A method for regulating ECC volume stability using CFB ash

Abstract

This invention discloses a method for regulating the volume stability of ECC using CFB ash. The method includes the following steps: (1) mixing cement, CFB ash, fly ash, and fine aggregate, and stirring evenly to obtain a dry material; (2) mixing water, water-reducing agent, and polymer emulsion and adding them to the dry material, and stirring evenly to obtain a slurry; adding fibers to the slurry and stirring until the fibers are completely dispersed to obtain a modified ECC material. This invention provides a method for regulating the volume stability of ECC using CFB ash, which can improve the volume stability of ECC.

Description

Technical Field

[0001] This invention belongs to the field of engineering cement composite materials technology, specifically relating to a method for regulating the volume stability of ECC using CFB ash. Background Technology

[0002] Circulating fluidized bed (CFB) technology, as an advanced combustion technology, has been widely used in the energy and environmental fields. However, the byproducts of the CFB process—CFB ash (including fly ash and slag)—may contain heavy metals and other toxic chemicals. If these substances seep into soil or water bodies, they can cause water and soil pollution. Furthermore, the fine particulate matter in the ash, if directly released into the air, will increase air pollution. Therefore, how to recycle and utilize CFB ash has become an urgent ecological problem to be solved.

[0003] Engineering cement composites (ECCs) are widely used in the construction and civil engineering fields due to their excellent mechanical properties and durability. However, ECC materials may shrink and develop microcracks during long-term use, which can affect their structural integrity and durability. Therefore, improving the volume stability of ECCs is key to enhancing their application performance.

[0004] Traditional ECC typically uses fly ash as a cementing material and ordinary fine aggregate. Although fly ash increases the workability and certain performance aspects of ECC, some of its physical and chemical properties limit its performance in terms of volume stability.

[0005] CFB ash has a high sulfur content and good water retention capacity, making it a potential material for improving the shrinkage performance of ECC (Extremely Crushable Carbide). These unique properties of CFB ash offer new possibilities for improving ECC, particularly in enhancing its volume stability and shrinkage resistance. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for regulating the volume stability of ECC using CFB ash, which can improve the volume stability of ECC, in order to overcome the shortcomings of the prior art.

[0007] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows:

[0008] A method for regulating ECC volume stability using CFB ash is characterized by comprising the following steps:

[0009] (1) Mix cement, CFB ash, fly ash and fine aggregate, and stir evenly to obtain dry material;

[0010] (2) Water, water-reducing agent and polymer emulsion are mixed and added to the dry material, and stirred evenly to obtain a slurry; fibers are added to the slurry and stirred until the fibers are completely dispersed to obtain the modified ECC material;

[0011] The CFB ash is one or a mixture of CFB fly ash and CFB slag; the SO3 content in the CFB fly ash is 3-10 wt%, and the SO3 content in the CFB slag is 2-18 wt%; the polymer emulsion is a polyethylene-vinyl acetate emulsion.

[0012] In the above scheme, the raw materials, by weight, include: 20-40 parts cement, 10-40 parts CFB ash, 10-50 parts fly ash, 15-40 parts fine aggregate, 20-30 parts water, 0.1-1 parts water-reducing agent, 1-2 parts fiber, and 3-10 parts polymer emulsion.

[0013] In the above scheme, the CFB ash is a mixture of CFB fly ash and CFB slag, and the mass ratio of the CFB fly ash to the CFB slag is (2-3):1.

[0014] In the above scheme, the specific surface area of ​​the CFB fly ash is 300-700 m². 2 / kg.

[0015] In the above scheme, the particle size of the CFB fly ash is less than 0.1 mm; the particle size of the CFB slag is less than 4.75 mm. Compared with other cementing materials, CFB fly ash has a stronger water retention capacity; CFB slag has a high calcium and sulfur content, which can be used to replace fine aggregates and improve the volume stability of ECC.

[0016] In the above scheme, the cement is either silicate cement or ordinary silicate cement.

[0017] In the above scheme, the fine aggregate includes any one of quartz sand, natural sand and artificial sand.

[0018] In the above scheme, the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0019] In the above scheme, the fiber is PVA fiber with a diameter of 39 micrometers and a length of 10-15 mm.

[0020] In the above scheme, the fly ash is Class I fly ash.

[0021] The present invention also claims protection for the modified ECC material prepared by the above-mentioned method of controlling the volume stability of ECC using CFB ash.

[0022] In this invention, addressing the common shrinkage problem of ECC (Elastic Cemented Carbide) slag, the method provided utilizes the high sulfur content and unique porous structure of CFB ash to optimize ECC performance. CFB ash comprises CFB fly ash and CFB slag. The sulfur trioxide (SO3) component in CFB ash reacts with calcium hydroxide produced during cement hydration to form ettringite. This reaction not only consumes free water and slows down evaporation but also increases the volume of hydration products, forming a more stable structure and effectively reducing shrinkage. Furthermore, the formation of ettringite enhances the toughness of ECC, enabling the material to better absorb and disperse external loads under stress, reducing stress concentration caused by drying and temperature changes, and minimizing the formation of shrinkage cracks. The porous nature of CFB ash allows fibers and polymer emulsions to penetrate deeper into the micropores of the material, improving the bond between the cement matrix and reinforcing materials. The polymer emulsion (polyethylene-vinyl acetate emulsion) forms a network structure in ECC, enhancing the bond between the cement matrix and fibers and improving the toughness of the concrete. When combined with the porous structure of CFB ash, the polymer emulsion can better penetrate and fill the pores. This improved bonding helps retain internal moisture, further reducing shrinkage. Therefore, the use of CFB ash in ECC not only optimizes the microstructure of the material but also significantly improves its durability and stability.

[0023] In this invention, CFB fly ash replaces cementitious materials at a ratio of 0-50%, wherein the cementitious materials include cement and fly ash, to improve the drying shrinkage resistance of ECC; CFB slag is used as fine aggregate for ECC to reduce volume change of ECC by utilizing its porosity; the volume stability of ECC is optimized by adjusting the ratio of CFB fly ash and CFB slag in CFB ash slag; the early strength and durability of ECC are improved through chemical reaction by utilizing the sulfur content in CFB ash slag; and the ratio of cement to CFB ash slag is optimized to improve the overall performance of ECC.

[0024] Compared with existing technologies, the beneficial effects of this invention are:

[0025] (1) The present invention provides a method for regulating the volume stability of ECC by adding CFB ash slag to achieve the effect of regulating the volume stability of ECC. The CFB ash slag is divided into CFB fly ash and CFB slag. CFB fly ash replaces cement and fly ash as cementing material, and CFB slag replaces quartz sand as fine aggregate. This method mainly utilizes the characteristics of CFB ash slag being porous and having a high sulfur content to achieve the effect of regulating the volume stability of ECC. Moreover, the modified ECC material obtained is suitable for various building and engineering structures that require high volume stability.

[0026] (2) The method of regulating ECC volume stability using CFB ash provided by the present invention provides a new way for the recycling of CFB ash, which is conducive to environmental protection and resource reuse; and the raw materials are widely available, low in cost and simple in process. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail below with reference to specific embodiments. However, the described embodiments are only some embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] In this specific embodiment, the cement used is 42.5 grade ordinary Portland cement; the fine aggregate is quartz sand; the fiber is PVA fiber with a diameter of 39 micrometers and a length of 12 mm; the fly ash is Class I fly ash; both CFB fly ash and CFB slag are taken from a thermal power plant in Shanxi Province. The particle size of CFB fly ash is less than 0.1 mm, the particle size of CFB slag is less than 4.75 mm, the SO3 content in CFB fly ash is 7.66 wt%, and the specific surface area is 300-700 m². 2 / kg; SO3 content in CFB slag is 2-13.86wt%.; The water-reducing agent is HPWR-AUHPC60-1 type water-reducing agent, which is a high-efficiency polycarboxylate water-reducing agent; the polymer emulsion is polyethylene-vinyl acetate emulsion.

[0029] Example 1

[0030] This embodiment provides a method for regulating the volume stability of ECC using CFB ash, including the following steps:

[0031] Accurately weigh 2.24 kg of cement, 1.096 kg of fly ash, 1.644 kg of CFB fly ash, 1.79 kg of silica sand, 0.104 kg of fiber, 1.30 kg of water, 0.060 kg of water-reducing agent, and 0.498 kg of polymer emulsion. First, mix the cement, fly ash, and CFB fly ash evenly. Then, gradually add the silica sand, continuing to mix until the dry mixture is uniformly homogeneous. Pre-mix the water and water-reducing agent, and slowly add the water, water-reducing agent, and polymer emulsion to the dry mixture while stirring. Continue stirring to ensure that the cement, fly ash, CFB fly ash, silica sand, water, water-reducing agent, and polymer emulsion are thoroughly mixed to form a homogeneous slurry. Finally, add the fiber and continue stirring until the fiber is completely dispersed, ensuring that the fiber is evenly distributed in the mixture and avoiding agglomeration.

[0032] Modified ECC samples were prepared according to the above process and cast into molds measuring 100mm×100mm×400mm, 150mm×150mm×150mm, and 100mm×100mm×320mm, and cured under standard conditions for 24 hours. The shrinkage, compressive strength, and flexural strength of the samples were then tested. For shrinkage testing, reference points were marked at both ends or sides of the specimens; these reference points will be used for subsequent length measurements. The specimens were then placed in an environment with 50% relative humidity for further curing, and the shrinkage performance was measured after 28 days.

[0033] Example 2

[0034] This embodiment provides a method for regulating the volume stability of ECC using CFB ash, including the following steps:

[0035] Accurately weigh 2.24 kg of cement, 2.74 kg of fly ash, 1.074 kg of silica sand, 0.716 kg of CFB slag, 0.104 kg of fiber, 1.30 kg of water, 0.060 kg of water-reducing agent, and 0.498 kg of polymer emulsion. First, mix the cement, fly ash, and CFB fly ash evenly. Then, gradually add the silica sand, continuing to mix until the dry materials are uniformly mixed. Pre-mix the water and water-reducing agent, and slowly add the water, water-reducing agent, and polymer emulsion to the dry materials while stirring. Continue stirring to ensure that the cement, fly ash, silica sand, CFB slag, water, water-reducing agent, and polymer emulsion are fully mixed to form a homogeneous slurry. Finally, add the fiber and continue stirring until the fiber is completely dispersed, ensuring that the fiber is evenly distributed in the mixture and avoiding agglomeration. Modified ECC samples were prepared according to the above process and cast into molds measuring 100mm×100mm×400mm, 150mm×150mm×150mm, and 100mm×100mm×320mm, and cured under standard conditions for 24 hours. The shrinkage, compressive strength, and flexural strength of the samples were then tested. For shrinkage testing, reference points were marked at both ends or sides of the specimens; these reference points will be used for subsequent length measurements. The specimens were then placed in an environment with 50% relative humidity for further curing, and the shrinkage performance was measured after 28 days.

[0036] Example 3

[0037] This embodiment provides a method for regulating the volume stability of ECC using CFB ash, including the following steps:

[0038] Accurately weigh 2.24 kg of cement, 1.918 kg of fly ash, 2.062 kg of silica sand, 0.822 kg of CFB fly ash, 0.358 kg of CFB slag, 0.104 kg of fiber, 1.30 kg of water, 0.060 kg of water-reducing agent, and 0.498 kg of polymer emulsion. First, mix the cement, fly ash, and CFB fly ash evenly. Then, gradually add the silica sand, continuing to mix until the dry materials are uniformly mixed. Pre-mix the water and water-reducing agent, and slowly add the water, water-reducing agent, and polymer emulsion to the dry materials while stirring. Continue stirring to ensure that the cement, fly ash, CFB fly ash, silica sand, CFB slag, water, water-reducing agent, and polymer emulsion are fully mixed to form a homogeneous slurry. Finally, add the fiber and continue stirring until the fiber is completely dispersed, ensuring that the fiber is evenly distributed in the mixture and avoiding agglomeration.

[0039] Modified ECC samples were prepared according to the above process and cast into molds measuring 100mm×100mm×400mm, 150mm×150mm×150mm, and 100mm×100mm×320mm, and cured under standard conditions for 24 hours. The shrinkage, compressive strength, and flexural strength of the samples were then tested. For shrinkage testing, reference points were marked at both ends or sides of the specimens; these reference points will be used for subsequent length measurements. The specimens were then placed in an environment with 50% relative humidity for further curing, and the shrinkage performance was measured after 28 days.

[0040] Comparative Example 1

[0041] The preparation method of this comparative example is basically the same as that of Example 1, except that CFB fly ash is not added, and the amount of each raw material is as follows: cement 2.24 kg, fly ash 2.74 kg, quartz sand 1.79 kg, fiber 0.104 kg, water 1.30 kg, water-reducing agent 0.060 kg, polymer emulsion 0.498 kg.

[0042] Comparative Example 2

[0043] The preparation method of this comparative example is basically the same as that of comparative example 1, except that zeolite is used to replace the same amount of quartz sand. The amounts of each raw material are: cement 2.24 kg, fly ash 2.74 kg, zeolite 1.79 kg, fiber 0.104 kg, water 1.30 kg, water-reducing agent 0.060 kg, and polymer emulsion 0.498 kg.

[0044] The data on shrinkage properties, compressive strength, and flexural strength of the samples prepared in Examples 1-3, Comparative Examples 1 and 2 are shown in Table 1.

[0045] Table 1

[0046] Testing items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 <![CDATA[Dry shrinkage × 10 -6 (με)]]> 319 216 157 1262 713 Compressive strength (MPa) 69 62 56 41 52 Flexural strength (MPa) 23 24 27 17 14

[0047] As shown in Table 1, the modified ECC material prepared by the technical solution of the present invention can significantly reduce shrinkage performance while increasing compressive strength and flexural strength. Compared with traditional ECC material, the drying shrinkage of ECC with CFB ash is significantly reduced, and it has broad application prospects in the field of building materials.

[0048] In summary, the method for regulating the volume stability of ECC using CFB ash provided by this invention can improve the volume stability of ECC.

[0049] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A method for regulating ECC volume stability using CFB ash, characterized in that, Includes the following steps: (1) Mix cement, CFB ash, fly ash and fine aggregate, and stir evenly to obtain dry material; (2) Add water, water-reducing agent and polymer emulsion to the dry material and stir evenly to obtain slurry; The fiber is added to the slurry and stirred until the fiber is completely dispersed to obtain the modified ECC material; The raw materials, by weight, include: 20-40 parts cement, 10-40 parts CFB ash, 10-50 parts fly ash, 15-40 parts fine aggregate, 20-30 parts water, 0.1-1 parts water-reducing agent, 1-2 parts fiber, and 3-10 parts polymer emulsion. The CFB ash is a mixture of CFB fly ash and CFB slag, with a mass ratio of (2-3):1 between the CFB fly ash and the CFB slag; the SO3 content in the CFB fly ash is 3-10 wt%, and the SO3 content in the CFB slag is 2-18 wt%; the polymer emulsion is a polyethylene-vinyl acetate emulsion.

2. The method for regulating ECC volume stability using CFB ash as described in claim 1, characterized in that, The specific surface area of ​​the CFB fly ash is 300-700 m². 2 / kg.

3. The method for regulating ECC volume stability using CFB ash as described in claim 1, characterized in that, The CFB fly ash has a particle size of less than 0.1 mm; the CFB slag has a particle size of less than 4.75 mm.

4. The method for regulating ECC volume stability using CFB ash as described in claim 1, characterized in that, The cement is any one of silicate cement and ordinary silicate cement; the fine aggregate includes any one of quartz sand, natural sand and manufactured sand.

5. A method for regulating ECC volume stability using CFB ash as described in claim 1, characterized in that, The water-reducing agent is a polycarboxylate-based water-reducing agent.

6. The method for regulating ECC volume stability using CFB ash as described in claim 1, characterized in that, The fly ash is Class I fly ash.

7. The method for regulating ECC volume stability using CFB ash as described in claim 1, characterized in that, The fiber is PVA fiber with a diameter of 39 micrometers and a length of 10-15 mm.

8. A modified ECC material prepared by a method for regulating the volume stability of ECC using CFB ash as described in any one of claims 1-7.