A method for evaluating fiber uniformity of polypropylene fiber concrete

Abstract

The present invention provides a fiber uniformity evaluation method for polypropylene fiber concrete. In view of the high requirements for fiber dispersion uniformity in polypropylene fiber concrete tests, the fiber uniformity in the polypropylene fiber concrete test is ensured from two aspects of polypropylene fiber dosage and mixing process by designing experiments and optimizing processes. The polypropylene fiber dosage interval is determined and the dosage gradient is divided according to the requirements. The fiber uniformity value of polypropylene fiber under an incompatible volume dosage is determined by comprehensively analyzing the dispersion of polypropylene fibers during the mixing process, the dispersion of polypropylene fibers in cement slump tests and cement expansion tests, and the dispersion of polypropylene fibers in a vibration test. The fiber uniformity of the polypropylene fiber under an incompatible volume dosage is ensured by comprehensively considering construction and workability, and the undesirable volume dosage gradient is determined. The method can provide an effective reference for ensuring the mixing uniformity of the fiber concrete and has high operability.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of civil engineering technology, and in particular to a method for evaluating fiber uniformity of polypropylene fiber concrete. Background Art

[0002] Polypropylene fiber is the earliest synthetic fiber used for concrete reinforcement. Polypropylene fiber has low density, small single filament diameter, and low elastic modulus, but offers advantages such as high elongation, high tensile strength, and acid and alkali resistance. It effectively combines with cement concrete, improving its crack resistance. Compared to steel fiber, polypropylene fiber is less expensive and offers a high cost-effective approach to crack prevention. With increasing demands for bridge spans and durability, research on polypropylene fiber-reinforced concrete is actively underway.

[0003] At present, research on polypropylene fiber concrete often involves the preparation of polypropylene fiber concrete specimens with different dosages. However, due to the hydrophobicity of polypropylene fibers, when the fiber dosage is high, polypropylene fibers are not easy to diffuse naturally in water or mortar, and are prone to uneven distribution and agglomeration, which harms the general mechanical properties of cement concrete specimens. Its crack resistance cannot achieve the expected effect, making it difficult to achieve the experimental purpose. Summary of the Invention

[0004] In view of this, it is necessary to provide a fiber uniformity evaluation method for polypropylene fiber concrete to solve the problem in the existing technology that polypropylene fibers are not easy to diffuse naturally in water or mortar, and are prone to uneven distribution and agglomeration, which harms the general mechanical properties of cement concrete specimens and its crack resistance cannot achieve the expected effect, making it difficult to achieve the experimental purpose.

[0005] To solve the above technical problems, an embodiment of the present invention provides a method for evaluating fiber uniformity of polypropylene fiber concrete, comprising:

[0006] Determining a volumetric dosage range of the polypropylene fiber, and determining a plurality of volumetric dosage gradient values ​​according to the volumetric dosage range;

[0007] Prepare polypropylene fiber concrete respectively according to the plurality of volumetric dosage gradient values, and obtain a first fiber distribution index in the polypropylene fiber concrete corresponding to each volumetric dosage gradient value;

[0008] Performing a concrete slump test and a concrete expansion test on the polypropylene fiber concrete, monitoring and analyzing the mixing uniformity of the polypropylene fibers in the concrete slump test and the concrete expansion test according to a water washing method, and determining a second fiber distribution index of the polypropylene fiber concrete corresponding to each volumetric dosage gradient value;

[0009] Analyzing the mixing uniformity of the polypropylene fibers in the polypropylene fiber concrete according to the concrete vibration method, and determining the third fiber distribution index corresponding to each volumetric dosage gradient value;

[0010] The fiber uniformity value of the polypropylene fiber concrete corresponding to each volumetric dosage gradient value is determined according to the first fiber distribution index, the second fiber distribution index, and the third fiber distribution index.

[0011] In some possible implementations, preparing polypropylene fiber concrete according to the plurality of volumetric dosage gradient values ​​specifically includes:

[0012] The solid components in the concrete are mixed according to the mix ratio and then dry mixed;

[0013] After the mixture is evenly mixed, dry polypropylene fibers are added according to the volumetric dosage gradient value and dry-mixed again until the mixing uniformity of the polypropylene fibers reaches the preset dry-mixing standard;

[0014] Water is added according to the mixing ratio to perform wet mixing until the mixing uniformity of the polypropylene fibers reaches a preset wet mixing standard.

[0015] In some possible implementations, the solid components in the concrete are dry-mixed according to a mix ratio, dry polypropylene fibers are added after the mixture is uniformly mixed, and dry-mixed again until the mixing uniformity of the polypropylene fibers reaches a preset dry-mixing standard, specifically including:

[0016] Conduct moisture content tests on sand and stone in concrete aggregates and adjust the concrete mix ratio according to the moisture content;

[0017] Add sand, stone, cement, fly ash and mineral powder into the mixer according to the adjusted mix ratio, and perform the first dry mixing according to the preset first dry mixing time;

[0018] Add dry polypropylene fiber, cover the mixer inlet with plastic film, and perform a second dry mixing according to the preset second dry mixing time; stop stirring after the preset second dry mixing time is reached, sample the stirred mixture and test the dry mixing uniformity of the polypropylene fiber. If it is determined that the dry mixing uniformity meets the preset dry mixing standard, the dry mixing is completed.

[0019] In some possible implementations, after sampling the stirred mixture and detecting the dry mixing uniformity of the polypropylene fibers, the method further includes:

[0020] If the dry mixing uniformity is determined to be lower than a preset dry mixing standard, the dry mixing time is extended according to a preset time increment;

[0021] The mixture after the dry mixing time is extended is sampled, and the dry mixing uniformity of the polypropylene fiber is tested. If it is judged that the dry mixing uniformity is lower than the preset dry mixing standard, the dry mixing time is recorded and the corresponding volumetric dosage gradient value is marked.

[0022] In some possible implementations, water is added according to the mixing ratio to perform wet mixing until the mixing uniformity of the polypropylene fibers reaches a preset wet mixing standard, specifically including:

[0023] Determine the amount of water to be added according to the mix ratio, and divide the water into the first part of water and the second part of water according to the preset ratio;

[0024] Adding the first portion of water to the dry-mixed mixture, and performing the first wet mixing according to the preset first wet mixing time;

[0025] After mixing the second portion of water with the water reducing agent, add the mixture to the mixture after the first wet mixing, and perform the second wet mixing according to the preset second wet mixing time;

[0026] After reaching the preset second wet mixing time, stirring is stopped, the stirred mixture is sampled and the wet mixing uniformity of the polypropylene fiber is tested. If it is determined that the wet mixing uniformity meets the preset wet mixing standard, the wet mixing is completed.

[0027] In some possible implementations, after sampling the stirred mixture and detecting the uniformity of the wet mixing of the polypropylene fibers, the method further includes:

[0028] If the wet mixing uniformity is determined to be lower than a preset wet mixing standard, the wet mixing time is extended according to a preset time increment;

[0029] The mixture after the wet mixing time is extended is sampled, and the wet mixing uniformity of the polypropylene fiber is tested. If it is judged that the wet mixing uniformity is lower than the preset wet mixing standard, the wet mixing time is recorded and the corresponding volumetric dosage gradient value is marked.

[0030] In some possible implementations, obtaining the first fiber distribution index in the polypropylene fiber concrete corresponding to each volumetric dosage gradient value specifically includes:

[0031] The first fiber distribution index is determined according to the mixing uniformity of the polypropylene fibers during dry mixing and the mixing uniformity of the polypropylene fibers during wet mixing; the mixing uniformity includes a fiber distribution uniformity index value and a fiber agglomeration index value.

[0032] In some possible implementations, the mixing uniformity of the polypropylene fibers in the polypropylene fiber concrete is analyzed according to the concrete vibration method to determine the third fiber distribution index, specifically including:

[0033] The polypropylene fiber concrete is molded and vibrated using a vibrating platform or a vibrating rod to form a polypropylene fiber concrete specimen; a forming index and a surface fiber agglomeration index of the polypropylene fiber concrete specimen are determined; and a third fiber distribution index is determined based on the forming index and the surface fiber agglomeration index.

[0034] In some possible implementations, the polypropylene fiber concrete is molded and vibrated using a vibrating platform or a vibrating rod, specifically including:

[0035] The polypropylene fiber concrete is divided into a first layer of polypropylene fiber concrete and a second layer of polypropylene fiber concrete;

[0036] The first layer of polypropylene fiber concrete is added to the specimen mold and tamped evenly with a tamping rod. Then, the second layer of polypropylene fiber concrete is added to the specimen mold and vibrated according to a preset vibration time using a vibration platform to obtain a polypropylene fiber concrete specimen.

[0037] In some possible implementations, determining the forming index and the surface fiber agglomeration index of the polypropylene fiber concrete specimen includes:

[0038] The polypropylene fiber concrete specimen is subjected to a polishing treatment to determine the cement mortar precipitation state, molding state and surface fiber agglomeration state on the surface of the polypropylene fiber concrete specimen; a molding index is determined according to the cement mortar precipitation state and the molding state, and a surface fiber agglomeration index is determined according to the surface fiber agglomeration state.

[0039] In some possible implementations, after performing a polishing treatment on the polypropylene fiber concrete specimen, the method further includes:

[0040] If it is determined that cement mortar has precipitated or polypropylene fibers have agglomerated, the vibration time will be reduced according to the preset vibration time.

[0041] If it is determined that no cement mortar has precipitated, or the surface after polishing does not meet the requirements, the vibration time is increased according to the preset vibration time increment.

[0042] The beneficial effects of adopting the above embodiment are: from the two aspects of polypropylene fiber dosage and mixing process, the fiber uniformity in the polypropylene fiber concrete test is ensured by designing experiments and optimizing processes. In view of the high requirements for fiber dispersion uniformity in the polypropylene fiber concrete test, the polypropylene fiber dosage range is determined according to the requirements and the dosage gradient is divided; in the process of making polypropylene fiber concrete test blocks, the mixing process is optimized based on real-time monitoring of the mixing effect, observation of the molding effect of the polypropylene fiber concrete test blocks, and quantitative detection by the water washing method; by comprehensively analyzing the dispersion of polypropylene fibers during the mixing process, the dispersion of polypropylene fibers in the cement slump test and the cement expansion test, and the dispersion of polypropylene fibers in the vibration test, the fiber uniformity value of polypropylene fibers under unacceptable volume dosage is determined, and the fiber uniformity of the polypropylene fiber concrete test is ensured by comprehensive construction and workability and the poor volume dosage gradient is determined, which can provide an effective reference for ensuring the mixing uniformity of fiber concrete and has high operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 A schematic flow chart of an embodiment of a method for evaluating fiber uniformity of polypropylene fiber concrete provided by the present invention;

[0045] Figure 2 This is a specific flow chart of the fiber uniformity evaluation method for polypropylene fiber concrete provided by the present invention. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] Some of the blocks shown in the accompanying drawings are functional entities that do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different networks and / or processor systems and / or microcontroller systems.

[0048] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0049] At present, research on polypropylene fiber concrete often involves the preparation of polypropylene fiber concrete specimens with different dosages. However, due to the hydrophobicity of polypropylene fibers, when the fiber dosage is high, polypropylene fibers are not easy to diffuse naturally in water or mortar, and are prone to uneven distribution and agglomeration, which harms the general mechanical properties of cement concrete specimens. Its crack resistance cannot achieve the expected effect, making it difficult to achieve the experimental purpose.

[0050] Therefore, embodiments of the present invention provide a method for evaluating the fiber uniformity of polypropylene fiber concrete. This method ensures fiber uniformity during polypropylene fiber concrete testing by designing experiments and optimizing the process, taking into account the polypropylene fiber dosage and mixing process. This method will be described and illustrated below using multiple embodiments.

[0051] Figure 1 and Figure 2 A schematic flow chart of an embodiment of a method for evaluating fiber uniformity of polypropylene fiber concrete provided by the present invention is shown as follows: Figure 1 、 Figure 2 As shown in , a method for evaluating fiber uniformity of polypropylene fiber concrete comprises:

[0052] Step S1, determining a volume dosage range of polypropylene fiber, and determining a plurality of volume dosage gradient values ​​according to the volume dosage range;

[0053] Step S2: preparing polypropylene fiber concrete according to the plurality of volumetric dosage gradient values, mixing the solid components in the concrete according to a mix ratio and then dry-mixing the concrete, adding dry polypropylene fibers after the concrete is evenly mixed, and dry-mixing the concrete again until the mixing uniformity of the polypropylene fibers reaches a preset dry-mixing standard; adding water according to the mix ratio and wet-mixing the concrete until the mixing uniformity of the polypropylene fibers reaches a preset wet-mixing standard, and obtaining a first fiber distribution index in the polypropylene fiber concrete corresponding to each volumetric dosage gradient value;

[0054] Step S3, performing a concrete slump test and a concrete expansion test on the polypropylene fiber concrete, monitoring and analyzing the mixing uniformity of the polypropylene fibers in the concrete slump test and the concrete expansion test according to a water washing method, and determining a second fiber distribution index of the polypropylene fiber concrete corresponding to each volumetric dosage gradient value;

[0055] Step S4: analyzing the mixing uniformity of the polypropylene fibers in the polypropylene fiber concrete according to the concrete vibration method, and determining the third fiber distribution index corresponding to each volumetric dosage gradient value;

[0056] Step S5: determining the fiber uniformity value of the polypropylene fiber concrete corresponding to each volumetric dosage gradient value according to the first fiber distribution index, the second fiber distribution index, and the third fiber distribution index.

[0057] It's understood that concrete volumetric content refers to the volume of other materials added to one cubic meter of concrete; the impact of polypropylene fiber on concrete strength is related to its volume fraction. A gradient value refers to the uniform or uneven distribution of multiple volume parameters within a volume parameter range, from large to small or from small to large. These gradient values ​​together form a gradient table for evaluating different polypropylene fiber volume parameters. Concrete flexural toughness test specimens are prepared based on this polypropylene fiber volume parameter gradient table.

[0058] Since the dispersion uniformity of the polypropylene fiber is more difficult to control when the volume ratio of the polypropylene fiber is larger, in this embodiment, the dosage range should be avoided from being set within a higher volume ratio range, and the test groups with higher volume ratio dosages should be recorded and processed with emphasis.

[0059] In this embodiment, dry mixing refers to stirring and mixing the solid components in the concrete composition without adding water or other liquid additives, and wet mixing refers to adding water and admixtures to the stirred concrete and stirring and mixing them.

[0060] During concrete mixing, gravel, cement powder, and fiber filaments have their own properties, which can cause them to clump together. In particular, some polymer fibers are difficult to disperse during mixing, significantly impacting concrete mixing efficiency and reducing concrete performance. Therefore, in this embodiment, the uniformity of the polypropylene fiber mix includes both fiber distribution and fiber clumping.

[0061] Compared with the existing technology, in view of the higher requirements for fiber dispersion uniformity in polypropylene fiber concrete tests, the fiber uniformity in polypropylene fiber concrete tests is ensured from the two aspects of polypropylene fiber dosage and mixing process by designing experiments and optimizing processes. The polypropylene fiber dosage range is determined according to the requirements and the dosage gradient is divided. By comprehensively analyzing the dispersion of polypropylene fibers during mixing, the dispersion of polypropylene fibers in cement slump test and cement expansion test, and the dispersion of polypropylene fibers in vibration test, the fiber uniformity value of polypropylene fibers under unacceptable volume dosage is determined. The fiber uniformity of polypropylene fiber concrete tests is ensured by comprehensively considering construction and workability and the poor volume dosage gradient is determined. This can provide an effective reference for ensuring the mixing uniformity of fiber concrete and has high operability.

[0062] Based on the above embodiment, as a preferred implementation, the solid components in the concrete are dry-mixed according to the mix ratio, dry polypropylene fibers are added after the mixing is uniform, and dry-mixed again until the mixing uniformity of the polypropylene fibers reaches a preset dry-mixing standard, specifically comprising:

[0063] Conduct moisture content test on sand and stone in concrete aggregate, and adjust concrete mix ratio according to moisture content; according to requirements, the mix ratio of plain concrete can be designed in accordance with (JGJ55-2011) "Code for Design of Ordinary Concrete Mix Ratio", and its composition includes cement, fly ash, stone, sand, mineral powder, water, and water reducer; among them, cement is Portland cement, fly ash is Class F Grade I fly ash, stone as coarse aggregate is 5-20mm continuously graded crushed stone, and sand as fine aggregate can be 0-4.75mm machine-made sand. The mineral powder is S95 grade mineral powder, and the water reducer is polycarboxylate water reducer. The volume content range of polypropylene fiber should be set according to the specific test purpose requirements, and the preferred volume content range is 0.10% to 2.0%. The volume content range should be evenly divided, and the volume parameter gradient value should be no less than 5 groups. In addition, a control group without polypropylene fiber should be set. The moisture content of aggregate can be tested in accordance with (GB / T50080-2016) "Test Method for Performance of Ordinary Concrete Mixtures", and the mix ratio can be adjusted according to the moisture content.

[0064] According to the adjusted mix ratio, sand, stone, cement, fly ash and mineral powder are added into the mixer, and the first dry mixing is carried out according to the preset first dry mixing time.

[0065] Add dry polypropylene fiber, and use a plastic film to cover the mixer inlet to prevent the polypropylene fiber from floating out during the dry mixing process. Perform a second dry mixing according to a preset second dry mixing time. After the preset second dry mixing time is reached, stop stirring, sample the stirred mixture, and test the dry mixing uniformity of the polypropylene fiber. If it is determined that the dry mixing uniformity meets the preset dry mixing standard, the dry mixing is completed. In this embodiment, it is necessary to quantify the mixing uniformity. The numerical value of the mixing uniformity can be obtained by direct instrument detection, or the mixing uniformity can be determined by image recognition.

[0066] Based on the above embodiment, as a preferred embodiment, after sampling the stirred mixture and detecting the dry mixing uniformity of the polypropylene fiber, the method further includes:

[0067] If the dry mixing uniformity is determined to be lower than a preset dry mixing standard, the dry mixing time is extended according to a preset time increment;

[0068] The mixture after the dry mixing time is extended is sampled, and the dry mixing uniformity of the polypropylene fiber is tested. If it is judged that the dry mixing uniformity is lower than the preset dry mixing standard, the dry mixing time is recorded and the corresponding volumetric dosage gradient value is marked.

[0069] In this embodiment, after the predetermined dry mixing time is reached, the mixer is powered off and a small amount of the mixture is sampled to test the mixing performance. If the aggregate and polypropylene fibers are uniformly mixed without clumping, the mixing uniformity of the dosage gradient is considered good. If the polypropylene fibers are unevenly distributed and clumping occurs, the mixing uniformity of the dosage gradient is considered insufficient and the dry mixing time needs to be extended. Fiber dosages that still exhibit low uniformity after extended mixing time are recorded.

[0070] Based on the above embodiment, as a preferred embodiment, water is added according to the mixing ratio to perform wet mixing until the mixing uniformity of the polypropylene fibers reaches a preset wet mixing standard, which specifically includes:

[0071] Divide the water into the first portion of water and the second portion of water according to a preset ratio; for example, the first portion of water accounts for 90% and the second portion of water accounts for 10%.

[0072] Adding the first portion of water to the dry-mixed mixture, and performing the first wet mixing according to the preset first wet mixing time;

[0073] The second portion of water is mixed with the water reducer and then added, and a second wet mixing is performed according to the preset second wet mixing time;

[0074] After reaching the preset second wet mixing time, stirring is stopped, the stirred mixture is sampled and the wet mixing uniformity of the polypropylene fiber is tested. If it is judged that the wet mixing uniformity meets the preset wet mixing standard, the wet mixing is completed; if it is judged that the wet mixing uniformity is lower than the preset wet mixing standard, the wet mixing time is extended according to the preset time increment.

[0075] The mixture after the wet mixing time is extended is sampled, and the wet mixing uniformity of the polypropylene fiber is tested. If it is judged that the wet mixing uniformity is lower than the preset wet mixing standard, the wet mixing time is recorded and the corresponding volumetric dosage gradient value is marked.

[0076] After the predetermined wet mixing time is reached, the power supply of the mixer is cut off, and a small amount of polypropylene fiber concrete is taken from the mixer to check the mixing condition. If it is detected that there is no fiber clumping in the sampled fiber concrete and it is evenly distributed in the aggregate, it is judged that the mixing uniformity of the polypropylene fiber concrete is good. If the mixing uniformity is poor and clumping occurs, the mixing time should be increased as appropriate, and the fiber content whose mixing uniformity is still low after the mixing time is extended should be recorded.

[0077] Based on the above embodiment, as a preferred implementation, obtaining the first fiber distribution index in the polypropylene fiber concrete corresponding to each volumetric dosage gradient value specifically includes:

[0078] The first fiber distribution index is determined according to the mixing uniformity of the polypropylene fibers during dry mixing and the mixing uniformity of the polypropylene fibers during wet mixing; the mixing uniformity includes a fiber distribution uniformity index value and a fiber agglomeration index value.

[0079] On the basis of the above embodiment, the distribution of polypropylene fibers in the dry mixing and wet mixing processes is digitized to obtain the dry mixing uniformity and the wet mixing uniformity. The dry mixing uniformity and the wet mixing uniformity are linearly weighted added according to preset weights to obtain a first fiber distribution index.

[0080] In this embodiment, the detection method of the second fiber distribution index is the same as that in the above embodiment. The numerical value of the mixing uniformity can be obtained by direct instrument detection, or by image recognition method, in which the number and size of fiber clumps are used as a negative parameter item to deduct points from the fiber distribution index.

[0081] Based on the above embodiment, as a preferred implementation, the mixing uniformity of the polypropylene fibers in the polypropylene fiber concrete is analyzed according to the concrete vibration method to determine the third fiber distribution index, which specifically includes:

[0082] The polypropylene fiber concrete is molded and divided into a first layer of polypropylene fiber concrete and a second layer of polypropylene fiber concrete; the first layer of polypropylene fiber concrete is added into the specimen mold, and after being tamped evenly with a tamping rod, the second layer of polypropylene fiber concrete is added into the specimen mold, and vibrated according to a preset vibration time using a vibration platform to obtain a polypropylene fiber concrete specimen.

[0083] The polypropylene fiber concrete is molded and vibrated using a vibrating platform or a vibrating rod to form a polypropylene fiber concrete specimen; the molding index and the surface fiber agglomeration index of the polypropylene fiber concrete specimen are determined; the polypropylene fiber concrete specimen is polished to determine the cement mortar precipitation state, molding state and surface fiber agglomeration state on the surface of the polypropylene fiber concrete specimen; the molding index is determined based on the cement mortar precipitation state and the molding state, and the surface fiber agglomeration index is determined based on the surface fiber agglomeration state.

[0084] A third fiber distribution index is determined according to the forming index and the surface fiber agglomeration index.

[0085] If it is determined that cement mortar has precipitated or polypropylene fibers have agglomerated, the vibration time is reduced according to the preset vibration time.

[0086] If it is determined that no cement mortar has precipitated, or the surface after polishing does not meet the requirements, the vibration time is increased according to the preset vibration time increment.

[0087] If cement slurry is precipitated, the specimen is full as a whole, and can be polished relatively smoothly, it is judged that the polypropylene fiber uniformity is good; if the vibration effect is poor, it is difficult to polish, and the surface fiber agglomeration phenomenon is serious, the fiber content should be recorded.

[0088] In this embodiment, the molding conditions of the polypropylene fiber concrete specimens were analyzed, including the cement slurry precipitation, the molding conditions of the specimens (compared with the standard specimens), and the agglomeration of the polypropylene fibers, to further evaluate the uniformity of fiber dispersion.

[0089] Based on the above embodiment, as a preferred implementation, the first fiber distribution index, the second fiber distribution index, and the third fiber distribution index can be linearly or exponentially added to determine the fiber uniformity value of the polypropylene fiber concrete corresponding to each volumetric dosage gradient value, thereby providing a reference for the volumetric dosage of the polypropylene fiber.

[0090] In order to verify the effectiveness of the method of the embodiment of the present invention, the bending toughness test of polypropylene fiber concrete of the large-span hollow continuous rigid frame bridge polypropylene fiber concrete project is combined in this embodiment.

[0091] Step S1: Based on the experimental requirements, the C55 cement concrete required for the bridge superstructure was selected for mix ratio calculation. The mix ratio of the plain concrete was designed according to the "Code for Mix Ratio Design of Ordinary Concrete" (JGJ55-2011). The calculated results, calculated per ton, showed the following composition and content: 400 kg of cement, 40 kg of fly ash, 1104 kg of stone, 677 kg of sand, 70 kg of mineral powder, 153 kg of water, and 5.61 kg of water reducer.

[0092] According to engineering experience, the polypropylene fiber dosage suitable for crack resistance of bridge structures is approximately 0.10% to 0.50%. The proposed polypropylene fiber density is 910kg / m3, the monofilament length is 12mm, the monofilament diameter is 18 to 48μm, the breaking strength is greater than 358Mpa, and the elastic modulus is greater than 3.5Gpa. The preliminary polypropylene fiber dosage grouping is shown in Table 1 below:

[0093] Table 1 Polypropylene fiber content gradient

[0094]

[0095]

[0096] According to this dosage gradient table, bending toughness test specimens are made. According to the requirements of the "Technical Specifications for the Application of Fiber Concrete" (JGJ / T221-2010), when the fiber length is not more than 40mm, prism specimens with a size of 100mm×100mm×400mm should be used, and 3 specimens should be prepared for each dosage.

[0097] The larger the volume ratio of the polypropylene fiber, the more difficult it is to control the uniformity of fiber dispersion. In this embodiment, in addition to not setting the dosage range within a higher volume ratio range, the test group with a higher volume ratio dosage should also be recorded and processed carefully.

[0098] S2. Use a mixer to mix the raw materials, monitor the dispersion of the fibers in the aggregate and binder at each mixing stage, and optimize the mixing process in real time. The specific implementation steps are as follows:

[0099] S21. Test the moisture content of sand and stone in aggregate in accordance with (GB / T50080-2016) "Test Method for Performance of Ordinary Concrete Mixtures" and adjust the mix ratio according to the moisture content.

[0100] S22. Add sand, stone, cement, fly ash and mineral powder into a small compulsory mixer and dry mix for 3 minutes.

[0101] S23. Add dry polypropylene fiber and cover the mixer inlet with plastic film, and then dry mix for 3 minutes.

[0102] S24. After the predetermined dry mixing time has elapsed, the mixer is powered off. A small amount of the mixture is taken from the mixer to observe the mixing progress. If the aggregate and polypropylene fiber are evenly mixed without obvious clumping, the mixing uniformity of the dosage gradient is considered good. If the polypropylene fiber is unevenly distributed and clumping occurs, the mixing uniformity of the dosage gradient is considered insufficient and the dry mixing time needs to be extended. Fiber dosages that still show low uniformity after extended mixing time are recorded.

[0103] S25, add 90% of the water and wet mix for 3 minutes, then add the remaining 10% of the water mixed with the water reducer, and wet mix for another 3 minutes.

[0104] S26. After the predetermined wet mixing time is reached, cut off the power supply of the mixer, take a small amount of polypropylene fiber concrete from the mixer and observe the mixing situation. If there is no obvious clumping of fibers in the sampled fiber concrete and they are evenly distributed in the aggregate, it is considered that the polypropylene fiber concrete has a good mixing uniformity. If the mixing uniformity is poor and clumping occurs, increase the mixing time as appropriate, and record the fiber content if the mixing uniformity is still low after the extended mixing time.

[0105] Before mixing the test specimens, please note that the aggregate used in the test should be tested for moisture content in accordance with (GB / T50080–2016) "Test Methods for Properties of Ordinary Concrete Mixtures," and the amount of water should be adjusted based on the moisture content. Before dry mixing, ensure that the inner wall of the mixing drum is moist and free of visible water. The polypropylene fiber used in the test should be kept as dry as possible before mixing to maximize the grinding effect between the aggregates. When adding polypropylene fiber for dry mixing, cover the mixer feed port with plastic film to prevent the polypropylene fiber from floating out during the dry mixing process.

[0106] During mixing, the order of adding raw materials can be adjusted according to actual conditions. In principle, aggregate should be added before polypropylene fiber, and water should be added after polypropylene fiber. This is to maximize the mutual grinding effect between the aggregates on the dispersion of polypropylene fiber and prevent the undispersed polypropylene fiber from agglomerating when it comes into contact with water. If the moisture content of the aggregate used is high, cement, fly ash and other binders should be added after the aggregates, and then the polypropylene fiber should be added for dry mixing. The dry mixing time should be appropriately extended.

[0107] S3. Carry out cement slump and expansion tests and take samples for water washing to monitor the fiber dispersion uniformity.

[0108] S4. Place the mixed polypropylene fiber concrete in a mold and vibrate it using a vibrating platform or a vibrating rod. Observe the surface slurry separation and the dispersion of the polypropylene fibers on the surface. Control the vibration time and evaluate the fiber dispersion. The specific implementation steps are as follows:

[0109] S41. Add polypropylene fiber concrete into the specimen mold in two layers. After adding the first layer of polypropylene fiber concrete, use a tamping rod to tamp it evenly before adding the second layer.

[0110] S42. Use a vibrating platform to vibrate for 10 seconds.

[0111] S43. After the predetermined vibration time is reached, cut off the power supply, use a cement scraper to polish the surface of the specimen, and observe whether there is any polypropylene fiber agglomeration or precipitation. If such a situation occurs, the vibration time should be appropriately reduced. If there is no cement mortar precipitation and it is difficult to polish the surface, the vibration time should be appropriately increased.

[0112] S44. If cement slurry is precipitated, the specimen is full as a whole, and can be polished relatively smoothly, it is considered that the polypropylene fiber uniformity is good. If the vibration effect is poor, it is difficult to polish, and the surface fiber agglomeration is serious, the fiber content should be recorded.

[0113] Summary: Taking into account the mixing of the polypropylene fiber concrete in step S2, the cement slump and expansion test results in step S3, and the specimen formation in step S4, it is concluded that in this polypropylene fiber concrete flexural toughness test, the polypropylene fibers were well dispersed in specimens with fiber content of 0-0.5%. After optimizing the mixing process, the 0.7% fiber content met the test requirements. However, even after optimizing the mixing process, the 1-2% fiber content still had difficulty achieving uniform dispersion and exhibited poor workability, requiring attention in subsequent testing. Overall, the specimens met the test requirements, ensuring the accuracy of the test results.

[0114] The above is a detailed introduction to the method and device for recommending entry and exit from a tidal river section based on ship fuel consumption provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for evaluating fiber uniformity of polypropylene fiber concrete, characterized in that: include: Determining a volumetric dosage range of the polypropylene fiber, and determining a plurality of volumetric dosage gradient values ​​according to the volumetric dosage range; Prepare polypropylene fiber concrete respectively according to the plurality of volumetric dosage gradient values, and obtain a first fiber distribution index in the polypropylene fiber concrete corresponding to each volumetric dosage gradient value; Performing a concrete slump test and a concrete expansion test on the polypropylene fiber concrete, monitoring and analyzing the mixing uniformity of the polypropylene fibers in the concrete slump test and the concrete expansion test according to a water washing method, and determining a second fiber distribution index of the polypropylene fiber concrete corresponding to each volumetric dosage gradient value; Analyzing the mixing uniformity of the polypropylene fibers in the polypropylene fiber concrete according to the concrete vibration method, and determining the third fiber distribution index corresponding to each volumetric dosage gradient value; Determining a fiber uniformity value of the polypropylene fiber concrete corresponding to each volumetric dosage gradient value according to the first fiber distribution index, the second fiber distribution index, and the third fiber distribution index; Obtaining the first fiber distribution index in the polypropylene fiber concrete corresponding to each volumetric dosage gradient value includes: Determining a first fiber distribution index based on the mixing uniformity of the polypropylene fibers during dry mixing and the mixing uniformity of the polypropylene fibers during wet mixing; the mixing uniformity includes a fiber distribution uniformity index value and a fiber agglomeration index value; The mixing uniformity of the polypropylene fibers in the polypropylene fiber concrete is analyzed according to the concrete vibration method to determine the third fiber distribution index, which specifically includes: The polypropylene fiber concrete is molded and vibrated using a vibrating platform or a vibrating rod to form a polypropylene fiber concrete specimen; a forming index and a surface fiber agglomeration index of the polypropylene fiber concrete specimen are determined; and a third fiber distribution index is determined based on the forming index and the surface fiber agglomeration index.

2. The method for evaluating fiber uniformity of polypropylene fiber concrete according to claim 1, characterized in that: The method of preparing polypropylene fiber concrete according to the plurality of volumetric dosage gradient values ​​specifically includes: The solid components in the concrete are mixed according to the mix ratio and then dry mixed; After the mixture is evenly mixed, dry polypropylene fibers are added according to the volumetric dosage gradient value and dry-mixed again until the mixing uniformity of the polypropylene fibers reaches the preset dry-mixing standard; Water is added according to the mixing ratio to perform wet mixing until the mixing uniformity of the polypropylene fibers reaches a preset wet mixing standard.

3. The method for evaluating fiber uniformity of polypropylene fiber concrete according to claim 2, wherein the solid components in the concrete are dry-mixed according to a mix ratio, dry polypropylene fibers are added after the concrete is mixed uniformly, and dry-mixed again until the mixing uniformity of the polypropylene fibers reaches a preset dry-mixing standard, specifically comprising: Conduct moisture content tests on sand and stone in concrete aggregates and adjust the concrete mix ratio according to the moisture content; Add sand, stone, cement, fly ash and mineral powder into the mixer according to the adjusted mix ratio, and perform the first dry mixing according to the preset first dry mixing time; Add dry polypropylene fiber, cover the mixer inlet with plastic film, and perform a second dry mixing according to the preset second dry mixing time; After the preset second dry mixing time is reached, stirring is stopped, the stirred mixture is sampled and the dry mixing uniformity of the polypropylene fiber is tested. If it is determined that the dry mixing uniformity meets the preset dry mixing standard, the dry mixing is completed.

4. The method for evaluating fiber uniformity of polypropylene fiber concrete according to claim 3, characterized in that: After sampling the stirred mixture and detecting the dry mixing uniformity of the polypropylene fibers, the method further comprises: If the dry mixing uniformity is determined to be lower than a preset dry mixing standard, the dry mixing time is extended according to a preset time increment; The mixture after the dry mixing time is extended is sampled, and the dry mixing uniformity of the polypropylene fiber is tested. If it is judged that the dry mixing uniformity is lower than the preset dry mixing standard, the dry mixing time is recorded and the corresponding volumetric dosage gradient value is marked.

5. The method for evaluating fiber uniformity of polypropylene fiber concrete according to claim 2, characterized in that: Adding water according to the mixing ratio to perform wet mixing until the mixing uniformity of the polypropylene fibers reaches a preset wet mixing standard, specifically comprising: Determine the amount of water to be added according to the mix ratio, and divide the water into the first part of water and the second part of water according to the preset ratio; Adding the first portion of water to the dry-mixed mixture, and performing the first wet mixing according to the preset first wet mixing time; After mixing the second portion of water with the water reducing agent, add the mixture to the mixture after the first wet mixing, and perform the second wet mixing according to the preset second wet mixing time; After reaching the preset second wet mixing time, stirring is stopped, the stirred mixture is sampled and the wet mixing uniformity of the polypropylene fiber is tested. If it is determined that the wet mixing uniformity meets the preset wet mixing standard, the wet mixing is completed.

6. The method for evaluating fiber uniformity of polypropylene fiber concrete according to claim 5, characterized in that: After sampling the stirred mixture and detecting the uniformity of the wet mixing of the polypropylene fibers, the method further comprises: If the wet mixing uniformity is determined to be lower than a preset wet mixing standard, the wet mixing time is extended according to a preset time increment; The mixture after the wet mixing time is extended is sampled, and the wet mixing uniformity of the polypropylene fiber is tested. If it is judged that the wet mixing uniformity is lower than the preset wet mixing standard, the wet mixing time is recorded and the corresponding volumetric dosage gradient value is marked.

7. The method for evaluating fiber uniformity of polypropylene fiber concrete according to claim 1, characterized in that: The polypropylene fiber concrete is molded and vibrated using a vibrating platform or a vibrating rod, specifically comprising: The polypropylene fiber concrete is divided into a first layer of polypropylene fiber concrete and a second layer of polypropylene fiber concrete; The first layer of polypropylene fiber concrete is added to the specimen mold and tamped evenly with a tamping rod. Then, the second layer of polypropylene fiber concrete is added to the specimen mold and vibrated according to a preset vibration time using a vibration platform to obtain a polypropylene fiber concrete specimen.

8. The method for evaluating fiber uniformity of polypropylene fiber concrete according to claim 7, characterized in that: Determine the forming index and surface fiber agglomeration index of polypropylene fiber concrete specimens, including: The polypropylene fiber concrete specimen is subjected to a polishing treatment to determine the cement mortar precipitation state, molding state and surface fiber agglomeration state on the surface of the polypropylene fiber concrete specimen; a molding index is determined according to the cement mortar precipitation state and the molding state, and a surface fiber agglomeration index is determined according to the surface fiber agglomeration state.

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