Lightweight high-strength high-toughness cement-based composite material and preparation method thereof

Abstract

The invention discloses a lightweight high-strength high-toughness cement-based composite material and a preparation method thereof. The composite material is prepared from the following components in parts by mass: 1000 parts of a cementing material, 200-400 parts of fine aggregate, 150-250 parts of water, 10-30 parts of a water reducing agent, 14-23 parts of synthetic fiber and 10-30 parts of silicon dioxide aerogel. The preparation method comprises the following steps: mixing and stirring 1000 parts of the cementing material, 200-400 parts of the fine aggregate and 10-30 parts of the silicon dioxide aerogel to obtain a dry material, then adding 10-30 parts of the water reducing agent and 150-250 parts of the water into the dry material, mixing and stirring to obtain neat paste, and finally adding 14-23 parts of the synthetic fiber into the neat paste while stirring, and mixing and stirring to obtain slurry. The light-weight, high-strength and high-toughness cement-based composite material is few in component variety, simple in preparation method, low in volume weight, high in strength and large in ultimate tensile strain, and the problems that a traditional light-weight and high-toughness cement-based material is large in light-weight aggregate mixing amount, low in strength, poor in ductility and stability and the like are solved; and the method has a wide application prospect in infrastructures such as high-rise building structure facades and large-span bridge structure pavement layers.

Description

Technical Field

[0001] This invention relates to the field of cement materials technology, and in particular to a lightweight, high-strength, and high-toughness cement-based composite material and its preparation method. Background Technology

[0002] Lightweight aggregates (such as hollow glass microspheres, fly ash hollow microspheres, and rubber particles) are often introduced into high-toughness cement-based materials as "artificial defects" due to their low density, low strength, and weak interfacial bonding characteristics [1 Wang Hua, Yang Chaoshuai, Li Daqiang, et al., A lightweight high-ductility concrete and its preparation method, CN 118221407 B; 2 Gou Hongxiang, Zhu Mintao, Dong Saiyang, et al., A lightweight high-ductility cement-based composite material that can be used for 3D printing and its preparation method, CN 112876165 B; 3 Gou Hongxiang, Zhu Mintao, Gao Shuangshuang, et al., A lightweight high-strength high-ductility cement-based cementitious composite material and its preparation method, CN 112694342A]. The incorporation of lightweight aggregates not only helps to enhance the tensile ductility of materials but also allows for the preparation of lightweight high-toughness cement-based composite materials. Thanks to their lightweight nature, these materials have shown significant application value in high-rise buildings, long-span structures, and offshore floating platforms [4 Guo Rongxin, Fu Chaoshu, Lin Zhiwei, et al., Multi-scale reinforced lightweight high-ductility cement-based composite materials and their preparation methods, CN 114057456 B]. Although traditional lightweight aggregates have made some progress in the preparation of lightweight high-toughness cement-based materials, there are still performance bottlenecks (such as low compressive strength, mostly below 50 MPa), and the proportion of lightweight aggregates introduced is relatively large (up to 20-40% of cementitious materials).

[0003] To achieve precise control over the cracking behavior of high-toughness cement-based materials and synergistically obtain excellent comprehensive performance, developing new methods for introducing lightweight aggregates and preparing lightweight, high-strength, and high-toughness cement-based composite materials are of great significance for promoting the advancement of materials technology. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a lightweight, high-strength, and high-toughness cement-based composite material with relatively simple material composition and its preparation method, addressing the technical problem of how to achieve precise control over material properties using a small amount of novel lightweight aggregate. The lightweight, high-strength, and high-toughness cement-based material of this invention combines advantages such as high strength, good ductility, lightweight, and simple preparation process, and has broad application prospects in engineering projects with requirements for both strength and weight (such as bridge deck pavement layers for long-span bridge structures and exterior insulation layers for ultra-high-rise building structures).

[0005] This invention is achieved through the following technical solution: This invention provides a lightweight, high-strength, and high-toughness cement-based composite material, comprising the following components in parts by weight: 1000 parts of cementitious material, 200-400 parts of fine aggregate, 150-250 parts of water, 10-30 parts of water-reducing agent, 14-23 parts of synthetic fiber, and 10-30 parts of silica aerogel.

[0006] Furthermore, the cementitious material is composed of cement components, fly ash components, and silica fume components mixed in a mass ratio of 2:1:1 to 6:4:1.

[0007] Specifically, the cement is one of silicate cement, ordinary silicate cement, high-alumina cement, and sulfoaluminate cement.

[0008] Specifically, the silica content of the silica ash is greater than 85%; Specifically, the fine aggregate is either quartz sand or river sand, with a particle size of less than 0.5 mm; the water is drinking water or tap water.

[0009] Specifically, the water-reducing agent is any one or more of lignin sulfonate water-reducing agents, naphthalene sulfonate water-reducing agents, melamine-based water-reducing agents, polycarboxylate water-reducing agents, casein water-reducing agents, and polycarboxylate-based water-reducing agents.

[0010] Specifically, the silica aerogel is a white powder with a porosity greater than 90%.

[0011] Specifically, the synthetic fiber is one or more of polyvinyl alcohol fiber, polyethylene fiber, polypropylene fiber, carbon fiber, aramid fiber, and aromatic polyamide fiber, with a fiber volume fraction of 1.0~3.0%, a diameter of 10~80μm, and a length of 4~20mm.

[0012] This invention also provides a method for preparing a lightweight, high-strength, and high-toughness cement-based composite material, comprising the following steps: (1) Weigh cement, silica fume, fine aggregate, water, water-reducing agent, synthetic fiber and silica aerogel according to the mass ratio; (2) Cement, silica fume, fine aggregate and silica aerogel are mixed to obtain the first mixture; (3) Add the water-reducing agent and water to the first mixture and stir thoroughly to obtain the second mixture; (4) Add the synthetic fibers to the second mixture in small amounts and stir thoroughly to obtain a fresh slurry.

[0013] Specifically, the stirring speed in step (2) is 120~140 r / min and the duration is 1~2 min; the stirring speed in step (3) is 140~280 r / min and the duration is 4~6 min; the stirring speed in step (4) is 140~280 r / min and the duration is 4~6 min.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Significantly reduce material density and achieve lightweight structure. By incorporating a small amount of nanoporous aerogel into high-toughness cement-based materials, a portion of the high-density cement matrix is ​​effectively replaced. Aerogel itself is one of the lightest solid materials in the world, and its introduction can significantly reduce the overall density of the composite material, thus producing lightweight cement-based materials. This is beneficial for reducing the self-weight of buildings, reducing foundation load, saving structural materials, and facilitating transportation and construction; (2) Maintaining good mechanical strength and excellent toughness while reducing density is the core breakthrough of this invention. Traditional lightweight materials often sacrifice strength, while the nano-aerogel in this invention can not only serve as a lightweight filler, but its huge specific surface area and nano-effect can also tightly bind with cement hydration products, optimizing the interface structure, thereby maintaining high compressive strength while reducing density. More importantly, it inherits the tensile hardening characteristics of high-toughness cement-based materials, has the ability to develop multiple cracks, and exhibits high toughness and ductility, avoiding the brittle failure of ordinary concrete; (3) It endows the material with excellent thermal performance, realizing the integration of thermal insulation and structure. Aerogel has extremely low solid thermal conductivity and nanoscale porous structure, which can effectively suppress air convection and heat radiation, and is currently the best-performing solid thermal insulation material. The thermal conductivity of composite materials incorporating aerogel is significantly reduced, and it has excellent thermal insulation performance. This allows the material to be used as both a load-bearing material and a thermal insulation material in building structures, realizing "structure-insulation integration", simplifying building construction and improving building energy efficiency; (4) Improve the durability and dimensional stability of the material. On the one hand, the incorporation of aerogel can refine the pore structure of cement-based materials, reduce the proportion of harmful pores, thereby reducing the penetration of moisture and corrosive ions, and improving the material's resistance to freeze-thaw cycles, chloride ion corrosion, and chemical corrosion. On the other hand, lightweight aerogel particles have a certain degree of elasticity, which can absorb and dissipate internal stress to a certain extent, reduce microcracks caused by drying shrinkage and temperature changes, thereby improving the material's volume stability and long-term durability. Attached Figure Description

[0015] Figure 1 The total porosity of the embodiments and comparative examples of the present invention; Figure 2The distribution of different apertures is shown in the embodiments and comparative examples of the present invention; Figure 3 The density is for the embodiments and comparative examples of the present invention; Figure 4 The compressive strength of the embodiments and comparative examples of the present invention; Figure 5 The tensile stress-strain curves are for embodiments and comparative examples of the present invention. Detailed Implementation

[0016] To make the features and advantages of the present invention more apparent and understandable, the present invention will be further described below with reference to specific embodiments. It should be noted that the described embodiments are only some embodiments of the present invention, and the present invention is not limited thereto.

[0017] This invention discloses a lightweight, high-strength, and high-toughness cement-based composite material, comprising the following components in parts by weight: 1000 parts of cementitious material, 200-400 parts of fine aggregate, 150-250 parts of water, 10-30 parts of water-reducing agent, 14-23 parts of synthetic fiber, and 10-30 parts of silica aerogel. Wherein: The cementitious material is composed of cement components, fly ash components and silica fume components mixed in a mass ratio of 2:1:1 to 6:4:1; The cement is one of P.II. 52.5 Portland cement and PO 52.5 ordinary Portland cement. The specific surface area of ​​P.II.52.5 cement is 330 m². 2 / kg, free calcium oxide content ≤1.0%, magnesium oxide content ≤5.0%, alkali content ≤0.60%; PO 52.5 cement specific surface area is 360 m² 2 / kg, free calcium oxide content ≤1.5%, magnesium oxide content ≤5.0%, alkali content ≤0.60%; The fly ash is Class I, Type F fly ash, with a fineness (residue on a 45μm square-hole sieve) ≤12% and a density of 2.31 g / cm³. 3 ; The silica ash has a silica content greater than 85%, an average particle size of 0.2 μm, and a specific surface area of ​​18000 m². 2 / kg; The fine aggregate is either quartz sand or river sand, with a particle size of less than 0.5 mm; The water is drinking water or tap water or other fresh water; The water-reducing agent is one or more of lignin sulfonate water-reducing agents, naphthalene sulfonate water-reducing agents, melamine water-reducing agents, polycarboxylate water-reducing agents, casein water-reducing agents, and polycarboxylate water-reducing agents, preferably a polycarboxylate water-reducing agent; Silica aerogel is a white powder with a porosity greater than 90%. Synthetic fibers include polyvinyl alcohol fiber, polyethylene fiber, polypropylene fiber, carbon fiber, and aramid fiber. One or more aromatic polyamide fibers, with a fiber volume fraction of 1.0-3.0%, a diameter of 10-80 μm, and a length of 4-20 mm. This invention also discloses a method for preparing a lightweight, high-strength, and high-toughness cement-based composite material, the steps of which are as follows: (1) Weigh cement, silica fume, fine aggregate, water, water-reducing agent, synthetic fiber and silica aerogel according to the mass ratio; (2) Cement, silica fume, fine aggregate and silica aerogel are mixed to obtain the first mixture; (3) Add the water-reducing agent and water to the first mixture and stir thoroughly to obtain the second mixture; (4) Add the synthetic fibers to the second mixture in small amounts and stir thoroughly to obtain a fresh slurry.

[0018] Wherein: the stirring speed in step (2) is 120~140 r / min and the duration is 1~2 min; the stirring speed in step (3) is 140~280 r / min and the duration is 4~6 min; the stirring speed in step (4) is 140~280 r / min and the duration is 4~6 min.

[0019] The specific details of Examples 1-5 and the comparative examples are as follows:

[0020] Example 1: The mix proportion (mass ratio) of the lightweight, high-strength and high-toughness cement-based composite material in this example is shown in Table 1.

[0021] Table 1 ; The cement is silicate cement with a silica content of more than 96% in silica fume; the fine aggregate is ground quartz sand; the water-reducing agent is a solid powder polycarboxylate superplasticizer; and the synthetic fiber is polyethylene fiber with a length of 12 mm.

[0022] The preparation steps are as follows (the total preparation time is 10~15min): slowly stir cement, silica fume, fine aggregate, and silica aerogel (120r / min) for 2min; add water-reducing agent and water and stir quickly (240r / min) for 4min; add fiber in small amounts several times and stir quickly (240r / min) for 6min; pour into a mold and test the properties of the freshly mixed slurry material.

[0023] Example 2: This example increases the amount of aerogel content based on Example 1. The material proportions (mass ratios) are shown in Table 2.

[0024] Table 2 ; The material composition characteristics described above are the same as those in Example 1.

[0025] The preparation steps are the same as in Example 1, and the total preparation time is 10-15 minutes.

[0026] Example 3: This example increases the amount of aerogel content based on Example 2. The material proportions (mass ratios) are shown in Table 3.

[0027] Table 3 ; The material composition characteristics described above are the same as those in Example 2.

[0028] The preparation steps are the same as in Example 1, and the total preparation time is 10-15 minutes.

[0029] Example 4: The mix proportion (mass ratio) of the lightweight, high-strength, and high-toughness cement-based composite material in this example is shown in Table 4.

[0030] Table 4 ; The cement mentioned above is ordinary Portland cement, with silica content of more than 94% in silica fume; the fine aggregate is finely ground river sand; the water-reducing agent is solid powder polycarboxylate superplasticizer; and the synthetic fiber is 12mm long polyvinyl alcohol fiber.

[0031] The preparation steps are the same as in Example 1, and the total preparation time is 10-15 minutes.

[0032] Example 5: The mix proportion (mass ratio) of the lightweight, high-strength, and high-toughness cement-based composite material in this example is shown in Table 5.

[0033] Table 5 ; The cement is silicate cement with a silica content of more than 96% in silica fume; the fine aggregate is finely ground quartz sand; the water-reducing agent is a solid powder polycarboxylate superplasticizer; and the synthetic fiber is 12mm long polypropylene fiber.

[0034] The preparation steps are the same as in Example 1, and the total preparation time is 10-15 minutes.

[0035] Comparative Example 1: This comparative example is based on Examples 1-3 without the addition of aerogel. The material proportions (mass ratios) are shown in Table 6.

[0036] Table 6 ;

[0037] The material composition characteristics described above are the same as those in Examples 1-3.

[0038] The preparation steps are as follows (the total preparation time is 10~15min): slowly stir cement, silica fume and fine aggregate (120r / min) for 2min; add water-reducing agent and water and stir quickly (240r / min) for 4min; add fiber in small amounts several times and stir quickly (240r / min) for 6min; pour into mold and test the performance of the freshly mixed slurry material.

[0039] The performance testing is as follows: To verify the pore structure, density, strength, and ductility of the lightweight, high-strength, and high-toughness cement-based composite material prepared in this invention, the material properties were tested.

[0040] (a) Pore structure and density The pore structure of the material was measured using a mercury porosimeter (MIP). The specific procedure was as follows: First, a 1 cm³ sample was collected from the core region of the molded specimen. 3 Before the MIP test, the test sample was immersed in isopropanol to terminate the hydration reaction; then the sample was taken out and placed in a drying oven at 60°C to dry until the moisture and isopropanol in the sample were completely evaporated and the quality was stable; finally, the pore structure and density of the sample were measured.

[0041] (b) Compressive strength The cement-based composite materials obtained in the examples and comparative examples were subjected to compressive strength tests according to the standards "Test Method for Mechanical Properties of High-Ductility Fiber-Reinforced Cement-Based Composite Materials" (JC / T 2461-2018) and "Standard for Test Methods of Basic Properties of Building Mortar" (JGJ / T70-2009). The compressive strength specimens were 70.7mm × 70.7mm × 70.7mm cubic blocks, and the loading rate was 240kN / min.

[0042] (c) Tensile properties The cement-based composite materials obtained in the examples and comparative examples were subjected to tensile tests according to the standard "Test Method for Mechanical Properties of High-Ductility Fiber-Reinforced Cement-Based Composite Materials" (JC / T 2461-2018). Dumbbell-shaped specimens were used for the tensile tests, and the loading rate was 0.5 mm / min.

[0043] The specific implementation results are as follows: like Figure 1 and Figure 2 The figures show the total porosity and distribution of different pore sizes of the embodiments and comparative examples of the present invention, respectively, obtained by MIP measurement. Figure 3 The density of the embodiments and comparative examples of the present invention obtained by measurement; Figure 4 and Figure 5 The table shows the compressive strength and tensile constitutive relations (stress-strain curves) of the embodiments and comparative examples of the present invention, respectively. Table 7 summarizes the performance parameters of the embodiments and comparative examples.

[0044] Table 7 .

[0045] A comparison of the performance parameters of the cement-based composite materials in Examples 1-5 and Comparative Example 1 shows that the cement-based composite material provided by this invention is lightweight, high-strength, and high-toughness; the material density is related to the silica aerogel content and can be reduced to 1624 kg / m³. 3 The compressive strength can reach over 100 MPa, and the tensile strength and ultimate tensile strain can reach 8.5 MPa and 6.8%, respectively. The incorporation of silica aerogel significantly increases the total porosity of the material, resulting in a decrease in material density (11.2-27.3%), thus achieving a lighter material. Due to the increased porosity, the strength of the examples decreased. Compared to the comparative example without aerogel (compressive and tensile strengths of 124.08 MPa and 9.01 MPa, respectively), the compressive strength of the examples ranged from 62.86 to 101.55 MPa, and the tensile strength ranged from 7.26 to 8.50 MPa, representing decreases of 18.2-49.3% and 5.7-19.4%, respectively. The incorporation of aerogel can optimize the pore structure distribution of the material, reduce the proportion of harmful pores, and make the crack development more saturated under tensile loads, thereby improving the tensile ductility of the material. Compared to the comparative example, the ultimate tensile strain of the examples increased to 5.84-6.81%. Silica aerogel, with its unique lightweight and highly porous three-dimensional network structure, effectively reduces the density of cement-based composite materials while optimizing the internal structure of the material. This verifies the feasibility of the present invention in synergistically regulating the lightweight and mechanical strength of high-toughness cement-based composite materials by introducing aerogel as a functional component.

[0046] Although the above embodiments have described the present invention in detail, those skilled in the art should understand that various modifications or improvements can be made based on the disclosure of the present invention without departing from the scope of the present invention, and such modifications or improvements are all within the protection scope of the present invention.

Claims

1. A lightweight, high-strength, and high-toughness cement-based composite material, characterized in that, The product contains the following components in parts by weight: 1000 parts cementitious material, 200-400 parts fine aggregate, 150-250 parts water, 10-30 parts water-reducing agent, 14-23 parts synthetic fiber, and 10-30 parts silica aerogel.

2. The lightweight, high-strength, and high-toughness cement-based composite material according to claim 1, characterized in that: The cementitious material is composed of cement components, fly ash components and silica fume components mixed in a mass ratio of 2:1:1 to 6:4:

1.

3. The lightweight, high-strength, and high-toughness cement-based composite material according to claim 1, characterized in that: The cement is one of silicate cement, ordinary silicate cement, high-alumina cement, and sulfoaluminate cement.

4. The lightweight, high-strength, and high-toughness cement-based composite material according to claim 1, characterized in that: The silica content of the silica ash is greater than 85%.

5. The lightweight, high-strength, and high-toughness cement-based composite material according to claim 1, characterized in that: The fine aggregate is either quartz sand or river sand, with a particle size of less than 0.5 mm; the water is drinking water or tap water.

6. The lightweight, high-strength, and high-toughness cement-based composite material according to claim 1, characterized in that: The water-reducing agent is any one or more of the following: lignin sulfonate water-reducing agent, naphthalene sulfonate water-reducing agent, melamine water-reducing agent, polycarboxylate water-reducing agent, casein water-reducing agent, and polycarboxylate water-reducing agent.

7. The lightweight, high-strength, and high-toughness cement-based composite material according to claim 1, characterized in that: The silica aerogel is a white powder with a porosity greater than 90%.

8. The lightweight, high-strength, and high-toughness cement-based composite material according to claim 1, characterized in that: The synthetic fiber is one or more of polyvinyl alcohol fiber, polyethylene fiber, polypropylene fiber, carbon fiber, aramid fiber, and aromatic polyamide fiber, with a fiber volume fraction of 1.0~3.0%, a diameter of 10~80μm, and a length of 4~20mm.

9. A method for preparing a lightweight, high-strength, and high-toughness cement-based composite material according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Weigh cement, silica fume, fine aggregate, water, water-reducing agent, synthetic fiber and silica aerogel according to the mass ratio; (2) Cement, silica fume, fine aggregate and silica aerogel are mixed to obtain the first mixture; (3) Add the water-reducing agent and water to the first mixture and stir thoroughly to obtain the second mixture; (4) Add the synthetic fibers to the second mixture in small amounts and stir thoroughly to obtain a fresh slurry.

10. The preparation method according to claim 9, characterized in that: The stirring process in step (2) has a rotation speed of 120~140 r / min and a duration of 1~2 min; the stirring process in step (3) has a rotation speed of 140~280 r / min and a duration of 4~6 min; the stirring process in step (4) has a rotation speed of 140~280 r / min and a duration of 4~6 min.

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