Fair-faced concrete for power plant chimneys and its preparation method

Abstract

A fair-faced concrete for a power plant chimney and its preparation method belong to the technical field of concrete materials. The present invention aims to provide a fair-faced concrete for a power plant chimney and its preparation method that can meet special performance requirements such as high temperature resistance and corrosion resistance, and at the same time have good appearance quality and self-cleaning ability. Each cubic meter of the fair-faced concrete for a power plant chimney in the present invention includes the following components: cement: 285 - 305 kg, fly ash: 40 - 50 kg, metakaolin: 25 - 35 kg, coarse aggregate: 931 - 961 kg, manufactured sand: 740 - 780 kg, shale ceramsite: 40 - 60 kg, polydimethylsiloxane emulsion: 3.7 - 5.6 kg, water reducer: 4.1 - 4.5 kg, mixing water: 152 - 155 kg. The preparation method includes: soaking the shale ceramsite in a TiO2 suspension with a concentration of 9 g / L for 24 h and then taking it out and draining; first adding the cementitious material, metakaolin and part of the mixing water and stirring; then adding the shale ceramsite and the coarse aggregate and stirring; finally adding the manufactured sand, the remaining mixing water, the polydimethylsiloxane emulsion and the water reducer, and fully stirring to obtain a concrete mixture.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete materials, and particularly to fair-faced concrete for power plant chimneys and a preparation method thereof. Background Art

[0002] With the continuous progress of modern industrial technology, as an important facility for industrial waste gas emission, the material performance requirements of power plant chimneys are also increasing day by day.

[0003] The concrete of power plant chimneys is exposed to a high-temperature flue gas environment for a long time, and is prone to problems such as cracking and spalling due to the action of thermal stress. Traditional concrete materials cannot withstand the erosion of high-temperature flue gas for a long time, which has become a key problem restricting the performance improvement of power plant chimneys.

[0004] Secondly, during the operation of power plant chimneys, they will come into contact with flue gas containing acidic gases. These gases combine with moisture to form a strongly corrosive medium, causing serious chemical corrosion to the concrete. This corrosion not only weakens the strength and durability of the concrete, but also accelerates the corrosion of steel bars, further threatening the overall stability of the chimney.

[0005] At the same time, since power plant chimneys are usually exposed to harsh environmental conditions, pollutants are likely to erode the surface of ordinary concrete. However, fair-faced concrete has a smooth and dense surface, which can effectively reduce the adhesion and penetration of pollutants, meeting both functional requirements and taking into account aesthetics and economy. However, at present, traditional fair-faced concrete lacks self-cleaning ability and requires regular manual cleaning or other maintenance measures, which not only increases the operating cost but also may bring potential safety hazards.

[0006] Therefore, how to prepare concrete that meets the performance requirements of the physical structure of power plant chimneys has become an urgent technical problem to be solved. At present, no patent involves the preparation technology of special fair-faced concrete for power plant chimneys. Although some patents can meet certain performance requirements of power plant chimney concrete, there are still obvious deficiencies:

[0007] As the Chinese invention patent (CN115124291A) discloses a high-temperature resistant concrete and its preparation method: Although the anti-cracking performance of the concrete is improved, the acid corrosion and self-cleaning ability are not fully considered, and the actual requirements of the chimney cannot be fully met. A high-temperature resistant concrete is proposed, which includes the following components by mass: 200-250 parts of cement, 150-180 parts of fly ash, 80-100 parts of slag powder, 800-1000 parts of volcanic rock, 400-450 parts of slag, 300-400 parts of coal-to-liquid, 300-600 parts of microsilica powder, 15-20 parts of water reducing agent, 300-400 parts of steel slag powder, 100-200 parts of titanium carbide silicon powder, 100-200 parts of ferrochrome slag, 4-8 parts of fiber, and 170-200 parts of water. Although the technical solution of this patent can alleviate the large-scale changes in the concrete structure at high temperatures and reduce the occurrence of cracking, and stabilize the mechanical properties to a certain extent, due to the use of steel slag powder and ferrochrome slag, the acid corrosion resistance of the concrete is poor, and there may be a risk of heavy metal dissolution polluting the environment.

[0008] Again, the Chinese invention patent (CN117776655A) discloses a high-titanium heavy slag sodium silicate acid- and heat-resistant concrete and its preparation method, including: by weight ratio, sodium silicate: sodium fluorosilicate: refractory mud: high-titanium heavy slag sand: high-titanium heavy slag gravel = 1:(0.15-0.18):(1.20-1.50):(2.00-2.30):(3.00-3.30). The high-titanium heavy slag sodium silicate concrete prepared by this patent has good acid and heat resistance, and can significantly improve the service life of buildings in acidic media. However, the sodium silicate concrete is relatively brittle and prone to cracking due to temperature changes or stress concentration, especially in a high-temperature and highly corrosive environment such as a chimney. Cracks may lead to a decrease in acid resistance and heat resistance under long-term use conditions.

[0009] Again, the Chinese invention patent (CN117550855A) discloses a high-temperature resistant fair-faced concrete. A high-temperature resistant fair-faced concrete, the raw materials of the concrete include the following components by weight: 148-173 parts of water, 380-445 parts of cement, 5.5-8.9 parts of water reducing agent, 590-697 parts of river sand, 1-150 parts of manufactured sand, 946-1020 parts of crushed stone, 10-15 parts of silica fume, 10-15 parts of sodium carbonate, 10-15 parts of silicon carbide, and 35-55 parts of high-temperature resistant material. Through this patent, fair-faced concrete with good high-temperature resistance and excellent appearance quality can be prepared. However, it is mentioned in the patent that sodium carbonate is used, and this component may decompose at high temperatures to generate sodium oxide, which further reacts with acidic gases to form sodium sulfate. Sodium sulfate crystallizes and expands inside the concrete, which may cause the concrete to crack and further exacerbate the acid corrosion problem, and the acid corrosion resistance is not good. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide fair-faced concrete for a power plant chimney that can meet the performance requirements of high temperature resistance and acid corrosion resistance of chimney concrete in the service state, and at the same time has excellent apparent quality and self-cleaning function, and a preparation method thereof.

[0011] One technical solution provided by the present invention is a kind of fair-faced concrete for a power plant chimney, and each cubic meter includes components:

[0012] Cement: 285 - 305 kg,

[0013] Fly ash: 40 - 50 kg,

[0014] Metakaolin: 25 - 35 kg,

[0015] Coarse aggregate: 931 - 961 kg,

[0016] Manufactured sand: 740 - 780 kg,

[0017] Shale ceramsite: 40 - 60 kg, and the shale ceramsite needs to be soaked in TiO2 suspension and then drained,

[0018] Polydimethylsiloxane emulsion: 3.7 - 5.6 kg,

[0019] Water reducing agent: 4.1 - 4.5 kg,

[0020] Mixing water: 152 - 155 kg.

[0021] For the fair-faced concrete for a power plant chimney of the present invention, the specific surface area of the metakaolin is 650 - 700 m² / kg. The high specific surface area enables the metakaolin particles to effectively fill the micro-pores of the cement stone, reduce the porosity and refine the pore size distribution. The total content of its high-activity SiO2 and Al2O3 ≥ 95%, and the mass ratio of SiO2 / Al2O3 is 1.1 - 1.2:1, with sufficient pozzolanic activity, which can react with the hydration products of cement to generate dense calcium aluminosilicate gel, improving the acid corrosion resistance and high temperature resistance of the concrete.

[0022] For the fair-faced concrete for a power plant chimney of the present invention, the shale ceramsite is 600-grade crushed stone type shale ceramsite with a particle size of 5 - 10 mm, with continuous gradation, water absorption rate of 8.5% - 9.5%, and porosity of 35% - 38%. The shale ceramsite is fired at high temperature and has excellent thermal stability. Its strong water absorption rate and large porosity enable the photocatalyst to easily adhere to the surface of the ceramsite for loading, and the pre-wetted ceramsite can release internal water in the concrete to compensate for the concrete shrinkage and prevent the concrete from cracking.

[0023] The present invention relates to fair-faced concrete for a power plant chimney. The solid content of the polydimethylsiloxane emulsion is 45% - 50%, which not only ensures the film compactness to block the penetration of corrosive media but also maintains the uniform dispersion of emulsion particles in the cement matrix. The pH value is 6.5 - 8.0. On the one hand, it avoids the damage of the passivation film on the surface of the steel bar in an acidic environment, and on the other hand, it inhibits the excessive hydrolysis and condensation reaction of siloxane molecules under alkaline conditions.

[0024] The present invention relates to fair-faced concrete for a power plant chimney, wherein the cement is 42.5-grade ordinary Portland cement; the fly ash is Class C Grade II fly ash.

[0025] The present invention relates to fair-faced concrete for a power plant chimney, wherein the coarse aggregate has a particle size of 5 - 25 mm and a continuous gradation; the manufactured sand has a particle size of 0.16 mm - 5 mm, a fineness modulus of 2.5 - 3.1, an MB value < 1.0, and a stone powder content of 5 - 8%.

[0026] The present invention relates to fair-faced concrete for a power plant chimney, wherein the water reducer is a polycarboxylate superplasticizer, the water reduction rate is not less than 25%, and the solid content is 15%.

[0027] The present invention relates to fair-faced concrete for a power plant chimney, wherein the water-binder ratio of the concrete is 0.41 - 0.42, and the sand ratio is 42% - 43%.

[0028] Another technical solution provided by the present invention is a preparation method of fair-faced concrete for a power plant chimney, which includes the following steps:

[0029] S1. Immerse the shale ceramsite in a TiO2 suspension with a concentration of 9 g / L for 24 h, then take it out and drain it to obtain shale ceramsite loaded with TiO2 in a saturated surface-dry state;

[0030] S2. When feeding materials, first put in the cementitious materials, metakaolin and 80% of the water, and stir for 1 minute to prepare a cement paste with a relatively high water-binder ratio;

[0031] S3. Put in the coarse aggregate and the wetted shale ceramsite, and stir thoroughly for 1 minute to make the cement paste wrap the coarse aggregate and the ceramsite and embed into the pores of the ceramsite;

[0032] S4. Then put in the manufactured sand, the remaining water, the polydimethylsiloxane emulsion and the water reducer, and stir thoroughly for 2 minutes to finally obtain fair-faced concrete for a power plant chimney.

[0033] The difference between the fair-faced concrete for a power plant chimney and its preparation method of the present invention and the prior art lies in that the fair-faced concrete for a power plant chimney and its preparation method of the present invention have the following technical effects:

[0034] (1) In the present invention, the shale ceramsite is soaked in a TiO2 suspension for pre-wetting treatment, so that the surface of the ceramsite is uniformly loaded with the photocatalytic active substance TiO2. During the setting and hardening process of the concrete, the loaded TiO2 gradually migrates to the surface of the concrete and is stably distributed, thereby endowing the concrete with excellent self-cleaning function. In practical applications, TiO2 can effectively decompose the organic pollutants attached to the surface of the concrete through photocatalysis, significantly reducing the later maintenance cost and keeping the outer surface of the chimney concrete clean all the time. Since the shale ceramsite is fired at high temperature, its internal structure is dense and has excellent stability, and it can maintain good physical and chemical properties in high temperature environments and is not easily cracked or peeled due to thermal stress. Therefore, in high temperature environments such as chimneys, the concrete doped with shale ceramsite exhibits more excellent high temperature resistance, can effectively avoid structural damage caused by thermal expansion, and further improve the service life and reliability of the concrete. Moreover, the ceramsite has a water return effect, which can continuously provide hydration for unhydrated cement or fly ash particles, improving the degree of cement hydration and generating more dense gel phases, thereby preventing the concrete from being eroded by sulfates and reducing the generation and development of microcracks.

[0035] (2) In the present invention, by introducing metakaolin and internally mixing polydimethylsiloxane emulsion, the acid corrosion resistance and high temperature resistance of the concrete are further improved. In terms of acid corrosion resistance, metakaolin enhances the impermeability and acid corrosion resistance of the concrete from the inside by filling the internal pores of the concrete and forming a dense calcium aluminosilicate gel, while the polydimethylsiloxane emulsion migrates to the surface of the concrete and forms a dense silicone film to block the penetration of acidic substances from the outside. In terms of high temperature resistance, the combination of the two forms an "internal and external double protection" mechanism, significantly improving the overall acid corrosion resistance of the concrete; in terms of high temperature resistance, metakaolin significantly improves the high temperature stability of the concrete from the inside by virtue of its high melting point characteristics and the high temperature resistant minerals generated through secondary hydration reactions. At the same time, after the polydimethylsiloxane emulsion decomposes under high temperature conditions, it forms a dense silica protective film, providing excellent heat insulation performance and antioxidant protection for the concrete from the outside. The two act synergistically through the internal and external combination method, not only effectively reducing the damage of high temperature to the internal structure of the concrete, but also significantly enhancing the thermal stability and thermal damage resistance of the chimney concrete under high temperature working conditions. In addition, the fine particle effect of metakaolin can optimize the microstructure of the concrete, reduce the porosity, thereby reducing the thermal expansion and contraction stress caused by temperature changes and inhibiting the expansion of microcracks. The elastic film layer formed by the polydimethylsiloxane emulsion can also effectively buffer the stress concentration of the concrete during temperature difference changes, further improving the crack resistance of the concrete and making it have higher durability and reliability under complex environmental conditions.

[0036] (3) In the technical solution of the preparation method of fair - faced concrete for power plant chimneys, the shale ceramsite is soaked in a TiO2 suspension with a concentration of 9 g / L for 24 h and then taken out and drained to obtain shale ceramsite loaded with TiO2 in a saturated surface - dry state, which not only wets the shale ceramsite but also introduces photocatalytic particles through the ceramsite loading method; first, the cementitious material, metakaolin and part of the mixing water are added and stirred to form a cement paste with a relatively high water - binder ratio, then the shale ceramsite and coarse aggregate are added and stirred, and the cement paste wraps the shale ceramsite and coarse aggregate, and the cement paste can fully embed into the pores on the surface of the shale ceramsite to form a relatively smooth - surfaced ceramsite, improving the fluidity of the mixture and also reducing the water absorption of the shale ceramsite in the later stage, thereby improving the workability of the mixture; finally, the manufactured sand, the remaining mixing water, polydimethylsiloxane emulsion and water - reducing agent are added, and after full stirring, a concrete mixture is obtained, ensuring the uniformity of each component of the concrete. Detailed implementation manners

[0037] The following examples are used to illustrate the present invention, but do not limit the scope of the present invention.

[0038] The raw materials in the following examples are as follows:

[0039] (1) Cement: 42.5 - grade ordinary Portland cement;

[0040] (2) Fly ash: Class C Grade II fly ash;

[0041] (3) Metakaolin: Specific surface area 672 m 2 / kg, mainly composed of silicon - aluminum oxides, with SiO2 and Al2O3 contents of 50.67% and 44.34% respectively;

[0042] (4) Coarse aggregate: Particle size 5 - 25 mm, continuous gradation, apparent density 2700 kg / m 3 ;

[0043] (5) Manufactured sand: Fineness modulus 2.7, MB value 0.8, stone powder content 6.4%;

[0044] (6) Shale ceramsite: 600 - grade crushed - stone - type shale ceramsite with a particle size of 5 - 10 mm, continuous gradation, water absorption rate 8.5 - 9.5%, porosity 35 - 38%;

[0045] (7) Polydimethylsiloxane emulsion: Solids content 45% - 50%, pH value 6.5 - 8.0;

[0046] (8) Water - reducing agent: Polycarboxylate superplasticizer with a water - reducing rate of 25%, solids content 15%;

[0047] (9) Mixing water: Ordinary tap water.

[0048] Example 1

[0049] A fair-faced concrete for a power plant chimney according to the present invention comprises the following components per cubic meter:

[0050] Cement: 305 kg,

[0051] Fly ash: 40 kg,

[0052] Metakaolin: 25 kg,

[0053] Coarse aggregate: 961 kg,

[0054] Machine-made sand: 730 kg,

[0055] Shale ceramsite: 40 kg,

[0056] Polydimethylsiloxane emulsion: 5.6 kg,

[0057] Water reducer: 4.1 kg,

[0058] Mixing water: 152 kg.

[0059] In this example, the sand ratio of the concrete is 42%, the dosage of the water reducer is 1.1%, and the water-binder ratio is 0.41.

[0060] In addition, this example also provides a preparation method for the fair-faced concrete for a power plant chimney, and the specific steps are as follows:

[0061] S1. Immerse the shale ceramsite in a TiO2 suspension with a concentration of 9 g / L for 24 h, then take it out and drain it to obtain the shale ceramsite loaded with TiO2 in a saturated surface-dry state;

[0062] S2. When feeding materials, first put in the cementitious materials, metakaolin and 80% of the water, and stir for 1 minute to prepare a cement paste with a relatively high water-binder ratio;

[0063] S3. Then put in the coarse aggregate and the wetted shale ceramsite, and stir thoroughly for 1 minute to make the cement paste wrap the coarse aggregate and the ceramsite and embed into the pores of the ceramsite;

[0064] S4. Then put in the machine-made sand, the remaining water, the polydimethylsiloxane emulsion and the water reducer, and stir thoroughly for 2 minutes to finally obtain the fair-faced concrete for a power plant chimney.

[0065] Example 2

[0066] A fair-faced concrete for a power plant chimney according to the present invention comprises the following components per cubic meter:

[0067] Cement: 290 kg,

[0068] Fly ash: 50 kg,

[0069] Metakaolin: 30 kg,

[0070] Coarse aggregate: 951 kg,

[0071] Machine-made sand: 730 kg,

[0072] Shale ceramsite: 50 kg,

[0073] Polydimethylsiloxane emulsion: 4.6 kg,

[0074] Water reducing agent: 4.1 kg,

[0075] Mixing water: 154 kg.

[0076] In this embodiment, the sand ratio of the concrete is 42%, the dosage of the water reducing agent is 1.1%, and the water-binder ratio is 0.41.

[0077] In addition, this embodiment also provides a preparation method for fair-faced concrete used in a power plant chimney, and the preparation method is the same as that in Embodiment 1.

[0078] Embodiment 3

[0079] A fair-faced concrete for a power plant chimney according to the present invention includes the following components per cubic meter:

[0080] Cement: 285 kg,

[0081] Fly ash: 50 kg,

[0082] Metakaolin: 35 kg,

[0083] Coarse aggregate: 951 kg,

[0084] Machine-made sand: 750 kg,

[0085] Shale ceramsite: 50 kg,

[0086] Polydimethylsiloxane emulsion: 4.6 kg,

[0087] Water reducing agent: 4.5 kg,

[0088] Mixing water: 154 kg.

[0089] In this embodiment, the sand ratio of the concrete is 43%, the dosage of the water reducing agent is 1.2%, and the water-binder ratio is 0.42.

[0090] In addition, this embodiment also provides a preparation method for fair-faced concrete used in a power plant chimney, and the preparation method is the same as that in Embodiment 1.

[0091] Embodiment 4

[0092] The fair-faced concrete for a power plant chimney of the present invention includes the following components per cubic meter:

[0093] Cement: 290 kg,

[0094] Fly ash: 50 kg,

[0095] Meta-kaolin: 30 kg,

[0096] Coarse aggregate: 951 kg,

[0097] Machine-made sand: 750 kg,

[0098] Shale ceramsite: 50 kg,

[0099] Polydimethylsiloxane emulsion: 3.7 kg,

[0100] Water reducer: 4.5 kg,

[0101] Mixing water: 155 kg.

[0102] In this embodiment, the sand ratio of the concrete is 43%, the dosage of the water reducer is 1.2%, and the water-binder ratio is 0.42.

[0103] In addition, this embodiment also provides a preparation method for the fair-faced concrete for a power plant chimney, and the preparation method is the same as that of Example 1.

[0104] Example 5

[0105] The fair-faced concrete for a power plant chimney of the present invention includes the following components per cubic meter:

[0106] Cement: 285 kg,

[0107] Fly ash: 50 kg,

[0108] Meta-kaolin: 35 kg,

[0109] Coarse aggregate: 941 kg,

[0110] Machine-made sand: 750 kg,

[0111] Shale ceramsite: 60 kg,

[0112] Polydimethylsiloxane emulsion: 3.7 kg,

[0113] Water reducer: 4.5 kg,

[0114] Mixing water: 155 kg.

[0115] In this embodiment, the sand ratio of the concrete is 43%, the dosage of the water reducer is 1.2%, and the water-binder ratio is 0.42.

[0116] In addition, this embodiment also provides a method for preparing plain concrete for a power plant chimney, and the preparation method is the same as that in Embodiment 1.

[0117] Comparative Example 1

[0118] A kind of plain concrete for power plant chimney without using metakaolin, comprising the following components per cubic meter:

[0119] Cement: 285kg,

[0120] Fly ash: 85kg,

[0121] Coarse aggregate: 941kg,

[0122] Machine-made sand: 750kg,

[0123] Shale ceramsite: 60kg,

[0124] Polydimethylsiloxane emulsion: 3.7kg,

[0125] Water reducing agent: 4.5kg,

[0126] Mixing water: 155kg.

[0127] In this comparative example, the concrete sand ratio is 43%, the water reducing agent dosage is 1.2%, and the water-cement ratio is 0.42.

[0128] In addition, this comparative example also provides a method for preparing plain concrete for power plant chimneys without using metakaolin, and the specific steps are as follows:

[0129] S1. Soak the shale ceramsite in a TiO2 suspension with a concentration of 9 g / L for 24 hours, then take it out and drain it to obtain shale ceramsite loaded with TiO2 in a saturated surface dry state;

[0130] S2. When adding materials, first add cementitious materials and 80% of water, stir for 1 minute, and prepare cement paste with a relatively high water-binder ratio;

[0131] S3, add coarse aggregate and moistened shale ceramsite, and stir thoroughly for 1 minute so that the cement paste can wrap the coarse aggregate and ceramsite and embed into the pores of the ceramsite;

[0132] S4, adding machine-made sand, the remaining water, polydimethylsiloxane emulsion and water reducing agent, stirring thoroughly for 2 minutes, and finally obtaining plain concrete for power plant chimney.

[0133] Comparative Example 2

[0134] A kind of plain concrete for chimney of power plant without using ceramsite, each cubic meter of which comprises the following components:

[0135] Cement: 285kg,

[0136] Fly ash: 50 kg,

[0137] Metakaolin: 35 kg,

[0138] Coarse aggregate: 1001 kg,

[0139] Manufactured sand: 750 kg,

[0140] Polydimethylsiloxane emulsion: 3.7 kg,

[0141] Water reducing agent: 4.5 kg,

[0142] Mixing water: 155 kg.

[0143] In this comparative example, the sand ratio of the concrete is 43%, the dosage of the water reducing agent is 1.2%, and the water-binder ratio is 0.42.

[0144] In addition, this comparative example also provides a preparation method of fair-faced concrete for a power plant chimney without using ceramsite, and the specific steps are as follows:

[0145] S1. When feeding materials, first put in the cementitious materials, metakaolin and 80% of the water, and stir for 1 minute to prepare a cement paste with a relatively high water-binder ratio;

[0146] S2. Then put in the coarse aggregate and stir for 1 minute sufficiently to make the cement paste wrap the coarse aggregate;

[0147] S3. Then put in the manufactured sand, the remaining water, the polydimethylsiloxane emulsion and the water reducing agent, and stir for 2 minutes sufficiently to finally obtain the fair-faced concrete for a power plant chimney.

[0148] Comparative Example 3

[0149] A kind of fair-faced concrete for a power plant chimney without using polydimethylsiloxane emulsion, and each cubic meter includes the following components:

[0150] Cement: 285 kg,

[0151] Fly ash: 50 kg,

[0152] Metakaolin: 35 kg,

[0153] Coarse aggregate: 941 kg,

[0154] Manufactured sand: 750 kg,

[0155] Shale ceramsite: 60 kg,

[0156] Water reducing agent: 4.5 kg,

[0157] Mixing water: 155 kg.

[0158] In this comparative example, the concrete sand ratio is 43%, the water reducing agent dosage is 1.2%, and the water-cement ratio is 0.42.

[0159] In addition, this comparative example also provides a method for preparing plain concrete for power plant chimneys without using polydimethylsiloxane emulsion, and the specific steps are as follows:

[0160] S1. Soak the shale ceramsite in a TiO2 suspension with a concentration of 9 g / L for 24 hours, then take it out and drain it to obtain shale ceramsite loaded with TiO2 in a saturated surface dry state;

[0161] S2. When adding materials, first add cementitious materials, metakaolin and 80% of water, stir for 1 minute, and prepare cement paste with a relatively high water-binder ratio;

[0162] S3, add coarse aggregate and moistened shale ceramsite, and stir thoroughly for 1 minute so that the cement paste can wrap the coarse aggregate and ceramsite and embed into the pores of the ceramsite;

[0163] S4. Add machine-made sand, the remaining water and the water reducing agent, stir thoroughly for 2 minutes, and finally obtain the plain concrete for the chimney of the power plant.

[0164] Comparative Example 4

[0165] A conventionally prepared plain concrete for power plant chimneys includes the following components per cubic meter:

[0166] Cement: 285kg,

[0167] Fly ash: 50kg,

[0168] Metakaolin: 35kg,

[0169] Coarse aggregate: 941kg,

[0170] Machine-made sand: 750kg,

[0171] Shale ceramsite: 60kg,

[0172] Polydimethylsiloxane emulsion: 3.7kg,

[0173] Water reducing agent: 4.5kg,

[0174] Mixing water: 155kg.

[0175] In this comparative example, the concrete sand ratio is 43%, the water reducing agent dosage is 1.2%, and the water-cement ratio is 0.42.

[0176] In addition, this comparative example also provides a method for preparing a conventionally prepared plain concrete for a power plant chimney, and the specific steps are as follows:

[0177] S1. When feeding materials, first put in coarse aggregate, manufactured sand, and shale ceramsite, and stir for 1 minute;

[0178] S3. Then put in the cementitious material and stir thoroughly for 1 minute;

[0179] S3. Then put in water and admixture, and stir thoroughly for 2 minutes to finally obtain fair - faced concrete for power plant chimneys.

[0180] Comparative Example 5

[0181] A kind of conventional fair - faced concrete, including the following components per cubic meter:

[0182] Cement: 285 kg,

[0183] Fly ash: 85 kg,

[0184] Coarse aggregate: 1001 kg,

[0185] Manufactured sand: 750 kg,

[0186] Water - reducing agent: 4.5 kg,

[0187] Mixing water: 155 kg.

[0188] In this comparative example, the sand ratio of the concrete is 43%, the dosage of the water - reducing agent is 1.2%, and the water - binder ratio is 0.42.

[0189] In addition, this comparative example also provides a preparation method for ordinary fair - faced concrete, and the specific steps are as follows:

[0190] S1. When feeding materials, first put in coarse aggregate and manufactured sand, and stir for 1 minute;

[0191] S3. Then put in the cementitious material and stir thoroughly for 1 minute;

[0192] S3. Then put in water and admixture, and stir thoroughly for 2 minutes to finally obtain fair - faced concrete for power plant chimneys.

[0193] Perform performance tests on the concrete of Examples 1 - 2 and Comparative Examples 1 - 5. Among them, select 10 mg / L methylene blue aqueous solution as the organic matter to be measured, cover it on the surface of the photocatalytic concrete, and under the irradiation of ultraviolet light, the methylene blue solution is decomposed with the photocatalytic reaction. At the same time, use an ultraviolet spectrophotometer to measure the absorbance of the methylene blue aqueous solution, and characterize the photocatalytic self - cleaning efficiency of the concrete according to the change in the concentration of the methylene blue solution. Conduct a high - temperature test using a building materials burning and inspection furnace at 600 °C, with an overall heating rate of about 20 °C / min. When the test block reaches a temperature of 600 °C, keep it warm for 3 h. After the test, turn off the heating equipment, and wait for the test block to cool naturally to room temperature before testing the compressive strength.

[0194] The anti-sulfate erosion performance was tested according to the reference specification GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", and the corrosion resistance coefficient of the compressive strength after 150 times of dry-wet cycles of anti-sulfate was measured. The test results are shown in Table 1.

[0195] Table 1 Test Results of Concrete Performance

[0196]

[0197] Combining all the examples, it can be seen that through the reasonable proportioning of each component in the present invention, a fair-faced concrete for power plant chimneys can be obtained. According to the specific requirements of the project, the fluidity of the concrete can be adjusted by adjusting the proportion in the components of the present invention.

[0198] Combining Example 5 with Comparative Examples 1-3, it can be seen that when metakaolin in the proportion of the present invention is lacking, the compressive strength, high-temperature resistance and acid corrosion resistance of the concrete decrease; when shale ceramsite is lacking, the fluidity and compressive strength of the concrete are improved, but the high-temperature resistance and acid corrosion resistance also decrease, and it is impossible to introduce photocatalytic particles by the loading method using the characteristics of large water absorption rate and porosity of ceramsite, and the self-cleaning performance cannot be imparted to the concrete by this convenient means; when polydimethylsiloxane emulsion is lacking, the high-temperature resistance and acid corrosion resistance of the concrete also decrease, and the degree of decrease is the most obvious.

[0199] Combining Example 5 with Comparative Example 4, it can be seen that through the preparation process of the fair-faced concrete for power plant chimneys preferably of the present invention, various performances such as the self-cleaning ability, high-temperature resistance and acid corrosion resistance of the concrete in the present invention can be more fully stimulated.

[0200] Combining Example 5 with Comparative Example 5, it can be seen that a fair-faced concrete for power plant chimneys prepared by the present invention has stronger fluidity and fewer surface pores than conventional fair-faced concrete. While having excellent high-temperature resistance and acid corrosion resistance, it also has self-cleaning ability, and can fully meet the aesthetic and functional requirements of the concrete for power plant chimneys.

[0201] Although the present invention has been described in detail above with general descriptions and specific examples, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope claimed by the present invention.

Claims

1. Fair-faced concrete for a power plant chimney, characterized in that: Per cubic meter includes components: Cement: 285 - 305 kg, Fly ash: 40 - 50 kg, Metakaolin: 25 - 35 kg, Coarse aggregate: 931 - 961 kg, Machine-made sand: 740 - 780 kg, Shale ceramsite: 40 - 60 kg, and the shale ceramsite needs to be soaked in TiO2 suspension and then drained, Internally mixed polydimethylsiloxane emulsion: 3.7 - 5.6 kg, Water reducer: 4.1 - 4.5 kg, Mixing water: 152 - 155 kg.

2. The fair-faced concrete for a power plant chimney according to claim 1, wherein: The specific surface area of the metakaolin is 650-700 m 2 / kg, the total content of highly active SiO2 and Al2O3 in the metakaolin is ≥95%, and the mass ratio of SiO2 / Al2O3 is 1.1-1.2:

1.

3. The fair-faced concrete for a power plant chimney according to claim 1, wherein: The shale ceramsite is 600 - grade crushed shale ceramsite with a size of 5 - 10 mm, continuous gradation, water absorption rate of 8.5% - 9.5%, and porosity of 35 - 38%.

4. The fair-faced concrete for a power plant chimney according to claim 1, wherein: The polydimethylsiloxane emulsion has a solid content of 45% - 50% and a pH value of 6.5 - 8.

0.

5. The fair-faced concrete for a power plant chimney according to claim 1, characterized in that: The cement is 42.5 - grade ordinary Portland cement; the fly ash is Class C Grade II fly ash.

6. The fair-faced concrete for a power plant chimney according to claim 1, characterized in that: The coarse aggregate has a particle size of 5 - 25 mm and continuous gradation; the machine-made sand has a particle size of 0.16 mm - 5 mm, fineness modulus of 2.5 - 3.1, MB value < 1.0, and stone powder content of 5 - 8%.

7. A fair-faced concrete for a power plant chimney according to claim 1, characterized in that: The water reducer is a polycarboxylate superplasticizer with a water reduction rate of not less than 25% and a solid content of 15%.

8. A fair-faced concrete for a power plant chimney according to claim 1, characterized in that: The water-binder ratio of the concrete is 0.41 - 0.42, and the sand ratio is 42% - 43%.

9. A preparation method of fair-faced concrete for a power plant chimney, characterized in that: To prepare per cubic meter of concrete, the following steps are included: S1. Soak 40 - 60 kg of shale ceramsite in TiO2 suspension with a concentration of 9 g / L for 24 h, then take it out and drain to obtain shale ceramsite loaded with TiO2 in a saturated surface-dry state; S2. When feeding materials, first put in cement: 285 - 305 kg, fly ash: 40 - 50 kg, metakaolin 25 - 35 kg and 80% of 152 - 155 kg of water, and stir for 1 minute to prepare cement paste; S3. Put in 931 - 961 kg of coarse aggregate and the wetted shale ceramsite, and stir thoroughly for 1 minute to make the cement paste wrap the coarse aggregate and ceramsite and embed into the pores of the ceramsite; S4. Then put in 740 - 780 kg of machine-made sand, the remaining water, 3.7 - 5.6 kg of polydimethylsiloxane emulsion and 4.1 - 4.5 kg of water reducer, and stir thoroughly for 2 minutes to finally obtain fair-faced concrete for power plant chimneys.

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