Fiber rubber chip seal for inhibiting reflection crack of pavement and optimization design method thereof

Abstract

The application provides an optimal design method of a fiber rubber macadam seal coat for inhibiting pavement reflection cracks, comprising the following steps: determining optimal fibers; determining optimal aggregate; using the amount of the optimal fibers, the scattering amount of the optimal aggregate and the amount of rubber asphalt as variables, preparing multiple groups of third test pieces through orthogonal test; combining the third test pieces with a base layer and an overlay layer with cracks to prepare fourth test pieces and perform reflection crack simulation test; and determining the combination of the optimal crack resistance materials according to the test results. The application takes the anti-reflection crack capacity of the fiber rubber asphalt macadam seal coat itself as the main evaluation index, and has the advantages of scientificity, rationality and accuracy compared with the prior art. The fiber rubber macadam seal coat obtained by the design method has excellent anti-reflection crack capacity, can significantly improve the crack resistance of the composite pavement, reduce the pavement maintenance and repair cost, prolong the service life of the pavement, and has a wide popularization and application prospect.

Description

Technical Field

[0001] This invention belongs to the field of optimization design technology for anti-reflective crack sealing layers for pavements, specifically relating to an optimization design method for fiber rubber macadam sealing layers that suppress reflective cracks in pavements, and also relating to a fiber rubber macadam sealing layer that suppresses reflective cracks in pavements. Background Technology

[0002] Cracks are one of the major pavement defects. To mitigate reflective cracking in semi-rigid base pavements and the reflection of cracks from existing pavements to the overlay, stress-absorbing layers are often incorporated into the pavement structure. Among these, chip seal is the most commonly used stress-absorbing layer. Traditional chip seal primarily consists of asphalt and crushed stone. The mix design mainly relies on experience to determine the amounts of asphalt and crushed stone, or uses McLeod's theory, which assumes 100% aggregate coverage and that the asphalt binder fills 70% of the average height of the aggregate.

[0003] However, neither of these two methods considered the anti-reflective cracking capability of the chip seal pavement during the design process, making them highly susceptible to subjective influences. The anti-reflective cracking capability of a chip seal pavement generally refers to the rate at which cracks propagate from the bottom to the surface under repeated vehicle loads; the slower the propagation, the better the crack resistance. Although some studies have used the addition of rubber-modified asphalt and a certain proportion of fiber to the pavement to increase its anti-reflective cracking capability, traditional designs have not adequately considered how to determine the amount of fiber used.

[0004] Therefore, how to scientifically, accurately, and rationally design a sealing layer structure with good anti-reflective crack performance is not only of great significance for reducing road maintenance and repair costs and extending the service life of the road, but also a technical problem that urgently needs to be solved. Summary of the Invention

[0005] One of the objectives of this invention is to provide an optimized design method for fiber rubber macadam seals that suppress reflective cracking in road surfaces.

[0006] The second objective of this invention is to provide a fiber rubber macadam seal that suppresses reflective cracking in road surfaces.

[0007] One of the technical solutions adopted by this invention to achieve its objective is to provide an optimized design method for fiber rubber macadam seal layer that suppresses reflective cracking in road surfaces, comprising the following steps:

[0008] S1. Different fibers are combined with rubber asphalt to prepare multiple sets of first specimens. Tensile tests are performed on the first specimens to obtain force-ductility curves. The optimal fiber is determined based on the force-ductility curves.

[0009] S2. Rubber asphalt is bonded to the surface of different types of pretreated aggregates to obtain multiple sets of second specimens. Pull-out tests are performed on the second specimens to obtain the pull-out strength. The optimal aggregate is determined based on the pull-out strength test results.

[0010] S3. Using the optimal fiber dosage, optimal aggregate spreading amount, and rubber asphalt dosage as variables, conduct orthogonal experiments to prepare multiple sets of third specimens.

[0011] S4. Following the stacking order from bottom to top—the base layer with cracks, the third specimen, and the overlay—a fourth specimen is formed. The fourth specimen is placed in a reflective crack simulation device, and the fatigue number of cycles corresponding to the complete cracking of the fourth specimen is tested. Based on the test results, the optimal combination of materials for crack resistance of the fiber rubber macadam seal is determined.

[0012] Further, in step S1, determining the optimal fiber based on the force-ductility curve includes: determining the peak tensile force F based on the force-ductility curve. max And the strain yield energy W, to determine the optimal fiber type and length.

[0013] Furthermore, in step S2, the pretreatment of the aggregate includes grinding, cleaning and drying the aggregate, and then placing it under a heat preservation condition of 140-180°C.

[0014] Further, in step S2, determining the optimal aggregate based on the pull-out strength test results includes: selecting the aggregate corresponding to the maximum pull-out strength as the optimal aggregate based on the pull-out strength test results of the second specimen.

[0015] Furthermore, in step S3, the optimal fiber dosage is 60–120 g / m². 2 The optimal aggregate spreading rate is 12–18 kg / m³. 2 The dosage of rubber asphalt is 1.8–2.4 kg / m³. 2 In this invention, the optimal amount of fiber, the optimal amount of aggregate spread, and the amount of rubber asphalt are all added based on the area of ​​the road surface.

[0016] Furthermore, the base course with cracks is made of old asphalt pavement with crack width of 1-5 mm; the overlay is made of asphalt mixture; in the fourth specimen, the thickness ratio of the base course with cracks, the third specimen and the overlay is (3-8):1:(3-8).

[0017] Further, in step S4, the reflective crack simulation device includes: a steel mold with grooves and a loading device, wherein a buffer pad is laid at the bottom of the grooves of the steel mold. Preferably, the buffer pad is selected from rubber pads, and its thickness is 2-3 cm. In this invention, the buffer pad can reduce the friction between the specimen and the steel mold, allowing the specimen to undergo lateral deformation under load.

[0018] Furthermore, in step S4, the method for testing the number of fatigue cycles corresponding to the complete cracking of the fourth specimen includes: placing the fourth specimen above the buffer pad inside the steel mold and applying a load to the top of the fourth specimen; observing the crack development during the test and recording the number of fatigue cycles corresponding to the complete cracking of the fourth specimen.

[0019] Preferably, during the load application process, the loading waveform is a half-wave sine wave, the loading frequency is 5 to 25 Hz, and the peak value of the applied load is 2 to 4 kN.

[0020] The second objective of this invention is to provide a fiber rubber macadam seal that suppresses reflective cracking in road surfaces, wherein the fiber rubber macadam seal is prepared by the optimization design method described in one of the objectives of this invention.

[0021] Furthermore, the fiber-rubber crushed stone seal comprises fibers, aggregates, and rubber asphalt. The fibers are selected from basalt fibers with a length of 7.5 cm; the aggregates are selected from basalt crushed stone.

[0022] Preferably, the amount of fiber used is 80-120 g / m². 2 The amount of crushed stone used is 12-18 kg / m³. 2 The dosage of rubber asphalt is 1.8–2.4 kg / m³. 2 Under these conditions, the fourth specimen underwent more than 12,000 fatigue cycles before it completely cracked.

[0023] More preferably, the amount of fiber used is 100-120 g / m². 2 The amount of crushed stone used is 14-16 kg / m³. 2 The dosage of rubber asphalt is 2.2–2.4 kg / m³. 2 Under these conditions, the fourth specimen underwent more than 15,000 fatigue cycles before it completely cracked.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) This invention provides an optimized design method for fiber-reinforced rubber macadam seal layers to suppress reflective cracking in pavements. This method uses the inherent anti-reflective cracking capability of the fiber-reinforced rubber asphalt macadam seal layer as the main evaluation index. First, a force-ductility test is used to optimize the selection of fibers, and a pull-out strength test is used to optimize the selection of aggregates to determine the optimal raw materials. Further, the amount of the optimal raw materials is used as a variable in orthogonal experiments to prepare multiple test specimens. A reflective cracking simulation device is used to test the fatigue number of times the test specimens completely crack. Based on the test results, the optimal combination of materials for crack resistance in the fiber-reinforced rubber macadam seal layer is determined. This invention, by screening multiple factors affecting the crack resistance of the fiber-reinforced rubber macadam seal layer, determines and comprehensively evaluates them hierarchically. Compared with previous technologies, this evaluation method has advantages in scientific rigor, rationality, and accuracy.

[0026] (2) The fiber-reinforced rubber chip seal for suppressing reflective cracking in pavements provided by this invention. Tests showed that, under conditions of a half-wave sine wave loading waveform, a loading frequency of 10Hz, and a peak applied load of 4KN, the specimen underwent over 7000 fatigue cycles before complete cracking, with a maximum of 19532 cycles. This demonstrates excellent resistance to reflective cracking and significantly improves the crack resistance of composite pavements. The fiber-reinforced rubber chip seal for suppressing reflective cracking in pavements and its design method provided by this invention can reduce pavement maintenance and repair costs and extend pavement service life, showing broad prospects for promotion and application. Attached Figure Description

[0027] Figure 1 A flowchart illustrating an optimized design method for a fiber rubber macadam seal layer to suppress reflective cracking in road surfaces, provided by an embodiment of the present invention.

[0028] Figure 2 This is a force-delay curve diagram from an embodiment of the present invention;

[0029] Figure 3 This is a photograph of the actual specimen used for force ductility measurement in an embodiment of the present invention.

[0030] Figure 4 This is a test diagram of the force-dust-measuring specimen in an embodiment of the present invention;

[0031] Figure 5 This is a force ductility diagram of glass fiber / rubber asphalt in an embodiment of the present invention;

[0032] Figure 6 This is a force ductility diagram of basalt fiber / rubber asphalt in an embodiment of the present invention;

[0033] Figure 7 This is a force ductility diagram of alkali-free glass fiber / rubber asphalt in an embodiment of the present invention;

[0034] Figure 8This is a pull-out strength test diagram from an embodiment of the present invention;

[0035] Figure 9 This is a physical image of the fourth specimen with a three-layer structure in an embodiment of the present invention;

[0036] Figure 10 This is a schematic diagram of the structure of the reflection crack simulation device in an embodiment of the present invention;

[0037] Figure 11 This is a fatigue crack resistance test diagram from an embodiment of the present invention;

[0038] Figure 12 This is a diagram showing the effect of fiber dosage on crack resistance in embodiments of the present invention;

[0039] Figure 13 This is a diagram showing the effect of crushed stone dosage on crack resistance in an embodiment of the present invention;

[0040] Figure 14 This diagram illustrates the effect of rubber asphalt dosage on crack resistance in embodiments of the present invention. Detailed Implementation

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0043] like Figure 1 As shown, this invention provides an optimized design method for fiber-reinforced rubber chip seal layers to suppress reflective cracking in road surfaces. The method includes the following steps:

[0044] Step 1: Determine the optimal fiber type and length:

[0045] Different types and lengths of fibers were combined with rubber asphalt to prepare multiple sets of first specimens. Tensile tests were performed on each first specimen to obtain force-ductility curves, such as... Figure 2 As shown; the peak tensile force F according to the force-ductility curve. max And the strain yield energy W, to determine the optimal fiber type and length.

[0046] In this invention, three types of fibers suitable for road stress absorption layers are selected, including glass fiber, basalt fiber, and alkali-free glass fiber, with fiber lengths of 0cm, 3cm, 6cm, and 7.5cm, respectively.

[0047] like Figure 3 As shown, different types and lengths of fibers were used to make force ductility test specimens. The first pour was half the volume of the mold. Then, the three types of fibers were evenly placed on the asphalt using tweezers. The fiber mass was 5% of the asphalt mass, and the fiber lengths were 0cm, 3cm, 6cm, and 7.5cm, respectively. Then, the asphalt was poured a second time, slightly higher than the mold. After cooling, it was leveled with a scraper. Finally, the specimen was immersed in a water bath at 5℃ for 1 to 1.5 hours to obtain the first specimen.

[0048] like Figure 4 As shown, the specimen was installed in the force-ductility measuring instrument, and the instrument was started to begin the test. The tensile rate was 5 cm / min, and the stress and ductility curves of the fiber-reinforced asphalt tensile test were obtained, as shown. Figure 5-7 As shown. Figure 5-7 In the diagram, XJ represents rubber asphalt, B represents glass fiber, X represents basalt fiber, and W represents alkali-free glass fiber; 3, 6, and 7.5 represent fiber length.

[0049] according to Figure 5-7 The performance test curve was used to calculate the maximum tensile force F. max Maximum extension D max The strain yield energy W is shown in Table 1 below:

[0050] Table 1

[0051]

[0052] It can be seen from Table 1 above that

[0053] By comparing F max Based on the size of W, the fiber type was determined to be basalt fiber with a length of 7.5 cm.

[0054] Step 2: Determine the optimal type of aggregate:

[0055] Rubber asphalt was bonded to the surfaces of different types of pretreated aggregates to obtain multiple sets of second specimens. Pull-out tests were performed on the second specimens to obtain the pull-out strength. The optimal aggregate type was determined based on the pull-out strength test results.

[0056] This invention selects four different aggregate types: basalt, granite, sandstone, and diabase. The pretreatment method for the aggregates includes: first, grinding the aggregate surface to a smooth finish; then, rinsing the ground aggregate with clean water and placing it in an oven at 160°C for two hours; weighing 0.0314g of rubber asphalt; placing the asphalt on the heated rock surface and gently pressing it with a pull-out head to bond the two together; after cooling to room temperature (20°C), a pull-out test can be conducted using the PosiTest fully automatic pull-out adhesion tester. Figure 8 As shown in Table 2, the tensile strength at failure was measured.

[0057] Table 2

[0058] basalt granite sandstone diabase Pull-out strength / MPa 1.27 0.71 0.85 1.18

[0059] It can be seen from Table 2 above that

[0060] By comparing the pull-out strength, the optimal aggregate type (i.e., the type of crushed stone) was determined to be basalt.

[0061] Step 3: Design orthogonal experiments

[0062] The amount of fiber, the amount of crushed stone, and the amount of rubber asphalt were used as variables in an orthogonal experiment to prepare multiple sets of third specimens. In this invention, the fiber dosage was selected to be in the range of 60–120 g / m³. 2 The application rate of crushed stone with a particle size of 5-10mm is 12-18 kg / m³. 2 Rubberized asphalt has a strength of 1.8–2.4 kg / m³. 2 Each influencing factor was selected with four levels, and the design was carried out according to the L16(45) orthogonal experimental table, as shown in Table 3 below:

[0063] Table 3

[0064]

[0065] Step 4: Simulation Test

[0066] Following the stacking order from bottom to top—the cracked base layer, the third specimen, and the overlay—the fourth specimen was formed. The structure of the fourth specimen is as follows: Figure 9 As shown. Figure 10 As shown, the fourth specimen was placed in a reflective crack simulation device, and the number of fatigue cycles corresponding to the complete cracking of the fourth specimen was tested. Based on the test results, the optimal combination of materials for crack resistance of the fiber rubber chip seal was determined.

[0067] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0068] The amounts of fiber, crushed stone, and rubber asphalt used in Examples 1-16 of this invention are shown in Table 4 below.

[0069] Table 4

[0070]

[0071]

[0072] In the above table,

[0073] The fiber is basalt fiber, with a length of 7.5 cm, a monofilament tensile strength of 4.53 GPa, an elastic modulus of 62.6 GPa, and an elongation at break of 1.70%; the crushed stone is basalt, with a particle size of 4.75–9.5 mm and an apparent density of 2.928 g / cm³. 3 It has a water absorption rate of 0.54%, a crushing value of 8.5%, and a Los Angeles abrasion value of 6.6%. The rubber asphalt is prepared by adding 20% ​​of 40-mesh rubber powder to No. 90 base asphalt. The penetration at 25℃ is 5.2mm and the softening point is 59℃.

[0074] Example 1

[0075] This embodiment provides a fiber-rubber asphalt chip seal, the raw materials of which, by weight, include 0.06 parts fiber, 12 parts chip, and 1.8 parts rubber asphalt.

[0076] The preparation method of the fiber rubber asphalt macadam seal is as follows: a layered spreading method is adopted, that is, a layer of rubber asphalt + a layer of fiber + a layer of rubber asphalt + a layer of macadam are spread in sequence. During the preparation process, the uniformity of the spreading of fiber, asphalt and macadam is ensured as much as possible. Finally, it is compacted to obtain the fiber rubber asphalt macadam seal.

[0077] Example 2-15

[0078] The difference between Examples 2-15 and Example 1 is that the raw material amounts in Example 1 are adjusted according to the fiber amount, crushed stone amount and rubber asphalt amount shown in Table 4, while the other steps remain unchanged, to obtain a fiber rubber asphalt crushed stone seal.

[0079] Performance testing

[0080] The fiber-reinforced rubber asphalt macadam seal layer prepared in Examples 1-16 was used as the third specimen. Following the stacking order from bottom to top—the base layer with cracks, the third specimen, and the overlay—a fourth specimen was formed. The structure of the fourth specimen is as follows: Figure 9 As shown. The fourth specimen was placed in the reflective crack simulation device, and the number of fatigue cycles corresponding to the complete cracking of the fourth specimen was tested.

[0081] Figure 10This is a schematic diagram of the reflective crack simulation device used in this invention. The device is a U-shaped steel mold with a rubber pad placed at the bottom inside. The rubber pad measures 26cm × 7cm × 2.5cm. The cracked base layer, the third specimen, and the overlay are stacked sequentially from bottom to top. The cracked base layer is a 4cm thick pavement with vertical cracks measuring 3mm wide. The third specimen (fiber rubber asphalt macadam seal) prepared in this invention is placed on top of the cracked base layer and has a thickness of 1cm. Above the third specimen is the overlay, which is an asphalt mixture measuring 24cm × 7cm × 3cm.

[0082] After the above-mentioned specimens are prepared, first place the specimens in the heat preservation chamber of the universal testing machine for 1 hour at a temperature of 15℃, and then immediately place them in the mold to begin the test. Figure 11 As shown, during the test, a strip load was applied along the width direction on the top surface of the asphalt concrete. The loading area was 4cm × 7cm (7cm × 4cm × 2cm steel strips were used in this invention). The loading waveform was a half-wave sine wave with a loading frequency of 10Hz, and the peak load was 4KN. The development of cracks was observed during the test, and the number of fatigue cycles corresponding to the complete cracking of the specimen was recorded. At least two specimens were tested in parallel. If the results of two specimens differed significantly, a second test was conducted, and the average of the two closest values ​​was taken as the final result. The crack resistance test results (number of fatigue cycles) of Examples 1-16 are shown in Table 5 below.

[0083] Table 5

[0084]

[0085]

[0086] Furthermore, a range analysis was performed on the experimental results in Table 5, such as... Figure 12 , 13 As shown in Figure 14, the optimal combination of materials with crack resistance was obtained.

[0087] Based on the results of the previous test:

[0088] Under the conditions of a half-wave sine wave loading waveform, a loading frequency of 10Hz, and an applied peak load of 4KN, the invention uses basalt fiber, basalt crushed stone, and rubber asphalt to prepare a fiber rubber crushed stone seal layer. The fatigue cycles corresponding to the complete cracking of the specimen can reach more than 7000.

[0089] Furthermore, a comparison of the above results shows that the amount of fiber, the amount of crushed stone, and the amount of rubber asphalt have a significant impact on the fatigue number of times the specimen completely cracks: when the fiber content is 80–120 g / m³... 2The amount of crushed stone used is 12-18 kg / m³. 2 The dosage of rubber asphalt is 1.8–2.4 kg / m³. 2 At that time, the fatigue cycle count corresponding to the complete cracking of the fourth specimen was over 12,000; furthermore, when the fiber content was 100–120 g / m²... 2 The amount of crushed stone used is 14-16 kg / m³. 2 The dosage of rubber asphalt is 2.2–2.4 kg / m³. 2 At that time, the fatigue cycle count corresponding to the complete cracking of the fourth specimen was more than 15,000.

[0090] Among them, the optimal crack-resistant material combination obtained by optimized design is A4B2C4, which means the fiber content is 120g / m². 2 The amount of crushed stone used is 14 kg / m³. 2 The amount of rubber asphalt used is 2.4 kg / m³. 2 Under these conditions, the fourth specimen reached a fatigue cycle count of 19,532 when it completely cracked, demonstrating a significant improvement in crack resistance.

[0091] In summary, this invention provides an optimized design method for fiber-reinforced rubber chip seal pavement to suppress reflective cracking. This method uses the inherent anti-reflective cracking capability of the fiber-reinforced rubber chip seal pavement as the primary evaluation index. By screening multiple factors affecting the crack resistance of the fiber-reinforced rubber chip seal pavement, it determines and comprehensively evaluates these factors at different levels. Compared to previous technologies, this evaluation method has advantages in scientific rigor, rationality, and accuracy. The fiber-reinforced rubber chip seal pavement obtained by this design method exhibits excellent anti-reflective cracking capability, significantly improving the crack resistance of composite pavements, reducing pavement maintenance and repair costs, and extending pavement service life, thus possessing broad prospects for promotion and application.

[0092] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. An optimized design method for fiber-reinforced rubber chip seal layers to suppress reflective cracking in road surfaces, characterized in that, Includes the following steps: S1. Different fibers are combined with rubber asphalt to prepare multiple sets of first specimens. Tensile tests are performed on the first specimens to obtain force ductility curves. Based on the peak tensile force and strain yield energy of the force ductility curves, the optimal fiber is determined to be basalt fiber with a length of 7.5 cm. S2. Rubber asphalt is bonded to the surface of different types of pretreated aggregates to obtain multiple sets of second specimens. Pull-out tests are performed on the second specimens to obtain the pull-out strength. Based on the maximum tensile strength, the optimal aggregate is determined to be basalt crushed stone; S3. Using the amount of basalt fiber (7.5 cm in length), the amount of basalt gravel spread, and the amount of rubber asphalt as three variables, an orthogonal experiment was conducted to prepare multiple sets of third specimens; wherein, the amount of basalt fiber was 60~120 g / m 2 The amount of basalt gravel spread is 12~18 kg / m³. 2 The amount of rubber asphalt used is 1.8~2.4 kg / m³. 2 ; S4. The fourth specimen is formed by stacking the base layer with cracks, the third specimen, and the overlay layer from bottom to top. The fourth specimen is placed in a reflective crack simulation device to test the number of fatigue cycles corresponding to the complete cracking of the fourth specimen. Based on the test results, the optimal combination of materials for crack resistance in the fiber-reinforced rubber chip seal layer was determined; in the optimal combination of materials for crack resistance, the basalt fiber content is 100~120 g / m². 2 Basalt gravel spreading rate: 14-16 kg / m³ 2 The amount of rubber asphalt used is 2.2~2.4 kg / m³. 2 .

2. The optimization design method according to claim 1, characterized in that, In step S2, the pretreatment of the aggregate includes grinding, cleaning and drying the aggregate, and then placing it under a heat preservation condition of 140~180℃.

3. The optimization design method according to claim 1, characterized in that, In step S4, the base course with cracks is an old asphalt pavement with a crack width of 1-5 mm; the overlay is an asphalt mixture; in the fourth specimen, the thickness ratio of the base course with cracks, the third specimen, and the overlay is (3-8):1:(3-8).

4. The optimization design method according to claim 1, characterized in that, In step S4, the reflective crack simulation device includes: a steel mold with a groove and a loading device, wherein a buffer pad is laid at the bottom of the groove of the steel mold.

5. The optimization design method according to claim 4, characterized in that, In step S4, the method for testing the number of fatigue cycles corresponding to the complete cracking of the fourth specimen includes: placing the fourth specimen above the buffer pad inside the steel mold and applying a load to the top of the fourth specimen; observing the crack development during the test and recording the number of fatigue cycles corresponding to the complete cracking of the fourth specimen.

6. A fiber-reinforced rubber chip seal for suppressing reflective cracking in road surfaces, characterized in that, The fiber rubber chip seal is prepared by the optimized design method according to any one of claims 1-5.

Images