Inorganic nanofiber reinforced concrete composite material for light building material

Abstract

The invention discloses an inorganic nanofiber reinforced concrete composite material for a lightweight building material, and relates to the technical field of advanced inorganic non-metallic materials, the composite material is prepared from cement, lightweight aggregate, fine aggregate, modified inorganic nanofiber, a mineral admixture, a water reducer, a dispersant and water, the modified inorganic nanofibers are subjected to surface activation treatment through a silane coupling agent, the interface bonding strength with a cement matrix is improved, the preparation method comprises the steps of nanofiber surface modification, ultrasonic dispersion, dry material mixing, wet material stirring, aggregate adding and forming and curing, the dry apparent density of the prepared composite material is 1400-1600 kg / m < 3 >, the 28-day compressive strength reaches 35-45 MPa, and the composite material is suitable for being used as a cement-based composite material. The light-weight high-strength light-weight building material has the characteristics of light weight, high strength, good crack resistance and excellent durability, and is suitable for the fields of novel wall materials and light-weight building materials.

Description

Technical Field

[0001] This invention relates to the field of advanced inorganic non-metallic materials technology, specifically to inorganic nanofiber reinforced concrete composite materials for lightweight building materials. Background Technology

[0002] Lightweight aggregate concrete is a type of concrete made from lightweight coarse aggregates, ordinary sand, cement, and water, with a density not exceeding 1900 kg / m³. 3 Its lightweight properties have driven its widespread use in high-rise buildings and large-span structures. Lightweight aggregate concrete is widely used in industrial and civil buildings and other projects, which can reduce the self-weight of the structure, improve the seismic performance of the structure, save material usage, and improve the building function (thermal insulation and fire resistance).

[0003] However, cement-based composites have the weakness of brittleness, which is attributed to their low strain capacity, resulting in poor crack resistance and tensile strength. Fibers strengthen the cement matrix by bearing external loads and form a dense system in concrete to prevent cracks, but they cannot prevent the generation of microcracks such as nanoscale cracks.

[0004] Nanomaterials typically have a particle size of 1–100 nm. The particles are extremely small but have a large specific surface area. This characteristic gives them special properties such as high surface activity and strong oxidizing properties. Incorporating nanomaterials into concrete can improve and enhance the physical and mechanical properties of concrete to a certain extent. Nanomaterials can repair nanoscale pores and cracks, as well as enhance or modify the performance of concrete.

[0005] Replacing micron-sized fibers with carbon nanotubes can enhance the impact resistance of ultra-high performance concrete. However, the weak wettability and low dispersibility of carbon nanotubes, as well as the weak interfacial bonding between carbon nanotubes and the concrete matrix, limit the full realization of their reinforcing effect. Existing technologies suffer from problems such as poor nanofiber dispersibility, weak interfacial bonding with the matrix, and insignificant reinforcing effect, making it difficult to meet the dual requirements of lightweight building materials for mechanical properties and durability.

[0006] Therefore, there is an urgent need to develop a lightweight building material concrete composite that can fully utilize the reinforcing effect of inorganic nanofibers and possess excellent comprehensive performance. Summary of the Invention

[0007] The purpose of this invention is to provide inorganic nanofiber reinforced concrete composite materials for lightweight building materials.

[0008] To achieve the above objectives, the present invention provides the following technical solution: Inorganic nanofiber reinforced concrete composite material for lightweight building materials is prepared from the following components in parts by weight: 100 parts cement, 30-50 parts lightweight aggregate, 60-80 parts fine aggregate, 0.5-2.0 parts modified inorganic nanofiber, 15-25 parts mineral admixture, 0.8-1.5 parts water-reducing agent, 0.3-0.6 parts dispersant, and 35-45 parts water; The modified inorganic nanofibers are inorganic nanofibers that have undergone surface activation treatment, and the inorganic nanofibers are selected from one of nano-silica fibers and nano-alumina fibers; The surface activation treatment method is as follows: Inorganic nanofibers were surface modified by placing them in a silane coupling agent solution with a mass concentration of 1-3%, a treatment temperature of 50-70℃, and a treatment time of 2-4 hours.

[0009] The inorganic nanofibers have a diameter of 20-100 nm and a length of 1-10 μm.

[0010] As a further aspect of the present invention: the silane coupling agent is selected from γ-aminopropyltriethoxysilane and γ-methacryloxypropyltrimethoxysilane.

[0011] As a further aspect of the present invention: the lightweight aggregate is selected from one of ceramsite, expanded perlite, and pumice; The apparent density of the lightweight aggregate is 300-800 kg / m³. 3 The particle size is 5-15mm.

[0012] As a further aspect of the present invention: the fine aggregate is natural river sand with a fineness modulus of 2.3-2.8.

[0013] As a further aspect of the present invention: the mineral admixture is selected from silica fume and fly ash; The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent with a water reduction rate of not less than 25%. The dispersant is hydroxypropyl methylcellulose with a viscosity of 100,000-150,000 mPa·s.

[0014] This invention also provides a method for preparing inorganic nanofiber reinforced concrete composite materials for lightweight building materials, comprising the following steps: Step 1: Inorganic nanofibers are added to a silane coupling agent solution for surface modification treatment. After filtration, washing, and drying, modified inorganic nanofibers are obtained. Step 2: Dissolve the dispersant in water, add the modified inorganic nanofibers, and ultrasonically disperse for 20-40 minutes to obtain a nanofiber dispersion. Step 3: Dry mix cement, mineral admixtures and fine aggregates for 1-3 minutes; Step 4: Add the nanofiber dispersion, water-reducing agent, and remaining water to the dry mixture and stir for 3-5 minutes to form a slurry; Step 5: Add lightweight aggregate to the slurry and stir for 2-4 minutes to obtain concrete mixture; Step 6: Pour the concrete mixture into shape and cure it for 28 days to obtain the composite material.

[0015] As a further aspect of the present invention: in step one, the number of washing cycles is 3-5, the drying temperature is 60-80℃, and the drying time is 8-12 hours.

[0016] As a further aspect of the present invention: in step two, the frequency of ultrasonic dispersion is 20-40kHz.

[0017] As a further aspect of the present invention: in step six, the standard curing conditions are a temperature of 20±2℃ and a relative humidity of 95%.

[0018] Compared with the prior art, the beneficial effects of the present invention by adopting the above technical solution are as follows: (1) The present invention uses a silane coupling agent to perform surface activation treatment on inorganic nanofibers, introduces active functional groups on the fiber surface, enhances the chemical bonding between nanofibers and cement hydration products, and improves the interfacial bonding strength.

[0019] (2) The present invention adopts a combination of dispersant and ultrasonic dispersion technology, which effectively solves the problem of nanofiber agglomeration, realizes the uniform distribution of nanofiber in concrete matrix, and gives full play to the reinforcing and toughening effect of nanofiber.

[0020] (3) The dry apparent density of the composite material prepared by this invention is 1400-1600 kg / m³. 3 The compressive strength reaches 35-45 MPa and the flexural strength reaches 4.5-6.0 MPa after 28 days. Compared with ordinary lightweight concrete, the compressive strength is increased by 20-35% and the flexural strength is increased by 30-50%.

[0021] (4) The composite material prepared by the present invention has excellent crack resistance. The nanofibers form a three-dimensional network structure in the matrix, which effectively inhibits the initiation and propagation of microcracks and improves the toughness and durability of the material.

[0022] (5) The raw materials used in this invention are widely available, the preparation process is simple and controllable, and it is suitable for industrial production and application. It can be widely used in new wall materials, lightweight building materials and other fields. Attached Figure Description

[0023] Figure 1 This is a process flow diagram for preparing inorganic nanofiber reinforced concrete composite materials for lightweight building materials according to the present invention.

[0024] Figure 2 This is a schematic diagram of the structure of the modified inorganic nanofibers of the present invention.

[0025] Figure 3 This is a schematic diagram of the microstructure of the composite material of the present invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0027] Example 1 An inorganic nanofiber reinforced concrete composite material for lightweight building materials is prepared from the following components in parts by weight: 100 parts cement (P.O42.5 ordinary Portland cement), ceramsite (apparent density 500 kg / m³) 3 40 parts of the following ingredients: 5-10 mm particle size, 70 parts of natural river sand (fineness modulus 2.6), 1.0 part of modified nano-silica fiber (diameter 50 nm, length 5 μm), 20 parts of silica fume, 1.2 parts of polycarboxylate superplasticizer, 0.5 parts of hydroxypropyl methylcellulose (viscosity 120000 mPa·s), and 40 parts of water.

[0028] The preparation method is as follows: Step 1: Preparation of modified nano-silica fibers: A 2% γ-aminopropyltriethoxysilane solution was prepared, and nano-silica fibers were added to the solution. The solution was stirred for 3 hours under a constant temperature water bath at 60℃. After filtration, the solution was washed 4 times with deionized water and dried in an oven at 70℃ for 10 hours to obtain modified nano-silica fibers.

[0029] Step 2: Preparation of the dispersion: Propyl methyl cellulose was dissolved in 20 parts of water, stirred evenly, and then 1.0 part of modified nano-silica fiber was added. The mixture was then dispersed using ultrasonic waves at 30 kHz for 30 minutes to obtain a nanofiber dispersion.

[0030] Step 3: Mixing dry ingredients: Mix mud, 20 parts silica fume, and 70 parts natural river sand in a mixer for 2 minutes.

[0031] Step 4: Mixing the wet materials: Add the powder, 1.2 parts water-reducing agent and 20 parts water to the dry mixture and stir for 4 minutes to form a slurry.

[0032] Step 5: Adding aggregates: Add to the slurry and continue stirring for 3 minutes.

[0033] Step Six: Shaping and Curing The sample was placed into a 100mm×100mm×100mm cube mold and vibrated to form. It was then cured for 28 days under standard conditions of 20±2℃ and 95% relative humidity.

[0034] Performance test results: Dry apparent density 1520 kg / m³ 3 The compressive strength after 28 days is 42.3 MPa, and the flexural strength is 5.6 MPa.

[0035] Example 2 An inorganic nanofiber reinforced concrete composite material for lightweight building materials is prepared from the following components in parts by weight: 100 parts cement, expanded perlite (apparent density 350 kg / m³) 3 35 parts of the following ingredients: 8-15mm particle size, 65 parts of natural river sand (fineness modulus 2.4), 0.8 parts of modified nano-alumina fiber (diameter 30nm, length 3μm), 18 parts of fly ash, 1.0 part of polycarboxylate superplasticizer, 0.4 parts of hydroxypropyl methylcellulose, and 38 parts of water.

[0036] The preparation method is as follows: Step 1: Preparation of modified nano-alumina fibers: The nano-alumina fibers were added to a 1.5% γ-methacryloxypropyltrimethoxysilane solution and stirred in a 55°C constant temperature water bath for 2.5 hours. After filtration, the fibers were washed three times with deionized water and dried in a 65°C oven for 9 hours to obtain modified nano-alumina fibers.

[0037] Steps two through six are the same as in Example 1.

[0038] Performance test results: Dry apparent density 1450 kg / m³ 3 The compressive strength after 28 days is 38.6 MPa, and the flexural strength is 5.2 MPa.

[0039] Example 3 An inorganic nanofiber reinforced concrete composite material for lightweight building materials is prepared from the following components in parts by weight: 100 parts cement, pumice (apparent density 600 kg / m³) 3 45 parts of the following ingredients: 5-12mm particle size, 75 parts of natural river sand (fineness modulus 2.7), 1.5 parts of modified nano-silica fiber (diameter 80nm, length 8μm), 23 parts of silica fume, 1.4 parts of polycarboxylate superplasticizer, 0.55 parts of hydroxypropyl methylcellulose, and 42 parts of water.

[0040] The preparation method is as follows: Step 1: Preparation of modified nano-silica fibers: The nano-silica fiber was added to a 2.5% γ-aminopropyltriethoxysilane solution and stirred in a 65°C constant temperature water bath for 3.5 hours. After filtration, it was washed 5 times with deionized water and dried in a 75°C oven for 11 hours to obtain the modified nano-silica fiber.

[0041] Steps two through six are the same as in Example 1.

[0042] Performance test results: Dry apparent density 1580 kg / m³ 3 The compressive strength after 28 days is 44.8 MPa, and the flexural strength is 5.9 MPa.

[0043] Comparative Example 1 The same formulation and process as in Example 1 were used, except that no modified nanofibers were added.

[0044] Performance test results: Dry apparent density 1500 kg / m³ 3 The compressive strength after 28 days is 32.5 MPa, and the flexural strength is 3.8 MPa.

[0045] Comparative Example 2 The same formulation and process as in Example 1 were used, except that untreated nano-silica fibers were used.

[0046] Performance test results: Dry apparent density 1515 kg / m³ 3 The compressive strength after 28 days is 36.8 MPa, and the flexural strength is 4.5 MPa.

[0047] By comparing the performance data of the embodiments and the comparative examples, it can be seen that: (1) Compared with Comparative Example 1, the compressive strength of Example 1 with added modified inorganic nanofibers increased by 30.2% and the flexural strength increased by 47.4%, indicating that inorganic nanofibers have a significant enhancing effect on the mechanical properties of composite materials.

[0048] (2) Compared with Comparative Example 2, Example 1, which adopted surface activation treatment, showed an increase of 14.9% in compressive strength and 24.4% in flexural strength, indicating that surface activation treatment effectively improved the interfacial bonding strength between nanofibers and the matrix and enhanced the reinforcing effect.

[0049] The above embodiments are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

Claims

1. An inorganic nanofiber reinforced concrete composite material for lightweight building materials, characterized in that, It is prepared from the following components in parts by weight: 100 parts cement, 30-50 parts lightweight aggregate, 60-80 parts fine aggregate, 0.5-2.0 parts modified inorganic nanofiber, 15-25 parts mineral admixture, 0.8-1.5 parts water-reducing agent, 0.3-0.6 parts dispersant, and 35-45 parts water; The modified inorganic nanofibers are inorganic nanofibers that have undergone surface activation treatment, and the inorganic nanofibers are selected from one of nano-silica fibers and nano-alumina fibers; The surface activation treatment method is as follows: Inorganic nanofibers were surface modified by placing them in a silane coupling agent solution with a mass concentration of 1-3%, a treatment temperature of 50-70℃, and a treatment time of 2-4 hours.

2. The inorganic nanofiber reinforced concrete composite material for lightweight building materials according to claim 1, characterized in that: The inorganic nanofibers have a diameter of 20-100 nm and a length of 1-10 μm.

3. The inorganic nanofiber reinforced concrete composite material for lightweight building materials according to claim 1, characterized in that: The silane coupling agent is selected from γ-aminopropyltriethoxysilane and γ-methacryloxypropyltrimethoxysilane.

4. The inorganic nanofiber reinforced concrete composite material for lightweight building materials according to claim 1, characterized in that: The lightweight aggregate is selected from one of the following: ceramsite, expanded perlite, and pumice. The apparent density of the lightweight aggregate is 300-800 kg / m³. 3 The particle size is 5-15mm.

5. The inorganic nanofiber reinforced concrete composite material for lightweight building materials according to claim 1, characterized in that: The fine aggregate is natural river sand with a fineness modulus of 2.3-2.

8.

6. The inorganic nanofiber reinforced concrete composite material for lightweight building materials according to claim 1, characterized in that: The mineral admixture is selected from either silica fume or fly ash; The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent with a water reduction rate of not less than 25%. The dispersant is hydroxypropyl methylcellulose with a viscosity of 100,000-150,000 mPa·s.

7. A method for preparing an inorganic nanofiber reinforced concrete composite material for lightweight building materials as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Inorganic nanofibers are added to a silane coupling agent solution for surface modification treatment. After filtration, washing, and drying, modified inorganic nanofibers are obtained. Step 2: Dissolve the dispersant in water, add the modified inorganic nanofibers, and ultrasonically disperse for 20-40 minutes to obtain a nanofiber dispersion. Step 3: Dry mix cement, mineral admixtures and fine aggregates for 1-3 minutes; Step 4: Add the nanofiber dispersion, water-reducing agent, and remaining water to the dry mixture and stir for 3-5 minutes to form a slurry; Step 5: Add lightweight aggregate to the slurry and stir for 2-4 minutes to obtain concrete mixture; Step 6: Pour the concrete mixture into shape and cure it for 28 days to obtain the composite material.

8. The inorganic nanofiber reinforced concrete composite material for lightweight building materials according to claim 7, characterized in that: In step one, the washing is performed 3-5 times, the drying temperature is 60-80℃, and the drying time is 8-12 hours.

9. The inorganic nanofiber reinforced concrete composite material for lightweight building materials according to claim 7, characterized in that: In step two, the frequency of ultrasonic dispersion is 20-40kHz.

10. The inorganic nanofiber reinforced concrete composite material for lightweight building materials according to claim 7, characterized in that: In step six, the standard curing conditions are a temperature of 20±2℃ and a relative humidity of 95%.

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