Determination Method of Fiber Parameters in Crack-Resistant Cement-Stabilized Macadam

Abstract

The present invention provides a method for determining fiber parameters in crack-resistant cement stabilized macadam. The method includes the following steps: respectively determining the minimum diameter and the maximum diameter of the fiber; obtaining the average value of the minimum diameter and the maximum diameter to determine the target diameter of the fiber; incorporating fibers of different lengths into the cement stabilized macadam to prepare a first group of semi-circular bending specimens, and determining the target length of the fiber by detecting the fracture energy of the first group of semi-circular bending specimens; incorporating the fibers with the determined target diameter and target length into the cement stabilized macadam at different dosages to prepare a second group of semi-circular bending specimens, and determining the target dosage of the fiber by detecting the fracture energy of the second group of semi-circular bending specimens. The method for determining fiber parameters of the crack-resistant cement stabilized macadam of the present invention improves the dispersibility and the tensile property of the fiber, can enhance the crack resistance of the cement stabilized macadam, and the crack resistance is significantly improved.

Description

Technical Field

[0001] The present invention relates to a method for determining fiber parameters in crack-resistant cement stabilized macadam, belonging to the field of road engineering materials. Background Art

[0002] The raw materials of semi-rigid base courses are convenient to obtain, have good integrity and strong stability. Therefore, semi-rigid base asphalt pavements are widely used in China. Cement stabilized macadam is the most widely used structural form in semi-rigid base courses. However, cement stabilized macadam is sensitive to temperature and humidity and has low tensile strength. When the external environment changes, it is easy to cause large shrinkage deformation of the structure, resulting in the problem of base course cracks. The base course cracks are reflected to the surface layer under the repeated action of vehicle loads, resulting in failures such as pumping, water damage and settlement, leading to insufficient durability of asphalt pavements. Strengthening the crack resistance of semi-rigid base courses is the key to improving the service life of roads and ensuring road safety. Therefore, crack-resistant cement stabilized macadam has been a research hotspot in recent years.

[0003] Crack-resistant cement stabilized macadam is to incorporate modifiers such as fibers and rubber powder into cement stabilized macadam materials. The fibers will have a firm adhesion effect with cement particles and aggregates, enhancing the splitting resistance and shrinkage resistance of cement stabilized macadam. Therefore, it can significantly improve the crack resistance of the base course and extend the overall service life of the pavement.

[0004] In recent years, polypropylene fibers have been widely used due to their advantages of high strength, stable chemical properties, strong corrosion resistance and low cost. However, most of the polypropylene fibers currently used in cement stabilized macadam are fine fibers, that is, the fiber diameter is less than 100um. Fine fibers are easy to agglomerate into fiber bundles during mixing, with poor dispersibility, uneven distribution in cement stabilized macadam, difficult to play an ideal tensile role, and lacking a unified and efficient evaluation method when selecting fibers. As a result, the fiber specifications used in cement stabilized macadam materials are inconsistent, and the crack resistance of cement stabilized macadam materials is difficult to determine, restricting the popularization of crack-resistant cement stabilized macadam technology.

[0005] Currently, most of the fibers added to cement stabilized macadam are fine fibers with small diameters. Although the material strength, splitting resistance and shrinkage resistance have been improved to a certain extent compared with ordinary cement stabilized macadam, the improvement effect is not ideal in actual engineering applications. During the construction process, the construction characteristics of fine fibers with small diameters are poor, not easy to disperse during mixing with the mixture, and easy to form fiber agglomerates, resulting in uneven distribution of fibers in cement stabilized macadam, affecting the improvement of the strength and anti-fatigue ability of the cement stabilized macadam base course by fibers, directly affecting the durability of the pavement and leading to the disease of fatigue cracking.

[0006] Reference Document 1 discloses a polypropylene fiber modified cement stabilized macadam and its preparation method. Among them, the polypropylene fiber modified cement stabilized macadam comprises the following components in parts by weight: aggregate 95 - 105 parts; portland cement 4.0 - 4.5 parts; modified polypropylene fiber 0.01 - 0.18 parts; water 3.5 - 4.0 parts. However, it does not involve how to determine the addition amount of the modified polypropylene fiber, which requires a large number of repetitive experiments in the preparation of the modified cement stabilized macadam, and the obtained modified cement stabilized macadam cannot ensure its optimal crack resistance ability.

[0007] Reference Document 2 discloses a crack-resistant rubber powder fiber cement stabilized macadam base material. The crack-resistant rubber powder fiber cement stabilized macadam base material comprises the following components: cement stabilized macadam, rubber powder and polypropylene fiber material. Among them, the cement stabilized macadam is composed of cement, aggregate and water, and part of the fine aggregate in the aggregate is replaced by the same mass of rubber powder. Similarly, this material also does not involve how to determine the addition amount of the modified polypropylene fiber, resulting in a large number of repetitive experiments in the preparation of the cement stabilized macadam base, and the obtained modified cement stabilized macadam cannot ensure its optimal crack resistance ability.

[0008] Reference Documents:

[0009] Reference Document 1: CN111196702A

[0010] Reference Document 2: CN108929076A Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] In view of the technical problems existing in the prior art, such as: poor fiber dispersion, difficult to accurately weigh, poor construction characteristics, etc. in the crack-resistant cement stabilized macadam, the purpose of the present invention is to provide a method for determining fiber parameters in the crack-resistant cement stabilized macadam, and by analyzing the fiber dispersion in the cement stabilized macadam, the grip force with the cement mortar, and the crack resistance ability of the cement stabilized macadam, to determine the optimal diameter, optimal length and optimal dosage of the fiber.

[0013] Solutions for Solving the Problems

[0014] The present invention provides a method for determining fiber parameters in the crack-resistant cement stabilized macadam, which comprises the following steps:

[0015] Respectively determine the minimum diameter of the fiber and the maximum diameter of the fiber;

[0016] Obtain the average value of the minimum diameter and the maximum diameter, and determine the target diameter of the fiber;

[0017] Fibers of different lengths are incorporated into cement stabilized macadam to prepare a first group of semi-circular bending specimens, and the fracture energy of the first group of semi-circular bending specimens is detected to determine the target length of the fibers;

[0018] Fibers with determined target diameter and target length are incorporated into cement stabilized macadam at different dosages to prepare a second group of semi-circular bending specimens, and the fracture energy of the second group of semi-circular bending specimens is detected to determine the target dosage of the fibers.

[0019] According to the method for determining fiber parameters in crack-resistant cement stabilized macadam according to the present invention, wherein determining the minimum diameter of the fibers comprises the following steps:

[0020] Obtain fibers of various different diameters;

[0021] After each type of fiber is respectively mixed with cement stabilized macadam, it is equally divided into two or more mass test specimens to be tested;

[0022] Separate the fibers from the cement stabilized macadam in the mass test specimens to be tested;

[0023] Obtain the difference Δm between the maximum mass m max and the minimum mass m min of the fibers in each mass test specimen of each type of fiber;

[0024] Determine the minimum diameter of the fibers based on the ratio of the difference Δm to the total weight of each type of fiber.

[0025] According to the method for determining fiber parameters in crack-resistant cement stabilized macadam according to the present invention, wherein when the difference Δm is 10% or less of the total weight of the same type of fiber, obtain the smallest fiber diameter among the fibers of different diameters, and this smallest fiber diameter is the minimum diameter of the fibers.

[0026] According to the method for determining fiber parameters in crack-resistant cement stabilized macadam according to the present invention, wherein determining the minimum diameter of the fibers further comprises the following steps:

[0027] Obtain fibers of various different diameters;

[0028] After each type of fiber is respectively mixed with cement stabilized macadam, separate the fibers from the cement stabilized macadam to obtain fiber bundles;

[0029] Determine the minimum diameter of the fibers based on the ratio of the number of fibers in the fiber bundles to the total number of each type of fiber.

[0030] Determination method of fiber parameters in crack-resistant cement stabilized macadam according to the present invention, wherein when the ratio of the number of fibers in the fiber bundle to the total number of the same kind of fibers is 15% or less, the minimum fiber diameter among fibers of different diameters is obtained, and this minimum fiber diameter is the minimum diameter of the fiber.

[0031] Determination method of fiber parameters in crack-resistant cement stabilized macadam according to the present invention, wherein determining the maximum diameter of the fiber includes the following steps:

[0032] Obtain various fibers with different diameters;

[0033] Insert fibers with different diameters into multiple groups of cement mortar respectively to obtain specimens to be held;

[0034] Detect the holding force of the specimens to be held;

[0035] Determine the maximum diameter of the fiber based on the ratio of the holding force to the cross-sectional area of the fiber.

[0036] Determination method of fiber parameters in crack-resistant cement stabilized macadam according to the present invention, wherein the fiber diameter corresponding to the maximum value of the ratio of the holding force to the cross-sectional area of the fiber is the maximum diameter of the fiber.

[0037] Determination method of fiber parameters in crack-resistant cement stabilized macadam according to the present invention, wherein in the first group of semi-circular bending specimens, the fiber length corresponding to the first group of semi-circular bending specimens with the maximum fracture energy is the target length of the fiber.

[0038] Determination method of fiber parameters in crack-resistant cement stabilized macadam according to the present invention, wherein in the second group of semi-circular bending specimens, the fiber dosage corresponding to the second group of semi-circular bending specimens with the maximum fracture energy is the target dosage of the fiber.

[0039] Determination method of fiber parameters in crack-resistant cement stabilized macadam according to the present invention, wherein the diameter of the fiber is 100 μm or more.

[0040] Effects of the invention

[0041] The determination method of fiber parameters of the crack-resistant type cement stabilized macadam of the present invention improves the dispersibility and tensile properties of the fiber, can enhance the crack resistance of the cement stabilized macadam, and the crack resistance is significantly improved. Description of the drawings

[0042] Figure 1 Shows a schematic diagram of the semi-circular bending test of the present invention;

[0043] Explanation of reference numerals :

[0044] 1: Load roller; 2: Cement stabilized macadam semi-circular bending specimen;

[0045] 3: Notch; 4: Support roller. Specific implementation manners

[0046] The following is a detailed description of the content of the present invention. The description of the technical features recorded below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0047] In this specification, the numerical range expressed by "numerical value A to numerical value B" means a range including the endpoint numerical values A and B.

[0048] In this specification, unless otherwise specified, "plural", "multiple kinds", "multiple" and the like in "plural" mean a numerical value of 2 or more.

[0049] In this specification, the terms "substantially", "generally" or "essentially" mean that the error is within 5% or within 3% or within 1% compared with the relevant perfect standard or theoretical standard.

[0050] In this specification, unless otherwise specified, "%" all represents mass percentage content.

[0051] In this specification, the meaning expressed by "can" includes the meanings of both performing a certain process and not performing a certain process.

[0052] In this specification, "optional" or "optionally" means that the subsequent described event or situation may or may not occur, and this description includes the situation where the event occurs and the situation where the event does not occur.

[0053] In this specification, the "some specific / preferred embodiments", "some other specific / preferred embodiments", "embodiments" and the like mentioned refer to the specific elements (for example, features, structures, properties and / or characteristics) related to the embodiment, which are included in at least one of the embodiments described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements can be combined in various embodiments in any suitable manner.

[0054] In this specification, unless otherwise specified, "room temperature" can be 10 - 40°C.

[0055] The present invention provides a method for determining fiber parameters in crack-resistant cement stabilized macadam, which includes the following steps:

[0056] Respectively determine the minimum diameter and the maximum diameter of the fiber;

[0057] Obtain the average value of the minimum diameter and the maximum diameter to determine the target diameter of the fiber;

[0058] Incorporate fibers of different lengths into the cement stabilized macadam to obtain a first group of semi-circular bending specimens, and determine the target length of the fiber by detecting the fracture energy of the first group of semi-circular bending specimens;

[0059] Incorporate the fibers with the determined target diameter and target length into the cement stabilized macadam at different dosages to obtain a second group of semi-circular bending specimens, and determine the target dosage of the fiber by detecting the fracture energy of the second group of semi-circular bending specimens.

[0060] The method for determining fiber parameters in the crack-resistant cement stabilized macadam of the present invention improves the dispersibility and tensile properties of the fibers, can enhance the crack-resistant ability of the cement stabilized macadam, and the crack-resistant ability is significantly improved. The present invention determines the coarse fiber parameters suitable for the cement stabilized macadam from three aspects: diameter, length, and dosage, studies the crack-resistant performance of the cement stabilized macadam material under different fiber parameters, designs a method for determining the fiber parameters in the crack-resistant cement stabilized macadam, and conducts performance evaluation research.

[0061] In the present invention, the fiber can be one or a combination of two or more of polyolefin fiber, polyester fiber, polyamide fiber, polyacrylonitrile fiber, polyvinyl formal fiber, polyvinyl chloride fiber, polyurethane fiber, etc. Preferably, polyolefin fiber is used in the present invention. The polyolefin fiber is made by melt spinning of thermoplastic elastomer, can withstand high temperature of 220 °C, has the properties of chlorine bleach resistance and strong acid and strong base treatment, and has the characteristics of extremely strong ultraviolet degradation resistance and other properties of a new type of elastic filament. Specifically, the polyolefin fiber can be polyethylene fiber, polypropylene fiber, etc. Further, due to the stable chemical properties, strong acid and alkali resistance, and low cost of polypropylene fiber, it can improve the tensile performance and shrinkage resistance of the cement stabilized macadam, and can be applied to the crack-resistant cement stabilized macadam. Therefore, polypropylene fiber is preferably used.

[0062] When the fiber diameter is relatively large, it is not easy to agglomerate during the mixing process with the crushed stone, which can improve the dispersion uniformity of the fiber in the crushed stone material, and when the fiber diameter is larger, it has stronger bending and tensile ability. Specifically, the diameter of the fiber in the present invention is above 100 μm. The inventor of the present invention found that the monofilament diameter of the fiber with a diameter above 100 μm is larger, has a stronger reinforcing effect, and the fiber with a larger diameter has better dispersion in the cement stabilized macadam, is less likely to agglomerate, and the holding force between the fiber monofilament and the cement stabilized macadam is greater. Therefore, incorporating the fiber with a larger diameter into the cement stabilized macadam can improve the crack-resistant performance and shrinkage resistance of the cement stabilized macadam base layer, and increase the durability of the road surface. However, if the fiber diameter is too large, it will cause a decrease in the number of fibers under the same fiber dosage, thereby reducing the holding force per unit area of the fiber and affecting the overall crack-resistant ability of the cement stabilized macadam.

[0063] The minimum diameter of the fiber can be determined in two ways in the present invention.

[0064] In some specific embodiments, the first method for determining the minimum diameter of the fiber includes the following steps:

[0065] Obtain fibers with various different diameters;

[0066] After mixing each fiber with cement stabilized macadam respectively, divide the mixture into two or more equal - mass test specimens to be tested;

[0067] Separate the fibers from the cement stabilized macadam in the test specimens to be tested;

[0068] Obtain the difference Δm between the maximum mass m max and the minimum mass m min of the fibers in each test specimen to be tested for each fiber;

[0069] Determine the minimum diameter of the fiber according to the ratio of the difference Δm in the total weight of each fiber.

[0070] In the present invention, after mixing the fibers and the cement stabilized macadam, by comparing the maximum mass differences between groups of fibers and observing the agglomeration end - state of the fibers under a microscope, the dispersibility of thick fibers with different diameters is evaluated to determine the minimum diameter of the fiber.

[0071] Specifically, in the present invention, the first method for determining the minimum diameter of the fiber may include the following steps:

[0072] Obtain fibers with different diameters greater than 100 μm. To more accurately determine the maximum mass m max and the minimum mass m min in the test specimens to be tested, each fiber can be divided into two or more groups. After mixing each group with cement stabilized macadam respectively, divide the cement stabilized macadam after mixing in each group into three or more equal - mass test specimens to be tested, that is, determine the maximum mass m max and the minimum mass m min in the test specimens to be tested by taking the average value;

[0073] Then soak each test specimen to be tested in water to separate the fibers from the cement stabilized macadam in the test specimen to be tested;

[0074] After drying the separated fibers, obtain the difference Δm (taking the average value of two or more groups of fibers) between the maximum mass m max and the minimum mass m min of the fibers in each test specimen to be tested for each group of fibers of each fiber;

[0075] Determine the minimum diameter of the fiber according to the ratio of the difference Δm to the total weight of the same kind of fiber.

[0076] By comparing the maximum mass difference Δm of the fibers, the smaller the value of Δm, the better the fiber dispersibility, and preliminarily evaluate the dispersibility of coarse fibers with different diameters in cement stabilized macadam. Specifically, in the present invention, when the difference Δm is less than 10% of the total weight of the same kind of fiber, obtain the smallest fiber diameter among the fibers with different diameters, and this smallest fiber diameter is the minimum diameter of the fiber. If in the same test process, the differences Δm of more than two fiber diameters are all less than 10% of the total weight of the same kind of fiber, then the diameter with the smallest difference Δm less than 10% of the total weight of the same kind of fiber can be selected as the minimum diameter. For example, when conducting the test, the differences Δm of three fiber diameters are all less than 10% of the total weight of the same kind of fiber, and the corresponding diameters are 200mm, 300mm, and 400mm respectively, then 200mm is selected as the minimum diameter of the fiber.

[0077] Furthermore, for the mixing method of cement stabilized macadam and fiber, the present invention does not make a special limitation, and some common mixing methods in the art can be used.

[0078] For the relevant gradation or parameters of the aggregate or cement stabilized macadam, the present invention does not make a special limitation and can be selected according to needs. That is, the method of the present invention is applicable to aggregates or cement stabilized macadam with any feasible gradation or parameters. For the relevant parameters of cement, the present invention does not make a special limitation and can be selected according to needs.

[0079] In some other specific embodiments, the second method for determining the minimum diameter of the fiber further includes the following steps:

[0080] Obtain fibers with a variety of different diameters;

[0081] After mixing each kind of fiber with cement stabilized macadam respectively, separate the fiber from the cement stabilized macadam to obtain a fiber bundle;

[0082] Determine the minimum diameter of the fiber according to the ratio of the number of fibers in the fiber bundle to the total number of each kind of fiber.

[0083] Specifically, in the present invention, the second method for determining the minimum diameter of the fiber may include the following steps:

[0084] Obtain fibers with different diameters of more than 100μm, which is similar to the first method, and the relevant experiments can also be carried out by taking the average value.

[0085] After mixing each type of fiber with cement stabilized macadam respectively, the fiber and the cement stabilized macadam are separated by screening to obtain fiber bundles.

[0086] By means of microscopic observation, observe the number of fiber bundles in the fiber specimen, and determine the minimum diameter of the fiber according to the ratio of the number of fibers in the fiber bundle to the total number of fibers of each type of fiber.

[0087] In the present invention, a fiber group in which three or more fibers are wound together and not completely dispersed is defined as a fiber bundle. By means of microscopic observation, observe the number of fiber bundles in the fiber specimen, and evaluate the dispersibility of thick fibers with different diameters in cement stabilized macadam by comparing the proportion of the fiber bundle in the total number of fibers.

[0088] Specifically, when the ratio of the number of fibers in the fiber bundle to the total number of fibers of the same type of fiber is 15% or less, obtain the minimum fiber diameter among different diameter fibers, and this minimum fiber diameter is the minimum diameter of the fiber. If in the same test process, the ratio of the number of fibers in the fiber bundles corresponding to two or more fiber diameters to the total number of fibers of the same type of fiber is 15% or less, then the minimum diameter among those with the ratio of the number of fibers in the fiber bundle to the total number of fibers of the same type of fiber being 15% or less can be selected as the minimum diameter. For example, during the test, the ratio of the number of fibers in three fiber bundles to the total number of fibers of the same type of fiber is 15% or less, which are 10%, 12%, and 14% respectively, and the corresponding diameters are 200mm, 300mm, and 400mm respectively. Then select 200mm as the minimum diameter of the fiber.

[0089] In some specific embodiments, determining the maximum diameter of the fiber includes the following steps:

[0090] Obtain fibers with a variety of different diameters;

[0091] Insert fibers with different diameters into multiple groups of cement mortar respectively to obtain specimens to be held;

[0092] Detect the holding force of the specimens to be held;

[0093] Determine the maximum diameter of the fiber according to the ratio of the holding force to the cross-sectional area of the fiber.

[0094] In the present invention, fine aggregate, cement and water are mixed and stirred to form cement mortar. By measuring the holding force between the fiber monofilament and the cement mortar, calculate the ratio of the holding force corresponding to different diameter fibers to the fiber cross-sectional area, evaluate the reinforcing effect of different diameter fibers in cement stabilized macadam, and determine the maximum diameter of the fiber.

[0095] When determining the maximum diameter of the fiber, since the holding force is measured, it is necessary to insert a fiber of a certain length into the cement mortar. At this time, the length of the fiber used has nothing to do with the length of the fiber used in the crack-resistant cement stabilized macadam. Specifically, when measuring the holding force, fibers with a length of 30-100 mm can be selected, inserted into the cement mortar by more than 10 mm, and then the holding force of the test piece to be held is detected. Specifically, the holding force between the fiber and the cement mortar can be measured by pulling the fiber out of the cement mortar using a tensiometer.

[0096] Furthermore, regarding the preparation method of the cement mortar, the present invention is not particularly limited and can be some common preparation methods in the art. In the present invention, fine aggregate generally refers to aggregate with a screening size of 0-2.36 mm. Regarding the relevant parameters of the cement, the present invention is not particularly limited and can be selected as needed.

[0097] Specifically, the present invention obtains the fiber diameter corresponding to the maximum value of the ratio of the holding force to the cross-sectional area of the fiber as the maximum diameter of the fiber.

[0098] Furthermore, the average value of the minimum diameter and the maximum diameter is obtained, so that the target diameter of the fiber can be determined, and this average value is the target diameter of the fiber. This target diameter is the optimal diameter of the fiber in the crack-resistant cement stabilized macadam.

[0099] In some specific embodiments, the present invention incorporates fibers with determined target diameters and different lengths into the cement stabilized macadam to obtain a first group of semi-circular bending test pieces, and determines the target length of the fiber by detecting the fracture energy of the first group of semi-circular bending test pieces. Specifically, a first group of semi-circular bending test pieces can be prepared, and the fracture energy at the time of specimen failure can be obtained through a semi-circular bending test to evaluate the influence of fiber length on the crack resistance strength of the cement stabilized macadam, and the target length of the fiber can be determined, which is the optimal length of the fiber;

[0100] Specifically, among the first group of semi-circular bending test pieces, the fiber length corresponding to the first group of semi-circular bending test pieces with the maximum fracture energy is the target length of the fiber.

[0101] Furthermore, the present invention incorporates fibers with determined target diameters and target lengths into the cement stabilized macadam at different dosages to prepare a second group of semi-circular bending test pieces, and determines the target dosage of the fiber by detecting the fracture energy of the second group of semi-circular bending test pieces. Specifically, a second group of semi-circular bending test pieces can be prepared, and the fracture energy at the time of specimen failure can be obtained through a semi-circular bending test to evaluate the influence of fiber dosage on the crack resistance strength of the cement stabilized macadam, and the target dosage of the fiber can be determined, which is the optimal dosage of the fiber;

[0102] Specifically, among the second group of semi-circular bending specimens, the fiber dosage corresponding to the second group of semi-circular bending specimens with the maximum fracture energy is the target fiber dosage.

[0103] The present invention proposes a method for determining fiber parameters based on fiber dispersibility and the anti-cracking strength of cement stabilized macadam. Compared with fine fiber anti-cracking cement stabilized macadam, the fiber dispersibility and anti-cracking performance of the anti-cracking cement stabilized macadam based on fibers are improved. The present invention can effectively improve the durability of cement stabilized macadam, and lay a theoretical foundation for guiding the application and production of polypropylene coarse fibers suitable for anti-cracking cement stabilized macadam, as well as the practical engineering application of coarse fiber type anti-cracking cement stabilized macadam.

[0104] Examples

[0105] The following will describe the implementation scheme of the present invention in detail with reference to examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the examples, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained commercially.

[0106] In the examples, the preparation method of the semi-circular bending specimens is as follows:

[0107] Fibers with different dosages are respectively and fully mixed with cement stabilized macadam;

[0108] Referring to T0843-2009 of JTG E51-2009 "Test Procedures for Inorganic Binding Material Stabilized Materials for Highway Engineering", prepare cement stabilized macadam specimens with a diameter × height of 150 mm × 150 mm. After the specimens are formed, they are cured for 7 days;

[0109] After curing, cut a cylindrical specimen with a thickness of 24.7 mm + 2 mm from the middle of the specimen, divide the specimen into two along the diameter, and cut a slit with a length of 15 mm + 0.5 mm and a width not exceeding 1.5 mm in the middle of the semi-circular bending specimen to obtain the semi-circular bending specimen.

[0110] According to the method of the present invention, the semi-circular bending test steps are as follows:

[0111] The semi-circular bending specimens are kept warm in an environmental chamber at 25°C ± 0.5°C for 2 h;

[0112] During the test and heat preservation of the specimen, the temperature of the specimen should be kept at 25°C ± 0.5°C. After the specimen is taken out of the environmental chamber, the test should be completed within 6 minutes.

[0113] Apply the initial load. First, apply an initial stress of 0.1 KN ± 0.01 KN to the specimen at a loading rate of 0.05 KN / s, and record the initial load.

[0114] After reaching the initial load of 0.1 KN, conduct the test at a rate of 50 mm / min through a linear loading control system. When the load drops below 0.1 KN, the test stops.

[0115] In the embodiment, the parameters of the cement used are shown in Table A below:

[0116] Table A

[0117]

[0118] The parameters of the aggregate used are shown in Table B below:

[0119] Table B

[0120]

[0121] The screening results of the aggregate used are shown in Table C below:

[0122] Table C

[0123]

[0124] The gradation of the cement-stabilized macadam used is shown in Table D below:

[0125] Table D

[0126]

[0127] Example 1

[0128] (1) Take five kinds of fibers with different diameters (100 μm, 200 μm, 300 μm, 400 μm, and 500 μm) respectively. Each kind of fiber is divided into 3 groups, and the mass of each group of fiber specimens is 50 g. Mix them evenly with the cement-stabilized macadam specimens. Among them, the mass of cement in each group is 250 g, the mass of aggregate is 5000 g, and the mass of water is 250 g. First, stir the aggregate and cement for 15 s, then add the fiber and stir for 15 s, and finally, add water and stir for 45 s. After mixing evenly, divide each group of specimens into four parts (A, B, C, D) with the same mass by the quartering method. Separate the fiber from the cement-stabilized macadam by the water washing method, and after drying, obtain the difference Δm between the minimum mass and the maximum mass of the three groups of fibers in each of the four parts (A, B, C, D) of the fiber. i , take the average value of the Δm of the three groups of fibers i as the Δm of this kind of fiber. The results are shown in Table 1.

[0129] Table 1 Fiber Mass Results

[0130]

[0131] As can be seen from Table 1, as the fiber diameter increases, Δm gradually decreases, the agglomerated fibers gradually decrease, and the dispersibility is better. The average values of Δm of the fibers with diameters of 200μm, 300μm, 400μm, and 500μm are all below 3.0g, and the average values of Δm of the fibers with diameters of 200μm, 300μm, 400μm, and 500μm are all below 10% of the total weight of the same kind of fiber. Among them, the fiber with a diameter of 200μm has the smallest diameter, so the fiber with a diameter of 200μm is used as the minimum diameter R of the fiber in the crack-resistant cement stabilized macadam min 。

[0132] (2) Mix the five kinds of fibers with the cement stabilized macadam material respectively. Among them, each group of fiber specimens is 10g, the cement mass is 50g, and the mass of one portion of aggregate is 1000g. First, stir the aggregate and cement for 15s, then add the fiber and stir for 15s. Separate the fiber from the cement stabilized macadam by screening, observe the number of fibers in the formed fiber bundle through a microscope, and evaluate the fiber dispersibility by the ratio of the number of fibers in the fiber bundle to the total number of fibers. The smaller the ratio, the better the dispersibility. Among them, a fiber bundle is a fiber group in which three or more fibers are wound together and not completely dispersed. The results are shown in Table 2

[0133] Table 2 Statistical results of fiber bundles

[0134]

[0135] The inventor of the present invention found that when the number of fibers in the fiber bundle / the total number of fibers is below 15%, the dispersibility is good. As can be seen from Table 2, the proportion of the fibers with a diameter of 200μm in the fiber bundles with diameters of 200μm, 300μm, 400μm, and 500μm to the total number of fibers is below 15%. Among them, the fiber with a diameter of 200μm has the smallest diameter. Therefore, the fiber with a diameter of 200μm is used as the minimum diameter R of the fiber in the crack-resistant cement stabilized macadam min 。

[0136] (3) Stir 3000 g of fine aggregate (0 - 2.36 mm), 500 g of cement, and 500 g of water evenly to make cement mortar. Divide the fibers with diameters of 200 μm, 300 μm, 400 μm, and 500 μm into 5 groups respectively (denoted as: Fiber 1 - 5), and then insert them into the five groups of cement mortar respectively. The total length of the fiber is 20 cm, and the inserted part is 5 cm. Use a tensiometer to pull the fiber out of the cement mortar to test the grip force between each group of fibers and the cement mortar. Take the average value of the grip force of each group of fibers as the final grip force F of this group. Calculate the ratio F’ of the grip force corresponding to the fibers with different diameters to the fiber cross-sectional area, and evaluate the reinforcement effect of the fibers with different diameters. The test results are shown in Table 3.

[0137] Table 3 Test results of grip force between fibers with different diameters and cement mortar

[0138]

[0139] According to Table 3, as the fiber diameter increases, the ratio F’ of the grip force to the fiber cross-sectional area first increases and then decreases. When the fiber diameter is 400 μm, the fiber grip force is the largest. Therefore, 400 μm is selected as the maximum diameter R of the fiber in the crack-resistant cement stabilized macadam. max 。

[0140] Find the minimum diameter R min and the maximum diameter R max of the average value R i =(200 + 400) / 2 = 300 μm, which is used as the optimal diameter of the fiber incorporated into the cement stabilized macadam.

[0141] (4) Select three kinds of fibers with lengths of 10 mm, 20 mm, and 30 mm and a diameter of 300 μm. Incorporate the fibers with different lengths into the cement stabilized macadam at a dosage of 1.0‰ respectively to prepare three groups of specimens. Among them, the number of specimens in each group is 3. Obtain the fracture energy Gf at the failure of the specimens through the semi-circular bending test, evaluate the influence of the fiber length on the crack resistance strength of the cement stabilized macadam, and determine the optimal fiber length. The gradation composition of the cement stabilized macadam is shown in Table 4, and the test results are shown in Table 5.

[0142] Table 4 Gradation composition of cement stabilized macadam

[0143]

[0144] Table 5 SCB test results of cement stabilized macadam with fibers of different lengths

[0145]

[0146] According to the data in Table 5, fibers with lengths of 10 mm, 20 mm, and 30 mm are applied to cement stabilized macadam, and their fracture energies are compared. The fracture energy of the fiber cement stabilized macadam with a fiber length of 20 mm is the largest. Therefore, the optimal fiber length is 20 mm.

[0147] (5) Fibers with a diameter of 300 μm and a length of 20 mm are divided into three groups and incorporated into cement stabilized macadam. The fiber dosages are 0.5‰, 1.0‰, and 1.5‰ respectively. Semi-circular bending specimens of cement stabilized macadam with different fiber dosages are prepared, with 3 specimens in each group. The fracture energy Gf at the failure of the specimens is obtained through the semi-circular bending test to evaluate the influence of fiber dosage on the anti-cracking strength of cement stabilized macadam and determine the optimal fiber dosage. The test results are shown in Table 6.

[0148] Table 6 Influence of Different Fiber Dosages on the SCB Test of Cement Stabilized Macadam

[0149]

[0150] According to the data in Table 6, when the fiber diameter is 300 μm, the fracture energy of cement stabilized macadam reaches the maximum value at a fiber dosage of 1.0‰. When the fiber dosage is 1.5‰, the fracture energy shows a downward trend and is less than the fracture energy at a fiber dosage of 1.0‰. Therefore, in order to ensure the overall anti-cracking performance of cement stabilized macadam, the fiber dosage should not be excessive, and 1.0‰ is selected as the optimal fiber dosage for anti-cracking cement stabilized macadam.

[0151] According to the method of the present invention, the fiber diameter of this embodiment is finally determined to be 300 μm and the dosage is 1.0‰.

[0152] Comparative Example

[0153] According to the cement stabilized macadam gradation in the above embodiment, fine fibers with a diameter of 30 μm and a length of 20 mm are added, and the fiber dosage is 1.0‰. Semi-circular bending specimens are prepared, with 3 specimens. The fracture energy Gf at the failure of the specimens is obtained through the semi-circular bending test. The preparation method of the semi-circular bending specimens and the operation method of the semi-circular bending test are the same as those in the embodiment. The test results are shown in Table 7.

[0154] Table 7 SCB Test Results of Cement Stabilized Macadam with Added Fine Fibers

[0155]

[0156] As can be seen from Table 7, at a fiber dosage of 1.0‰, the fracture energy of the cement stabilized macadam with added fine fibers is less than that of the fiber cement stabilized macadam in the embodiment. This proves that the anti-cracking ability of the fiber cement stabilized macadam is better.

[0157] It can be seen from the comparison between the above embodiments and comparative examples that the present invention comprehensively evaluates the dispersion of fibers by calculating the maximum mass difference Δm of each part of the cement stabilized macadam specimen and using the microscopic observation method, evaluates the reinforcement effect of fibers with different diameters by measuring the holding force between the fibers and the cement mortar, and can determine the optimal diameter range of the coarse fibers suitable for cement stabilized macadam through the dispersion evaluation and the holding force evaluation; the anti-cracking ability of the cement stabilized macadam under different fiber lengths and fiber dosages is evaluated through the semi-circular bending test, and the optimal length and optimal dosage of the coarse fibers suitable for the cement stabilized macadam can be determined. The present invention can efficiently and accurately determine the specifications and dosages of the coarse fibers suitable for the anti-cracking type cement stabilized macadam, improve the dispersion and tensile strength of the fibers in the cement stabilized macadam, and thus enhance the anti-cracking ability of the semi-rigid base course.

[0158] It should be noted that although the technical solutions of the present invention are introduced by specific examples, those skilled in the art can understand that the present invention should not be limited thereto.

[0159] The above has described the embodiments of the present invention. The above description is exemplary and not exhaustive, and is also not limited to the disclosed embodiments. Many modifications and changes are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application or the improvement of the technology in the market, or to enable other ordinary skilled in the art in the technical field to understand the disclosed embodiments.

Claims

1. A method for determining fiber parameters in crack-resistant cement-stabilized macadam, characterized in that, It includes the following steps: Determine the minimum diameter and the maximum diameter of the fiber respectively; Obtain the average value of the minimum diameter and the maximum diameter to determine the target diameter of the fiber; Incorporate fibers of different lengths into cement stabilized macadam to prepare a first group of semi-circular bending specimens, and determine the target length of the fiber by detecting the fracture energy of the first group of semi-circular bending specimens; Incorporate the fibers with the determined target diameter and target length into cement stabilized macadam at different dosages to prepare a second group of semi-circular bending specimens, and determine the target dosage of the fiber by detecting the fracture energy of the second group of semi-circular bending specimens; wherein, Determining the minimum diameter of the fiber includes the following steps: Obtain fibers with a variety of different diameters; After mixing each kind of fiber with cement stabilized macadam respectively, divide it into two or more equal-mass test specimens to be tested; Separate the fiber from the cement stabilized macadam in the test specimen to be tested; Get the maximum mass m of each fiber in each mass sample to be tested. max and minimum mass m min The difference Δm; Determine the minimum diameter of the fiber according to the ratio of the difference Δm to the total weight of each kind of fiber; Determining the maximum diameter of the fiber includes the following steps: Obtain fibers with a variety of different diameters; Insert the fibers with different diameters into multiple groups of cement mortar respectively to obtain holding test specimens; Detect the holding force of the holding test specimens; Determine the maximum diameter of the fiber according to the ratio of the holding force to the cross-sectional area of the fiber.

2. The method for determining fiber parameters in crack-resistant cement stabilized macadam according to claim 1, characterized in that, When the difference Δm is less than 10% of the total weight of the same kind of fiber, obtain the minimum fiber diameter among the fibers with different diameters, and this minimum fiber diameter is the minimum diameter of the fiber.

3. The method for determining fiber parameters in crack-resistant cement stabilized macadam according to claim 1 or 2, characterized in that, Determining the minimum diameter of the fiber further includes the following steps: Obtain fibers with a variety of different diameters; After mixing each kind of fiber with cement stabilized macadam respectively, separate the fiber from the cement stabilized macadam to obtain a fiber bundle; Determine the minimum diameter of the fiber according to the ratio of the number of fibers in the fiber bundle to the total number of each kind of fiber.

4. The method for determining fiber parameters in crack-resistant cement stabilized macadam according to claim 3, characterized in that, When the ratio of the number of fibers in the fiber bundle to the total number of the same kind of fiber is less than 15%, obtain the minimum fiber diameter among the fibers with different diameters, and this minimum fiber diameter is the minimum diameter of the fiber.

5. The method for determining fiber parameters in crack-resistant cement stabilized macadam according to claim 1 or 2, characterized in that, The fiber diameter corresponding to the maximum value of the ratio of the holding force to the cross-sectional area of the fiber is the maximum diameter of the fiber.

6. The method for determining fiber parameters in crack-resistant cement stabilized macadam according to claim 1 or 2, characterized in that Among the first group of semi-circular bending specimens, the fiber length corresponding to the first group of semi-circular bending specimens with the maximum fracture energy is the target length of the fiber.

7. The method for determining fiber parameters in crack-resistant cement stabilized macadam according to claim 1 or 2, characterized in that, Among the second group of semi-circular bending specimens, the fiber dosage corresponding to the second group of semi-circular bending specimens with the maximum fracture energy is the target dosage of the fiber.

8. The method for determining fiber parameters in crack-resistant cement stabilized macadam according to claim 1 or 2, characterized in that, The diameter of the fiber is 100 μm or more.

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