Preparation method of high-performance cement-based composite material based on papermaking white mud modification

Abstract

The invention discloses a preparation method of a high-performance cement-based composite material based on papermaking white mud modification. Ordinary Portland cement and fly ash are used as cementing materials, 1-15 wt% of papermaking white mud is doped, and aggregate, water and a water reducing agent are matched, so that the mechanical property of the cement-based material is enhanced, and cracks are reduced. According to the method, active CaCO3 and alkaline substances in the papermaking white mud are creatively utilized, and the 7d compressive strength is improved by 7-50%, the 7d breaking strength is improved by 15-40% and the crack area is reduced by 30-40% by promoting the secondary hydration reaction and optimizing the pore structure. The preparation process is a two-step process of dry mixing and wet mixing. The technology realizes resource utilization of industrial solid wastes, is suitable for large-scale application of production of road bases, building blocks, prefabricated parts and the like, and has remarkable social and economic benefits and engineering application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of cement-based mixtures, and particularly relates to a method for preparing a high-performance cement-based composite material modified by papermaking white mud. Background Art

[0002] As a typical high-energy-consuming and high-emission industry, the papermaking industry produces papermaking white mud in the alkali recovery process, which is a difficult-to-treat calcareous solid waste. The moisture content of this solid waste reaches 45-60%, and its main components are amorphous calcium carbonate (60-90 wt%) and residual alkali metal compounds, and its appearance is gray or white. Most enterprises mainly stack papermaking white mud in the open air and landfill it in selected locations, with a low comprehensive utilization rate. A large amount of stacking will lead to environmental risks such as soil alkalization and groundwater chloride pollution. The large production of papermaking white mud has brought a heavy treatment burden to enterprises. Therefore, how to effectively utilize papermaking white mud and realize the resourceization of waste has become an urgent problem to be solved in the papermaking industry and related fields.

[0003] With the enhancement of environmental awareness and the increasing strictness of environmental protection policies, enterprises are facing higher environmental protection requirements, and the resource utilization of papermaking white mud has received extensive attention. For example, a large amount of papermaking white mud is produced in Guangxi every year. Through technical research and industrial application, the comprehensive utilization of papermaking white mud has been realized. The specific methods include using it in building materials such as cement production, desulfurization agents, and sintered bricks to replace some traditional materials, reduce environmental pollution and realize the recycling of resources. Using papermaking white mud as a reinforcing material for cement-based composites is a resource comprehensive utilization method that conforms to the concept of circular economy. It can not only reduce waste emissions, reduce environmental pollution, but also create certain economic benefits for enterprises and meet the requirements of sustainable development. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing a high-performance cement-based composite material modified by papermaking white mud for the current recycling of papermaking white mud, so as to solve the large amount of papermaking white mud produced every year, reduce environmental pollution, and at the same time improve the mechanical properties and crack resistance of the cement-based composite material. The prepared high-performance cement-based composite material modified by papermaking white mud has better engineering applicability.

[0005] Based on the above object, the present invention proposes the following technical solutions:

[0006] A method for preparing a high-performance cement-based composite material modified by papermaking white mud, comprising the following steps:

[0007] Cement, aggregate, papermaking white mud, water and water reducing agent are successively added to a mortar mixer and stirred evenly to obtain a high-performance papermaking white mud cement mortar; cement, fly ash, fine aggregate, coarse aggregate I, coarse aggregate II, papermaking white mud, water and water reducing agent are successively added to a concrete mixer and stirred evenly to obtain a high-performance papermaking white mud concrete.

[0008] Preferably, the above-mentioned high-performance crack-resistant papermaking white mud cement mortar is composed of the following raw materials in parts by weight: 375-565 parts of cement, 1300-1700 parts of aggregate, 3-60 parts of papermaking white mud, 215-245 parts of water, and 4-10 parts of water reducing agent.

[0009] Preferably, the above-mentioned high-performance papermaking white mud concrete is composed of the following raw materials in parts by weight: 375-565 parts of cement, 35-55 parts of fly ash, 740-780 parts of fine aggregate, 200-215 parts of coarse aggregate I, 790-830 parts of coarse aggregate II, 24-60 parts of papermaking white mud, 145-165 parts of water, and 4-10 parts of water reducing agent.

[0010] Preferably, the above-mentioned cement is P.O42.5 ordinary Portland cement.

[0011] Preferably, the above-mentioned fly ash is class F secondary fly ash.

[0012] Preferably, the aggregate in the above-mentioned high-performance crack-resistant papermaking white mud cement mortar is standard sand or river sand.

[0013] Preferably, the fine aggregate of the above-mentioned high-performance papermaking white mud concrete is river sand.

[0014] Preferably, the above-mentioned coarse aggregate I is crushed stone with a particle size of 5-10 mm.

[0015] Preferably, the above-mentioned coarse aggregate II is crushed stone with a particle size of 10-230 mm.

[0016] Preferably, the water reducing agent used above is a high-performance polycarboxylate liquid water reducing agent.

[0017] A high-performance cement-based composite material modified with papermaking white mud prepared by the preparation method of any one of the above.

[0018] The mechanism of the high-performance cement-based composite material modified with papermaking white mud mainly includes the following aspects:

[0019] 1. Papermaking white mud (mainly composed of micron-sized calcium carbonate) can achieve a multi-scale filling effect in cement-based materials, fill the pores (1-10 μm) of hydration products and the voids (10-100 μm) between cement particles, form a gradient densified structure, and significantly improve the density of cement-based materials.

[0020] 2. In the highly alkaline environment (pH > 12.5) generated by the hydration of cement, silicon and aluminum oxides in papermaking white mud can react with the hydration product Ca(OH) of cement 2 to form secondary C-S-H gel, further improving the strength and durability of the matrix. At the same time, calcium carbonate in white mud can react with hydrated aluminate to form carboaluminate (CO 3 -AFm phase), forming a stable network structure, reducing the generation and expansion of microcracks, and enhancing the strength and toughness of cement-based composites.

[0021] 3. Calcium carbonate in papermaking white mud forms a pH buffer system at the carbonation front of cement-based materials to stabilize the pH in the carbonation zone at 8.5 - 9.5, delaying the destruction of the passivation film on the surface of cement-based materials, and thus slowing down the carbonation rate.

[0022] 4. Calcium carbonate in papermaking white mud has good lubrication effect, which can reduce the friction between particles in cement-based materials, improve the fluidity of cement-based materials, and make construction easier. In addition, clay minerals (such as kaolin) contained in papermaking white mud help to enhance the cohesion of cement-based materials, reduce bleeding and segregation phenomena, and improve their workability.

[0023] Compared with the prior art, the significant advantages of the present invention are as follows:

[0024] (1) The papermaking white mud of the present invention belongs to solid waste in the papermaking industry. Applying it to cement materials increases the comprehensive utilization ways of white mud, reduces the negative impact on the environment, and has significant environmental protection benefits.

[0025] (2) The preparation process provided by the present invention is simple and low-cost, and is suitable for large-scale applications such as road bases, building blocks, and precast component production.

[0026] (3) This solution provides a method for preparing high-performance cement-based composites modified with papermaking white mud. This method can not only improve the mechanical properties and crack resistance of cement-based materials, but also improve the fluidity and cohesion of cement-based materials, reduce bleeding and segregation phenomena, and at the same time slow down the carbonation process of cement-based materials.

[0027] (4) The method provided by the present invention can not only consume a large amount of papermaking white mud, reduce its accumulation, save resources, and reduce environmental pollution, but also significantly improve the mechanical properties and crack resistance of cement-based materials, and contribute to improving the application effect of papermaking white mud in building materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a morphology diagram of papermaking white mud.

[0029] Figure 2It is the optical microscope morphology diagram of papermaking white mud.

[0030] Figure 3 It is the wavelength dispersive X-ray fluorescence spectrum composition analysis diagram of papermaking white mud.

[0031] Figure 4 It is the diagram of the influence of the mass ratio of papermaking white mud in cement on the growth rates of the 7-day flexural and compressive strengths of cement mortar.

[0032] Figure 5 It is the comparison diagram of the crack resistance experiment of papermaking white mud. Specific implementation manners

[0033] Next, the technical solutions of the present invention will be described in detail in combination with specific comparative examples and embodiments, but the protection scope of the present invention is not limited to this embodiment.

[0034] For those not specified in the embodiments of the present invention, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. The raw materials, equipment, etc. without indicating the manufacturer can be obtained as conventional products through commercial purchase.

[0035] The cement mortar mixing equipment used in the following examples is a JJ-5 type planetary mixer, and the concrete mixing equipment is an HJW-60 single horizontal shaft mixer. The present invention can also use other similar cement mortar and concrete mixing equipment.

[0036] Comparative example 1

[0037] A preparation method of a high-performance cement-based composite material modified with papermaking white mud includes the following steps:

[0038] Preparation of the cement mortar blank sample:

[0039] Cement, standard sand, water and water reducer are sequentially added to the mortar mixer and stirred evenly to obtain the cement mortar raw material. The cement mortar raw material is composed of the following raw materials in parts by weight: 450 parts of cement, 1350 parts of aggregate, 225 parts of water, and 5 parts of water reducer.

[0040] Comparative example 2

[0041] A preparation method of a high-performance cement-based composite material modified with papermaking white mud includes the following steps:

[0042] Preparation of the concrete blank sample:

[0043] Cement, fly ash, fine aggregate, coarse aggregate I, coarse aggregate II, water and water reducing agent are sequentially added to a concrete mixer and stirred evenly to obtain concrete raw materials. The concrete raw materials are composed of the following raw materials in parts by weight: 432 parts of cement, 48 parts of fly ash, 777 parts of fine aggregate, 210 parts of coarse aggregate I, 793 parts of coarse aggregate II, 160 parts of water, and 5.5 parts of water reducing agent.

[0044] Example 3

[0045] A preparation method of a high-performance cement-based composite material modified by papermaking white mud, comprising the following steps:

[0046] Preparation of high-performance crack-resistant cement mortar modified by papermaking white mud:

[0047] Cement, standard sand, papermaking white mud, water and water reducing agent are sequentially added to a mixer and stirred evenly to obtain raw materials for high-performance crack-resistant cement mortar. The raw materials for high-performance crack-resistant cement mortar are composed of the following raw materials in parts by weight: 450 parts of cement, 1350 parts of aggregate, 4.5 parts of papermaking white mud, 225 parts of water, and 5 parts of water reducing agent.

[0048] Example 4

[0049] A preparation method of a high-performance cement-based composite material modified by papermaking white mud, comprising the following steps:

[0050] Preparation of high-performance crack-resistant cement mortar modified by papermaking white mud:

[0051] Cement, standard sand, papermaking white mud, water and water reducing agent are sequentially added to a mixer and stirred evenly to obtain raw materials for high-performance crack-resistant cement mortar. The raw materials for high-performance crack-resistant cement mortar are composed of the following raw materials in parts by weight: 450 parts of cement, 1350 parts of aggregate, 13.5 parts of papermaking white mud, 225 parts of water, and 5 parts of water reducing agent.

[0052] Example 5

[0053] A preparation method of a high-performance cement-based composite material modified by papermaking white mud, comprising the following steps:

[0054] Preparation of high-performance crack-resistant cement mortar modified by papermaking white mud:

[0055] Cement, standard sand, papermaking white mud, water and water reducing agent are sequentially added to a mixer and stirred evenly to obtain raw materials for high-performance crack-resistant cement mortar. The raw materials for high-performance crack-resistant cement mortar are composed of the following raw materials in parts by weight: 450 parts of cement, 1350 parts of aggregate, 27 parts of papermaking white mud, 225 parts of water, and 6 parts of water reducing agent.

[0056] Example 6

[0057] A preparation method of a high-performance cement-based composite material modified by papermaking white mud, comprising the following steps:

[0058] Preparation of high-performance crack-resistant cement mortar modified by papermaking white mud:

[0059] Add cement, standard sand, papermaking white mud, water and water reducer into a mixer in sequence and stir evenly to obtain the raw materials of high-performance crack-resistant cement mortar. The raw materials of high-performance crack-resistant cement mortar are composed of the following raw materials in parts by weight: 450 parts of cement, 1350 parts of aggregate, 45 parts of papermaking white mud, 225 parts of water, and 9 parts of water reducer.

[0060] Example 7

[0061] A preparation method of a high-performance cement-based composite material modified by papermaking white mud, comprising the following steps:

[0062] Preparation of high-performance crack-resistant cement mortar modified by papermaking white mud:

[0063] Add cement, standard sand, papermaking white mud, water and water reducer into a mixer in sequence and stir evenly to obtain the raw materials of high-performance crack-resistant cement mortar. The raw materials of high-performance crack-resistant cement mortar are composed of the following raw materials in parts by weight: 450 parts of cement, 1350 parts of aggregate, 135 parts of papermaking white mud, 225 parts of water, and 13 parts of water reducer.

[0064] Example 8

[0065] A preparation method of a high-performance cement-based composite material modified by papermaking white mud, comprising the following steps:

[0066] Preparation of concrete blank sample:

[0067] Add cement, fly ash, fine aggregate, coarse aggregate I, coarse aggregate II, papermaking white mud, water and water reducer into a concrete mixer in sequence and stir evenly to obtain the concrete raw materials. The concrete raw materials are composed of the following raw materials in parts by weight: 432 parts of cement, 48 parts of fly ash, 777 parts of fine aggregate, 210 parts of coarse aggregate I, 793 parts of coarse aggregate II, 29 parts of papermaking white mud, 160 parts of water, and 9 parts of water reducer.

[0068] Put the cement mortar samples of the above Comparative Example 1 and Examples 2-7 into a standard mold of 40mm×40mm×160mm. After filling half of the sample, vibrate it on a vibrating table for 1 minute, then fill in the remaining sample and vibrate for another 1 minute. Finally, scrape the surface of the specimen flat and cover it with a plastic sheet to prevent the water from evaporating too quickly. Place it in a standard curing box for 24 hours. After the specimen is formed, remove the mold, submerge the specimen in water, and then place it in the standard curing box for standard curing. Conduct tests in accordance with the relevant provisions of "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-2021) and "Determination of Fluidity of Cement Mortar" (GB / T 2419-2005) to measure the basic working performance and mechanical properties of the cement mortar.

[0069] Put the concrete mixtures of the above Comparative Example 2 and Example 8 into standard molds of 150mm×150mm×150mm and 150mm×150mm×550mm. Fill the mold completely at one time with a slight surplus. Start the vibrating table until a milky cement paste appears on the surface of the concrete. During the vibration process, add concrete at any time to keep the mold always full and record the vibration time. After the vibration is completed, scrape off the excess concrete and use a trowel to level the surface initially. After the specimen has shrunk, use the trowel to level the specimen carefully again. After the specimen is formed, cover the surface with a wet cloth and let it stand at room temperature of 20℃±5℃ and relative humidity greater than 50% for one day and night, then put the intact specimen into the standard curing room for curing. Conduct tests in accordance with the relevant provisions of "Test Regulations for Cement and Cement Concrete in Highway Engineering" (JTG 3420-2020) to measure the basic working performance and mechanical properties of the cement mortar.

[0070] Table 1

[0071]

[0072]

[0073] Figure 1 is the morphology diagram of papermaking white mud, Figure 2 is the optical microscope morphology diagram of papermaking white mud.

[0074] Figure 3 is the wavelength dispersive X-ray fluorescence spectroscopy composition analysis diagram of papermaking white mud.

[0075] Figure 4 is the diagram showing the influence of the mass ratio of papermaking white mud to cement on the growth rates of the 7-day flexural and compressive strengths of cement soil. It can be seen from the figure that within the test dosage range, papermaking white mud has an obvious enhancing effect on the flexural and compressive strengths of cement mortar. The maximum growth rates reach 37.5% and 46.3% respectively when the mass ratio to cement is 30%.

[0076] Figure 5It is a comparison chart of the anti-cracking experiment of papermaking white mud. It can be seen from the chart that the anti-cracking property of papermaking white mud in concrete is very obvious, and the cracking area is reduced by 30-40%.

[0077] By utilizing the properties of the high-performance cement-based composite material modified with papermaking white mud, the present invention not only realizes the recycling of papermaking waste, reduces environmental pollution and saves resources, but also significantly enhances the mechanical properties of the cement-based material. The present invention has the following advantages:

[0078] (1) Green and environmentally friendly. It realizes the efficient recycling of papermaking waste, converts this industrial by-product of papermaking white mud into high-value-added building materials, effectively reduces environmental pollution and resource waste, and conforms to the concept of green development.

[0079] (2) Excellent performance. Compared with the control example, the growth rate of the flexural strength of the present invention is up to 37.5%, the growth rate of the compressive strength is up to 46.3%, and the cracking area is reduced by 30-40%. It is superior to traditional cement-based materials and can meet the engineering requirements of high strength and high durability.

[0080] (3) Simple preparation process. Adopting the two-step method of dry mixing - wet mixing, directly incorporating papermaking white mud, without complex equipment, low production cost, stable and controllable quality, suitable for large-scale industrial production, especially suitable for fields such as road bases, building blocks and precast components.

[0081] Matters not covered by the present invention are well-known technologies.

[0082] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a high-performance cement-based composite material based on modified papermaking white mud, characterized in that: The steps include: Add cement, aggregate, papermaking mud, water and water reducing agent to a mortar mixer in sequence and mix evenly to obtain papermaking mud high-performance anti-cracking cement mortar; add cement, fly ash, fine aggregate, coarse aggregate I, coarse aggregate II, papermaking mud, water and water reducing agent to a concrete mixer in sequence and mix evenly to obtain papermaking mud high-performance concrete.

2. The method for preparing a high-performance cement-based composite material based on modified papermaking white mud according to claim 1, characterized in that: The papermaking white mud comes from papermaking waste.

3. The method for preparing a high-performance cement-based composite material based on modified papermaking white mud according to claim 1, characterized in that: The papermaking white mud high-performance cement mortar is composed of the following raw materials in parts by weight: 375-565 parts of cement, 1300-1700 parts of aggregate, 3-60 parts of papermaking white mud, 215-245 parts of water, and 4-10 parts of water reducing agent.

4. The method for preparing a high-performance cement-based composite material based on modified papermaking white mud according to claim 1, characterized in that: The papermaking white mud high-performance concrete is composed of the following raw materials in parts by weight: 375-565 parts of cement, 35-55 parts of fly ash, 740-780 parts of fine aggregate, 200-215 parts of coarse aggregate I, 790-830 parts of coarse aggregate II, 24-60 parts of papermaking white mud, 145-165 parts of water, and 4-10 parts of water reducing agent.

5. The method for preparing a high-performance cement-based composite material based on modified papermaking white mud according to claim 1, characterized in that: The mass of the papermaking white mud is 1-10wt% of the mass of cement.

6. The method for preparing a high-performance cement-based composite material based on modified papermaking white mud according to claim 1, characterized in that: In the experimental method, a water reducing agent is required to adjust the working performance of the cement mortar to ensure that its expansion is between 18 and 22 cm.

7. A high-performance cement-based composite material modified with papermaking white mud prepared by the experimental method according to any one of claims 1 to 6.

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