of concrete.

[0021] Preferably, the reinforcement ratio in the specimen of step 7 is 2.5% to 5.0%, and the water-cement ratio of the specimen is 0.2 to 0.3.

[0022] In the solution of this application, an appropriate amount of PS particles is incorporated, not for improving the heat insulation performance of concrete. Although on the one hand, it can reduce the cost of concrete, the main purpose is to act as an artificial defect, increasing the cracking tendency of the UHPC matrix when bearing tensile stress, and it can also act as a micro agitator to promote the uniform dispersion of steel fibers, greatly improving the mechanical properties of UHPC. This not only brings higher safety and reliability to engineering structures, but also provides a solid foundation and possibility for the further development of engineering structures to adapt to more complex and harsh load and environmental conditions; UHPC incorporated with PS particles shows significant advantages in aspects such as tensile mechanical properties, fiber distribution optimization, strain hardening ability, crack width control, and ultimate tensile strain improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of Embodiment 1 of the present invention.

[0024] Figure 2 It is an elevation view of the specimen of Embodiment 1 of the present invention.

[0025] Figure 3 It is a schematic diagram of the reinforcement layout on the top surface of the specimen of Embodiment 1 of the present invention.

[0026] Figure 4 For Embodiment 1 of the present invention Figure 2 It is a schematic cross-sectional view in the A-A direction.

[0027] Figure 5 For Embodiment 1 of the present invention Figure 2 It is a schematic cross-sectional view in the B-B direction. DETAILED DESCRIPTION OF THE INVENTION

[0028] The following is further detailed through specific embodiments:

[0029] The reference numerals in the accompanying drawings of the specification include: specimen 1, steel bar 2.

[0030] Example 1:

[0031] A preparation method of high-performance fiber concrete mixed with PS particles, as shown in the appendix Figure 1 includes

[0032] Step 1: Prepare UHPC premix.

[0033] The UHPC premix specifically includes materials with the following proportions: cement 1, water 0.248, silica fume 0.089, mineral powder 0.252, microbeads 0.040, water reducer 0.010, steel fiber 0.196, quartz sand 1.258.

[0034] Step 2: Dry-mix the UHPC premix to mix it evenly.

[0035] In this step, first stir and mix all the powders except quartz sand for 1 - 3 minutes, preferably 2 minutes, with a dry-mixing speed of 90 - 110 rpm / min, preferably 100 rpm / min, and then add quartz sand and stir and mix for 1 - 2 minutes, preferably 1 minute. During the mixing process of the powders and quartz sand, the powders such as cement may have started to absorb moisture or hydrate. If the quartz sand is added too early, its particles may interfere with the bonding of the powder particles, resulting in uneven mixing. Adding quartz sand later helps to avoid this uneven distribution and ensures that the sand grains can be fully mixed with other components at the appropriate time.

[0036] In this step, the quartz sand is first treated by the mixing method to form super-hydrophobic quartz sand. During the cement hydration process, especially the surface water-repellent effect of the hydrophobic quartz sand will reduce the surface energy of the hydrophobic sand, resulting in a decrease in the bonding force between the hydrophobic sand and the matrix, and can reduce the cracking strength of UHPC.

[0037] Step 3: Keep the mixer running, add water to the mixed powders, and continue to stir.

[0038] In this step, the entire water addition process takes 30S, and then stir for 3 minutes.

[0039] Step 4: Disperse the steel fibers, add the dispersed steel fibers to the mixing pot, and continue to stir.

[0040] In this step, manually disperse the steel fibers. After adding the steel fibers to the mixing pot, adjust the stirring speed to 190 - 210 rpm / min, preferably 200 rpm / min, and stir for 2 - 5 minutes, preferably 3 minutes.

[0041] In this step, the steel fiber is a hook-shaped copper-plated fine steel fiber. The content of the hook-shaped copper-plated fine steel fiber in the specimen 1 is 1% to 2%, preferably 2%. The hook-shaped steel fiber (also called hook-shaped steel fiber) is characterized in that both ends of the fiber are designed to be hook-shaped or curved, similar to the shape of a hook. The shape of the hook end can better embed the fiber into the concrete matrix, increase the mechanical bonding force between the fiber and the concrete, and prevent the fiber from falling off or slipping under load. This allows the steel fiber to more effectively share the stress in the concrete and improve the tensile strength and crack resistance of the concrete.

[0042] In this step, the steel fibers are gradually added into the stirring pot in small amounts and multiple times to avoid adding all the steel fibers into the stirring pot at one time, so as to prevent the steel fibers from agglomerating and causing uneven distribution of the steel fibers.

[0043] The stirring pot in this scheme is a 10L planetary mixer.

[0044] Step 5: Disperse the PS particles, put the dispersed PS particles into the stirring pot, and continue stirring for the preset time.

[0045] Among them, the PS particles are surface hydrophobic PS particles, the particle size of the PS particles is 3-4 mm, the particle density is 900-1100 kg / m3, and the particle density is preferably 1010 kg / m3. The amount of PS particles in specimen 1 is 1%-4%, preferably 2%, and the particle size of fine aggregate in the UHPC premix is ​​0.1-0.3 mm. The surface hydrophobic PS particles are taken as artificial defects and added to the UHPC. The appropriate amount of PS particles can not only serve as artificial defects to increase the cracking tendency of the UHPC matrix when subjected to tensile stress, but also can be used as micro-stirring to promote the uniform dispersion of steel fibers, greatly improving the mechanical properties of UHPC. Specifically, in the mixing stage of UHPC, the spherical PS particles can be evenly dispersed in the UHPC matrix, and the spherical structure can also help the steel fibers to be better dispersed and reduce the possibility of fiber agglomeration. Thereby helping the steel fibers to be better dispersed and reducing the occurrence of agglomeration.

[0046] Step 6: After mixing, add the mixture to the steel mold coated with the coating agent.

[0047] Step 7: After pouring is completed, the specimen 1 is allowed to stand for forming and then demoulded for curing.

[0048] Preferably, in step 7, the test piece 1 is placed in a concrete curing room for curing, the curing temperature is 25-28° C., and the humidity is 96%-99%.

[0049] In this step, after pouring, a plastic film is covered on the surface of the specimen 1. At the same time, the plastic film covers the surface of the specimen 1, effectively reducing the evaporation of water, keeping the concrete surface moist, and promoting the full hydration of cement, thereby improving the strength and durability of the concrete.

[0050] In Specimen 1 in this step, the reinforcement ratio is 2.5% - 5.0%. In this embodiment, high-strength steel bars are used for Steel Bar 2, with the model HRB635. The water-cement ratio of Specimen 1 is 0.2 - 0.3, preferably 0.248.

[0051] In this solution, by appropriately adding PS particles as artificial defects, the cracking tendency of the UHPC matrix under tensile stress is increased; at the same time, it can also act as a micro-agitator to promote the uniform dispersion of steel fibers, significantly improving the mechanical properties of UHPC; UHPC with PS particles added shows significant advantages in aspects such as tensile mechanical properties, fiber distribution optimization, strain hardening ability, crack width control, and ultimate tensile strain improvement, not only bringing higher safety and reliability to engineering structures, but also providing a solid foundation and possibility for the further development of engineering structures to adapt to more complex and harsh load and environmental conditions; the combination of high-performance fiber concrete with low-volume end-hooked copper-plated micro steel fibers and high-strength steel bars reduces costs while significantly improving the mechanical properties of UHPC.

[0052] Example 2

[0053] The difference between this embodiment and Example 1 is that the content of PS particles is 1%.

[0054] Example 3

[0055] The difference between this embodiment and Example 1 is that the content of PS particles is 4%.

[0056] Comparative Example 1

[0057] The difference between this embodiment and Example 1 is that no PS particles are added.

[0058] An axial tensile test was conducted on Specimen 1 prepared from the concrete of the above-mentioned examples and comparative examples. The uniaxial tensile stress-strain test was carried out with reference to the Swiss code (specific reference document: MCS-EPFL R. Ultra-high performance fibre reinforced cement-based composites (UHPFRC) construction material, dimensioning und application [S]. Lausanne, Switzerland: Ecole Polytechnique Federale de Lausanne (EPFL), 2016.). The shape of Specimen 1 was dog-bone type. The tensile strength of Specimen 1 was tested using a universal testing machine with a load capacity of 100 t. The axial tensile test was carried out under displacement control. The test steps were divided into preloading and formal loading, and the loading rates were 1 mm / min and 0.3 mm / min respectively. When the tensile force reached 0.5 kN, the preloading ended and the formal loading began. When the tensile stress of Specimen 1 dropped to 50% of the peak tensile stress, the loading ended. To collect the actual elongation of the middle part of Specimen 1, two high-precision displacement gauges were fixed on Specimen 1 using a special bracket, and the gauge length was 200 mm. To ensure the universality and accuracy of the data, three specimens 1 were used for the axial tensile test in each example and comparative example. The structure of Specimen 1 is specifically shown in Appendix Figure 2 ~Appendix Figure 5 as shown. The overall structure of Specimen 1 was made by the prior art and will not be described in detail here.

[0059] Table 4.2 details the key information of the axial tensile curves of each Specimen 1 of the above-mentioned examples and comparative examples, including the elastic limit (f Ute ), elastic strain (ε Ute ), tensile strength (f Utu ), ultimate tensile strain (ε Utu ), and strain hardening rate (f Utu / f Ute ). As shown in the figure, there are significant differences in the axial tensile strain behavior among different groups. The experimental results show that after adding PS particles, the tensile performance of UHPC has been significantly improved.

[0060] Table 4.2 Detailed parameters of axial tensile performance at 28 days

[0061]

[0062] Table 4.3 UHPC crack parameters

[0063]

[0064]

[0065] In the above table, F2.0-1 represents the first UHPC specimen with a fiber doping content of 2% without adding PS particles in Comparative Example 1, F2.0-2 represents the second UHPC specimen with a fiber doping content of 2% without adding PS particles in Comparative Example 1, and F2.0-3 represents the third UHPC specimen with a fiber doping content of 2% without adding PS particles in Comparative Example 1. PS1-1 represents the first UHPC specimen with a fiber doping content of 2% and a PS particle content of 1% in Example 2, PS1-2 represents the second UHPC specimen with a fiber doping content of 2% and a PS particle content of 1% in Example 2, and PS1-3 represents the third UHPC specimen with a fiber doping content of 2% and a PS particle content of 1% in Example 2. F2.4-1 represents the first UHPC specimen with a fiber doping content of 2.4% without adding PS particles, and the meanings of the rest of the parameter names are the same as above. In the above table, when the parameters change in different proportions, three groups of tests are carried out to ensure the accuracy of the test data.

[0066] According to the data of the above F2.4-1, F2.4-2 and F2.4-3 groups, it can be seen that for the F2.4 group where the rest of the parameters are the same as those of the F2.0 group except that the fiber doping content is increased from 2.0% to 2.4%, the PS particles have a good improvement effect on the axial tensile mechanical properties of UHPC, approaching the effect of fibers on the axial tensile properties of UHPC, and the PS particles can be used to improve the axial tensile mechanical properties of UHPC.

[0067] It can be seen from the data in the above table that after adding PS particles, the tensile strength of UHPC has increased significantly. The average tensile strengths of the PS1, PS2, and PS4 groups are 10.17 MPa, 11.58 MPa, and 9.37 MPa respectively, which are increased by 17.2%, 33.4%, and 7.9% respectively compared with the control group. The tensile strength shows a trend of first increasing and then decreasing with the increase of the PS content. In this experiment, the tensile strength reaches the maximum value of 11.58 MPa when the PS particle content is 2%. The elastic limits of the PS1 and PS2 groups also increase slightly compared with the control group, by 3.2% and 5.5% respectively. However, when the PS particle content continues to increase to 4%, the elastic limit decreases, and the elastic limit of the PS4 group decreases by 3.8% compared with the control group. However, compared with the change in the ultimate tensile strength, the change in the elastic limit after adding PS particles is less obvious.

[0068] At the optimal dosage of 2%, the ultimate tensile strain increased by 174.8% compared to the control group without PS particles. The introduction of PS particles optimized the distribution of steel fibers, making the fibers more inclined to align along the pouring direction and the tensile stress direction, thus enhancing the bridging effect of the fibers. After adding PS particles, UHPC showed a more obvious tensile strain strengthening effect in the axial tensile test, presenting a multi-crack cracking mode, which not only enhanced the strain capacity of the material but also improved its potential self-healing ability. Although the addition of PS particles led to an increase in the number of cracks in UHPC, its crack width control ability was improved, and the average crack width under the ultimate tensile strain state decreased. The incorporation of PS particles significantly increased the ultimate tensile strain of UHPC, which demonstrated the effectiveness of PS particles in improving the ductility of UHPC materials. The dosage of PS particles had a significant impact on the mechanical properties of UHPC, and there was an optimal incorporation ratio. That is, at a volume dosage of 2%, UHPC exhibited the best tensile properties and ductility. Generally speaking, UHPC incorporated with PS particles showed significant advantages in terms of tensile mechanical properties, fiber distribution optimization, strain strengthening ability, crack width control, and ultimate tensile strain improvement.

[0069] For other reagents with similar properties and the selection of similar reaction parameters, those skilled in the art can determine the above based on common general knowledge. The above are only examples of the present invention, and common general knowledge such as specific structures, characteristics, and reactant ratios known in the art are not described in detail here. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can be made, such as simply adjusting the parameter selection within or near the specified parameter range. These should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to explain the content of the claims.

Claims

1. A method for preparing high-performance fiber concrete mixed with PS particles, characterized in that: include: Step 1: Prepare UHPC premix; Step 2: Dry mix the UHPC premix evenly; Step 3: Keep the mixer running, add water to the mixed powder, and continue stirring; Step 4: Disperse the steel fibers, add the dispersed steel fibers into the stirring pot, and continue stirring; Step 5: Disperse the PS particles, put the dispersed PS particles into the stirring pot, and continue stirring for a preset time; Step 6: After the mixing is completed, add the mixture to the steel mold coated with the coating agent; Step 7: After pouring is completed, the specimen is allowed to stand and form, then demoulded and cured.

2. The method for preparing high-performance fiber concrete mixed with PS particles according to claim 1, characterized in that: The PS particles are surface hydrophobic PS particles, the particle size of the PS particles is 3-4 mm, the particle density is 900-1100 kg / m3, the dosage of the PS particles in the test piece is 1%-4%, and the particle size of the fine aggregate in the UHPC premix is ​​0.1-0.3 mm.

3. The method for preparing high-performance fiber concrete mixed with PS particles according to claim 1, characterized in that: In step 2, all powders except quartz sand are first stirred and mixed, and then quartz sand is added and stirred and mixed.

4. The method for preparing high-performance fiber concrete mixed with PS particles according to claim 3, characterized in that: In step 2, all powders except quartz sand are first stirred and mixed for 1 to 3 minutes at a dry mixing speed of 90 to 110 rpm / min, and then quartz sand is added and stirred and mixed for 1 to 2 minutes.

5. The method for preparing high-performance fiber concrete mixed with PS particles according to claim 3, characterized in that: The quartz sand in step 2 is processed into super-hydrophobic quartz sand by a mixing method.

6. The method for preparing high-performance fiber concrete mixed with PS particles according to claim 1, characterized in that: After adding the steel fiber in step 4, the stirring speed is adjusted to 190-210 rpm / min and stirred for 2-5 minutes.

7. The method for preparing high-performance fiber concrete mixed with PS particles according to claim 1, characterized in that: The steel fibers are end hook-shaped copper-plated fine steel fibers, and the content of the end hook-shaped copper-plated fine steel fibers in the test piece is 1% to 2%.

8. The method for preparing high-performance fiber concrete mixed with PS particles according to claim 1, characterized in that: In step 7, the test piece is placed in a concrete curing room for curing at a curing temperature of 25-28° C. and a humidity of 96%-99%.

9. The method for preparing high-performance fiber concrete mixed with PS particles according to claim 1, characterized in that: In the step 7, after pouring, the surface of the test piece is covered with a plastic film.

10. The method for preparing high-performance fiber concrete mixed with PS particles according to claim 1, characterized in that: The reinforcement ratio of the specimen in step 7 is 2.5% to 5.0%, and the water-cement ratio of the specimen is 0.2 to 0.3.

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