Single-layer prefabricated coarse-aggregate grouting UHPC slab, functionally graded high-performance cement-based fiber composite slab and preparation method

Abstract

The present invention discloses a single-layer precast coarse-aggregate grouting UHPC board, a functionally graded high-performance cement-based fiber composite board, and a preparation method thereof. The single-layer precast coarse-aggregate grouting UHPC board comprises the following raw material components in parts by weight: 900-1000 parts of ultra-high-performance grouting material and 1650-1800 parts of coarse aggregate. The functionally graded high-performance cement-based fiber composite board comprises a middle anti-penetration layer formed by integral grouting and front crack-resistant layers and back anti-spalling layers located on the front and back sides thereof. Both the front crack-resistant layer and the back anti-spalling layer are formed by grouting the ultra-high-performance grouting material and steel fibers, and the middle anti-penetration layer is formed by grouting the ultra-high-performance grouting material and coarse aggregate. The single-layer precast coarse-aggregate grouting UHPC board and the functionally graded high-performance cement-based fiber composite board prepared by the present invention both have good anti-penetration performance, and large-volume and large-size coarse aggregate is used in the preparation process, greatly reducing the dosage of the cementitious material and reducing the economic and environmental costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of building structural materials, and particularly relates to a single-layer precast coarse-aggregate grouted UHPC board, a functionally graded high-performance cement-based fiber composite board, and a preparation method thereof. Background Art

[0002] Currently, the impact resistance of buildings and structures is limited, and the integrity and stability of the structure cannot be guaranteed in the face of external impact or collision loads, often causing a large degree of casualties and property losses. At the same time, with the development of the civil engineering field towards multi-functionality and sustainability, higher requirements are put forward for the strength, toughness, impact resistance performance, etc. of building materials and structures. Due to the low material strength and poor structural stiffness of traditional concrete structures, they cannot resist large impact loads, and a large number of fragments peel off and spatter during the failure process, causing secondary damage to personnel and equipment.

[0003] Ultra High Performance Concrete (UHPC) is a new type of cement-based composite material with high strength, high toughness, and high durability. Compared with traditional building materials, it can significantly improve the load-bearing performance and impact resistance of structures. Therefore, it has broad application prospects in engineering fields such as high-rise buildings, marine structures, nuclear power barriers, and military bunkers. Currently, in the preparation of UHPC, technical means such as removing coarse aggregates, reducing the water-binder ratio, and special curing are mostly used. While ensuring the mechanical properties and durability of the matrix, it also brings problems such as high cost and large shrinkage. At the same time, the UHPC protective impact-resistant structure often has a large thickness, and the material utilization efficiency is not high, which greatly limits its popularization and application in the civil engineering field. Therefore, it is urgent to study aspects such as the material preparation and structural optimization of UHPC, enhance its protective impact resistance performance of materials and structures, improve the material utilization efficiency, and reduce the engineering cost. Summary of the Invention

[0004] In order to overcome the deficiencies in the prior art, one of the purposes of the present invention is to provide a single-layer precast coarse-aggregate grouted UHPC board. Introducing large-volume and large-size coarse aggregates into the UHPC matrix is beneficial to improving the impact resistance of the structure, reducing economic and environmental costs, and improving the current situation of limited aggregate substitution amount in traditional ultra-high performance concrete containing coarse aggregates.

[0005] Another purpose of the present invention is to provide a preparation method for a single-layer precast coarse-aggregate grouted UHPC board. Through the casting method of grouting molding, it effectively solves the technical problem that it is difficult to apply large-volume and large-size coarse aggregates in actual engineering.

[0006] The third object of the present invention is to provide a functionally graded high-performance cement-based fiber composite board. Compared with the single-layer precast coarse aggregate grouted UHPC board, the functionally graded UHPC composite board has a low cracking risk under high-speed impact loads, and there will be no phenomenon of a large amount of debris spalling and splashing on its back, reducing the risk of secondary injury to personnel and equipment.

[0007] The fourth object of the present invention is to provide a functionally graded high-performance cement-based fiber composite board. Through the casting method of grouting molding, the front crack resistance layer, the middle anti-penetration layer and the back anti-spalling layer are integrally grouted and molded, effectively solving the problems of difficult construction and low bonding strength of the front crack resistance layer, the middle anti-penetration layer and the back anti-spalling layer in actual engineering.

[0008] To solve the above technical problems, the present invention is realized through the following technical solutions:

[0009] A single-layer precast coarse aggregate grouted UHPC board comprises the following raw material components in parts by weight: 900-1000 parts of ultra-high performance grouting material and 1650-1800 parts of coarse aggregate.

[0010] Preferably, the particle size range of the coarse aggregate is selected from one of 5-8 mm, 8-16 mm and 16-25 mm.

[0011] Preferably, the ultra-high performance grouting material comprises the following raw material components in parts by weight: 916 parts of cement, 61 parts of silica fume, 244 parts of limestone powder, 808 parts of fine sand, 281 parts of water, 21 parts of water reducer, and the particle size range of the fine sand is 0-0.2 mm.

[0012] A preparation method of a single-layer precast coarse aggregate grouted UHPC board comprises:

[0013] (1) Weigh raw materials according to the designed ratio;

[0014] (2) Uniformly pre-fill coarse aggregate in a mold;

[0015] (3) Preparation of ultra-high performance grouting material: Add cement, silica fume, limestone powder and fine sand into a mixing pan and stir for 2 min. After stirring evenly, add 80% of water and continue to mix and stir for 3 min. Finally, mix the water reducer with the remaining water and pour it into the mixing pan and stir for 5 min;

[0016] (4) Inject the ultra-high performance grouting material into the mold pre-filled with coarse aggregate through a grouting pipe, vibrate it densely, and obtain the single-layer precast coarse aggregate grouted UHPC board after curing.

[0017] Preferably, the fluidity of the ultra-high performance grouting material prepared in step (3) is 38-40 cm, the flow time of the V-shaped funnel is 7-7.5 s, and the 28-day compressive strength > 140 MPa.

[0018] A functionally graded high-performance cement-based fiber composite board, comprising a middle anti-penetration layer formed by integral grouting molding and a front crack resistance layer and a back anti-spalling layer located on the front and back sides thereof. Both the front crack resistance layer and the back anti-spalling layer are formed by grouting molding of ultra-high performance grouting material and steel fibers, and the middle anti-penetration layer is formed by grouting molding of ultra-high performance grouting material and coarse aggregates.

[0019] Preferably, the volume fraction of steel fibers in both the front crack resistance layer and the back anti-spalling layer is 1%, and the steel fibers are 13-mm copper-plated steel fibers.

[0020] Preferably, the weight parts of the raw material components in the middle anti-penetration layer are: 1350-1450 parts of ultra-high performance grouting material and 1100-1200 parts of coarse aggregates. Among them, the raw material composition of the ultra-high performance grouting material is the same as that of the ultra-high performance grouting material in the single-layer precast coarse aggregate grouting type UHPC board, and the particle size range of the coarse aggregates is also selected from one of 5-8 mm, 8-16 mm and 16-25 mm.

[0021] Preferably, when the particle size of the coarse aggregates is 16-25 mm, the ultimate safety thickness of the composite board is 80 mm.

[0022] A preparation method of a functionally graded high-performance cement-based fiber composite board, comprising:

[0023] (1) Weigh raw materials according to the designed ratio;

[0024] (2) First, place a layer of steel fibers at the bottom of the mold, then place coarse aggregates on the upper part of the steel fibers, and finally place a layer of steel fibers on the top layer;

[0025] (3) Preparation of ultra-high performance grouting material: Add cement, silica fume, limestone powder and fine sand to the mixing pot and stir for 2 min. After stirring evenly, add 80% of the water and continue to mix and stir for 3 min. Finally, mix the water reducer and the remaining water and pour them into the mixing pot and stir for 5 min;

[0026] (4) Inject the ultra-high performance grouting material into the mold through a grouting pipe, vibrate it densely, and after curing, obtain the described functionally graded high-performance cement-based fiber composite board.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] (1) Introducing large-volume and large-size coarse aggregates into the UHPC matrix is beneficial to improving the impact resistance of the structure, reducing economic and environmental costs, and improving the current situation of limited aggregate replacement amount in traditional ultra-high performance concrete containing coarse aggregates. Through the casting method of grouting molding, the present invention effectively solves the technical problem that it is difficult to apply large-volume and large-size coarse aggregates in practical engineering. The volume fraction of coarse aggregates in ultra-high performance concrete with coarse aggregates formed by ordinary mixing method is 35-40%, while that in ultra-high performance concrete with coarse aggregates formed by pre-placing coarse aggregates and grouting method reaches 56%-61%. Moreover, no coarse aggregates need to be added during the mixing process of the grouting method, the mixing amount is small, and the molding method is simple, which is suitable for the field of large-scale engineering construction.

[0029] (2) The results of high-speed bullet penetration tests show that the penetration depth of bullets in pre-placed coarse aggregate grouted ultra-high performance concrete is reduced by 7%-14% compared with traditional ultra-high performance fiber-reinforced concrete.

[0030] (3) The functionally graded UHPC composite panel is composed of ultra-high performance fiber-reinforced concrete and pre-placed coarse aggregate grouted ultra-high performance concrete. Compared with the single-layer pre-placed coarse aggregate grouted concrete, the functionally graded UHPC composite panel has a low cracking risk under high-speed impact loads, and there will be no phenomenon of a large amount of debris spalling and splashing on its back, reducing the risk of secondary injury to personnel and equipment.

[0031] (4) UHPC has excellent mechanical properties and durability compared with traditional concrete, but it still has defects itself. The brittleness of UHPC materials is relatively large, and there are relatively large risks when applied to protective structures. The content of cementitious materials in UHPC is extremely high, resulting in high economic and environmental costs, which limits its popularization and application in large-scale engineering structures. According to the failure mode of concrete structures under high-speed impact loads, the present invention uses ultra-high performance fiber-reinforced concrete and pre-placed coarse aggregate grouted UHPC to design a functionally graded high-performance cement-based fiber composite panel, and divides the composite panel into a crack-resistant layer, a penetration-resistant layer, and a spall-resistant layer. Among them, the crack-resistant layer and the spall-resistant layer adopt ultra-high performance fiber-reinforced concrete, and the penetration-resistant layer adopts pre-placed coarse aggregate grouted ultra-high performance concrete. The functionally graded high-performance cement-based fiber composite panel prepared by the present invention has good penetration resistance, and large-volume and large-size coarse aggregates are used in the preparation process, greatly reducing the amount of cementitious materials used and reducing economic and environmental costs. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of a single-layer pre-placed coarse aggregate grouted UHPC panel prepared by the present invention.

[0033] Figure 2 It is a schematic structural diagram of a functionally graded UHPC composite panel prepared by the present invention.

[0034] Figure 3 Graph of the high-speed bullet impact test results for different types of ultra-high performance concrete slabs with different aggregate sizes.

[0035] Figure 4 Graph of the test results of the ultimate safety thickness of ultra-high performance fiber-reinforced concrete and functionally graded UHPC composite slabs.

[0036] Figure 5 Graph of the high-speed bullet impact test results of the single-layer precast coarse-aggregate grouted UHPC slabs prepared in Examples 1-3 of the present invention, where Figure 5 A is the test graph with a coarse aggregate size of 5-8 mm, Figure 5 B is the test graph with a coarse aggregate size of 8-16 mm, Figure 5 C is the test graph with a coarse aggregate size of 16-25 mm.

[0037] Figure 6 Graph of the high-speed bullet impact test results of the functionally graded UHPC composite slabs prepared in Examples 4-6 of the present invention, where Figure 6 A is the test graph with a coarse aggregate size of 5-8 mm, Figure 6 B is the test graph with a coarse aggregate size of 8-16 mm, Figure 6 C is the test graph with a coarse aggregate size of 16-25 mm.

[0038] Figure 7 For Figure 6 Cross-sectional view of the high-speed bullet impact failure of C.

[0039] In the figure: 1 - Front crack resistance layer, 2 - Middle anti-penetration layer, 3 - Back spalling prevention layer. Detailed implementation method

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation schemes of the present invention are described below in conjunction with specific embodiments, but it should not be construed as a limitation to the present invention, and only for example.

[0041] In the following embodiments, the test methods or testing methods described, unless otherwise specified, are all conventional methods; the reagents and materials described, unless otherwise specified, are all obtained from conventional commercial channels or prepared by conventional methods.

[0042] Example 1

[0043] As Figure 1 shown, this example introduces a single-layer precast coarse-aggregate grouted UHPC slab, where the coarse aggregate is 5-8 mm basalt gravel. The diameter of the single-layer precast coarse-aggregate grouted UHPC slab is 300 mm and the thickness is 100 mm.

[0044] Preparation method:

[0045] (1) Weigh the materials;

[0046] (2) Uniformly place coarse aggregates with a size of 5 - 8 mm in the steel mold in advance;

[0047] (3) Preparation of ultra - high - performance grouting material: Add cement, silica fume, limestone powder and fine sand to the mixing pan and stir for 2 min. After stirring evenly, add 80% of the water and continue to mix and stir for 3 min. Finally, mix the water - reducing agent with the remaining water and pour it into the mixing pan and stir for 5 min;

[0048] (4) Inject the ultra - high - performance grouting material into the mold with pre - placed coarse aggregates through the grouting pipe and vibrate it densely.

[0049] High - speed bullet penetration test:

[0050] Conduct a high - speed bullet impact test on the target specimen using a 7.62×51 mm bullet. The distance between the target specimen and the launching device is 30 m, and the incident speed of the bullet is 843 m / s. After the impact test, cut the target specimen axially from the impact point and measure the bullet penetration depth.

[0051] After testing, the bullet penetration depth of the single - layer pre - placed coarse - aggregate grouted UHPC plate is 52.5 mm.

[0052] Example 2

[0053] As Figure 1 shown, this example introduces a single - layer pre - placed coarse - aggregate grouted UHPC plate, where the coarse aggregate is 8 - 16 mm basalt gravel. The diameter of the single - layer pre - placed coarse - aggregate grouted UHPC plate is 300 mm and the thickness is 100 mm.

[0054] Preparation method:

[0055] (1) Weigh the materials;

[0056] (2) Uniformly place coarse aggregates with a size of 8 - 16 mm in the steel mold in advance;

[0057] (3) Preparation of ultra - high - performance grouting material: Add cement, silica fume, limestone powder and fine sand to the mixing pan and stir for 2 min. After stirring evenly, add 80% of the water and continue to mix and stir for 3 min. Finally, mix the water - reducing agent with the remaining water and pour it into the mixing pan and stir for 5 min;

[0058] (4) Inject the ultra - high - performance grouting material into the mold with pre - placed coarse aggregates through the grouting pipe and vibrate it densely.

[0059] High - speed bullet penetration test:

[0060] A high-speed bullet impact test was conducted on the target using a 7.62×51mm bullet. The distance between the target and the launch device was 30m, and the bullet's impact velocity was 843m / s. After the impact test, the target was cut axially from the impact point to measure the bullet penetration depth.

[0061] According to the test, the bullet penetration depth of the single-layer pre-set coarse aggregate grouting UHPC board is 51 mm.

[0062] Example 3

[0063] like Figure 1 As shown, this embodiment introduces a single-layer pre-set coarse aggregate grouting type UHPC board, wherein the coarse aggregate is 16-25 mm basalt crushed stone. The single-layer pre-set coarse aggregate grouting type UHPC board has a diameter of 300 mm and a thickness of 100 mm.

[0064] Preparation method:

[0065] (1) Weigh the materials;

[0066] (2) Pre-place 16-25 mm coarse aggregate evenly in the steel mold;

[0067] (3) Preparation of ultra-high performance grouting material: Cement, silica fume, limestone powder and fine sand were added to a mixing pot and stirred for 2 minutes. After stirring evenly, 80% of water was added and continued to mix and stir for 3 minutes. Finally, the water reducer and the remaining water were mixed and poured into a mixing pot and stirred for 5 minutes.

[0068] (4) Inject the ultra-high performance grouting material into the mold where the coarse aggregate is placed in advance through the grouting pipe, and vibrate it to make it dense.

[0069] High-speed bullet penetration test:

[0070] A high-speed bullet impact test was conducted on the target using a 7.62×51mm bullet. The distance between the target and the launch device was 30m, and the bullet's impact velocity was 843m / s. After the impact test, the target was cut axially from the impact point to measure the bullet penetration depth.

[0071] According to the test, the bullet penetration depth of the single-layer pre-set coarse aggregate grouting UHPC panel is 49.5 mm.

[0072] Example 4

[0073] like Figure 2 As shown, this embodiment introduces a functional gradient high-performance cement-based fiber composite board, wherein the coarse aggregate is 5-8 mm basalt crushed stone. The single-layer pre-set coarse aggregate grouting type UHPC board has a diameter of 300 mm and a thickness of 100 mm.

[0074] Preparation method:

[0075] (1) Weigh the materials;

[0076] (2) First, place a layer of steel fibers at the bottom of the steel mold, then place 5 - 8 mm coarse aggregates on top of the steel fibers, and finally place a layer of steel fibers on the top layer;

[0077] (3) Preparation of ultra - high - performance grouting material: Add cement, silica fume, limestone powder, and fine sand to the mixing pan and stir for 2 min. After stirring evenly, add 80% of the water and continue to mix and stir for 3 min. Finally, mix the water - reducing agent with the remaining water and pour it into the mixing pan and stir for 5 min;

[0078] (4) Inject the ultra - high - performance grouting material into the steel mold through the grouting pipe and vibrate it densely.

[0079] High - speed bullet penetration test:

[0080] Conduct a high - speed bullet impact test on the target specimen using a 7.62×51 mm bullet. The distance between the target specimen and the launching device is 30 m, and the incident speed of the bullet is 843 m / s. After the impact test, cut the target specimen axially from the impact point and measure the bullet penetration depth.

[0081] After testing, the bullet penetration depth of the functional - gradient high - performance cement - based fiber composite board is 56.5 mm.

[0082] Example 5

[0083] As Figure 2 shown, this example introduces a functional - gradient high - performance cement - based fiber composite board, in which the coarse aggregates are 8 - 16 mm basalt gravel. The diameter of the single - layer pre - placed coarse - aggregate grouting UHPC board is 300 mm and the thickness is 100 mm.

[0084] Preparation method:

[0085] (1) Weigh the materials;

[0086] (2) First, place a layer of steel fibers at the bottom of the steel mold, then place 8 - 16 mm coarse aggregates on top of the steel fibers, and finally place a layer of steel fibers on the top layer;

[0087] (3) Preparation of ultra - high - performance grouting material: Add cement, silica fume, limestone powder, and fine sand to the mixing pan and stir for 2 min. After stirring evenly, add 80% of the water and continue to mix and stir for 3 min. Finally, mix the water - reducing agent with the remaining water and pour it into the mixing pan and stir for 5 min;

[0088] (4) Inject the ultra - high - performance grouting material into the steel mold through the grouting pipe and vibrate it densely.

[0089] High - speed bullet penetration test:

[0090] A high-speed bullet impact test was carried out on the target using 7.62×51mm bullets. The distance between the target and the launching device was 30m, and the incident velocity of the bullet was 843m / s. After the impact test, the target was axially cut along the impact point to measure the bullet penetration depth.

[0091] After testing, the bullet penetration depth of the functionally graded high-performance cement-based fiber composite board was 56mm.

[0092] Example 6

[0093] As Figure 2 shown, this example introduces a functionally graded high-performance cement-based fiber composite board, in which the coarse aggregate is 16 - 25mm basalt gravel. The diameter of the single-layer precast coarse aggregate grouted UHPC board is 300mm, and the thickness is 100mm.

[0094] Preparation method:

[0095] (1) Weigh the materials;

[0096] (2) First, place a layer of steel fibers at the bottom of the steel mold, then place 16 - 25mm coarse aggregate on top of the steel fibers, and finally place a layer of steel fibers on the top layer;

[0097] (3) Preparation of ultra-high performance grouting material: Add cement, silica fume, limestone powder and fine sand to the mixing pan and stir for 2 minutes. After stirring evenly, add 80% of the water and continue to mix and stir for 3 minutes. Finally, mix the water reducer and the remaining water and pour them into the mixing pan and stir for 5 minutes;

[0098] (4) Inject the ultra-high performance grouting material into the steel mold through the grouting pipe and vibrate it densely.

[0099] High-speed bullet penetration test:

[0100] A high-speed bullet impact test was carried out on the target using 7.62×51mm bullets. The distance between the target and the launching device was 30m, and the incident velocity of the bullet was 843m / s. After the impact test, the target was axially cut along the impact point to measure the bullet penetration depth.

[0101] After testing, the bullet penetration depth of the functionally graded high-performance cement-based fiber composite board was 55mm, and the ultimate safety thickness was 80mm, as Figure 4 shown.

[0102] Comparative Example 1

[0103] This comparative example is ultra-high performance fiber-reinforced concrete, in which the coarse aggregate is 5 - 8mm basalt gravel. The diameter of the UHPC board is 300mm, and the thickness is 100mm.

[0104] Preparation method:

[0105] (1) Weigh the materials;

[0106] (2) Add cement, silica fume, limestone powder and fine sand into the mixing pan and mix for 1 min. After mixing evenly, add 75% of the water and continue to mix for 1 min. Mix the water reducer with the remaining 25% of the water and pour it into the mixing pan and mix for 3 min. Add steel fibers and mix for 2.5 min. Finally, add coarse aggregates and mix for 2.5 min;

[0107] (3) Pour the specimens and vibrate them densely.

[0108] High-speed bullet penetration test:

[0109] Conduct a high-speed bullet impact test on the target specimen using a 7.62×51mm bullet. The distance between the target specimen and the launching device is 30 m, and the incident speed of the bullet is 843 m / s. After the impact test, cut the specimen axially from the impact point and measure the bullet penetration depth.

[0110] After testing, the bullet penetration depth of the ultra-high performance fiber-reinforced concrete is 59.5 mm.

[0111] Comparative Example 2

[0112] This comparative example is ultra-high performance fiber-reinforced concrete, in which the coarse aggregate is 8 - 16 mm basalt gravel. The diameter of the UHPC plate is 300 mm and the thickness is 100 mm.

[0113] Preparation method:

[0114] (1) Weigh the materials;

[0115] (2) Add cement, silica fume, limestone powder and fine sand into the mixing pan and mix for 1 min. After mixing evenly, add 75% of the water and continue to mix for 1 min. Mix the water reducer with the remaining 25% of the water and pour it into the mixing pan and mix for 3 min. Add steel fibers and mix for 2.5 min. Finally, add coarse aggregates and mix for 2.5 min;

[0116] (3) Pour the specimens and vibrate them densely.

[0117] High-speed bullet penetration test:

[0118] Conduct a high-speed bullet impact test on the target specimen using a 7.62×51mm bullet. The distance between the target specimen and the launching device is 30 m, and the incident speed of the bullet is 843 m / s. After the impact test, cut the specimen axially from the impact point and measure the bullet penetration depth.

[0119] After testing, the bullet penetration depth of the ultra-high performance fiber-reinforced concrete is 59 mm.

[0120] Comparative Example 3

[0121] This comparative example is ultra-high performance fiber reinforced concrete, in which the coarse aggregate is 16 - 25 mm basalt gravel. The diameter of the UHPC plate is 300 mm and the thickness is 100 mm.

[0122] Preparation method:

[0123] (1) Weigh the materials;

[0124] (2) Add cement, silica fume, limestone powder and fine sand to the mixing pan and mix for 1 min. After mixing evenly, add 75% of the water and continue to mix for 1 min. Mix the water reducer with the remaining 25% of the water and pour it into the mixing pan and mix for 3 min. Add steel fibers and mix for 2.5 min. Finally, add coarse aggregate and mix for 2.5 min;

[0125] (3) Pour the specimens and vibrate them densely.

[0126] High-speed bullet penetration test:

[0127] Use a 7.62×51 mm bullet to conduct a high-speed bullet impact test on the target specimen. The distance between the target specimen and the launching device is 30 m, and the incident speed of the bullet is 843 m / s. After the impact test, cut the target specimen axially from the impact point and measure the bullet penetration depth.

[0128] After testing, the bullet penetration depth of the ultra-high performance fiber reinforced concrete is 53 mm.

[0129] From Figure 3 The test data shows that the larger the particle size of the coarse aggregate, the shallower the bullet penetration depth of the ultra-high performance fiber reinforced concrete, the single-layer precast coarse aggregate grouted UHPC plate, and the functionally graded UHPC composite plate. Therefore, increasing the particle size of the coarse aggregate can enhance the bullet penetration resistance of the UHPC plate.

[0130] From Figure 3 The test data shows that under the same thickness, the bullet penetration resistance performance is: single-layer precast coarse aggregate grouted UHPC plate > functionally graded UHPC composite plate > ultra-high performance fiber reinforced concrete. In this experiment, the volume fraction of the coarse aggregate in the single-layer precast coarse aggregate grouted UHPC plate is 56 - 61%, the volume fraction of the coarse aggregate in the functionally graded UHPC composite plate is 35 - 40%, and the volume fraction of the coarse aggregate in the ultra-high performance fiber reinforced concrete is 36.2%. In terms of resisting bullet penetration, the effect of the coarse aggregate is better than that of the steel fiber. The cracks generated in the concrete under the impact load will pass through the coarse aggregate rather than the weak interfacial transition zone. The high-hardness coarse aggregate plays a shielding role in the crack propagation of the concrete slab. Secondly, the high-strength and high-hardness coarse aggregate will change the ballistic trajectory and wear the bullet, weakening the penetration ability of the bullet. Therefore, the higher the volume fraction of the coarse aggregate, the better the penetration resistance performance of the concrete slab.

[0131] From Figure 5 、 6 and the test results of 7, it can be seen that the crack resistance and spalling resistance of the functionally graded UHPC composite slab are higher than those of the single-layer precast coarse aggregate grouted UHPC slab. This is because the steel fibers added in the front crack-resistant layer and the back spalling-resistant layer can effectively prevent the concrete from cracking and spalling.

[0132] The above is only the preferred embodiment of the present invention. It should be noted that the above preferred embodiment should not be regarded as a limitation of the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. For those of ordinary skill in the art of this technology, without departing from the spirit and scope of the present invention, several improvements and refinements can also be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a functionally graded high-performance cement-based fiber composite board, characterized in that, The composite board comprises a middle anti-penetration layer formed by integral grouting, and a front crack-blocking layer and a back anti-stripping layer located on the front and rear sides thereof, wherein the front crack-blocking layer and the back anti-stripping layer are both formed by grouting of ultra-high performance grouting material and steel fiber, and the middle anti-penetration layer is formed by grouting of ultra-high performance grouting material and coarse aggregate; The weight parts of the raw material components in the middle anti-penetration layer are: 1350-1450 parts of ultra-high performance grouting material and 1100-1200 parts of coarse aggregate; the particle size range of the coarse aggregate is selected from one of 5-8 mm, 8-16 mm and 16-25 mm; the ultra-high performance grouting material includes the following raw material components by weight: 916 parts of cement, 61 parts of silica fume, 244 parts of limestone powder, 808 parts of fine sand, 281 parts of water, and 21 parts of water reducer, and the particle size range of the fine sand is 0-0.2 mm; the fluidity of the ultra-high performance grouting material is 38-40 cm, the V-funnel flow time is 7-7.5 s, and the 28d compressive strength is >140 MPa; The method for preparing the composite plate comprises: (1) Weigh the raw materials according to the designed ratio; (2) First, a layer of steel fiber is pre-placed at the bottom of the mold, then coarse aggregate is placed on top of the steel fiber, and finally a layer of steel fiber is placed on the top layer; (3) Preparation of ultra-high performance grouting material: Add cement, silica fume, limestone powder and fine sand into a mixing pot and stir. After stirring evenly, add 80% of water and continue to mix and stir. Finally, mix the water reducer with the remaining water and pour it into the mixing pot and stir. (4) The ultra-high performance grouting material is injected into the mold through a grouting pipe, vibrated and compacted, and cured to obtain the functional gradient high performance cement-based fiber composite board.

2. The preparation method of the functionally graded high-performance cement-based fiber composite board according to claim 1, characterized in that, The volume content of steel fiber in the front crack-resisting layer and the back anti-stripping layer is both 1%.

3. The preparation method of the functionally graded high-performance cement-based fiber composite board according to claim 1, characterized in that, When the coarse aggregate particle size is 16-25 mm, the ultimate safe thickness of the composite board is 80 mm.

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