Double-thin-layer UHPC-NC laminated bridge deck slab and construction method

Abstract

The invention relates to the technical field of bridge engineering, in particular to a double-thin-layer UHPC-NC laminated bridge deck slab and a construction method. The problem that an existing common bridge deck is poor in cracking durability is solved, and meanwhile the problems that an existing UHPC bridge deck is high in price and difficult to popularize are solved. The structure comprises a prefabricated UHPC bottom plate, a common concrete cast-in-place layer and a UHPC-CA top plate. The prefabricated UHPC bottom plate is prefabricated in a factory, and the common concrete cast-in-place layer is formed on the prefabricated UHPC bottom plate; and the UHPC-CA top plate is formed on the common concrete cast-in-place layer. By the adoption of the double-thin-layer UHPC-NC composite bridge deck slab composite structure, the purposes of reducing the engineering production cost, being more convenient to construct and better in durability can be achieved, meanwhile, the problems that UHPC is high in price and difficult to popularize can be solved, and the application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering, and in particular to a double-thin-layer UHPC-NC composite bridge deck and a construction method. Background Art

[0002] The bridge deck is located in the upper structure of the bridge and is laid directly on the main beam, cross beam and other load-bearing components of the bridge. Its main functions are: to bear various traffic loads such as vehicles and pedestrians, and to transfer these loads to the lower structure, to provide a flat and stable driving surface for vehicles and pedestrians, and to ensure traffic safety and comfort. Traditional steel-concrete composite beams are prone to cracking due to the poor tensile properties of concrete. The thickness of the concrete bridge deck that meets the design requirements is relatively large, and ordinary concrete bridge decks have various diseases such as cracking, corrosion, surface wear, water seepage, and spalling, which increase the maintenance cost.

[0003] In recent years, ultra-high performance concrete (UHPC) has been introduced into bridge engineering as a new type of high-performance concrete material. Compared with traditional concrete bridge decks, UHPC bridge decks are lighter and thinner, which can significantly reduce the overall weight of the bridge, reduce the pressure on the lower structure, and reduce the cost of foundation engineering. The high durability of UHPC bridge decks reduces the maintenance frequency and cost of bridges during use, and improves the economic benefits of bridges. Although UHPC bridge decks have good mechanical properties and durability, the high price of UHPC restricts its widespread application in actual engineering. Summary of the invention

[0004] The present invention provides a double-thin-layer UHPC-NC composite bridge deck and a construction method, aiming to combine the advantages of ultra-high performance concrete (UHPC) and conventional concrete (NC) to meet the strict requirements of modern bridge engineering on bridge deck in terms of strength, durability and economy.

[0005] The technical solution of the present invention is as follows:

[0006] One of the purposes of the present invention is to provide a double-thin-layer UHPC-NC composite bridge deck, comprising a prefabricated UHPC bottom plate (1), a common concrete cast-in-place layer (2) and a UHPC-CA top plate (3);

[0007] The prefabricated UHPC bottom plate (1) comprises a UHPC casting layer (1-1), a lower chord steel bar (1-2), an upper chord steel bar (1-3), a web steel bar (1-4), a prefabricated UHPC bottom plate longitudinal steel bar (1-5) and a prefabricated UHPC bottom plate transverse steel bar (1-6), wherein the lower chord steel bar (1-2), the upper chord steel bar (1-3) and the web steel bar (1-4) together constitute a truss bar structure, the prefabricated UHPC bottom plate longitudinal steel bar (1-5) and the prefabricated UHPC bottom plate transverse steel bar (1-6) are fixed in a transverse and longitudinal direction to form a first grid structure, the lower chord steel bar (1-2) is welded to the first grid structure, and UHPC is cast on the first grid structure to form a UHPC casting layer (1-1);

[0008] The ordinary concrete cast-in-place layer (2) is formed on the prefabricated UHPC base plate (1);

[0009] The UHPC-CA top plate (3) is formed on the ordinary concrete cast-in-place layer (2);

[0010] The UHPC-CA top plate (3) comprises a UHPC-CA cast-in-place layer (3-1), UHPC-CA top plate longitudinal steel bars (3-2) and UHPC-CA top plate transverse steel bars (3-3), wherein the UHPC-CA top plate longitudinal steel bars (3-2) and the UHPC-CA top plate transverse steel bars (3-3) are fixed in a transverse and longitudinal direction to form a second grid structure, the second grid structure is welded to the upper chord steel bars (1-3) of the prefabricated UHPC bottom plate (1), and UHPC-CA is cast on the second grid structure to form the UHPC-CA cast-in-place layer (3-1).

[0011] Furthermore, in the truss reinforcement structure, the lower chord reinforcement (1-2) and the upper chord reinforcement (1-3) are respectively located at the lower and upper ends of the truss reinforcement structure, and are welded together through the web reinforcement (1-4) to form a stable triangular structure.

[0012] Furthermore, the first grid structure fixes the prefabricated UHPC bottom plate longitudinal steel bars (1-5) and the prefabricated UHPC bottom plate transverse steel bars (1-6) together by welding or binding.

[0013] Furthermore, the UHPC-CA top plate (3) is connected to the ordinary concrete cast-in-place layer (2) via a second grid structure and chemical bonds during cement hydration, and is welded to the upper chord steel bars (1-3) of the prefabricated UHPC bottom plate (1) via the second grid structure and chemical bonds during cement hydration to connect to the prefabricated UHPC bottom plate (1), thereby cooperating with the prefabricated UHPC bottom plate (1) and the ordinary concrete cast-in-place layer (2) to bear loads.

[0014] Furthermore, when the ordinary concrete cast-in-place layer (2) is connected to the prefabricated UHPC base plate (1), when the ordinary concrete cast-in-place layer (2) is poured on the prefabricated UHPC base plate (1), the truss reinforcement is embedded in the ordinary concrete, and chemical bonds are formed during the cement hydration process to strengthen the connection.

[0015] Furthermore, the prefabricated UHPC base plate (1) also includes pre-tensioned prestressed steel wires (1-7). Before the UHPC casting layer (1-1) is cast, the pre-tensioned prestressed steel wires (1-7) are tensioned on a prestressed long line platform using a pre-tensioning method, and after the strength reaches the designed strength, the pre-tensioned prestressed steel wires (1-7) are symmetrically released bundle by bundle.

[0016] Another object of the present invention is to provide a construction method for a double-thin-layer UHPC-NC composite bridge deck, comprising the following steps:

[0017] Manufacturing a prefabricated UHPC bottom plate (1), including fixing the prefabricated UHPC bottom plate longitudinal steel bars (1-5) and the prefabricated UHPC bottom plate transverse steel bars (1-6) to form a first grid structure, welding the lower chord steel bars (1-2) and the upper chord steel bars (1-3) to form a truss bar structure, and pouring UHPC to form a UHPC pouring layer (1-1);

[0018] Casting a cast-in-place layer (2) of ordinary concrete on the prefabricated UHPC base plate (1);

[0019] The UHPC-CA cast-in-place layer longitudinal steel bars (3-2) and the UHPC-CA cast-in-place layer transverse steel bars (3-3) are fixed on the ordinary concrete cast-in-place layer (2) to form a second grid structure, and welded to the upper chord steel bars (1-3);

[0020] UHPC-CA is poured on the second grid structure to form a UHPC-CA cast-in-place layer (3-1).

[0021] Furthermore, when the prefabricated UHPC base plate 1 is prefabricated, it is also necessary to use a pre-tensioning method to tension the prestressed steel wires (1-7) on the prestressed long line platform, and then cast UHPC on the casting prestressed long line platform to form a UHPC casting layer (1-1). After the UHPC strength reaches more than 95% of the design strength and the curing age is not less than 7 days, the prestressed steel wires (1-7) are symmetrically placed one by one, and finally the prefabricated UHPC base plate (1) is cured to 28 days.

[0022] The beneficial effects of the present invention are as follows: the top and bottom layers of the double-thin-layer UHPC-NC composite bridge deck of the present invention are respectively made of UHPC (CA) and UHPC, which give full play to the high strength, high wear resistance, high durability and high toughness of UHPC (CA) materials. The middle layer uses ordinary concrete without affecting the stress performance and durability of the bridge deck, which greatly saves the engineering cost. The use of the composite plate makes the bridge deck construction more convenient, lighter and more standardized. The use of the double-thin-layer UHPC-NC composite bridge deck composite structure can achieve the purpose of reducing engineering production costs, making construction more convenient and more durable. At the same time, it can solve the problem of high price and difficulty in promoting UHPC, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : Schematic diagram of the overall structure of the double-thin-layer UHPC-NC composite bridge deck;

[0024] Figure 2 : Schematic diagram of longitudinal section layout of prefabricated UHPC bottom plate of double-thin-layer UHPC-NC composite bridge deck;

[0025] Figure 3 : Schematic diagram of the plan layout of the prefabricated UHPC bottom plate of the double-thin UHPC-NC composite bridge deck;

[0026] Figure 4 : Schematic diagram of cross-section arrangement of prefabricated UHPC bottom plate of double-thin-layer UHPC-NC composite bridge deck;

[0027] Figure 5 : Schematic diagram of the longitudinal section layout of the cast-in-place layer of the double-thin-layer UHPC-NC composite bridge deck;

[0028] Figure 6 : Schematic diagram of cross-section arrangement of cast-in-place layer of double-thin-layer UHPC-NC composite bridge deck;

[0029] As shown in the figure: precast UHPC bottom plate 1; UHPC casting layer 1-1; lower chord steel bars 1-2; upper chord steel bars 1-3; web bar steel bars 1-4; precast UHPC bottom plate longitudinal steel bars 1-5; precast UHPC bottom plate transverse steel bars 1-6; prestressed prestressed steel wires 1-7; ordinary concrete cast-in-place layer 2; UHPC-CA top plate 3; UHPC-CA cast-in-place layer 3-1; UHPC-CA top plate longitudinal steel bars 3-2; UHPC-CA top plate transverse steel bars 3-3. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific embodiments:

[0031] Example 1

[0032] The double-thin UHPC-NC composite bridge deck involved in the present invention is an innovative structural design, which aims to combine the advantages of ultra-high performance concrete (UHPC) and conventional concrete (NC) to meet the strict requirements of modern bridge engineering on bridge decks in terms of strength, durability and economy. Figure 1 The bridge deck shown is composed of a prefabricated UHPC bottom plate 1, a conventional concrete cast-in-place layer 2 and a UHPC-CA top plate 3.

[0033] As an important foundation part of the bridge deck, the prefabricated UHPC bottom plate 1 plays the main role of force transmission and structural support. The prefabricated UHPC bottom plate 1 fully utilizes the high strength and excellent durability of the UHPC material.

[0034] The ordinary concrete cast-in-place layer 2 is located on the prefabricated UHPC bottom plate 1, and works in conjunction with the prefabricated UHPC bottom plate 1 to further enhance the overall performance of the bridge deck. The ordinary concrete cast-in-place layer 2 not only serves as a filling material to fill the uneven parts of the surface of the prefabricated UHPC bottom plate 1, but also forms an integral structure with the prefabricated UHPC bottom plate 1 through chemical bond connection with the prefabricated UHPC bottom plate 1 and mechanical connection with the truss reinforcement to bear the load together. As a result, the bridge deck can meet the strength requirements while reducing material costs and improving the economy of the structure.

[0035] The UHPC-CA top plate 3 is the top structure of the bridge deck. The UHPC-CA top plate 3 is mainly responsible for bearing the direct loads during vehicle driving, such as wheel pressure and friction. The good wear resistance and impact resistance of the UHPC-CA top plate 3 can effectively protect the internal structure of the bridge deck from direct damage by external loads. At the same time, the UHPC-CA top plate 3 is also closely connected to the lower ordinary concrete cast-in-place layer 2 and the prefabricated UHPC bottom plate 1. Through the arrangement and connection of steel bars, it is ensured that the load can be effectively transferred from the upper layer to the lower structure, realizing the coordinated force of the entire bridge deck structure.

[0036] Prefabricated UHPC base plate 1 Figure 2 , 3 , 4. The prefabricated UHPC bottom plate 1 is composed of a UHPC casting layer 1-1, a lower chord steel bar 1-2, an upper chord steel bar 1-3, a web bar steel bar 1-4, a prefabricated UHPC bottom plate longitudinal steel bar 1-5, a prefabricated UHPC bottom plate transverse steel bar 1-6 and a pre-tensioned prestressed steel wire 1-7.

[0037] The lower chord steel bars 1-2, the upper chord steel bars 1-3 and the web bars 1-4 together constitute the truss bar structure in the prefabricated UHPC base plate 1. The truss bar structure can effectively transfer and disperse the load, thereby improving the bearing capacity of the prefabricated UHPC base plate 1. The lower chord steel bars 1-2 and the upper chord steel bars 1-3 are respectively located at the lower and upper ends of the truss bar structure. The lower chord steel bars 1-2 and the upper chord steel bars 1-3 are welded together through the web bars 1-4 to form a stable triangular structure. The triangular structure has high mechanical stability and bearing capacity, and can withstand large axial and bending forces. The longitudinal steel bars 1-5 of the prefabricated UHPC base plate and the transverse steel bars 1-6 of the prefabricated UHPC base plate are fixed in the transverse and longitudinal directions to form a first grid structure. The first grid structure provides transverse and longitudinal reinforcement for the prefabricated UHPC base plate 1, and can prevent cracks and deformation of the UHPC casting layer 1-1 during the stress process. The prefabricated UHPC bottom plate longitudinal reinforcement 1-5 and the prefabricated UHPC bottom plate transverse reinforcement 1-6 are usually fixed together by welding or binding to form a stable grid structure. UHPC is poured on the first grid structure to form a UHPC pouring layer 1-1.

[0038] The prestressed steel wire 1-7 is a special design in the prefabricated UHPC base plate 1. When the prefabricated base plate (1) is prefabricated, the prestressed tendons 1-7 are first tensioned on the prestressed long line platform by using the prestressing method, and then UHPC is cast on the casting prestressed long line platform to form a UHPC cast-in-place layer (1). After the UHPC strength reaches more than 95% of the design strength and the curing age is not less than 7 days, the prestressed tendons are symmetrically tensioned one by one, and finally the prefabricated UHPC components are cured to 28 days.

[0039] The connection between the ordinary concrete cast-in-place layer 2 and the prefabricated UHPC base plate 1 is mainly achieved through truss bars and chemical bonds formed by cement hydration. As a mechanical connection method, the truss bars play a role in transferring loads and strengthening the connection between the prefabricated UHPC base plate 1 and the ordinary concrete cast-in-place layer 2. When the ordinary concrete cast-in-place layer 2 is poured on the prefabricated UHPC base plate 1, the truss bars are embedded in the ordinary concrete, so that there is a direct mechanical connection between the ordinary concrete and the prefabricated UHPC base plate 1. At the same time, during the cement hydration process of the ordinary concrete cast-in-place layer 2, the chemical components in the cement will react chemically with the substances on the surface of the prefabricated UHPC base plate 1 to form chemical bonds, making the connection between the two tighter and stronger. This dual connection method can not only ensure that the load can be smoothly transferred from the prefabricated UHPC base plate 1 to the ordinary concrete cast-in-place layer 2, but also prevent the ordinary concrete cast-in-place layer 2 from separating from the prefabricated UHPC base plate 1 during use.

[0040] like Figure 5 and 6As shown, the UHPC-CA top plate 3 is connected to the ordinary concrete cast-in-place layer 2 through the second grid structure formed by the longitudinal steel bars 3-2 of the UHPC-CA top plate 3 and the transverse steel bars 3-3 of the UHPC-CA top plate 3 and the chemical bonds in the cement hydration process. When the UHPC-CA top plate 3 is cast on the ordinary concrete cast-in-place layer 2, the second grid structure is embedded in the ordinary concrete cast-in-place layer 2 to form a mechanical connection. UHPC-CA is cast on the second grid structure to form a UHPC-CA cast-in-place layer 3-1. During the cement hydration process, the cement components in the UHPC-CA cast-in-place layer 3-1 react chemically with the substances on the surface of the ordinary concrete cast-in-place layer 2 to form chemical bonds, thereby enhancing the connection strength between the two. The connection between the UHPC-CA top plate 3 and the prefabricated UHPC bottom plate 1 is achieved by welding the second grid structure fixed to the upper chord steel bars 1-3 of the prefabricated UHPC bottom plate 1 and the chemical bonds in the cement hydration process. This connection method ensures that the UHPC-CA top plate 3 can be tightly integrated with the lower structure, and the load can be effectively transferred from the UHPC-CA top plate 3 to the ordinary concrete cast-in-place layer 2 and the prefabricated UHPC bottom plate 1, thereby achieving coordinated force of the entire bridge deck structure.

[0041] The specific construction methods are as follows:

[0042] The longitudinal reinforcement 1-5 of the prefabricated UHPC bottom plate and the transverse reinforcement 1-6 of the prefabricated UHPC bottom plate are fixed in the horizontal and vertical directions according to the design requirements to form a first grid structure. Then, the lower chord reinforcement 1-2 is welded to the first grid structure. Next, the lower chord reinforcement 1-2 is welded to the upper chord reinforcement 1-3 through the web reinforcement 1-4 to form a truss reinforcement. Then, UHPC is poured on the first grid structure to form a UHPC pouring layer 1-1, and pre-tensioned prestressed steel wires 1-7 are applied at an appropriate time. Thus, the production of the prefabricated UHPC bottom plate 1 is completed.

[0043] When the prefabricated UHPC base plate 1 is prefabricated, it is also necessary to use the pre-tensioning method to tension the prestressed steel wires 1-7 on the prestressed long line platform, and then cast the UHPC on the casting prestressed long line platform to form the UHPC casting layer 1-1. After the UHPC strength reaches more than 95% of the design strength and the curing age is not less than 7d, the prestressed steel wires 1-7 are symmetrically placed one by one, and finally the prefabricated UHPC base plate 1 is cured to 28d.

[0044] The prepared prefabricated UHPC bottom plate 1 is placed at a predetermined position. A cast-in-place layer 2 of ordinary concrete is poured on the prefabricated UHPC bottom plate 1 .

[0045] On the ordinary concrete cast-in-place layer 2, the UHPC-CA top plate longitudinal steel bars 3-2 and the UHPC-CA top plate transverse steel bars 3-3 are fixed in the horizontal and vertical directions to form a second grid structure, and are welded to the upper chord steel bars 1-3 of the prefabricated UHPC bottom plate 1. Finally, UHPC-CA is poured on the second grid structure to form a UHPC-CA cast-in-place layer 3-1, and a UHPC-CA top plate 3 is formed.

[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0047] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A double-thin-layer UHPC-NC composite bridge deck, characterized in that: It includes a prefabricated UHPC base plate (1), a common concrete cast-in-place layer (2) and a UHPC-CA top plate (3); The prefabricated UHPC bottom plate (1) comprises a UHPC casting layer (1-1), a lower chord steel bar (1-2), an upper chord steel bar (1-3), a web steel bar (1-4), a prefabricated UHPC bottom plate longitudinal steel bar (1-5) and a prefabricated UHPC bottom plate transverse steel bar (1-6), wherein the lower chord steel bar (1-2), the upper chord steel bar (1-3) and the web steel bar (1-4) together constitute a truss bar structure, the prefabricated UHPC bottom plate longitudinal steel bar (1-5) and the prefabricated UHPC bottom plate transverse steel bar (1-6) are fixed in a transverse and longitudinal direction to form a first grid structure, the lower chord steel bar (1-2) is welded to the first grid structure, and UHPC is cast on the first grid structure to form a UHPC casting layer (1-1); The ordinary concrete cast-in-place layer (2) is formed on the prefabricated UHPC base plate (1); The UHPC-CA top plate (3) is formed on the ordinary concrete cast-in-place layer (2); The UHPC-CA top plate (3) comprises a UHPC-CA cast-in-place layer (3-1), UHPC-CA top plate longitudinal steel bars (3-2) and UHPC-CA top plate transverse steel bars (3-3), wherein the UHPC-CA top plate longitudinal steel bars (3-2) and the UHPC-CA top plate transverse steel bars (3-3) are fixed in a transverse and longitudinal direction to form a second grid structure, the second grid structure is welded to the upper chord steel bars (1-3) of the prefabricated UHPC bottom plate (1), and UHPC-CA is cast on the second grid structure to form the UHPC-CA cast-in-place layer (3-1).

2. A double-thin-layer UHPC-NC composite bridge deck according to claim 1, characterized in that: In the truss reinforcement structure, the lower chord reinforcement (1-2) and the upper chord reinforcement (1-3) are respectively located at the lower and upper ends of the truss reinforcement structure, and are welded together through the web reinforcement (1-4) to form a stable triangular structure.

3. The double-thin-layer UHPC-NC composite bridge deck according to claim 1, characterized in that: The first grid structure fixes the prefabricated UHPC bottom plate longitudinal steel bars (1-5) and the prefabricated UHPC bottom plate transverse steel bars (1-6) together by welding or binding.

4. The double-thin-layer UHPC-NC composite bridge deck according to claim 1, characterized in that: The UHPC-CA top plate (3) is connected to the ordinary concrete cast-in-place layer (2) via a second grid structure and chemical bonds in the cement hydration process, is welded to the upper chord steel bars (1-3) of the prefabricated UHPC bottom plate (1) via the second grid structure and is connected to the prefabricated UHPC bottom plate (1) via chemical bonds in the cement hydration process, and cooperates with the prefabricated UHPC bottom plate (1) and the ordinary concrete cast-in-place layer (2) to bear loads.

5. The double-thin-layer UHPC-NC composite bridge deck according to claim 1, characterized in that: When the ordinary concrete cast-in-place layer (2) is connected to the prefabricated UHPC base plate (1), when the ordinary concrete cast-in-place layer (2) is poured on the prefabricated UHPC base plate (1), the truss reinforcement is embedded in the ordinary concrete, and chemical bonds are formed during the cement hydration process to strengthen the connection.

6. A double-thin-layer UHPC-NC composite bridge deck according to any one of claims 1 to 5, characterized in that: The prefabricated UHPC base plate (1) further comprises pre-tensioned prestressed steel wires (1-7). Before the UHPC casting layer (1-1) is cast, the pre-tensioned prestressed steel wires (1-7) are tensioned on a prestressed long line platform using a pre-tensioning method, and after the strength reaches the designed strength, the pre-tensioned prestressed steel wires (1-7) are symmetrically released bundle by bundle.

7. A construction method for a double-thin-layer UHPC-NC composite bridge deck according to any one of claims 1 to 6, characterized in that The following steps are involved: Manufacturing a prefabricated UHPC bottom plate (1), including fixing the prefabricated UHPC bottom plate longitudinal steel bars (1-5) and the prefabricated UHPC bottom plate transverse steel bars (1-6) to form a first grid structure, welding the lower chord steel bars (1-2) and the upper chord steel bars (1-3) to form a truss bar structure, and pouring UHPC to form a UHPC pouring layer (1-1); Casting a cast-in-place layer (2) of ordinary concrete on the prefabricated UHPC base plate (1); The UHPC-CA cast-in-place layer longitudinal steel bars (3-2) and the UHPC-CA cast-in-place layer transverse steel bars (3-3) are fixed on the ordinary concrete cast-in-place layer (2) to form a second grid structure, and welded to the upper chord steel bars (1-3); UHPC-CA is poured on the second grid structure to form a UHPC-CA cast-in-place layer (3-1).

8. The construction method of a double-thin-layer UHPC-NC composite bridge deck according to claim 7, characterized in that: When the prefabricated UHPC base plate 1 is prefabricated, it is also necessary to use a pre-tensioning method to tension the prestressed steel wires (1-7) on the prestressed long line platform, and then cast UHPC on the casting prestressed long line platform to form a UHPC casting layer (1-1). After the UHPC strength reaches more than 95% of the design strength and the curing age is not less than 7 days, the prestressed steel wires (1-7) are symmetrically placed one by one, and finally the prefabricated UHPC base plate (1) is cured to 28 days.

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