Preparation method of assembled UHPC-ECC guardrail

Abstract

The invention discloses a preparation method of a split mounting type UHPC-ECC (Ultra High Performance Concrete-Engineered Cementitious Composite) guardrail. According to the method, UHPC is adopted for prefabricating a head-on collision surface, and an ECC material is adopted for prefabricating a supporting surface; a concave opening and a convex opening are correspondingly formed in the upper portion and the lower portion of the head-on collision face and the upper portion and the lower portion of the supporting face respectively, the concave opening and the convex opening are spliced into an internally-hollow cavity type structure through mortise and tenon joint, reserved communicating hole channels are transversely formed in the concave opening and the convex opening, reinforcing steel bars are inserted into the reserved hole channels in a penetrating mode, and finally the assembled UHPC-ECC guardrail is obtained by internally filling a filling material and curing the filling material. The advantages of high strength and compactness of the ultra-high performance concrete UHPC are fully played, and the reinforcing ribs are arranged on the back of the collision face, so that impact resistance and salt freezing resistance of the collision face are achieved; and on the other hand, deformation caused by impact on the guardrail is resisted through the high strain rate of the engineering cement-based composite material ECC, and effective protection is achieved. Secondly, the splicing units form an integral structure through the connecting steel bars, and constraint of the internal filling materials and the bottom of the guardrail is reduced through the rubber cushion layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of highway traffic safety facilities - guardrails, and particularly relates to a preparation method for a prefabricated UHPC-ECC guardrail. Background Art

[0002] Guardrails are an important part of highway traffic safety facilities. Highway guardrails include cable guardrails, corrugated beam guardrails, concrete guardrails, bridge guardrails and railings, median opening guardrails, and buffer facilities, etc. Among them, as an important material for median guardrails, the safety and durability of concrete guardrails during use are of great significance for maintaining driving safety. Concrete guardrails are usually made of C30 - C35 reinforced concrete structures, and are mainly divided into the following three categories according to the construction process: 1) Cast-in-place concrete guardrails. It is necessary to bind and weld steel bars during construction, fabricate steel bar cages; then formwork and pour concrete. The construction process is cumbersome, and a large number of construction workers are required. Moreover, due to being restricted by the on-site curing environment, the quality of concrete often cannot be guaranteed. 2) Prefabricated concrete guardrails. The quality of each process such as mixing, pouring, and curing of concrete raw materials can be effectively guaranteed in the factory prefabrication of concrete guardrails. However, the prefabricated guardrails are heavy in self-weight, with high transportation costs and low transportation efficiency. 3) Slip form method guardrails. The construction speed of the slip form method is fast, but like the cast-in-place concrete guardrails, the slip form method construction also requires a large number of construction workers to bind steel bars, and the construction quality is not easy to guarantee. Secondly, ordinary concrete, especially in northern regions, is prone to freeze-thaw damage under the freeze-thaw action of deicing salts or snow melting agents in winter. The surface starts to peel off and extends inward to a certain thickness, gradually losing its protective function.

[0003] In response to this situation, the existing treatment measures are mainly to apply anti-corrosion coatings such as lithium silicate, silane coupling agents, or polyurethane on the surface of newly built or damaged concrete guardrails. For new projects, when the surface concrete has not been damaged, this treatment measure can last for 3 - 4 years; however, for concrete guardrails with damaged surfaces, this treatment measure can only last for 1 - 2 years. Summary of the Invention

[0004] Based on the problems existing in the above-mentioned prior art, in the development and manufacturing process of the guardrail, the present invention introduces ultra-high performance concrete (UHPC) material, and makes full use of its high internal density and excellent anti-permeability performance to effectively inhibit the entry and diffusion of corrosive ions such as chloride salts and water molecules, realizing the self-anti-corrosion function of the impact-facing surface of the guardrail; secondly, engineered cementitious composite (ECC) is introduced. ECC still has 90% of the residual strength after secondary loading after damage, and still has good integrity when the shrinkage deformation is 7%, effectively ensuring that the guardrail still maintains the structural integrity and does not reduce its protection ability after bearing vehicle impact or other loads. The prepared assembled UHPC-ECC guardrail (1) gives full play to the material characteristics of UHPC and ECC, effectively ensuring the durability and deformation resistance of the guardrail; (2) factory prefabricates the impact-facing surface and the supporting surface units, effectively improving the curing conditions of the precast concrete components and ensuring the production quality of the precast components; (3) simplifies the structure into assembled units, which can effectively improve the transportation efficiency of the guardrail; (4) omits the workload of tying and welding steel bars on site, effectively reducing the number of on-site construction personnel and reducing environmental pollution.

[0005] The preparation method of the assembled UHPC-ECC guardrail is as follows: use UHPC to prefabricate the impact-facing surface and ECC material to prefabricate the supporting surface; the impact-facing surface and the supporting surface are respectively provided with notches and protrusions up and down, and the notches and protrusions are assembled into an internal hollow cavity structure through tenon and mortise joints. The notches and protrusions at the top and bottom of the impact-facing surface and the supporting surface are provided with reserved communication channels horizontally, steel bars are inserted into the reserved channels, and finally the internal filling material is filled and cured to obtain the assembled UHPC-ECC guardrail.

[0006] The width of the notch and the protrusion is 200-300 mm.

[0007] The length of the impact-facing surface and the supporting surface is 4-6 m, the side thickness is 30-50 mm, and the top and bottom thickness is 50-70 mm.

[0008] The diameter of the channel is 12-16 mm.

[0009] Reinforcing ribs are arranged inside the impact-facing surface, 2-3 ribs are arranged horizontally and evenly, and 1 rib is arranged vertically at an interval of 1 m. The width of the rib is 50 mm and the thickness is 50 mm.

[0010] The slump of the impact-facing surface is 750-800 mm, and the compressive strength is 120-130 MPa; the slump of the supporting surface is 600-700 mm, and the compressive strength is 50-60 MPa.

[0011] A rubber pad with a thickness of 2-3 mm is laid at the bottom inside the guardrail.

[0012] The impact - facing surface and the inner surface of the supporting surface are sprayed with a waterproof layer, and then a layer of fiber composite material cloth or fiber composite material grid is pasted; the outer surface is sprayed with a heat - reflective heat - insulating coating.

[0013] The waterproof layer is a polyurethane layer, an acrylate layer or a silicone rubber layer.

[0014] The strength of the filling material is not less than 20 MPa, and the maximum particle size of the aggregate shall not be greater than 16 mm.

[0015] The present invention adopts engineered prefabricated impact - facing surfaces and supporting surfaces, which is convenient for on - site assembly. The present invention gives full play to the advantages of ultra - high - performance concrete (UHPC) being high - strength and dense, and reinforcing ribs are arranged behind the impact - facing surface to achieve impact resistance and salt - freeze resistance of the impact - facing surface; on the other hand, the high strain - rate of engineered cementitious composite (ECC) is used to resist the deformation generated by the impact on the guardrail, achieving effective protection. Secondly, connecting steel bars are used to form an integral structure for the assembled units, and rubber cushion layers are used to reduce the constraint between the internal filling material and the bottom of the guardrail. Brief Description of the Drawings

[0016] Figure 1 Structural schematic diagram of the assembled UHPC - ECC guardrail.

[0017] Figure 2 Structural schematic diagram of the impact - facing surface.

[0018] Figure 3 Structural schematic diagram of the supporting surface.

[0019] Figure 4 Schematic diagram of the assembly process.

[0020] Figure 5 Schematic diagram of the reinforcing rib of the impact - facing surface.

[0021] In the figure: 1. Impact - facing surface, 2. Supporting surface, 3. Top connecting steel bar, 4. Bottom connecting steel bar, 5. Rubber pad, 6. Convex notch, 7. Concave notch, 8. Reinforcing rib. Detailed Embodiments

[0022] The following further describes the preparation method of an assembled UHPC - ECC guardrail according to the present invention in combination with specific embodiments, but the protection scope of the present invention is not limited thereto. Embodiment

[0023] (1) Prefabrication of the impact - facing surface and the supporting surface: Ultra-high performance concrete UHPC with a slump flow of 750 mm and a compressive strength of 126 MPa; the slump flow of the engineered cementitious composite for engineering is 600 mm and the compressive strength is 57 MPa. Pour the above two materials into the corresponding molds respectively. The curing regime in the first stage is curing at 40 - 50 °C for 6 - 8 h, and demold when the compressive strength reaches 80 MPa; after the impact-facing surface and the supporting surface units are demolded, the second-stage curing is carried out, and the curing regime is curing at 70 - 80 °C for 16 - 18 h.

[0024] Structural features of the impact-facing surface and the supporting surface: The thickness of the impact-facing surface unit and the supporting surface unit is 30 mm, the length is 4 m, and the thicknesses of the top and bottom are both 60 mm. Notches and protrusions are respectively arranged corresponding to the upper and lower parts of the impact-facing surface and the supporting surface. Communication holes are transversely opened in the notches and protrusions, and the diameter of the holes is 12 mm. The concave and convex parts are combined, and the widths of the notches and protrusions are 240 mm. Reinforcing ribs are arranged inside one side of the impact-facing surface. Two reinforcing ribs are arranged along the forming direction, and one reinforcing rib perpendicular to the driving direction of the guardrail is arranged at an interval of 1 m along the height direction of the guardrail. The thickness and width of the reinforcing ribs are both 50 mm.

[0025] Functional treatment of the impact-facing surface and the supporting surface: A layer of polyurethane waterproof layer with a thickness of 1 mm is sprayed on the inner surface of the prefabricated impact-facing surface and supporting surface units, and a layer of carbon fiber composite fabric is pasted. A heat-reflective heat-insulating coating is sprayed on the outer surface.

[0026] (2) On-site installation: After transporting the impact-facing surface and supporting surface units that have undergone functional treatment to the construction site, they are spliced according to the mortise and tenon structure of concave and convex connection, and the top connecting steel bars and the bottom connecting steel bars are respectively inserted along the reserved holes at the top and bottom. A layer of rubber pad with a thickness of 2 mm is laid at the bottom of the inner cavity of the guardrail. The pipeline of the mortar pump is extended to the bottom of the cavity formed by the assembly, and C20 fine aggregate concrete is filled inside the guardrail, and natural curing is carried out to finally form an integral protective structure.

Claims

1. A preparation method of a prefabricated UHPC-ECC guardrail, characterized in that, The specific operation of the preparation method is as follows: The UHPC is used to prefabricate the impact-facing surface, and the ECC material is used to prefabricate the supporting surface; notches and protrusions are respectively arranged on the upper and lower parts of the impact-facing surface and the supporting surface, and the notches and protrusions are assembled into a cavity structure with a hollow interior through mortise and tenon joints. Reserved communication channels are horizontally opened in the notches and protrusions at the top and bottom of the impact-facing surface and the supporting surface, steel bars are inserted into the reserved channels, and finally, filling materials are filled inside and cured to obtain the assembled UHPC-ECC guardrail.

2. The preparation method of the assembled UHPC-ECC guardrail according to claim 1, characterized in that, The width of the notch and the protrusion is 200 - 300 mm.

3. The preparation method of the assembled UHPC-ECC guardrail according to claim 1, characterized in that, The length of the impact-facing surface and the supporting surface is 4 - 6 m, the side thickness is 30 - 50 mm, and the top and bottom thickness is 50 - 70 mm.

4. The preparation method of the assembled UHPC-ECC guardrail according to claim 1, characterized in that, The diameter of the channel is 12 - 16 mm.

5. The preparation method of the assembled UHPC-ECC guardrail according to claim 1, characterized in that, Reinforcing ribs are arranged inside the impact-facing surface, with 2 - 3 ribs evenly arranged horizontally and 1 rib arranged vertically at an interval of 1 m. The width of the rib is 50 mm and the thickness is 50 mm.

6. The preparation method of the assembled UHPC-ECC guardrail according to claim 1, characterized in that, The slump of the impact-facing surface is 750 - 800 mm, and the compressive strength is 120 - 130 MPa; the slump of the supporting surface is 600 - 700 mm, and the compressive strength is 50 - 60 MPa.

7. The preparation method of the assembled UHPC-ECC guardrail according to claim 1, characterized in that, A rubber pad with a thickness of 2 - 3 mm is laid at the bottom inside the guardrail.

8. The preparation method of the assembled UHPC-ECC guardrail according to claim 1, characterized in that, The inner surfaces of the impact-facing surface and the supporting surface are sprayed with a waterproof layer, and then a layer of fiber composite material cloth or fiber composite material grid is pasted; the outer surfaces are sprayed with heat-reflective heat-insulating paint.

9. The preparation method of the assembled UHPC-ECC guardrail according to claim 8, characterized in that, The waterproof layer is a polyurethane layer, an acrylate layer or a silicone rubber layer.

10. The preparation method of the assembled UHPC-ECC guardrail according to claim 1, characterized in that, The strength of the filling material is not less than 20 MPa, and the maximum particle size of the aggregate shall not be greater than 16 mm.

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