Dot matrix structure reinforced lightweight cement-based composite material and preparation method thereof

Abstract

The application provides a lattice structure reinforced lightweight cement-based composite material and a preparation method thereof, a three-dimensional periodic lattice skeleton is arranged in the lightweight cement-based material to construct a space support reinforcement system, so that the stress transmission path in the material is improved and the rapid expansion of the main crack is inhibited. Compared with the cement-based material without the lattice structure reinforcement, the application can significantly improve the compressive bearing capacity of the cement-based material, and the compressive strength is increased by about 20.9%. The lattice structure of the application can effectively inhibit the rapid penetration behavior of the crack in the stress process, so that the brittle failure mode of the lightweight concrete under the traditional matrix condition is changed from the single main crack to the progressive damage failure mode of the multiple crack cooperative expansion, thereby delaying the development of the damage localization, improving the ductility, the post-peak stability and the damage tolerance of the material, and effectively solving the problems of the existing lightweight concrete, such as the brittleness, the rapid crack expansion and the insufficient post-peak bearing capacity.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a lattice structure reinforced lightweight cement-based composite material and its preparation method. Background Technology

[0002] Lightweight concrete (also known as lightweight aggregate concrete or porous concrete) is a low-density cement-based composite material made by using cement as a binder and incorporating lightweight aggregates (such as vitrified microspheres, hollow glass microspheres, expanded perlite, etc.). Due to the introduction of a large number of lightweight porous components, the material has a low apparent density (typically 0.3-1.8 g / cm³). 3 With its advantages of low thermal conductivity, light weight, and excellent thermal insulation performance, it has been widely used in non-load-bearing walls, roof insulation, backfilling projects, and prefabricated buildings.

[0003] However, the high porosity of lightweight concrete also leads to a loose internal structure and reduced matrix density. When subjected to external loads, stress tends to concentrate at the pores and aggregate interfaces, forming localized weak points. Under compression conditions, cracks often initiate from these weak points and propagate rapidly, exhibiting typical brittle failure characteristics: failure occurs without obvious warning, the main crack quickly penetrates the entire specimen once formed, causing the material to suddenly lose its load-bearing capacity, resulting in a sharp drop in post-peak strength, low damage tolerance, and poor ductility. This brittle failure mode severely restricts the application of lightweight concrete in load-bearing structures or engineering scenarios with high safety requirements.

[0004] To improve the mechanical properties and brittle failure of lightweight concrete, existing technologies mainly employ the following reinforcement strategies: (1) Fiber random dispersion reinforcement technology By incorporating steel fibers, polypropylene fibers, basalt fibers, or carbon fibers into a concrete matrix, the bridging effect of the fibers can be used to suppress microcrack propagation and improve the toughness and crack resistance of the material. However, the fibers are randomly and disorderedly distributed in the matrix, resulting in a statistical and locally non-uniform reinforcement effect, making it difficult to directionally control the internal stress transmission path. At the same time, the interfacial bonding performance between the fibers and the cement matrix is ​​limited, making them prone to pull-out failure under high pressure stress. This results in a limited improvement in compressive bearing capacity and little effect on post-peak stability.

[0005] (2) Linear constraint reinforcement technology for steel bars / section steel Reinforcing steel mesh or steel frame structures are incorporated into concrete members to form reinforced concrete or steel-concrete composite structures, thereby improving overall load-bearing capacity and deformation capacity. However, steel reinforcement is a macroscopic structural enhancement method, with significant dimensional differences between the reinforced material and the concrete matrix. The steel reinforcement primarily bears tensile stress and has limited effect on inhibiting crack propagation and stress redistribution under compression in concrete. Furthermore, high steel reinforcement density significantly increases the structural self-weight, contradicting the design principle of lightweight concrete.

[0006] (3) Three-dimensional skeleton / lattice structure enhancement technology In recent years, with the development of additive manufacturing (3D printing) technology, periodic lattice structures (such as body-centered cubic (BCC) and face-centered cubic (FCC) topologies) have been widely studied in the fields of metals, polymers, and composite materials due to their advantages such as high specific strength, high specific stiffness, and strong designability. Some existing technologies apply lattice structures to cement-based materials, mainly using them as tensile reinforcements, fiber substitutes, or functional units that absorb energy through their own plastic deformation, focusing on toughening and energy dissipation performance under impact, bending, or explosion-proof conditions. However, existing technologies rarely involve the application of lattice structures under compression conditions in lightweight concrete, and have not fully considered the synergistic compression bearing mechanism of the lattice structure as a spatial force-transferring skeleton and a lightweight porous matrix. Furthermore, the influence of parameters such as lattice topology, unit cell size, and relative density on the compressive damage evolution mode and post-peak stability of lightweight concrete has not been systematically studied.

[0007] Therefore, there is an urgent need to develop a new reinforcement technology that is suitable for the compression conditions of lightweight concrete, can effectively reconstruct the internal stress transmission path, suppress rapid crack propagation, and improve post-peak stability. Summary of the Invention

[0008] To address the problems of high brittleness, rapid crack propagation, and insufficient post-crack load-bearing capacity in existing lightweight concrete, this invention provides a lattice-structure reinforced lightweight cement-based composite material and its preparation method. By setting a three-dimensional periodic lattice skeleton inside the lightweight cement-based material, a spatial support reinforcement system is constructed to improve the stress transmission path inside the material, inhibit the rapid propagation of the main crack, and thus improve the load-bearing capacity and ductility of the material.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a lattice structure reinforced lightweight cement-based composite material, comprising a lightweight cement-based material matrix and a three-dimensional spatial lattice structure embedded in the lightweight cement-based material matrix; the lattice structure is composed of periodic unit cells, and the unit cell topology is BCC, FCC or FBCC.

[0010] Preferably, the lattice structure is made of nylon carbon fiber composite material and is formed by FDM fused deposition modeling 3D printing process.

[0011] Preferably, the unit cell size of the lattice structure is 10 mm or 20 mm, and the radius of the skeleton of the lattice unit cell is 1 mm.

[0012] Preferably, when the unit cell size is 10 mm, the relative density of the lattice structure of the FCC topology is 19.7%, the relative density of the lattice structure of the BCC topology is 19.8%, and the relative density of the lattice structure of the FBCC topology is 33.0%; when the unit cell size is 20 mm, the relative density of the lattice structure of the FCC topology is 6.9%, the relative density of the lattice structure of the BCC topology is 6.0%, and the relative density of the lattice structure of the FBCC topology is 11.0%.

[0013] Preferably, the raw materials of the lightweight cement-based material matrix include, by weight: 500-600 parts of PO 52.5 ordinary Portland cement, 80-160 parts of silica fume, 40-80 parts of hollow glass microspheres, 130-170 parts of vitrified microspheres, 120-160 parts of water, and 20-40 parts of polycarboxylate superplasticizer.

[0014] Preferably, the volume of the lattice structure accounts for 6.0% to 33.0% of the total volume of the composite material.

[0015] This invention also provides a method for preparing the aforementioned lattice structure reinforced lightweight cement-based composite material, comprising the following steps: S1. A lattice structure is prepared using nylon carbon fiber composite material and FDM fused deposition modeling process. S2. Cement, vitrified microspheres, silica fume, and hollow glass microspheres are mixed evenly according to a preset ratio to obtain a dry mixture; water and polycarboxylate superplasticizer are mixed evenly to obtain a mixing liquid; the mixing liquid is added to the dry mixture and stirred thoroughly to make the components evenly dispersed to obtain a lightweight cement-based material slurry. S3. Place the lattice structure obtained in S1 in the center of the mold, and then pour the lightweight cement-based material slurry obtained in S2 into the mold so that the lattice structure is embedded in it and formed as a whole. Remove air bubbles by vibration. After the slurry has initially set, demold it and cure it to obtain the lattice structure reinforced lightweight cement-based composite material.

[0016] Compared with the prior art, the present invention has the following significant technical effects: 1. This invention introduces a periodic lattice skeleton of nylon carbon fiber prepared by FDM and embeds it integrally into lightweight concrete during the casting process, achieving a structural replacement for the traditional random reinforcement method. By introducing a three-dimensional lattice skeleton inside the lightweight concrete, a stable spatial support system is constructed, effectively improving the stress transmission path within the material, reducing the degree of local stress concentration, and thus improving the overall stress uniformity. The lattice structure acts as a constraint and support similar to a spatial skeleton within the concrete, transforming the material's load-bearing capacity from a matrix-dependent mode to a "matrix-structure collaborative load-bearing" mode, improving overall load-bearing efficiency and structural integrity.

[0017] 2. In terms of structure, unlike traditional randomly dispersed fiber reinforcement or linearly constrained steel bars, this invention employs a periodic spatial lattice structure with a defined topological configuration (BCC, FCC, FBCC), and achieves controllable adjustment of the internal force path through parameterized design of unit cell size and relative density. In terms of materials, this invention uses nylon carbon fiber composite material as the lattice body, which, compared to traditional steel bars or randomly reinforced materials, features lighter weight, greater design flexibility, and better structural continuity. Regarding macroscopic mechanical properties, compared to plain cement-based materials without lattice structure reinforcement, this invention significantly improves the compressive bearing capacity of cement-based materials. Test results show that the compressive strength of the plain cement-based material specimen is 43 MPa, while the compressive strength after lattice structure reinforcement can reach up to 52 MPa, an increase of approximately 20.9%. This indicates that the introduction of the lattice structure not only significantly improves the overall load-bearing capacity of the material but also transforms the mechanical properties from being controlled by a single material to being controlled by a structure-material synergy.

[0018] 3. The lattice structure of this invention can effectively suppress the rapid propagation of cracks during the stress process, transforming lightweight concrete from a brittle failure mode dominated by a single master crack under traditional solid conditions to a progressive damage failure mode of multiple cracks co-propagating, thereby improving the progressiveness and controllability of structural failure. Based on digital image correlation (DIC) analysis results, the lattice structure can significantly disperse local stress concentration and reconstruct the internal load-bearing path, thus delaying the localization of damage development and improving the ductility, post-peak stability, and damage tolerance of the material.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a topological diagram of the lattice structure unit cell of the present invention; Figure 2 This is a lattice structure diagram with a unit cell size of 20 mm in this invention; Figure 3 This is a lattice structure diagram with a unit cell size of 10 mm in this invention; Figure 4This is a DIC comparison chart of the compression failure trends of the material test blocks in the embodiments and comparative examples of the present invention, wherein plain concrete: comparative example 1, 20BCC: example 1, 20FCC: example 2, 20FBCC: example 3, 10BCC: example 4, 10FCC: example 5, 10FBCC: example 6. Detailed Implementation

[0021] The nylon carbon fiber composite material used in this invention is FDM nylon 12CF (PA12-CF) material, composed of polyamide 12 (PA12) and short-cut carbon fibers, with a density of 1.19 g / cm³. 3 The carbon fiber mass fraction is 35%. The lattice structure was fabricated by Guangzhou Chengxing Digital Technology Co., Ltd. using fused deposition modeling (FDM) technology.

[0022] In this invention, the relative density of the lattice structure refers to the proportion of the volume of the lattice solid material to the total envelope volume of the lattice, and is defined as follows:

[0023] in, : Relative density of lattice structure; V S V: The total volume of the solid rods (or walls) that make up the lattice; L : Total volume of the outer envelope of the lattice structure.

[0024] In this invention, the lattice volume fraction refers to the volume percentage of the lattice structure in the entire composite material, and is defined as follows:

[0025] in, : Lattice volume fraction, V L : Total volume of the outer envelope of the lattice structure, V C Total volume of composite material (sample block).

[0026] In the following specific embodiments, the overall size of the lattice structure is 42 mm × 42 mm × 40 mm, and the size of the test block is also designed to be 42 mm × 42 mm × 40 mm. Therefore, the relative density of the lattice structure and the volume fraction of the lattice are consistent.

[0027] Comparative Example 1 Lightweight cement-based materials without embedded lattice structures were prepared using a specimen measuring 42 mm × 42 mm × 40 mm. The preparation method is as follows: The lightweight cement-based material is composed of 550 parts of PO 52.5 ordinary Portland cement, 120 parts of silica fume, 55 parts of hollow glass microspheres, 160 parts of vitrified microspheres, 145 parts of water, and 30 parts of polycarboxylate superplasticizer. In the preparation process, the cement, vitrified microspheres, silica fume, and hollow glass microspheres are first mixed evenly according to a predetermined ratio to obtain a dry mixture. Then, water and the polycarboxylate superplasticizer are mixed to form a mixing liquid. The mixing liquid is then added to the dry mixture and mechanically stirred until the slurry is uniform and free of obvious agglomeration, thus obtaining the lightweight cement-based material slurry. The lightweight cement-based material slurry is then poured into a cubic mold and vibrated to remove internal air bubbles. After the slurry has initially set, it is demolded and then placed in a standard curing room for curing. The standard curing conditions are: temperature 20±2℃, relative humidity above 95%, and curing for 28 days, resulting in a plain lightweight cement-based material specimen (also called a raw specimen).

[0028] Uniaxial compression tests were conducted using a 100-ton universal testing machine. The test results showed that the compressive strength of the lightweight cement-based material specimen was 43 MPa. During the failure process, it mainly exhibited rapid penetration failure through a single main crack, which belongs to a typical brittle failure mode. Figure 4 ).

[0029] Example 1

[0030] This embodiment provides a lattice-structured reinforced lightweight cement-based composite material and its preparation method. The specimen size is 42 mm × 42 mm × 40 mm. The preparation method includes the following steps: S1, Lattice Structure Preparation A BCC topological lattice structure was fabricated using nylon carbon fiber composite material via FDM (Fused Deposition Modeling) 3D printing. The lattice unit cell has a skeleton radius of 1 mm, a unit cell size of 20 mm, and an overall lattice structure size of 42 mm × 42 mm × 40 mm, with a relative density of 6.0%. Figure 2 As shown on the left.

[0031] S2, Preparation of lightweight cement-based materials The lightweight cement-based material is composed of 550 parts of PO 52.5 ordinary Portland cement, 120 parts of silica fume, 55 parts of hollow glass microspheres, 160 parts of vitrified microspheres, 145 parts of water, and 30 parts of polycarboxylate superplasticizer.

[0032] In the preparation process, cement, vitrified microspheres, silica fume, and hollow glass microspheres are first mixed evenly in a predetermined ratio to obtain a dry mixture. Then, water and a polycarboxylate superplasticizer are mixed to form a mixing liquid. The mixing liquid is then added to the dry mixture and mechanically stirred until the slurry is uniform and free of obvious agglomeration, thus obtaining a lightweight cementitious material slurry with an apparent density of approximately 0.0012 g / mm³. 3 .

[0033] S3, Composite Material Preparation The prefabricated lattice structure was placed at the center of a cubic mold, and then lightweight cement-based material slurry was poured into the mold and vibrated to ensure that the slurry fully filled the internal space of the lattice structure and reduced internal air bubbles. After the slurry initially set, the mold was removed, and then the mold was placed in a standard curing room for curing. The standard curing conditions were: temperature 20±2℃, relative humidity above 95%, and curing for 28 days, resulting in lattice structure-reinforced lightweight cement-based composite material test blocks.

[0034] The experiment used a 100-ton universal testing machine for uniaxial compression testing. During the loading process, the load changes and failure modes of the specimen were recorded. The evolution of the strain field on the specimen surface and the crack propagation process were analyzed using DIC (Digital Image Correlation) technology.

[0035] The test results show that the compressive strength of the lattice structure reinforced lightweight cement-based composite material specimen prepared in this embodiment reaches 52 MPa, which is about 20.9% higher than that of the solid specimen of Comparative Example 1 (compressive strength of 43 MPa).

[0036] Meanwhile, combined with the experimental failure phenomena and DIC analysis results, it can be seen that the lattice structure can effectively improve the stress transmission path inside the material and disperse local stress concentration, delay the rapid crack propagation, and change the material failure mode from the rapid penetration failure of a single main crack under the condition of raw body to a progressive damage failure mode of multiple cracks co-propagating. Figure 4 (20BCC), thereby improving the post-peak stability, ductility and damage tolerance of the material.

[0037] Example 2

[0038] Lightweight cement-based composite material reinforced with FCC topological lattice structure was prepared using the same method as in Example 1, except that: the lattice structure is an FCC topological configuration, the radius of the skeleton of the lattice unit cell is 1 mm, the unit cell size is 20 mm, the overall size of the lattice structure is 42 mm × 42 mm × 40 mm, and the relative density is 6.9%. Figure 2 As shown in (middle).

[0039] After standard curing for 28 days, the specimens were subjected to uniaxial compression tests using a 100-ton universal testing machine. The test results showed that the compressive strength of the specimens in this embodiment reached 46 MPa, which is a certain improvement compared to the unconsolidated specimens. During the test, crack propagation exhibited a multi-regional dispersed development characteristic, and the failure process was more gradual than that of the unconsolidated specimens. Figure 4 (20FCC).

[0040] Example 3

[0041] Lightweight cement-based composite material reinforced with FBCC topological lattice structure was prepared using the same method as in Example 1, except that: the lattice structure is an FBCC topological configuration, the radius of the skeleton of the lattice unit cell is 1 mm, the unit cell size is 20 mm, the overall size of the lattice structure is 42 mm × 42 mm × 40 mm, and the relative density is 11.0%. Figure 2 As shown on the right.

[0042] After standard curing for 28 days, the specimens were subjected to uniaxial compression tests using a 100-ton universal testing machine. The test results showed that the compressive strength of the specimens in this embodiment reached 49 MPa. DIC analysis results indicated that the lattice structure effectively constrained localized stress concentration areas, slowed crack localization, and improved the post-peak stability of the material. Figure 4 ,20FBCC).

[0043] Example 4

[0044] Lightweight cement-based composite material reinforced with a BCC topological lattice structure was prepared using the same method as in Example 1, except that: the lattice structure is a BCC topological configuration, the radius of the skeleton of the lattice unit cell is 1 mm, the unit cell size is 10 mm, the overall size of the lattice structure is 42 mm × 42 mm × 40 mm, and the relative density is 19.8%. Figure 3 As shown on the left.

[0045] After standard curing for 28 days, the specimens were subjected to uniaxial compression tests using a 100-ton universal testing machine. The test results showed that the compressive strength of the specimens in this embodiment reached 46 MPa, which is a certain improvement compared to the unbonded specimens. Furthermore, the specimens exhibited good crack propagation inhibition ability during the compression test loading process. Figure 4 ,10BCC).

[0046] Example 5

[0047] Lightweight cement-based composite material reinforced with FCC topological lattice structure was prepared using the same method as in Example 1, except that: the lattice structure is an FCC topological configuration, the radius of the skeleton of the lattice unit cell is 1 mm, the unit cell size is 10 mm, the overall size of the lattice structure is 42 mm × 42 mm × 40 mm, and the relative density is 19.7%. Figure 3 As shown in (middle).

[0048] After standard curing for 28 days, the specimens were subjected to uniaxial compression tests using a 100-ton universal testing machine. The test results showed that the compressive strength of the specimens in this embodiment reached 49 MPa, and crack propagation was suppressed during failure, exhibiting a multi-crack progressive propagation failure characteristic. Figure 4 (10FCC).

[0049] Example 6

[0050] Lightweight cement-based composite material reinforced with FBCC topological lattice structure was prepared using the same method as in Example 1, except that: the lattice structure is an FBCC topological configuration, the radius of the skeleton of the lattice unit cell is 1 mm, the unit cell size is 10 mm, the overall size of the lattice structure is 42 mm × 42 mm × 40 mm, and the relative density is 33.0%. Figure 3 As shown on the right.

[0051] After standard curing for 28 days, the specimens were subjected to uniaxial compression tests using a 100-ton universal testing machine. The test results showed that the compressive strength of the specimens in this embodiment reached 46 MPa, and the crack propagation during failure was relatively gradual, exhibiting a progressive damage failure mode. Figure 4 ,10FBCC).

[0052] As demonstrated by the above embodiments and comparative examples, this invention, by embedding a three-dimensional periodic lattice structure within lightweight cement-based materials, effectively improves the internal stress transmission path, enhances the overall load-bearing capacity, and inhibits rapid crack propagation. Compared to plain lightweight cement-based materials without embedded lattice structures, the compressive strength of the specimens reinforced with the lattice structure increased to 46–52 MPa, with the highest increase being approximately 20.9%. Simultaneously, the material failure mode shifted from brittle, through-crack-controlled failure to a progressive damage failure mode involving the coordinated propagation of multiple cracks, significantly improving the material's ductility, post-peak stability, and damage tolerance.

[0053] This invention reconstructs the internal stress transmission path of lightweight concrete through a lattice structure, effectively inhibiting the rapid penetration of the main crack, promoting the coordinated propagation of multiple cracks, improving the material's post-peak load-bearing capacity and energy dissipation capacity, and realizing the transformation from material reinforcement to structural synergistic reinforcement, which has practical application value.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A lattice structure reinforced lightweight cementitious composite material, characterized by, It includes a lightweight cement-based material matrix and a three-dimensional spatial lattice structure embedded in the lightweight cement-based material matrix; the lattice structure is composed of periodic unit cells, and the unit cell topology is BCC, FCC or FBCC.

2. The lattice structure reinforced lightweight cement-based composite material according to claim 1, wherein, The lattice structure is made of nylon carbon fiber composite material and is formed by FDM fused deposition modeling 3D printing process.

3. The lattice-structured reinforced lightweight cement-based composite material according to claim 2, characterized in that, The unit cell size of the lattice structure is 10 mm or 20 mm, and the radius of the skeleton of the lattice unit cell is 1 mm.

4. The lattice structure reinforced lightweight cement-based composite material according to claim 3, characterized in that, When the unit cell size is 10 mm, the relative density of the lattice structure in the FCC topology is 19.7%, the relative density of the lattice structure in the BCC topology is 19.8%, and the relative density of the lattice structure in the FBCC topology is 33.0%. When the unit cell size is 20 mm, the relative density of the lattice structure of the FCC topology is 6.9%, the relative density of the lattice structure of the BCC topology is 6.0%, and the relative density of the lattice structure of the FBCC topology is 11.0%.

5. The lattice-structured reinforced lightweight cement-based composite material according to claim 1, characterized in that, The raw materials of the lightweight cement-based material matrix include, by weight: 500-600 parts of PO 52.5 ordinary Portland cement, 80-160 parts of silica fume, 40-80 parts of hollow glass microspheres, 130-170 parts of vitrified microspheres, 120-160 parts of water, and 20-40 parts of polycarboxylate superplasticizer.

6. The lattice-structured reinforced lightweight cement-based composite material according to claim 1, characterized in that, The volume of the lattice structure accounts for 6.0% to 33.0% of the total volume of the composite material.

7. A method for preparing a lattice-structured reinforced lightweight cement-based composite material according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. A lattice structure is prepared using nylon carbon fiber composite material and FDM fused deposition modeling process. S2. Cement, vitrified microspheres, silica fume, and hollow glass microspheres are mixed evenly according to a preset ratio to obtain a dry mixture; water and polycarboxylate superplasticizer are mixed evenly to obtain a mixing liquid; the mixing liquid is added to the dry mixture and stirred thoroughly to make the components evenly dispersed to obtain a lightweight cement-based material slurry. S3. Place the lattice structure obtained in S1 in the center of the mold, and then pour the lightweight cement-based material slurry obtained in S2 into the mold so that the lattice structure is embedded in it and formed as a whole. Remove air bubbles by vibration. After the slurry has initially set, demold it and cure it to obtain the lattice structure reinforced lightweight cement-based composite material.

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