An ultra-thin high-performance fiber concrete pavement overlay and a construction method thereof

Abstract

This invention relates to the field of pavement engineering technology and discloses an ultra-thin high-performance fiber-reinforced concrete pavement overlay and its construction method. The pavement includes an existing base course and a high-performance fiber-reinforced concrete overlay laid on top of the base course. The overlay is constructed from C100 high-performance fiber-reinforced concrete, with a 28-day compressive strength of not less than 100 MPa and a flexural tensile strength of not less than 6 MPa. This invention achieves a balance between ultra-thinness and high performance in the overlay by optimizing the mix proportions of the high-performance fiber-reinforced concrete and rationally selecting fiber parameters. This significantly reduces the self-weight and material consumption of the overlay, shortening the construction cycle. Furthermore, it possesses excellent mechanical properties, crack resistance, and wear resistance, making it suitable for old pavement reconstruction, heavy-duty pavement overlay, airport runway overlay, urban road upgrades, and special pavement projects with limitations on pavement thickness, showing broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of road engineering technology, specifically relating to an ultra-thin high-performance fiber concrete pavement overlay and its construction method. Background Technology

[0002] In road construction, with the continuous increase in traffic volume, the number of heavy-duty vehicles, and the extension of service life, existing road surfaces often experience problems such as damage, cracking, settlement, and decreased wear resistance, affecting their performance and safety. Currently, the main way to solve these problems is to lay an overlay layer on the existing ordinary concrete pavement. This overlay layer compensates for the performance defects of the original pavement, restores its load-bearing capacity and traffic quality, and extends its service life.

[0003] Existing road overlays are mostly made of ordinary concrete, asphalt concrete, or conventional steel fiber reinforced concrete (FRC). Among them, ordinary concrete overlays are relatively inexpensive, but have disadvantages such as low tensile strength, poor crack resistance, and long construction period. In order to ensure sufficient load-bearing capacity, the thickness of the overlay usually needs to reach more than 80mm, resulting in heavy self-weight of the overlay, large material consumption, increased load on the original base layer, and easy problems such as delamination and voids between the overlay and the base layer. Asphalt concrete overlays have a fast construction speed, but poor high temperature resistance and weak heavy load resistance, easy to rutting, bleeding and other diseases, and short service life. Although FRC overlays have improved crack resistance and tensile strength, it is difficult to achieve both high strength and thinness. To achieve a high compressive strength, such as above 80MPa, the thickness of the overlay still needs to be controlled at more than 50mm, and it cannot meet the requirements of some scenarios with strict restrictions on pavement thickness, such as the overlay of old bridge decks and the overlay of urban elevated roads. Summary of the Invention

[0004] The present invention aims to provide an ultra-thin high-performance fiber concrete pavement overlay and its construction method, in order to solve the technical problems of existing pavement overlays, such as large thickness, high self-weight, insufficient mechanical properties, difficulty in achieving both high strength and thinness, weak bonding between the overlay and the base layer, and long construction period.

[0005] To achieve the above objectives, this solution provides an ultra-thin high-performance fiber-reinforced concrete pavement overlay, which is installed on the base pavement and includes an interface bonding layer between the base pavement and the overlay. The overlay is made of high-performance fiber-reinforced concrete with a strength grade of C100. The 28-day compressive strength of the C100 high-performance fiber-reinforced concrete is greater than or equal to 100 MPa, and the standard value of its flexural tensile strength is greater than or equal to 6 MPa. The C100 high-performance fiber-reinforced concrete comprises the following raw materials in the following mass ratio: cement: nanocrystalline powder: fly ash: mineral powder: manufactured sand: resin: short fiber: water-reducing agent: defoamer: water = 400:200:200:200:1170: 5:10:5:1:200. The short fibers are coated on pre-absorbed resin and are PVA fibers or polypropylene fibers. The steel fiber volume content in the C100 high-performance fiber-reinforced concrete is 0.6%–1.5%. The applicant has found that in the preparation of high-strength concrete with a strength grade ≥ C80, problems such as unreasonable mix proportions, uneven steel fiber dispersion, and poor interfacial bonding performance often exist, leading to unstable mechanical properties of the concrete and difficulty in consistently meeting the C100 strength grade requirements. Furthermore, its flexural tensile strength is usually difficult to exceed 5 MPa, failing to meet the performance requirements of heavy-load, high-frequency traffic surfaces for overlays. In addition, in the existing overlay construction process, the interface treatment is not standardized, resulting in insufficient bond strength between the overlay and the original base layer, easily leading to delamination, peeling, and other defects, affecting the overall stability and service life of the overlay. C100 and higher grade concrete has been gradually applied in various engineering fields, possessing extremely high compressive and tensile strength and excellent durability. Ultra-high performance concrete (UHPC) can reach a strength grade of C120 or higher, exhibiting very excellent compressive, tensile, and flexural mechanical properties; however, due to its high cost, it has not yet been widely adopted. High-performance fiber concrete with a strength grade of C100 has significant mechanical and cost advantages in engineering practice because the fiber content can be adjusted as needed and its cost is much lower than that of UHPC. The inventors considered using high-performance fiber concrete with a strength grade of C100 for pavement overlays. By optimizing the mix proportion of high-performance fiber concrete and the steel fiber parameters, they aimed to solve the technical problems of insufficient strength, poor crack resistance, and weak interfacial bonding in ultra-thin overlays, and achieve a unified ultra-thin and high-performance overlay, namely, a strength grade of C100, compressive strength ≥100MPa, and flexural strength ≥6MPa.

[0006] This solution optimizes the mix proportions of high-performance fiber-reinforced concrete, rationally selects steel fiber parameters, and standardizes construction techniques to achieve uniformity between the overlay thickness and the C100 high-strength grade. This ensures the overlay possesses excellent compressive, flexural, tensile, crack-resistant, and abrasion-resistant properties, while reducing the overlay's self-weight and material usage, shortening the construction cycle, improving the bonding stability between the overlay and the original base layer, and extending the overall service life of the pavement. It provides a high-performance fiber-reinforced concrete pavement overlay for the repair and renovation of old cement concrete or asphalt pavements, suitable for projects such as old pavement reconstruction, heavy-duty pavement overlay, airport runway overlay, and urban road upgrades, especially suitable for scenarios with limited pavement thickness and high requirements for pavement mechanical properties.

[0007] In this scheme, the flexural strength of concrete is tested according to Chapter 10 of the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" GB / T 50081-2019. The specimens are 150mm×150mm×550mm prism specimens, with three-point loading, a support span of 450mm, and a loading rate of 0.08~0.10MPa / s. The specimen preparation and steel fiber dispersion control should meet the requirements of "Steel Fiber Reinforced Concrete" JG / T 472-2015.

[0008] The mixing ratio of cement, nanocrystalline powder, fly ash, mineral powder, manufactured sand, water-reducing agent, defoamer, and water is based on the quality control requirements for high-strength and high-performance concrete. A low water-cement ratio is used to ensure the density and strength of the concrete. The reasonable combination of nanocrystalline powder, fly ash, and mineral powder improves the activity of the cementitious material system, enhances the mechanical properties and durability of the concrete, and controls the total amount of cementitious materials to avoid excessive heat of hydration that could lead to cracking of the overlay, while also improving the durability and crack resistance of the concrete.

[0009] Furthermore, the nanocrystalline powder is micro-nano-scale stone powder. The mineral powder, being a nanocrystalline powder or micro-nano-scale stone powder, has a large specific surface area and high surface energy, making it a core component for finely controlling the microstructure in C100 concrete, used for nanoscale filling, crystal nucleation, and active hydration.

[0010] Furthermore, the cement used is P·O52.5 ordinary Portland cement, ensuring sufficient strength reserve to meet the strength requirements of C100 concrete; the fly ash is Class F Grade I fly ash, which can improve the workability of C100 concrete, reduce heat of hydration, and enhance long-term strength and durability; the mineral powder is S95 grade mineral powder with much higher activity than fly ash, possessing both pozzolanic activity and weak hydraulic properties. Its core value lies in enhancing the early and late strength of C100 concrete, significantly improving durability, and regulating heat of hydration, making it a core admixture for C100 high-performance, high-strength concrete.

[0011] Furthermore, the manufactured sand is prepared using stone scraps, with a particle size range of 2.3–3.0 mm, a mud content ≤1.0%, a mud lump content ≤0.5%, and a crushing value ≤10%. Using small-diameter aggregates ensures uniform distribution of aggregates in the ultra-thin overlay, avoiding localized stress concentration caused by large-diameter aggregates, while simultaneously improving the density and interfacial bonding performance of the concrete. High-quality manufactured sand aggregates also improve the workability of the concrete, ensuring compaction during pouring and preventing defects such as honeycomb and pitting. In C100 ultra-high strength high-performance concrete, manufactured sand is an essential fine aggregate. Its artificially controllable gradation, active stone powder content, and low defect index not only solve the gradation, purity, and stability problems of natural river sand in ultra-high strength systems but also form a synergistic compaction effect with the highly active cementitious system. From the aggregate skeleton, interfacial transition zone, workability of the mixture, to volume stability, it comprehensively supports C100 concrete in achieving compressive strengths above 100 MPa and high-performance requirements.

[0012] Furthermore, the water-reducing agent is a powder water-reducing agent with polycarboxylate as the main component, with a solid content of about 98%, a water reduction rate of not less than 30%, no chloride salts, and a slump loss over time (1h) ≤20mm. The high water reduction rate water-reducing agent can ensure that the concrete has good workability under low water-cement ratio conditions, which is convenient for the pouring and vibration of ultra-thin overlays. The absence of chloride salts can avoid corrosion of steel fibers and the original base layer. The small slump loss over time can ensure the stable construction performance of the concrete.

[0013] Furthermore, the defoamer is an organosilicon solid defoamer. In C100 ultra-high strength high-performance concrete, the defoamer is a key admixture for controlling gas, achieving density, maintaining strength, and improving durability. Its core function is to support the C100 concrete to achieve ultra-high strength performance from three dimensions: strength, density, and workability, by eliminating harmful air bubbles, optimizing the interface structure, and improving the density of the paste, while also taking into account the workability of construction and long-term durability.

[0014] Furthermore, the steel fibers are one or more of the following: hooked, corrugated, or microfiber steel fibers. The steel fiber diameter is 0.15 mm to 0.75 mm, the steel fiber length is 13 mm to 60 mm, and the aspect ratio is 40 to 120; the tensile strength is greater than or equal to 1100 MPa. The aspect ratio and volumetric content of the steel fibers are optimized to ensure that the steel fibers are uniformly dispersed in the concrete, effectively reinforcing and toughening the concrete, improving its flexural strength and crack resistance, while avoiding problems such as decreased workability and construction difficulties caused by excessive steel fiber content.

[0015] Furthermore, the surface of the steel fibers undergoes rust prevention treatment, with the rust prevention layer being copper plating, zinc plating, or an epoxy coating. This rust prevention treatment, along with the copper plating, zinc plating, or epoxy coating, effectively enhances the corrosion resistance of the steel fibers, preventing concrete cracking caused by steel fiber corrosion and extending the service life of the overlay.

[0016] Furthermore, the interface bonding layer uses epoxy resin adhesive or polymer cement grout, with a thickness of 0.5–1.5 mm and a bonding strength greater than or equal to 2.5 MPa. The interface bonding layer effectively improves the bonding strength between the overlay and the original substrate, preventing problems such as delamination, peeling, and voids, ensuring that the overlay and the original substrate work together to share the load.

[0017] Furthermore, the interfacial bonding layer is sprayed with fibers, specifically steel fibers. The connection between the overlay and the original base layer is prone to cracking under horizontal shear force, ultimately leading to delamination between the overlay and the original base layer. This solution involves spraying an additional layer of fibers onto the interfacial bonding layer, which helps improve the shear resistance at the connection between the overlay and the original base layer.

[0018] Furthermore, the surface of the high-performance fiber concrete overlay is provided with anti-slip texture, the depth of which is 1-2 mm and the spacing between the textures is 20-30 mm. The anti-slip texture can improve the anti-skid performance of the road surface and ensure vehicle traffic safety. The flatness error of the high-performance fiber concrete overlay is ≤3 mm / 3 m, ensuring the road surface's traffic comfort.

[0019] Furthermore, the resin is acrylic SAP with a particle size of 100μm-300μm and a resin content of 0.5% of the cementitious material mass; the short fiber length is 0.5-1mm, and the short fiber length is greater than the resin particle size; the short fiber is PVA fiber or polypropylene fiber, and the PVA fiber or polypropylene fiber content is 1.0% of the cementitious material mass. Because high-performance concrete has a low water-cement ratio, the internal water is rapidly consumed in the early stages of hydration, leading to self-shrinkage and early cracking. In this solution, small-particle pre-absorbed resin is added to the high-performance concrete to release water in the early stages of hydration, alleviating the problems of initial self-shrinkage and early cracking. Since the resin will have large pores after water loss, affecting the strength of the concrete, this solution uses short fibers to coat the pre-absorbed resin. Initially, the short fibers will form spiral or other curved shapes due to water absorption. After water loss, the short fibers will gradually straighten under the self-shrinkage of the concrete, compensating for the strength loss caused by the pores after the resin releases water, thus ensuring the strength of the concrete.

[0020] Furthermore, the base course pavement is provided with a grid-shaped groove, which is filled with C100 high-performance fiber-reinforced concrete. The top edge of the grid-shaped groove is chamfered. When a vehicle starts, brakes, or turns on the overlay pavement, it generates a large horizontal shear force. The overlay pavement transfers this horizontal shear force to the base course pavement, forming interlayer shear force. The high-performance fiber-reinforced concrete in the grid-shaped groove can enhance shear strength, which is beneficial for the base course pavement and the overlay pavement to share the stress together, avoiding delamination and cracking of the base course pavement and the overlay pavement. The chamfered top edge of the grid-shaped groove can further reduce stress concentration and effectively reduce the risk of delamination and cracking of the base course pavement and the overlay pavement.

[0021] Furthermore, the steel fiber content in the fiber-reinforced concrete at the top of the grid-shaped groove is greater than that in the fiber-reinforced concrete in the rest of the grid-shaped groove. This increases the fiber content at the connection between the overlay and the original base layer, effectively enhancing the resistance to shear stress damage and reducing the risk of separation between the overlay and the original base layer.

[0022] This invention also discloses a construction method for the above-mentioned high-performance fiber-reinforced concrete pavement overlay, comprising the following steps: (1) Base treatment: Clean, repair and grind the base road surface. After repair, the surface flatness error of the base is less than or equal to 5mm / 3m. Then roughen or chisel the surface of the base road. (2) Construction of interface bonding layer: Apply interface bonding layer evenly to the treated base road surface, with the coating thickness controlled at 0.5-1.5mm. After application, let stand for 10-20 minutes until the interface bonding layer is semi-dry. (3) Preparation of high-performance fiber concrete: According to the preset mix ratio, cement, nano-microcrystalline powder, fly ash, mineral powder and manufactured sand are put into the mixer and dry-mixed for 2-3 minutes. After mixing evenly, steel fibers are added and dry-mixed for 1-2 minutes to ensure that the steel fibers are evenly dispersed. Then, pre-absorbed resin and short fibers coated on its surface are added and stirred for 1-2 minutes to ensure that the monofilaments are dispersed and do not clump together. Finally, the dissolved water-reducing agent, organosilicon solid defoamer and water are added and wet-mixed for 3-5 minutes to prepare C100 high-performance fiber concrete. (4) Overlay pouring: The prepared C100 high-performance fiber concrete is evenly laid on the interface bonding layer and compacted by using a plate vibrator or vibrating beam for 30-60 seconds to avoid over-vibration that causes the steel fibers to float. During the pouring process, the thickness of the overlay is controlled according to the type of overlay. When using a combined type, the thickness of the overlay is greater than or equal to 25mm, and when used for bridge deck pavement, the thickness of the overlay is greater than or equal to 60mm. (5) Surface treatment: Before the high-performance fiber concrete sets, it is smoothed and then anti-slip texture is made. The depth of the anti-slip texture is 1-2 mm and the texture spacing is 20-30 mm. (6) Curing: After pouring, cover the surface of the high-performance fiber concrete with geotextile or plastic film for moist curing. The curing temperature is controlled at 20±2℃, the relative humidity is greater than or equal to 95%, and the curing time is not less than 14 days. (7) Quality inspection: After curing, the thickness, flatness, compressive strength, flexural strength and interfacial bond strength of the high-performance fiber concrete overlay are tested. Once the test is qualified, it can be put into use.

[0023] Furthermore, step (1) also includes processing a grid-shaped groove in the base pavement. In step (4), the grid-shaped groove is first filled with C100 high-performance fiber concrete to a predetermined depth, and then the overlay is poured. When a vehicle starts, brakes, or turns on the overlay, it will generate a large horizontal shear force. The overlay will transfer this horizontal shear force to the base pavement, forming interlayer shear force. The high-performance fiber concrete in the grid-shaped groove can enhance the shear strength, which is conducive to the base pavement and the overlay pavement sharing the stress together, and avoids the base pavement and the overlay pavement from splitting and cracking.

[0024] Compared with the prior art, the present invention has the following advantages: 1. Achieving a balance between ultra-thinness and high performance in overlay layers: This invention uses high-performance fiber-reinforced concrete to pour the pavement overlay. While ensuring strength, it can reduce the thickness compared to existing ordinary concrete overlay layers, achieving ultra-thinness and significantly reducing the self-weight and material usage of the overlay, thus reducing the load on the original base layer. Using C100 high-performance fiber-reinforced concrete, it ensures that the 28-day compressive strength of the overlay is not less than 100MPa and the standard value of flexural tensile strength is not less than 6MPa, exhibiting excellent mechanical properties and effectively bearing the load of heavy vehicles. This solves the technical problem of balancing high strength and thinness in existing overlay layers, making it suitable for scenarios with strict limitations on pavement thickness.

[0025] 2. Excellent crack resistance and durability: By optimizing the mix proportion of C100 high-performance fiber concrete and combining it with active admixtures such as nano-microcrystalline powder, fly ash, and mineral powder, the microstructure of the concrete is improved, enhancing its density. Simultaneously, the addition of high-quality steel fibers forms a three-dimensional network support structure within the concrete, effectively inhibiting the generation and propagation of concrete cracks and improving the crack resistance, wear resistance, and fatigue resistance of the overlay. The steel fiber surface is treated with rust prevention, and the interface bonding layer enhances the bonding stability between the overlay and the original base layer, effectively preventing cracking, peeling, voids, corrosion, and other defects in the overlay, extending its service life to over 30 years. This is significantly longer than the 5-8 years of existing asphalt concrete overlays, 15-20 years of ordinary plain concrete pavements, and 20-30 years of ordinary reinforced concrete pavements.

[0026] 3. Short construction period and convenient construction: The overlay layer of this invention is thin, with less concrete usage, and the C100 high-performance fiber concrete has good workability, making pouring and vibration convenient. The curing time is only 14 days, which is more than 50% shorter than the existing concrete overlay layer curing time of ≥28 days. This can effectively reduce the impact on traffic and is especially suitable for overlay projects in busy traffic areas such as urban roads and airport runways.

[0027] 4. Reasonable cost and strong practicality: By optimizing the mix ratio and rationally selecting raw materials, this invention controls the cost of raw materials while ensuring high performance; the overlay layer is thin, the construction workload is small, and the construction cost is low, which reduces the cost by 20% to 30% compared with existing overlay technologies; at the same time, the construction process is standardized and convenient, and it can be applied to a variety of scenarios such as old road reconstruction, heavy-duty road overlay, airport runway overlay, and old bridge deck overlay, which is highly practical and has broad application prospects.

[0028] 5. Green and environmentally friendly, energy-saving and emission-reducing: The mix proportion of this invention uses industrial waste such as slag powder, realizing the resource utilization of industrial waste, reducing the pollution from the stockpiling of industrial waste, and reducing the amount of cement used, thereby reducing carbon emissions in the cement production process, which is in line with the development trend of green building and energy conservation and emission reduction. In addition, the overlay layer has a long service life, which can reduce the workload and material consumption of later maintenance and renovation, further improving environmental benefits. Attached Figure Description

[0029] Figure 1 This is a schematic plan view of the high-performance fiber-reinforced concrete overlay in Embodiment 1 of the present invention.

[0030] Figure 2 for Figure 1 A schematic diagram of the AA-direction cross-section structure.

[0031] Figure 3 for Figure 1 A schematic diagram of the BB-direction cross-sectional structure. Detailed Implementation

[0032] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the following: The reference numerals in the accompanying drawings include: 1. base course, 2. interface bonding layer, 3. road overlay, 4. anti-skid texture, and 5. grid-shaped groove. Example 1:

[0033] This solution provides an ultra-thin, high-performance fiber-reinforced concrete pavement overlay, such as... Figure 1 , Figure 2 and Figure 3 As shown, the road overlay 3 is set on the base road 1, including the original base road 1 (old cement concrete road of urban main road) and the road overlay 3 laid on the surface of the original base road 1. In this embodiment, the thickness of the road overlay 3 is 30mm, and it is made of C100 high-performance fiber concrete.

[0034] The mix proportions (by mass) of the following components in C100 high-performance fiber-reinforced concrete are as follows: Cement: Nanocrystalline powder: Fly ash: Mineral powder: Manufactured sand: Resin: Short fiber: Water-reducing agent: Defoamer: Water = 400:200:200:200:1170: 5:10:5:1: 1:200. The resin is acrylic SAP with a particle size of 100μm-300μm, and the resin content is 0.5% of the cementitious material mass. The short fibers are PVA fibers or polypropylene fibers, which are coated on pre-absorbed resin. The short fibers have a length of 0.5-1mm and are longer than the resin particle size. The short fibers are PVA fibers or polypropylene fibers, and the PVA fiber or polypropylene fiber content is 1.0% of the cementitious material mass.

[0035] Because high-performance concrete has a low water-cement ratio, the water inside is rapidly consumed in the early stages of hydration, leading to problems such as autogenous shrinkage and early cracking. In this solution, small particles of pre-absorbed resin are added to the high-performance concrete to release water in the early stages of hydration, thus alleviating the problems of autogenous shrinkage and early cracking in the early stages of high-performance concrete. Since the resin will have large pores after losing water, affecting the strength of the concrete, this solution uses short fibers to coat the pre-absorbed resin. Initially, the short fibers will form spiral or other curved shapes due to water absorption. After the short fibers lose water, they will gradually straighten under the autogenous shrinkage of the concrete, compensating for the strength loss caused by the pores after the resin releases water.

[0036] Raw material selection: Cement is P·O52.5 ordinary Portland cement; fly ash is Class F Grade I fly ash; mineral powder is S95 grade mineral powder; manufactured sand is manufactured sand prepared from stone scraps; nano-crystalline powder is micro-nano grade stone powder; water-reducing agent is a powder water-reducing agent with polycarboxylate as the main component, with a solid content of about 98%; defoamer is an organosilicon solid defoamer; water is drinking water with a pH value of 6~8.

[0037] The steel fibers used are one or more of the following: hooked, corrugated, or microfiber type. The fiber diameter ranges from 0.15 mm to 0.75 mm, the fiber length from 13 mm to 60 mm, the aspect ratio from 40 to 120, and the volumetric content from 0.6% to 1.5%. The tensile strength of the steel fibers is greater than or equal to 1100 MPa. The optimized aspect ratio and volumetric content of the steel fibers ensure uniform dispersion in the concrete, effectively reinforcing and toughening it, improving the flexural strength and crack resistance of the concrete, while avoiding problems such as decreased workability and construction difficulties caused by excessive steel fiber content.

[0038] The steel fiber surface undergoes rust-proofing treatment, with the rust-proofing layer employing copper plating, zinc plating, or epoxy coating. This rust-proofing treatment effectively enhances the steel fiber's corrosion resistance, preventing concrete cracking caused by steel fiber corrosion and extending the service life of the overlay.

[0039] In this embodiment, copper-plated steel wire is used as the steel fiber. The steel fiber diameter is 0.20 mm, the steel fiber length is 13 mm, and the steel fiber aspect ratio is 65. The tensile strength is not less than 1100 MPa, and the steel fiber volume content is 1%.

[0040] Among them, the fly ash is Class F Grade I fly ash, which can improve the workability of C100 concrete, reduce the heat of hydration, and enhance long-term strength and durability. The mineral powder is S95 grade mineral powder with much higher activity than fly ash, and has both pozzolanic activity and weak hydraulic properties. Its core value is to improve the early and late strength of C100 concrete, significantly improve durability, and regulate the heat of hydration. It is a core admixture for C100 high-performance and high-strength concrete.

[0041] The particle size range of manufactured sand is 2.3 to 3.0 mm, with a mud content of ≤1.0%, a mud lump content of ≤0.5%, and a crushing value of ≤10%. Using small-sized aggregates can ensure that the aggregates are evenly distributed in the ultra-thin overlay layer, avoid local stress concentration caused by large-sized aggregates, and improve the compactness and interfacial bonding performance of concrete. At the same time, high-quality manufactured sand aggregates can improve the workability of concrete, ensure that the concrete is vibrated and compacted during the pouring process, and avoid defects such as honeycomb and pitting.

[0042] Water-reducing agent is a powder water-reducing agent with polycarboxylate as the main component. Its solid content is about 98%, the water reduction rate is not less than 30%, it does not contain chloride salt, and the slump loss over time (1h) is ≤20mm. Water-reducing agent with high water reduction rate can ensure that concrete has good workability under low water-cement ratio.

[0043] The flexural tensile strength of concrete was tested according to Chapter 10 of the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" GB / T 50081-2019. The specimens were 150mm×150mm×550mm prisms, with three-point loading, a support span of 450mm, and a loading rate of 0.08~0.10MPa / s. Specimen preparation and steel fiber dispersion control should simultaneously comply with the requirements of "Steel Fiber Reinforced Concrete" JG / T 472-2015. The 28-day flexural strength test values ​​of some C100 high-performance fiber reinforced concrete specimens with 1% steel fiber volume content are shown in Table 1.

[0044] An interface bonding layer 2 is provided between the existing base pavement 1 and the high-performance fiber concrete overlay. In this embodiment, an epoxy resin bonding layer with a thickness of 0.5~1.5mm and a bonding strength greater than or equal to 2.5MPa is provided between the base pavement 1 and the overlay 3. In this embodiment, the thickness is 1.0mm and the bonding strength is 3.0MPa. The surface of the high-performance fiber concrete overlay is provided with anti-slip texture 4. The depth of the anti-slip texture 4 is 1~2mm and the texture spacing is 20~30mm. In this embodiment, the depth is 1.5mm, the texture spacing is 25mm, and the flatness error is ≤2mm / 3m. By setting the anti-slip texture 4, the anti-slip performance of the pavement is improved, ensuring vehicle traffic safety; the flatness error of the high-performance fiber concrete overlay is ≤3mm / 3m, ensuring the comfort of the pavement.

[0045] The interfacial bonding layer 2 is sprayed with fibers, specifically steel fibers. The connection between the overlay layer 3 and the original base layer is prone to cracking under horizontal shear force, ultimately leading to delamination between the overlay layer 3 and the original base layer. This solution involves spraying an additional layer of fibers onto the interfacial bonding layer 2, which helps improve the shear resistance at the connection between the overlay layer 3 and the original base layer.

[0046] Furthermore, the base pavement 1 is provided with grid-shaped grooves 5, the dimensions of which are: 100mm wide, 50mm deep, and 2m apart. After applying the adhesive, C100 high-performance fiber concrete is simultaneously poured within the grid-shaped grooves 5 and the designed thickness of the overlay layer 3. When vehicles start, brake, or turn on the overlay layer 3, they will generate a large horizontal shear force. The overlay layer 3 will transfer this horizontal shear force to the base pavement 1, forming interlayer shear force. The high-performance fiber concrete in the grid-shaped grooves 5 can enhance the shear strength, which is conducive to the coordinated stress distribution between the base pavement 1 and the overlay layer 3, and prevents the base pavement 1 and the overlay layer 3 from delaminating and cracking.

[0047] The chamfered top edge of the grid-shaped groove 5 can further reduce stress concentration and effectively reduce the risk of delamination and cracking of the base pavement 1 and the pavement overlay 3.

[0048] The steel fiber content in the fiber-reinforced concrete at the top of the grid-shaped groove 5 is greater than that in the fiber-reinforced concrete in the rest of the grid-shaped groove 5. This additional increase in steel fiber content near the base course 1 effectively enhances the resistance of the joint to shear stress damage, reducing the risk of delamination and cracking between the base course 1 and the overlay 3.

[0049] The construction method is as follows: (1) Base treatment: Clean the surface dust and loose debris of the original base road 1, repair the damaged parts of the road, and use epoxy mortar to repair the cracks with a width of 0.3mm. After repair, the flatness error of the base surface is ≤4mm / 3m. Then, use a chisel to chisel the base surface to a depth of 2mm to increase the bonding area of ​​the interface. And process the grid-shaped groove 5 in the base road 1.

[0050] If there are cracks in the existing ordinary concrete pavement in this step, the cracks need to be repaired first. When the crack width is ≤0.5mm, epoxy mortar is used for injection repair; when the crack width is >0.5mm, grooved joint repair is used, and polyurethane joint sealant is used as the joint sealant material.

[0051] In this step, a grid-shaped groove is processed on the base pavement 1. The dimensions of the grid-shaped groove 5 are: 100mm wide, 50mm deep, and 2m apart. At the same time, the top edge of the grid-shaped groove 5 is chamfered.

[0052] (2) Construction of interface bonding layer 2: Apply epoxy resin adhesive evenly to the treated base surface with a coating thickness of 1.0 mm. After application, let stand for 15 minutes until the bonding layer is semi-dry.

[0053] In this step, after applying the epoxy resin adhesive, fibers are sprayed onto the adhesive. The fibers can specifically be steel fibers.

[0054] (3) Preparation of high-performance fiber concrete: According to the preset mix proportion, cement, nano-microcrystalline powder, fly ash, mineral powder, and manufactured sand are added to the mixer and dry-mixed for 2-3 minutes. After uniform mixing, steel fibers are added and dry-mixed for another 1-2 minutes to ensure uniform dispersion of steel fibers. Then, pre-absorbed resin and short fibers coated on its surface are added and stirred for 1-2 minutes to ensure that the monofilaments are dispersed and do not clump together. Finally, dissolved water-reducing agent, organosilicon solid defoamer, and water are added and wet-mixed for 3-5 minutes to prepare C100 high-performance fiber concrete. During the preparation process, the metering accuracy is controlled. The metering deviation of cementitious materials, water, and admixtures is ≤ ±0.4%, and that of aggregates is ≤ ±0.8%. The concrete spread is tested at 720 mm, the V-shaped funnel outflow time is 10 s, the pressure bleeding rate is 1.8%, and the workability is good.

[0055] The aforementioned resin is acrylic-based SAP with a particle size of 100μm-300μm and a resin content of 0.5% of the cementitious material mass. The short fiber length is 0.5-1mm, and the short fiber length is greater than the resin particle size. The short fiber is PVA fiber or polypropylene fiber, and the PVA fiber or polypropylene fiber content is 1.0% of the cementitious material mass. C100 high-performance fiber concrete comprises the following raw materials in the following mass ratio: cement: nanocrystalline powder: fly ash: mineral powder: manufactured sand: resin: short fiber: water-reducing agent: defoamer: water = 400:200:200:200:1170: 5:10:5:1:200; the steel fiber volume content in C100 high-performance fiber concrete is 0.6%~1.5%. Due to the low water-cement ratio of high-performance concrete, the internal water is rapidly consumed in the early stages of hydration, leading to problems such as autogenous shrinkage and early cracking. This solution mitigates the problems of early autogenous shrinkage and early cracking in high-performance concrete by adding pre-absorbed resin particles with small particles that release water during the initial hydration stage. At the same time, the short fibers gradually straighten under the autogenous shrinkage of the concrete after water loss, compensating for the strength loss caused by the pores after the resin releases water.

[0056] The process for coating short fibers onto resin is as follows: Short fibers are treated with cationic polyacrylamide (C-PAM) to impart a stable positive charge to their surface. Since the resin SPA particles are negatively charged, the short fibers and resin SPA particles attract each other, causing the short fibers to coat the resin SPA. The resin SPA particles are then placed in a mixing device equipped with two parallel and opposite metal plates connected to the positive and negative terminals of a power source to create an electrostatic field inside the mixing device. After the resin SPA particles are placed in the mixing device, charged short fibers are sprayed into the mixing device, and the short fibers quickly adhere to the surface of the resin SPA through the electrostatic field.

[0057] (4) Overlay pouring: The concrete is evenly laid on top of the interface bonding layer 2, and vibrated for 45 seconds with a plate vibrator to ensure compaction and avoid over-vibration; the thickness control ruler is used to detect in real time to ensure that the thickness of the overlay is 30mm and the pouring speed is 1.5m / min.

[0058] First, C100 high-performance fiber concrete is poured within the designed thickness of the grid-shaped groove 5. The steel fiber content in the fiber concrete at the top of the grid-shaped groove 5 is greater than that in the fiber concrete in the rest of the grid-shaped groove 5. Specifically, a portion of the C100 high-performance fiber concrete is used to add additional steel fibers to the top of the grid-shaped groove 5.

[0059] Then, C100 high-performance fiber-reinforced concrete is used to pour the overlay layer 3 of the designed thickness. When vehicles start, brake, or turn on the overlay layer 3, they generate significant horizontal shear forces. The overlay layer 3 transfers these horizontal shear forces to the base pavement 1, forming interlayer shear forces. The high-performance fiber-reinforced concrete within the grid-shaped grooves 5 enhances shear strength, which is beneficial for the base pavement 1 and the overlay layer 3 to share the load, preventing the base pavement 1 and the overlay layer 3 from delaminating and cracking. In this embodiment, the size and spacing of the grid-shaped grooves 5 are set according to the pavement structure calculation and the thickness of the overlay layer 3 to ensure the connection strength between the base pavement 1 and the overlay layer 3.

[0060] (5) Surface treatment: Before the concrete sets, use a power trowel to smooth it, and then use a grooving machine to create anti-slip texture 4 with a depth of 1.5 mm and a texture spacing of 25 mm. Clean up concrete debris from the surface.

[0061] (6) Curing: After the pouring is completed, cover with geotextile to keep it moist and maintain the curing temperature at 20±2℃ and the relative humidity at 96% for 14 days. During the curing period, vehicles and personnel are prohibited from passing through.

[0062] (7) Quality inspection: After the curing is completed, the thickness of the overlay is 30±1mm, the flatness error is 2mm / 3m; the compressive strength (150mm cube specimen) is 105MPa, the standard value of flexural strength (150mm×150mm×550mm prism specimen) is 11.4MPa; the interface bond strength is 3.0MPa. All test indicators meet the requirements. After being put into use, the road surface is smooth and there are no defects such as cracks or peeling. The performance is good.

[0063] This solution provides an ultra-thin high-performance fiber-reinforced concrete pavement overlay. By optimizing the mix proportion of high-performance fiber-reinforced concrete, rationally selecting steel fiber parameters, and standardizing construction techniques, the thickness of the ultra-thin overlay is made consistent with the C100 high-strength grade, ensuring that the overlay has excellent compressive and flexural strength, as well as crack resistance and wear resistance. At the same time, it reduces the self-weight and material consumption of the overlay, shortens the construction period, improves the bonding stability between the overlay and the original base layer, and extends the overall service life of the pavement. Example 2:

[0064] An ultra-thin high-performance fiber-reinforced concrete pavement overlay includes an existing base pavement 1 and an overlay pavement 3 laid on the surface of the existing base pavement 1. In this embodiment, the base pavement is an old bridge deck cement concrete pavement. The overlay pavement 3 in this embodiment has a thickness of 60 mm and is made of C100 high-performance fiber-reinforced concrete. The composition of the C100 high-performance fiber-reinforced concrete in this embodiment is the same as that in Embodiment 1 above. The specific difference is that the steel fibers in this embodiment are copper-plated steel wires with a diameter of 0.20 mm, a length of 20 mm, and a fiber aspect ratio of 100.

[0065] In this embodiment, an epoxy resin bonding layer with a thickness of 0.8 mm and a bonding strength of 2.6 MPa is provided between the original base pavement 1 and the high-performance fiber concrete overlay layer; the surface of the high-performance fiber concrete overlay layer is provided with anti-slip texture 4 with a depth of 1.0 mm, a texture spacing of 20 mm, and a flatness error of ≤3 mm / 3 m.

[0066] In this embodiment, the base road surface 1 is provided with a grid-shaped groove 5, and the specific structure is the same as in the above embodiment 1.

[0067] In this embodiment, the construction method is the same as in Embodiment 1, with the vibration time adjusted to 30s, the pouring speed to 1.0m / min, and the curing time to 14d. After curing, the following were tested: the overlay thickness was 60±0.5mm, the flatness error was 2.8mm / 3m, the compressive strength was 100MPa, the standard value of the flexural strength was 14.0MPa, and the interfacial bond strength was 3.2MPa. These results meet the thickness and performance requirements of the overlay on the old bridge deck. After being put into use, the overlay effectively reduced the self-weight of the bridge deck, improved the load-bearing capacity and crack resistance of the bridge deck, and the performance was stable.

[0068] The above two embodiments are merely examples of implementation methods of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An ultra-thin high-performance fiber reinforced concrete overlay pavement provided on a base pavement, characterized in that, It also includes an interface bonding layer disposed between the base pavement and the overlay pavement, wherein the overlay pavement is made of high-performance fiber-reinforced concrete with a strength grade of C100, wherein the 28-day compressive strength of the C100 high-performance fiber-reinforced concrete is greater than or equal to 100 MPa, and the standard value of the flexural tensile strength is greater than or equal to 6 MPa; the C100 high-performance fiber-reinforced concrete comprises raw materials in the following mass ratio: Cement: Nanocrystalline powder: Fly ash: Mineral powder: Manufactured sand: Resin: Short fiber: Water-reducing agent: Defoamer: Water = 400:200:200:200:1170:5:10:5:1:200:; The short fiber is coated on pre-absorbed resin, and the short fiber is PVA fiber or polypropylene fiber; The volumetric content of steel fiber in the C100 high-performance fiber concrete is 0.6% to 1.5%.

2. The ultra-thin high performance fiber reinforced concrete pavement overlay of claim 1, wherein, The nanocrystalline powder is micro-nano-sized stone powder.

3. The ultra-thin high performance fiber reinforced concrete pavement overlay of claim 1, wherein, The steel fibers are one or more of the following: end-hooked, corrugated, or microfiber steel fibers. The steel fiber diameter is 0.15 mm to 0.75 mm, the steel fiber length is 13 mm to 60 mm, the steel fiber aspect ratio is 40 to 120, and the tensile strength is greater than or equal to 1100 MPa.

4. The ultra-thin high performance fiber reinforced concrete pavement overlay of claim 1, wherein, The steel fiber surface is treated with rust prevention, and the rust prevention layer is made of copper plating, zinc plating or epoxy coating.

5. The ultra-thin high performance fiber reinforced concrete pavement overlay of claim 1, wherein, The interface bonding layer uses epoxy resin adhesive or polymer cement slurry, with a thickness of 0.5 to 1.5 mm and a bonding strength greater than or equal to 2.5 MPa.

6. The ultra-thin, high-performance fiber reinforced concrete pavement overlay of claim 1, wherein, The resin is acrylic SAP with a particle size of 100μm-300μm and a resin content of 0.5% of the cementitious material mass; the short fiber has a length of 0.5-1mm and the length of the short fiber is greater than the particle size of the resin; the PVA fiber or polypropylene fiber content is 1.0% of the cementitious material mass.

7. The ultra-thin, high-performance fiber reinforced concrete pavement overlay of claim 1, wherein, The base road surface is provided with a grid-shaped groove, which is used to fill C100 high-performance fiber concrete, and the top edge of the grid-shaped groove is chamfered.

8. The construction method of an ultra-thin high-performance fiber concrete pavement overlay layer according to claim 1, characterized in that, Includes the following steps: (1) Base treatment: Clean, repair and grind the base road surface. After repair, the surface flatness error of the base is less than or equal to 5mm / 3m. Then roughen or chisel the surface of the base road. (2) Construction of interface bonding layer: Apply interface bonding layer evenly to the treated base road surface, with the coating thickness controlled at 0.5-1.5mm. After application, let stand for 10-20 minutes until the interface bonding layer is semi-dry. (3) Preparation of high-performance fiber concrete: According to the preset mix ratio, cement, nano-microcrystalline powder, fly ash, mineral powder and manufactured sand are put into the mixer and dry-mixed for 2-3 minutes. After mixing evenly, steel fibers are added and dry-mixed for 1-2 minutes to ensure that the steel fibers are evenly dispersed. Then, pre-absorbed resin and short fibers coated on its surface are added and stirred for 1-2 minutes to ensure that the monofilaments are dispersed and do not clump together. Finally, the dissolved water-reducing agent, organosilicon solid defoamer and water are added and wet-mixed for 3-5 minutes to prepare C100 high-performance fiber concrete. (4) Overlay pouring: The prepared C100 high-performance fiber concrete is evenly laid on the interface bonding layer and compacted by using a plate vibrator or vibrating beam for 30-60 seconds to avoid over-vibration that causes the steel fibers to float. During the pouring process, the thickness of the overlay is controlled according to the type of overlay. When using a combined type, the thickness of the overlay is greater than or equal to 25mm, and when used for bridge deck pavement, the thickness of the overlay is greater than or equal to 60mm. (5) Surface treatment: Before the high-performance fiber concrete sets, it is smoothed and then anti-slip texture is made. The depth of the anti-slip texture is 1-2 mm and the texture spacing is 20-30 mm. (6) Curing: After pouring, cover the surface of the high-performance fiber concrete with geotextile or plastic film for moist curing. The curing temperature is controlled at 20±2℃, the relative humidity is greater than or equal to 95%, and the curing time is not less than 14 days. (7) Quality inspection: After curing, the thickness, flatness, compressive strength, flexural strength and interfacial bond strength of the high-performance fiber concrete overlay are tested. Once the test is qualified, it can be put into use.

9. The method of claim 8, wherein the method further comprises the steps of: providing a base layer of concrete; and applying a layer of the ultra-thin high performance fiber concrete pavement overlay to the base layer of concrete. The step (1) also includes processing a grid-shaped groove in the base road surface. In the step (4), C100 high-performance fiber concrete of a preset depth is first filled into the grid-shaped groove, and then the overlay layer is poured.

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