Straw fiber lightweight concrete and preparation method thereof

Abstract

The invention provides straw fiber lightweight concrete and a preparation method thereof, and belongs to the field of building materials. The invention provides straw fiber lightweight concrete, which is prepared from the following preparation raw materials in parts by mass: 360 to 400 parts of cement; 40 to 60 parts of fly ash; 600 to 650 parts of a ceramsite filter material; 600 to 650 parts of sand; 150 to 170 parts of water; 1-3 parts of straw fiber; and 4-5 parts of a water reducing agent. The ceramsite filter material which is hard in surface and internally provided with a large number of micropores is used as the coarse aggregate, so that the lightweight effect is achieved; straw fibers are doped, agricultural waste is utilized, the production cost is reduced, and environmental pollution is reduced. The straw fiber lightweight concrete disclosed by the invention has relatively good compressive property and splitting tensile property, and the preparation method has a wide prospect.

Description

Technical Field

[0002] This invention relates to the field of building materials, specifically to a straw fiber lightweight concrete and its preparation method. Background Technology

[0003] Traditional concrete suffers from problems such as high density, poor thermal insulation, and low compressive strength. Existing lightweight concrete often uses shale ceramsite or polystyrene particles as aggregates, which suffers from high cost, insufficient compressive strength, or poor durability. Meanwhile, the burning of agricultural straw causes severe environmental pollution, and its high-value utilization has become an industry challenge. Therefore, there is an urgent need to develop an environmentally friendly lightweight concrete that uses straw fiber as a reinforcing phase and industrial solid waste as an auxiliary raw material. Summary of the Invention

[0004] This invention provides a straw fiber lightweight concrete and its preparation method. The straw fiber lightweight concrete of this invention has good strength and thermal insulation properties.

[0005] This invention provides a straw fiber lightweight concrete, comprising the following raw materials by weight: 360-400 parts cement; 40-60 parts fly ash; 600-650 parts of ceramsite filter media; 600-650 parts of sand; 150-170 parts water; 1-3 parts straw fiber; 4-5 parts of water-reducing agent.

[0006] Preferably, the water-reducing agent includes a polycarboxylate-based high-efficiency water-reducing agent, and the water-reducing rate of the water-reducing agent is 20-30%.

[0007] Preferably, the water-reducing agent accounts for 1 to 3% of the total mass of the raw materials used in preparation.

[0008] Preferably, the cement comprises, by mass fraction: 61.8% CaO, 21.4% SiO2, 2.5% Fe2O3, 1.6% MgO, 1.6% MgO, 5.8% Al2O3, 0.4% TiO2, and the balance being impurities.

[0009] Preferably, the fineness modulus of the sand is 2 to 3.

[0010] Preferably, the fly ash includes secondary fly ash.

[0011] Preferably, the straw fiber includes wheat straw fiber.

[0012] Preferably, the mass of the straw fiber is 0.2 to 0.8% of the total mass of the raw materials.

[0013] Preferably, the nominal particle size of the ceramsite filter media is 4~6mm and the cylinder compressive strength is 6~9MPa.

[0014] This invention also provides a method for preparing the straw fiber lightweight concrete described in the above technical solution, characterized by comprising the following steps: The straw fiber lightweight concrete is obtained by mixing ceramsite filter material, sand, fly ash, cement, straw fiber, water and water-reducing agent, followed by molding and curing.

[0015] The coarse aggregate of this invention uses ceramsite filter media with a hard outer surface and a large number of micropores inside, achieving the effect of lightweighting; and straw fiber is added to utilize agricultural waste, reduce production costs and reduce environmental pollution. The straw fiber lightweight concrete of this invention exhibits good compressive strength, thermal insulation, and crack resistance, and its preparation method shows promising prospects: High compressive strength is due to the ceramsite filter material forming a skeletal structure within the concrete, dispersing external pressure. Furthermore, the high compressive strength of the ceramsite provides a certain level of compressive support while maintaining the lightweight nature of the concrete. High thermal insulation is due to the high porosity of the ceramsite filter material itself, with pores filled with air. Air is a poor conductor of heat, effectively preventing heat transfer and thus reducing the thermal conductivity of the concrete, improving its thermal insulation performance. Additionally, the straw fibers themselves possess a certain porosity, also contributing to thermal insulation. Their dispersed distribution within the concrete further enhances the insulation effect. Excellent crack resistance is due to the straw fibers acting as a "reinforcement" in the concrete. When the concrete is subjected to external forces or shrinkage stress due to temperature and humidity changes, the straw fibers can disperse the stress, preventing the generation and propagation of cracks and improving the concrete's crack resistance. Attached Figure Description

[0016] Figure 1 This is a scanning electron microscope image of straw fiber lightweight concrete from Example 1. Detailed Implementation

[0017] This invention provides a straw fiber lightweight concrete, comprising the following raw materials by weight: 360-400 parts cement; 40-60 parts fly ash; 600-650 parts of ceramsite filter media; 600-650 parts of sand; 150-170 parts water; 1-3 parts straw fiber; 4-5 parts of water-reducing agent.

[0018] The raw materials for preparing the straw fiber lightweight concrete provided by the present invention, by mass parts, include 360-400 parts of cement, which may be 370 parts, 380 parts or 390 parts in specific embodiments; the cement preferably includes, by mass fraction: CaO 61.8%, SiO2 21.4%, Fe2O3 2.5%, MgO 1.6%, Al2O3 5.8%, TiO2 0.4% and the balance being impurities, and the cement preferably includes ordinary Portland cement with a grade of 42.5.

[0019] Based on the unit mass fraction of the cement, the raw materials for preparing the straw fiber lightweight concrete provided by the present invention include 40-60 parts of fly ash. The fly ash preferably includes: 36.8% Al2O3, 45.1% SiO2, 4.5% CaO, 1.2% SO3, and the balance being impurities. In specific embodiments, it can be 45 parts, 50 parts, or 55 parts. The fly ash preferably includes secondary fly ash.

[0020] Based on the unit mass fraction of the cement, the raw materials for preparing the straw fiber lightweight concrete provided by the present invention include 600-650 parts of ceramsite filter media. The ceramsite filter media preferably comprises: 65% SiO2, 18% Al2O3, 7.2% Fe2O3, 3.5% MgO, and the balance being impurities. In specific embodiments, this can be 610 parts, 620 parts, 630 parts, or 640 parts. The nominal particle size of the ceramsite filter media is preferably 4-6 mm, and the cylinder compressive strength is preferably 6-9 MPa.

[0021] The raw materials for preparing the straw fiber lightweight concrete of the present invention, by mass fraction, include 600-650 parts of sand. The sand preferably includes, by mass fraction, 8.43% Al2O3, 84.81% SiO2, 0.57% CaO, 2.69% K2O, 1.77% Na2O, 0.82% Fe2O3, 0.35% MgO, 0.2% TiO2, and the balance being impurities. In specific embodiments, the amounts may be 610 parts, 620 parts, 630 parts, or 640 parts. The fineness modulus of the sand is preferably 2-3.

[0022] The raw materials for preparing the straw fiber lightweight concrete of the present invention, by mass fraction, include 150-170 parts of water, which may be 155, 160 or 165 parts in specific embodiments.

[0023] The raw materials for preparing the straw fiber lightweight concrete of the present invention, by mass fraction, include 1 to 3 parts of straw fiber, which may be 1.5 parts, 2 parts or 2.5 parts in specific embodiments; the mass of the straw fiber is preferably 0.5% of the total mass of the raw materials, and the straw fiber preferably includes wheat straw fiber.

[0024] The raw materials for preparing the straw fiber lightweight concrete of the present invention include 4-5 parts of water-reducing agent by mass fraction, which may be 4.2 parts, 4.5 parts or 4.8 parts in specific embodiments; the water-reducing agent preferably includes polycarboxylate-based high-efficiency water-reducing agent, the water reduction rate of the water-reducing agent is preferably 20-30%, and the mass of the water-reducing agent is preferably 1-3% of the total mass of the raw materials.

[0025] This invention also provides a method for preparing the straw fiber lightweight concrete described in the above technical solution, comprising the following steps: The straw fiber lightweight concrete is obtained by mixing ceramsite filter material, sand, fly ash, cement, straw fiber, water and water-reducing agent, followed by molding and curing.

[0026] In this invention, the mixture preferably includes: The ceramsite filter media, sand and fly ash are mixed in the first step to obtain the first premix; The first premix and cement are mixed a second time to obtain a second premix; The second premix and straw fiber are mixed in a third way to obtain a third premix; The third premix, water, and water-reducing agent are then mixed in a fourth process.

[0027] In this invention, the first mixing, the second mixing, and the third mixing are preferably carried out independently by stirring, and the stirring time is preferably 1 minute.

[0028] In this invention, the molding process preferably includes injecting the mixed slurry into a mold.

[0029] The lightweight concrete and its preparation method provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0030] Cement: 42.5 silicate cement, the composition of which, by mass fraction, is: CaO 61.8%, SiO2 21.4%, Fe2O3 2.5%, MgO 1.6%, Al2O3 5.8%, TiO2 0.4% and the balance being impurities.

[0031] Fly ash: Secondary fly ash, by mass fraction, the composition of the fly ash is: Al2O3 36.8%, SiO2 45.1%, CaO 4.5%, SO3 1.2% and the balance impurities.

[0032] Sand: Fineness modulus is 2. The composition of the sand by mass fraction is: Al2O3 8.43%, SiO2 84.81%, CaO 0.57%, K2O 2.69%, Na2O 1.77%, Fe2O3 0.82%, MgO 0.35%, TiO2 0.2% and balance impurities.

[0033] Straw fiber: wheat straw.

[0034] Water-reducing agent: Polycarboxylate-based high-efficiency water-reducing agent with a water reduction rate of 28%.

[0035] Examples 1-4, Comparative Examples 1-4 The preparation method is as follows: According to the proportions described in Table 1, weigh the ceramsite filter material or ceramsite, sand and fly ash and mix them at room temperature for 1 minute to obtain a first premix; mix the first premix with cement at room temperature for 1 minute to obtain a second premix; mix the second premix with straw fiber to obtain a third premix; mix the third premix with water and water-reducing agent to obtain the straw fiber lightweight concrete.

[0036] The fourth premix was vibrated at a vibration frequency of 100 Hz for 60 s to obtain a straw fiber lightweight concrete blank; the straw fiber lightweight concrete was cured at room temperature for 24 h, and then cured under standard conditions at 95% humidity and 25 ± 2 ℃.

[0037] Table 1. Composition ratio of straw fiber lightweight concrete in Examples 1-4 and Comparative Examples 1-4 (kg / m²) 3 )

[0038] Note: The dosages in Examples 1-4 and Comparative Examples 1-4 of this invention are based on a total volume of 1m³. 3 The proportions were determined. In Examples 1-4, the ceramsite filter media used was ceramsite filter media produced by Anhui Huaqi Environmental Protection Co., Ltd. (ceramsite filter media, nominal particle size 4-6mm, cylinder compressive strength 6-9MPa, composition by mass fraction: SiO2 65%, Al2O3 18%, Fe2O3 7.2%, MgO 3.5%, and balance impurities). In Examples 1-4 and Comparative Examples 1-4, the ceramsite used was 600-grade shale ceramsite produced by Gongyi Xinjiayuan Water Purification Materials Co., Ltd.

[0039] Test case The 28-day compressive strength and splitting tensile strength of the straw fiber lightweight concrete prepared in Examples 1-4 and Comparative Examples 1-4 were tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" GB / T50081-2019 and the "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete" GB / T50082-2009.

[0040] Table 2. Performance test results of straw fiber lightweight concrete in Examples 1-4 and Comparative Examples 1-4

[0041] Figure 1 This is a scanning electron microscope image of straw fiber lightweight concrete from Example 1.

[0042] Depend on Figure 1 It can be seen that the porosity of 28-day straw fiber lightweight concrete is relatively low. The cement particles in the concrete will continue to react with water to generate more hydration products, thereby filling the pores and strengthening the interface transition zone. At this time, the amount of CSH gel generated is large, and the density is significantly improved.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A lightweight concrete made from straw fiber, characterized in that, The preparation materials include the following ingredients in parts by weight: 360-400 parts cement; 40-60 parts fly ash; 600-650 parts of ceramsite filter media; 600-650 parts of sand; 150-170 parts water; 1-3 parts straw fiber; 4-5 parts of water-reducing agent.

2. The straw fiber lightweight concrete according to claim 1, characterized in that, The water-reducing agent includes a polycarboxylate-based high-efficiency water-reducing agent, and the water reduction rate of the water-reducing agent is 20-30%.

3. The straw fiber lightweight concrete according to claim 1, characterized in that, The mass of the water-reducing agent is 1-3% of the total mass of the raw materials used in preparation.

4. The straw fiber lightweight concrete according to claim 1, characterized in that, The cement comprises, by mass fraction: 61.8% CaO, 21.4% SiO2, 2.5% Fe2O3, 1.6% MgO, 1.6% Al2O3, 0.4% TiO2, and the balance being impurities.

5. The straw fiber lightweight concrete according to claim 1, characterized in that, The fineness modulus of the sand is 2 to 3.

6. The straw fiber lightweight concrete according to claim 1, characterized in that, The fly ash includes secondary fly ash.

7. The straw fiber lightweight concrete according to claim 1, characterized in that, The straw fiber includes wheat straw fiber.

8. The straw fiber lightweight concrete according to claim 1 or 7, characterized in that, The mass of the straw fiber is 0.2-0.8% of the total mass of the raw materials.

9. The straw fiber lightweight concrete according to claim 1, characterized in that, The nominal particle size of the ceramsite filter media is 4~6mm, and the cylinder compressive strength is 6~9MPa.

10. The method for preparing straw fiber lightweight concrete according to any one of claims 1 to 9, characterized in that, Includes the following steps: The straw fiber lightweight concrete is obtained by mixing ceramsite filter material, sand, fly ash, cement, straw fiber, water and water-reducing agent, followed by molding and curing.

Images