FULL-DEPTH ULTRA-THIN LONG-LIFE PAVEMENT STRUCTURE AND CONSTRUCTION METHOD THEREOF

Abstract

A full-depth ultra-thin long-life pavement structure and a construction method thereof are disclosured. The pavement structure is disposed on a subgrade, and the pavement includes from bottom to top: a composite joint layer, a fatigue-resistant layer, a load-bearing layer, a high-strength bonding layer and a skid-resistant wearing layer; the composite joint layer comprises a bottom layer and an upper layer, the bottom layer is a graded gravel layer, and the upper layer is an open-graded large-particle-size water-permeable polyurethane and gravel mixture layer; the fatigue-resistant layer is paved by a skeleton-interlocking structural polyurethane mixture; the load-bearing layer is paved by a suspended-dense typed polyurethane mixture; the high-strength bonding layer is formed by curing a polyurethane-based composite material; the skid-resistant wearing layer is paved by a high-viscosity and high-elasticity modified asphalt mixture.

Claims

1. A full-depth ultra-thin long-life pavement structure, wherein the full-depth long-life pavement structure is disposed on a subgrade, and the full-depth long-life pavement comprises from bottom to top: a composite joint layer, a fatigue-resistant layer, a load-bearing layer, a high-strength bonding layer and a skid-resistant wearing layer; the composite joint layer comprises a bottom layer and an upper layer, the bottom layer is a graded gravel layer, and the upper layer is an open-graded large-particle-size water-permeable polyurethane and gravel mixture layer; the fatigue-resistant layer is paved by a skeleton-interlocking structural polyurethane mixture; the load-bearing layer is paved by a suspended-dense typed polyurethane mixture; the high-strength bonding layer is formed by curing a polyurethane-based composite material; the skid-resistant wearing layer is paved by a high-viscosity and high-elasticity modified asphalt mixture.

2. The pavement structure of claim 1, wherein a thickness of the graded gravel layer is in a range of 6-15 cm; a thickness of the open-graded large-particle-size water-permeable polyurethane and gravel mixture layer is in a range of 8-12 cm; a thickness of the fatigue-resistant layer is in a range of 5-9 cm; a thickness of the load-bearing layer is in a range of 6-12 cm; a thickness of the high-strength bonding layer is in a range of 1-3 mm; a thickness of the skid-resistant wearing layer is in a range of 3-6 cm.

3. The pavement structure of claim 1, wherein the graded gravel layer is prepared by mixing aggregates with diameters of 0-5 mm, 5-10 mm, 10-20 mm and 20-30 mm according to a mass ratio of (25-35):(20-30):(40-50):(0.1-10).

4. The pavement structure of claim 1, wherein the open-graded large-particle-size water-permeable polyurethane and gravel mixture layer is a skeleton-pore structure mixture with a porosity of 15%-20% prepared by mixing a mineral aggregate and a polyurethane binder according to a mass ratio of (95-98):(2-5); the mineral aggregate is prepared by mixing aggregates with diameters of 0-3 mm, 3-5 mm, 5-10 mm, 10-20 mm and 20-30 mm according to a mass ratio of (25-35):(20-30): 20-40):(0.1-15):(0.1-15).

5. The pavement structure of claim 1, wherein the skeleton-interlocking structural polyurethane mixture is a mixture with a porosity of 13%-18% prepared by mixing a polyurethane binder and a mineral aggregate according to a mass ratio of (94-97):(3-6); the mineral aggregate is prepared by mixing a mineral powder and aggregates with diameters of 0-3 mm, 3-5 mm, 5-10 mm and 10-20 mm according to a mass ratio of (0.1-5):(0.1-10):(5-20):(25-50):(10-30).

6. The pavement structure of claim 1, wherein the suspended-dense typed polyurethane mixture is a mixture with a porosity of 2%-5% prepared by mixing a mineral aggregate, a rubber powder and a polyurethane binder according to a mass ratio of (92-95):(0-10):(3-6); the mineral aggregate is prepared by mixing a mineral powder and aggregates with diameters of 0-3 mm, 3-5 mm, 5-10 mm and 10-20 mm according to a mass ratio of (3-10):(30-40):(10-20):(10-30):(10-20).

7. The pavement structure of claim 1, wherein the polyurethane-based composite material is prepared by mixing a polyurethane binder, a filler, an additive and an anti-stripping agent according to a mass ratio of (56-85):(32-50):(5-12):(0.1-1); the filler is a light calcium powder; the additive is carbon black; the anti-stripping agent is a hydroxyl-terminated phosphorus-containing polyester.

8. The pavement structure of claim 1, wherein the high-viscosity and high-elasticity modified asphalt mixture is prepared by mixing an aggregate, a mineral powder and a high-viscosity and high-elasticity modified asphalt according to a mass ratio of (85-95):(5-10):(3-6), with a porosity of 3-5%; the high-viscosity and high-elasticity modified asphalt is one selected from the group consisting of a SBS composite modified asphalt, a polyurethane composite modified asphalt and a rubber powder composite modified asphalt; the mineral powder is a limestone powder; the aggregate is one selected from the group consisting of basalt and diabase.

9. The pavement structure of claim 3, wherein the aggregate is one selected from the group consisting of basalt and diabase; the mineral powder is a limestone powder.

10. A construction method of the full-depth ultra-thin long-life pavement structure of claim 1, comprising: 1) mixing the graded gravel with an on-site mixing method, wherein a stabilized soil mixer is used to mix for 2-4 times to obtain a mixture, and when a water content of the mixture is equal to or slightly greater than an optimal water content, a vibratory roller of 12 t or more is immediately used to roll the mixture from both sides to middle until a specified degree of compaction is reached; 2) producing mixtures for the open-graded large-particle-size water-permeable polyurethane and gravel mixture layer, the fatigue-resistant layer and the load-bearing layer by a batching asphalt mixing station, wherein materials are not required to be heated during construction, transported with a dump truck to a construction site, paved with an asphalt mixture paver at a speed of 1.5-2.0 m/min, and subjected to a static press with a steel wheel roller for 2-4 times at a speed of 2.5-3.5 km/h; for each layer, after compaction for 24-36 h, a next layer is constructed; 3) distributing the polyurethane composite material with a distributor for the high-strength bonding layer, with a distributing amount in a range of 1-3 kg/m.sup.2; 4) preparing the skid-resistant wearing layer by using the same construction method as that of a conventional hot-mixing modified asphalt mixture, to achieve the construction of the full-depth ultra-thin long-life pavement structure.

11. The pavement structure of claim 4, wherein the aggregate is one selected from the group consisting of basalt and diabase; the mineral powder is a limestone powder.

12. The pavement structure of claim 5, wherein the aggregate is one selected from the group consisting of basalt and diabase; the mineral powder is a limestone powder.

13. The pavement structure of claim 6, wherein the aggregate is one selected from the group consisting of basalt and diabase; the mineral powder is a limestone powder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 shows a schematic diagram of a full-depth ultra-thin long-life pavement structure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] In order for a better understanding of those skilled in the art to the technical solutions in the present disclosure, the disclosure will be described in detail below with reference to embodiments. The embodiments described are only parts of, rather than all of, the embodiments in the disclosure, and the present disclosure is not limited by the embodiments described below.

[0043] The “Outline for Building a Country with Strong Transportation Network” clearly states to “promote conserving and intensive utilization of resource” and “strengthen energy saving, emission reduction and pollution prevention”. The disclosure proposes a low-carbon and environmentally friendly full-depth ultra-thin long-life pavement structure, which has good integrity and durability, and may effectively reduce the number of maintenance, save investment and improve the level of road service. Moreover, the pavement structure has relatively thin structural layers, which may save a large amount of road construction materials and reduce energy consumption and emission, making contribution to the high-quality and green development of road construction.

Example 1 Preparation of the Full-Depth Ultra-Thin Long-Life Pavement Structure

[0044] 1. Pavement Structure Composition

[0045] As shown in FIG. 1, the full-depth ultra-thin long-life pavement structure in Example 1 was formed by paving a composite joint layer 1, a fatigue-resistant layer 2, a load-bearing layer 3, a high-strength bonding layer 4 and a skid-resistant wearing layer 5 on the top surface of a subgrade from bottom to top. The composite joint layer was composed of a graded gravel layer and an open-graded large-particle-size water-permeable polyurethane and gravel mixture layer from bottom to top. The technical indicators of the graded gravel layer are shown in Table 1. The open-graded large-particle-size water-permeable polyurethane and gravel mixture layer was a skeleton-pore structure mixture with a porosity of 15%-20% prepared by mixing a mineral aggregate and a polyurethane binder in proportion. The mineral aggregate was prepared by mixing limestone aggregates with diameters of 0-3 mm, 3-5 mm, 5-10 mm, 10-20 mm and 20-30 mm. The mixture type and mineral aggregate grading are shown in Table 2.

[0046] The fatigue-resistant layer was prepared by a skeleton-interlocking structural polyurethane mixture, which was prepared by mixing a polyurethane binder and a mineral aggregate. The mineral aggregate was a limestone powder and limestone aggregates with diameters of 0-3 mm, 3-5 mm, 5-10 mm and 10-20 mm. In the case that the optimization theory of aggregate interlocking was used to design the mineral aggregate grading, the influence of interference on the porosity of the mineral aggregate might be eliminated, thereby making the mixture finally form a single-discontinuous or a double-discontinuous grading skeleton-interlocking structure. The mixture designed by this method had the advantages such as large density, high stiffness modulus and good fatigue resistance, which might effectively reduce the amount of the binder. The mixture type and mineral aggregate grading are shown in Table 2.

[0047] The load-bearing layer was prepared by a suspended-dense structural polyurethane and rubber powder mixture, which was prepared by mixing a mineral aggregate, a rubber powder and a polyurethane binder. A 40 mesh rubber powder was used. A mass ratio of the rubber powder to the polyurethane binder was 22:78. The mixture type, mineral aggregate grading and binder amount are shown in Table 2.

[0048] The skid-resistant wearing layer was paved by a high-viscosity and high-elasticity modified asphalt mixture. The high-viscosity and high-elasticity modified asphalt mixture was prepared by mixing an aggregate, a mineral powder and a high-viscosity and high-elasticity modified asphalt, in which the high-viscosity and high-elasticity modified asphalt was prepared by mixing 5% of polyurethane, 6% of SBS, 2% of a viscosity modifier, 0.8% of a compatilizer and 86.2% of a matrix asphalt in mass percentage. The high-viscosity and high-elasticity modified asphalt had a needle penetration of 42 (0.1 mm), a softening point of 88° C., and a Brookfield viscosity at 135° C. of 2.8 Pa.Math.s. The mixture type, mineral aggregate grading and binder amount are shown in Table 2.

[0049] The polyurethane-based composite material was composed of a polyurethane binder, a light calcium carbonate, carbon black and a hydroxyl-terminated phosphorus-containing polyester. A mass ratio of these materials was 75:17:7:1. The mixture type and mineral aggregate grading of each structural layer are shown in Table 2. The technical indicators of mixtures in each structural layer are shown in Table 3.

TABLE-US-00001 TABLE 1 Grading range of graded gravel Cumulative passing percentage of each sieve (square-hole sieve, mm)/% Liquid Plasticity 31.5 19 9.5 4.75 2.36 0.6 0.075 limit/% index 100 95.4 68.7 48.5 29.3 14.8 5.6 17 5

TABLE-US-00002 TABLE 2 Mixtures and grading ranges of mineral aggregates Binder Type of material in Cumulative passing percentage of each sieve (mm)/% amount structural layer 31.5 26.5 19 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 /% Macropore 100 93.5 74.6 65.7 50.8 34.9 20.5 15.7 12.9 9.6 6.5 4.6 2.5 2.8 polyurethane gravel (PPM-25) Skeleton-interlocking 100 100 100 100 95.9 67.8 31 21.4 16.7 11.5 8.6 6.1 2.4 4 polyurethane mixture (PUM-13) Suspended-dense 100 100 97.9 86.6 73.4 67.1 48.1 35.9 28.5 20.5 14.9 10.7 5.7 4.3 typed polyurethane mixture (CPUM-13) High-viscosity and 100 100 100 100 81.8 61.2 24.2 19.9 16.8 14.5 12.4 10.9 10.1 5.9 high-elasticity modified asphalt mixture (SMA-13)

TABLE-US-00003 TABLE 3 Technical indicators of mixtures Mineral Dynamic Dynamic Type of material aggregate Marshall stability/ modulus at in structural layer Porosity/% gap rate/% Saturability/% stability/KN (time/mm) 20° C./MPa PPM-25 19.5 — — 40.8 23000 14300 PUM-13 19.6 — — 47.3 53000 21800 CPUM-13 4.6 — — 48.7 48000 17700 SMA-13 3.8 23 83.5 15.4 14000 14200

[0050] 2. Construction Method

[0051] For the graded gravel layer, a stabilized soil mixer was used to mix for 2-4 times to obtain a mixture. A vibratory roller of 20 t was used to roll the mixture from both sides to middle until the degree of compaction was greater than or equal to 95%.

[0052] For the open-graded large-particle-size water-permeable polyurethane and gravel mixture layer, the fatigue-resistant layer and the load-bearing layer, the mixtures for the layers were produced by a batching asphalt mixing station. The raw materials were not required to be heated during construction. They were transported with a dump truck to a construction site. An asphalt mixture paver was used for paving at a speed of 1.5 m/min, and a steel wheel roller was used for static press for 3 times at a speed of 2.5 km/h. For each layer, after compaction for 24 h, a next layer is constructed.

[0053] For the high-strength bonding layer, a distributor was used to distribute the polyurethane composite material, with a distributing amount of 1 kg/m.sup.2.

[0054] For the skid-resistant wearing layer, the same construction method as that of a conventional hot-mixing modified asphalt mixture was used. Thus, the full-depth ultra-thin long-life pavement structure was achieved, as shown in FIG. 1.

[0055] 3. Test Results

[0056] (1) The inclined shear test was used to test the interlaminar shear strength between the skid-resistant wearing layer and the load-bearing layer under different environmental conditions.

[0057] The test results are shown in Table 4.

TABLE-US-00004 TABLE 4 Interlaminar shear strength under different environmental conditions Test condition Shear strength/MPa Normal temperature 2.53 60° C. 1.73 After freeze-thaw cycle 1.58

[0058] By analyzing the data in Table 4, it may be seen that the interlaminar shear strength results under different test conditions are all greater than 1 MPa, indicating that the pavement structure has a good jointing at the interface between structural layers and a good integrity.

[0059] (2) The four-point bending fatigue test was used to test the fatigue life of the fatigue-resistant layer under different strain levels. The results are shown in Table 5.

TABLE-US-00005 TABLE 5 Fatigue life of fatigue-resistant layer under different strain levels Strain level/με Fatigue life/time 600 734700 700 428900 800 364220 1000 192980

[0060] Based on the extrapolation method, in accordance with the test data in Table 5, the fatigue performance equation (1) proposed by Carpenter S H et al. was used to calculate the fatigue limit of the mixture in the fatigue-resistant layer, which was 295με, and the fatigue life prediction equation (2) for the mixture in the fatigue-resistant layer was established. The fatigue limit of the modified asphalt mixture was about 100με, while the fatigue limit of the fatigue-resistant layer in the skeleton-interlocking structural polyurethane mixture was about 3 times that of the modified asphalt mixture, indicating that the fatigue-resistant layer had a strong ability to resist the repeated action of the traffic load.

LgN.sub.f=A−BLg(ε−ε.sub.r)  (1)

[0061] where ε.sub.r is the fatigue limit of the mixture, and N.sub.f is the fatigue life of the mixture.

LgN.sub.f=9.686−1.5408Lg(ε−295)  (2)

[0062] The pavement structure makes full use of the properties of the polyurethane mixture such as the excellent fatigue resistance, rutting resistance, energy saving and environmental protection to reduce the thickness of the long-life pavement, and to have good integrity and strong ability to resist the repeated actions of the traffic load. Also, the pavement structure is convenient for maintenance, saves energy and reduces emission, and is beneficial to environmental protection, providing a new type of structure and form for the long-life pavement construction.

Example 2 Comparison of the Full-Depth Ultra-Thin Long-Life Pavement Structure

[0063] 1. Advantage on Composition of Pavement Structure

[0064] The typical full-depth long-life asphalt pavement and combined long-life asphalt pavement were selected for comparative analysis. The pavement structures are shown in Table 6. The total thickness of the full-depth ultra-thin long-life pavement is only 81.0% of the structure II and 41.5% of the structure III, which significantly reduces the thickness of the long-life pavement.

TABLE-US-00006 TABLE 6 Pavement structures and thickness Pavement structure composition Total thickness/cm Full-depth ultra-thin 4 cm of SMA-13 + bonding layer + 6 cm of CPUM-13 + 8 cm 34 cm long-life pavement of PUM-13 + 6 cm of PPM-25 + 10 cm of graded gravel (structure I) Full-depth long-life 4 cm of SMA-13 + 10 cm of EME-16 + 11 cm of 42 cm asphalt pavement EME-20 + 10 cm of LSPM-25 + 7 cm of AC-13F (structure II) Combined long-life 4 cm of SMA-13 + 6 cm of AC-20 + 8 cm of AC-25 + 10 cm 82 cm asphalt pavement of LSPM-25 + 18 cm of cement stabilized gravel + 18 cm of (structure III) cement stabilized gravel + 18 cm of cement stabilized gravel

[0065] 2. Advantage on Cost of Pavement Structure

[0066] An expressway with a length of 1 km and a pavement width of 25 m was taken as an example. According to the current market prices of materials, the amount and cost of various materials for the three pavement structures as formulated in Table 6 were calculated, and the calculation results are shown in Table 7.

TABLE-US-00007 TABLE 7 Amount and cost of materials for three pavement structures Fatigue life of Minimum of Natural gas Material Total fatigue-resistant interlaminar consumption cost/ten-thousand amount of layer at 800 shear CO.sub.2 during material yuan mixture/t με/time strength/MPa emission/kg production/m.sup.3 Structure I 976.46 22250 364220 1.47 38335.3 19518.9 Structure II 943.74 26250 109950 0.95 392936.3 200069.4 Structure III 1198.75 51250 62500 0.48 249179.0 126873.2

[0067] By analyzing the data in Table 7, it may be seen that compared with the conventional long-life pavement structure, the ultra-thin long-life pavement has excellent fatigue-resistant performance and good integrity of pavement structure. The ultra-thin long-life pavement greatly reduces the thickness of the pavement structure. Compared with structure II and structure III, the amount of mixture is decreased by 15.2% and 56.6%, respectively. The material cost is increased by 3.5% compared to structure II, and is decreased by 8.1% compared to structure III. Moreover, since the polyurethane mixture in the ultra-thin long-life pavement is constructed at normal temperature, the CO.sub.2 emission and the natural gas consumption are reduced by 90.2% and 84.6%, respectively, compared with structure II and structure III. In conclusion, the recommended full-depth ultra-thin long-life pavement structure has significant economic and environmental benefits and is valuable for promotion and application.