A high-strength concrete and its construction method

Abstract

This application relates to the technical field of concrete, and specifically discloses a high-strength concrete and its construction method. The high-strength concrete is obtained by subjecting a concrete mixture to in-mold curing. The concrete mixture comprises the following components in parts by weight: 160-165 parts of water, 370-380 parts of portland cement, 88-92 parts of mineral admixture, 58-62 parts of tetracalcium ferroaluminate powder, 720-730 parts of medium sand, 980-1020 parts of crushed stone, and 10.4-18.9 parts of polycarboxylate water reducer. By using tetracalcium ferroaluminate powder to partially replace portland cement in this application, the contents of the gel phase and ettringite increase. Under the combined action of the gel phase and ettringite, the anti-shrinkage performance of the high-strength concrete is enhanced, the cracking phenomenon is better controlled, thereby obtaining a lower compressive-to-flexural ratio, improving the toughness of the concrete, and being beneficial to the long-term service of the high-strength concrete.

Description

Technical Field

[0001] This application relates to the technical field of concrete, and more specifically, it relates to a high-strength concrete and its construction method. Background Art

[0002] High-strength concrete generally refers to concrete with a strength grade above C50. Its high-strength performance is mainly achieved by adding high-performance water reducers (usually polycarboxylate water reducers) and setting a lower water-cement ratio (compared with ordinary concrete below C50, the water-binder ratio is higher, usually 0.4 - 0.6). Due to its compressive strength far exceeding that of ordinary concrete, high-strength concrete is widely used in various long-span bridges and buildings.

[0003] In the related art, there is a kind of high-strength concrete, and its mixture includes the following components in parts by weight: 163 parts of water, 436 parts of cement, 30 parts of fly ash, 90 parts of mineral admixture, 725 parts of medium sand, 1002 parts of crushed stone, and 13.9 parts of polycarboxylate water reducer. When using P.O42.5 cement, the 28d strength of this high-strength concrete can reach 70MPa.

[0004] Regarding the above-mentioned related art, the inventor believes that although the low water-binder ratio enables the high-strength concrete in the related art to have a relatively high compressive strength, it will also exacerbate the shrinkage of the concrete, resulting in a greatly increased risk of concrete cracking, which is not conducive to the long-term service of high-strength concrete. Summary of the Invention

[0005] In the related art, the water-binder ratio adopted in the mix proportion of high-strength concrete is relatively low, which exacerbates the shrinkage of the concrete and leads to a greatly increased risk of concrete cracking, being not conducive to the long-term service of high-strength concrete. To improve this defect, this application provides a high-strength concrete and its construction method.

[0006] In the first aspect, this application provides a high-strength concrete, adopting the following technical solution:

[0007] A kind of high-strength concrete, which is obtained by subjecting a concrete mixture to in-mold curing. The concrete mixture includes the following components in parts by weight: 160 - 165 parts of water, 370 - 380 parts of portland cement, 88 - 92 parts of mineral admixture, 58 - 62 parts of tetracalcium ferroaluminate powder, 720 - 730 parts of medium sand, 980 - 1020 parts of crushed stone, and 10.4 - 18.9 parts of polycarboxylate water reducer.

[0008] By adopting the above technical solution, on the basis of the mix proportion used in the related art, this application reduces the amount of portland cement and adds tetracalcium ferroaluminate powder as a supplement. The portland cement, mineral admixture, and tetracalcium ferroaluminate powder together serve as the cementitious material, increasing the content of tetracalcium ferroaluminate in the cementitious material.

[0009] In the cementitious material system mainly composed of Portland cement, there are mainly four mineral phases: dicalcium silicate (C2S), tricalcium silicate (C3S), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF). The hydration reaction mechanisms corresponding to these four mineral phases can be represented by the following reaction equations (H represents water, and CH represents calcium hydroxide):

[0010] 2C3S + 6H → C3S2H3 + 3CH

[0011] 2C2S + 4H → C3S2H3 + CH

[0012] C3A + 6H → C3AH6

[0013] C4AF + 2CH + 10H → C3AH6 + C3FH6

[0014] Among the products of the above hydration reactions, calcium silicate hydrate (i.e., C3S2H3, also known as CSH gel) and calcium ferrite hydrate (i.e., C3FH6) are gels, and the remaining hydration products are all crystals. Tetracalcium aluminoferrite consumes calcium hydroxide (crystal) in the hydration reaction and produces calcium ferrite hydrate (gel) and calcium aluminate hydrate, thereby converting a part of the crystal phase into a gel phase. In addition, the calcium aluminate hydrate (C3AH6) formed after the hydration of tetracalcium aluminoferrite will continue to react with calcium sulfate and finally be converted into ettringite. The toughness of the gel phase is better than that of the crystal phase. When the crystal phase is converted into the gel phase, the content of the gel phase in the concrete increases, and the toughness of the concrete is improved. Ettringite has an expansion effect and can resist various contractions generated in the concrete structure through its own expansion stress. Since the content of tetracalcium aluminoferrite in the cementitious material of this application increases, the contents of both the gel phase and ettringite in the concrete increase. Under the combined action of the gel phase and ettringite, high-strength concrete can obtain a lower compressive-to-flexural ratio under the same water-to-binder ratio condition (compared with the high-strength concrete in the related technology), thereby improving the toughness of the concrete and better controlling the cracking phenomenon, which is beneficial for the long-term service of high-strength concrete.

[0015] Preferably, in the concrete mixture, the weight parts of the polycarboxylate water reducer are 16.2 - 18.9 parts.

[0016] By adopting the above technical solution, the hydration product of tetracalcium aluminoferrite is positively charged, while the polycarboxylate water reducer has a large number of anionic groups. When the content of tetracalcium aluminoferrite in the cementitious material increases, the total adsorption amount of the polycarboxylate water reducer by the cementitious material also increases, which affects the water-reducing effect of the polycarboxylate water reducer. Therefore, this application increases the dosage of the polycarboxylate water reducer on the basis of the related technology, which helps to improve the fluidity of the concrete mixture.

[0017] Preferably, the tetracalcium aluminoferrite powder is prepared by the following method:

[0018] Mix calcium oxide, alumina, and iron oxide in a molar ratio of 4:1:1, grind them, then calcine at 800 - 1000 °C for 2 - 3 h, cool the calcined product, and then grind at 20 - 30 °C to obtain the tetracalcium aluminoferrite powder.

[0019] By adopting the above technical solution, calcium oxide, alumina, and iron oxide are used as raw materials for calcination, so that calcium oxide, alumina, and iron oxide react to form tetracalcium aluminoferrite, and then the tetracalcium aluminoferrite is cooled and ground to obtain the tetracalcium aluminoferrite powder.

[0020] Preferably, in the method for preparing the tetracalcium aluminoferrite powder, the cooled calcined product is mixed with liquid polyethylene glycol and then ground to obtain the tetracalcium aluminoferrite powder.

[0021] By adopting the above technical solution, liquid polyethylene glycol can come into full contact with tetracalcium aluminoferrite during grinding and adsorb on the surface of the obtained tetracalcium aluminoferrite powder. The steric hindrance of polyethylene glycol helps to reduce the excessive adsorption of tetracalcium aluminoferrite powder on the polycarboxylate superplasticizer and reduces the impact of tetracalcium aluminoferrite powder on the fluidity of the concrete mixture.

[0022] Preferably, the liquid polyethylene glycol is mixed with the cooled calcined product in a weight ratio of 1:(50 - 110).

[0023] By adopting the above technical solution, the weight ratio range of liquid polyethylene glycol to the calcined product is optimized, which helps to fully reduce the adsorption of tetracalcium aluminoferrite powder on the polycarboxylate superplasticizer.

[0024] Preferably, in the concrete mixture, the weight fraction of the polycarboxylate superplasticizer is 12.6 - 13.5 parts.

[0025] By adopting the above technical solution, under the action of polyethylene glycol, the adsorption amount of tetracalcium aluminoferrite powder on the polycarboxylate superplasticizer is reduced, thus reducing the total adsorption amount of the binder on the polycarboxylate superplasticizer. In this case, only 12.6 - 13.5 parts of the polycarboxylate superplasticizer in the concrete formula can achieve sufficient water-reducing effect.

[0026] Preferably, the mineral admixture is selected as modified steel slag powder, and the modified steel slag powder is prepared by the following method: Mix steel slag powder, bauxite, and quicklime, dry and grind them to obtain a raw powder with a calcium-silicon molar ratio of 2.7 - 2.8; calcine the raw powder at 1300 - 1350 °C for 40 - 50 min, then cool it, and then mix it with an alcohol amine grinding aid and grind to obtain the modified steel slag powder.

[0027] By adopting the above technical solution, the original hydration activity of steel slag powder is poor. However, during the calcination of the original powder, the iron in the steel slag reacts with quicklime and bauxite to form tetracalcium ferroaluminate, thereby improving the hydration activity of the steel slag powder. By using the modified steel slag powder as a mineral admixture, it is also possible to further increase the total amount of tetracalcium ferroaluminate in the cementitious material, thereby enhancing the anti-shrinkage performance of high-strength concrete, better controlling the cracking phenomenon, and being beneficial to the long-term service of high-strength concrete.

[0028] Preferably, in the method for preparing the modified steel slag powder, manganese dioxide is mixed with steel slag powder, bauxite, and quicklime.

[0029] By adopting the above technical solution, manganese dioxide can promote the formation of tetracalcium ferroaluminate, which helps to increase the content of tetracalcium ferroaluminate in the modified steel slag powder.

[0030] Preferably, the dosage of manganese dioxide accounts for 3-5% of the weight of the original powder.

[0031] By adopting the above technical solution, the dosage of manganese dioxide is optimized. It helps to fully increase the content of tetracalcium ferroaluminate in the modified steel slag powder on the premise of saving manganese dioxide.

[0032] In the second aspect, the present application provides a construction method for high-strength concrete, adopting the following technical solution.

[0033] A construction method for high-strength concrete includes the following steps:

[0034] (1) Mix portland cement, mineral admixture, tetracalcium ferroaluminate powder, gravel, and medium sand to obtain dry materials; mix water and polycarboxylate water reducer to obtain a water reducer solution;

[0035] (2) Dry-mix the dry materials, and then add the water reducer solution to the dry materials during the dry-mixing process, and continue to stir to obtain a concrete mixture;

[0036] (3) Place the concrete mixture into a mold for curing to obtain high-strength concrete.

[0037] By adopting the above technical solution, the construction method of the present application first prepares dry materials and a water reducer solution separately, and then mixes the two and performs mixing and in-mold curing to obtain high-strength concrete.

[0038] In summary, the present application has the following beneficial effects:

[0039] 1. By using tetracalcium aluminoferrite powder to partially replace Portland cement in this application, the contents of the gel phase and ettringite increase. Under the combined action of the gel phase and ettringite, the compressive-to-flexural ratio of high-strength concrete decreases, thereby improving the toughness of the concrete and better controlling the cracking phenomenon of the concrete, which is beneficial to the long-term service of high-strength concrete.

[0040] 2. In this application, the preferred mineral admixture is modified steel slag powder. The modified steel slag powder not only has better hydration activity than steel slag powder, but also can further increase the content of tetracalcium aluminoferrite in the cementitious material, which helps to improve the shrinkage resistance and crack resistance of the concrete and is beneficial to the long-term service of high-strength concrete. Detailed implementation manners

[0041] The following further elaborates on this application in combination with examples, preparation examples and comparative examples. All raw materials involved in this application can be obtained commercially.

[0042] Preparation example of tetracalcium aluminoferrite powder

[0043] The following takes Preparation Example 1 as an example for illustration.

[0044] Preparation Example 1

[0045] In this preparation example, the tetracalcium aluminoferrite powder is prepared according to the following method: Calcium oxide, aluminum oxide, and iron oxide are mixed in a molar ratio of 4:1:1, ball-milled, then calcined at 950 °C. After calcining for 2.5 h, the calcined product is cooled, and then ground at 25 °C to obtain the tetracalcium aluminoferrite powder.

[0046] Preparation Example 2

[0047] The difference between this preparation example and Preparation Example 1 is that in the method of preparing the tetracalcium aluminoferrite powder, the cooled liquid polyethylene glycol is mixed with the calcined product in a weight ratio of 1:50 and then ground to obtain the tetracalcium aluminoferrite powder.

[0048] As shown in Table 1, the difference between Preparation Examples 2 - 6 lies in that the liquid polyethylene glycol and the calcined product are mixed in different weight ratios.

[0049] Table 1 Weight ratio of liquid polyethylene glycol to calcined product

[0050] Sample Preparation Example 2 Preparation Example 3 Preparation Example 4 Preparation Example 5 Preparation Example 6 Liquid Polyethylene Glycol: Calcined Product 1:50 1:80 1:110 1:140 1:170

[0051] Preparation example of modified steel slag powder

[0052] The following takes Preparation Example 7 as an example for illustration.

[0053] Preparation Example 7

[0054] In this preparation example, the modified steel slag powder is prepared according to the following method:

[0055] Mix steel slag powder, bauxite and quicklime, and after drying and ball milling, obtain the original powder with a calcium-silicon molar ratio of 2.74; calcine the original powder at 1300 °C, cool it after calcining for 45 minutes, and then add triethanolamine, an alkanolamine grinding aid equivalent to 1% of the weight of the original powder, to the calcined original powder and grind it at 25 °C to obtain the modified steel slag powder.

[0056] Preparation Example 8

[0057] The difference between this preparation example and Preparation Example 7 lies in that in the method for preparing the modified steel slag powder, manganese dioxide is mixed together with steel slag powder, bauxite and quicklime, and the dosage of manganese dioxide accounts for 2.5% of the weight of the original powder.

[0058] As shown in Table 2, the difference between Preparation Examples 8-12 lies in the different percentages of the dosage of manganese dioxide in the weight of the original powder (hereinafter simply referred to as the manganese dioxide ratio).

[0059] Table 2 Manganese Dioxide Ratio

[0060] Sample Preparation Example 8 Preparation Example 9 Preparation Example 10 Preparation Example 11 Preparation Example 12 Proportion of Manganese Dioxide / % 2.5 3 4 5 5.5

[0061] Examples

[0062] Examples 1-5

[0063] The following takes Example 1 as an example for illustration.

[0064] Example 1

[0065] In this example, the high-strength concrete is constructed according to the following steps:

[0066] (1) Mix 370 kg of portland cement, 88 kg of mineral admixture, 58 kg of tetracalcium ferroaluminate powder, 980 kg of crushed stone and 720 kg of medium sand to obtain the dry material; mix 160 kg of water and 13.90 kg of polycarboxylate water reducer to obtain the water reducer solution; in this step, the type of portland cement is P.O42.5, the mineral admixture is steel slag powder, the tetracalcium ferroaluminate powder is prepared according to the method of Preparation Example 1, the crushed stone is 5-25 mm continuously graded crushed stone, the fineness modulus of the medium sand is 2.7, and the water reduction rate of the polycarboxylate water reducer is 24%;

[0067] (2) Dry-mix the dry material, and then add the water reducer solution to the dry material during the dry mixing process, and continue stirring to obtain the concrete mixture;

[0068] (3) Place the concrete mixture into the mold and perform standard curing to obtain the high-strength concrete.

[0069] As shown in Table 3, the difference between Examples 1-5 mainly lies in the different raw material ratios of the concrete mixture.

[0070] Table 3 Raw material ratio of concrete mixture

[0071]

[0072] Examples 6 - 10

[0073] As shown in Table 4, the difference between Examples 6 - 10 and Example 3 lies in the different dosages of polycarboxylate superplasticizer.

[0074] Table 4 Dosages of polycarboxylate superplasticizer

[0075] Sample Example 6 Example 7 Example 8 Example 9 Example 10 Polycarboxylate Superplasticizer / kg 15.5 16.2 17.8 18.9 19.3

[0076] Examples 11 - 15

[0077] As shown in Table 5, the difference between Examples 11 - 15 and Example 3 lies in the different preparation examples of tetracalcium ferroaluminate powder.

[0078] Table 5 Preparation examples of tetracalcium ferroaluminate powder

[0079] Sample Example 11 Example 12 Example 13 Example 14 Example 15 Preparation Example of Tetracalcium Ferroaluminate Powder Preparation Example 2 Preparation Example 3 Preparation Example 4 Preparation Example 5 Preparation Example 6

[0080] As shown in Table 6, the difference between Examples 16 - 20 and Example 11 lies in the different dosages of polycarboxylate superplasticizer.

[0081] Table 6 Dosages of polycarboxylate superplasticizer

[0082] Sample Example 16 Example 17 Example 18 Example 19 Example 20 Polycarboxylate Superplasticizer / % 13.7 13.5 13.1 12.6 12.2

[0083] Example 21

[0084] The difference between this example and Example 11 is that the mineral admixture is the modified steel slag powder of Preparation Example 7.

[0085] As shown in Table 7, the difference between Examples 21 - 26 lies in the different preparation examples of modified steel slag powder.

[0086] Table 7 Preparation examples of modified steel slag powder

[0087]

[0088] Comparative example

[0089] Comparative Example 1

[0090] This comparative example provides a high - strength concrete, which is constructed according to the following steps:

[0091] (1) Mix 436 kg of portland cement, 90 kg of mineral admixture, 1002 kg of crushed stone and 725 kg of medium sand to obtain dry materials; mix 163 kg of water and 13.9 kg of polycarboxylate superplasticizer to obtain a superplasticizer solution. In this step, the type of portland cement is P.O42.5, the mineral admixture is composed of fly ash and blast furnace slag powder mixed in a weight ratio of 1:2, the crushed stone is 5 - 25 mm continuously graded crushed stone, the fineness modulus of the medium sand is 2.7, and the water reduction rate of the polycarboxylate superplasticizer is 24%;

[0092] (2) Conduct dry mixing on the dry materials, and then add the superplasticizer solution to the dry materials during the dry mixing process, and continue stirring to obtain concrete mixture;

[0093] (3) Place the concrete mixture into the mold and conduct standard curing to obtain high-strength concrete.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Comparative Example 1 is that the mineral admixture is steel slag powder.

[0096] Performance testing method

[0097] Refer to the "Standard Test Method for Properties of Ordinary Concrete Mixtures" (GB / T 50080 - 2016) to detect the slump flow of the concrete mixtures of each example and comparative example, and then calculate the ratio of the slump flow of the concrete in each example and comparative example to that of Comparative Example 1. Define this ratio as the relative slump flow, and the results are shown in Table 8.

[0098] Refer to the "Standard Test Method for Physical and Mechanical Properties of Concrete" (GB / T 50081 - 2019) to detect the compressive strength and flexural strength of the high-strength concrete of each example and comparative example after standard curing for 90 days, and then calculate the ratio of the compressive strength to the flexural strength (compressive-flexural ratio). Calculate the ratio of the compressive-flexural ratio of each example and comparative example to that of Comparative Example 1, and define this ratio as the relative compressive-flexural ratio, and the results are shown in Table 8.

[0099] Table 8

[0100]

[0101]

[0102] Combined with Examples 1-5 and Comparative Example 1 and Table 8, it can be seen that the relative compression-flexure ratios measured in Examples 1-5 are all lower than that in Comparative Example 1, indicating that by using tetracalcium aluminoferrite powder to partially replace portland cement in this application, the contents of gel phase and ettringite increase. Under the combined action of the gel phase and ettringite, the anti-shrinkage performance of high-strength concrete is enhanced, the cracking phenomenon is better controlled, which is beneficial to the long-term service of high-strength concrete. In addition, the relative spread of Examples 1-5 is lower than that of Comparative Example 1, indicating that the addition of tetracalcium aluminoferrite powder affects the water-reducing effect of polycarboxylate superplasticizer and reduces the fluidity of the concrete mixture.

[0103] Combined with Examples 1-5, Comparative Example 1 and Comparative Example 2 and Table 8, it can be seen that the selection of steel slag as mineral admixture is not the main reason for the decrease in the relative compression-flexure ratio of Examples 1-5.

[0104] Combined with Example 3 and Comparative Examples 6-10 and Table 8, it can be seen that increasing the dosage of polycarboxylate superplasticizer can improve the fluidity of the concrete mixture on the basis of Example 3.

[0105] Combined with Example 3 and Examples 11-15 and Table 8, it can be seen that by adding liquid polyethylene glycol during grinding, the adsorption amount of tetracalcium aluminoferrite powder on polycarboxylate superplasticizer decreases. When the liquid polyethylene glycol is mixed with the cooled calcined product according to a weight ratio of 1:(50-110), the relative spread of the concrete mixture is close to that of Comparative Example 1, indicating that within this range, the polycarboxylate superplasticizer can fully exert its water-reducing effect.

[0106] Combined with Example 11, Examples 16-20 and Comparative Example 1 and Table 8, it can be seen that on the basis of Example 11, appropriately reducing the dosage of polycarboxylate superplasticizer will not have a significant impact on the relative spread. When the dosage of polycarboxylate superplasticizer is 12.6-13.5 kg, the concrete mixture can maintain relatively high fluidity (relative to Example 20), and the dosage of polycarboxylate superplasticizer is saved compared with Comparative Example 1.

[0107] Combined with Example 11 and Example 21 and Table 8, it can be seen that iron calcium aluminate is generated during the calcination of modified steel slag powder, improving the toughness of high-strength concrete. Therefore, the relative compression-flexure ratio of Example 21 is lower than that of Example 11.

[0108] Combined with Example 21, Examples 22 - 26 and Table 8, it can be seen that after adding manganese dioxide to the original powder, the modified steel slag powder contains more tetracalcium ferroaluminate, resulting in a further decrease in the measured relative flexural and compressive ratio. The relative flexural and compressive ratio of Example 22 is the highest among Examples 22 - 26, and its toughness is poor. Therefore, in order to obtain high-strength concrete with a higher relative flexural and compressive ratio, Example 22 and its corresponding Preparation Example 8 should be discarded. The results of Example 26 and Example 25 are close, indicating that on the premise of saving the dosage of manganese dioxide, Example 22 and its corresponding Preparation Example 12 should be discarded.

[0109] This specific embodiment is only an interpretation of the present application and is not a limitation thereof. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A high-strength concrete, characterized in that, The high-strength concrete is obtained by subjecting the concrete mixture to in-mold curing. The concrete mixture comprises the following components in parts by weight: 160 - 165 parts of water, 370 - 380 parts of portland cement, 88 - 92 parts of mineral admixture, 58 - 62 parts of tetracalcium ferroaluminate powder, 720 - 730 parts of medium sand, 980 - 1020 parts of crushed stone, and 10.4 - 18.9 parts of polycarboxylate water reducer; The tetracalcium ferroaluminate powder is prepared according to the following method: Calcium oxide, aluminum oxide, and iron oxide are mixed in a molar ratio of 4:1:1, ball-milled, and then calcined at 800 - 1000 °C for 2 - 3 h. After cooling the calcined product, it is mixed with liquid polyethylene glycol in a weight ratio of (50 - 110):1 and ground at 20 - 30 °C to obtain the tetracalcium ferroaluminate powder; The mineral admixture is selected as modified steel slag powder, and the modified steel slag powder is prepared according to the following method: Manganese dioxide, steel slag powder, bauxite, and quicklime are mixed, dried, and ball-milled to obtain a raw powder with a calcium-silicon molar ratio of 2.7 - 2.

8. The raw powder is calcined at 1300 - 1350 °C for 40 - 50 min and then cooled, and then mixed with an alcohol amine grinding aid and ground to obtain the modified steel slag powder.

2. The high-strength concrete according to claim 1, characterized in that, In the concrete mixture, the weight part of the polycarboxylate water reducer is 16.2 - 18.9 parts.

3. The high-strength concrete according to claim 1, characterized in that, In the concrete mixture, the weight part of the polycarboxylate water reducer is 12.6 - 13.5 parts.

4. The high-strength concrete according to claim 1, characterized in that, The dosage of the manganese dioxide accounts for 3 - 5% of the weight of the raw powder.

5. The construction method of the high-strength concrete according to any one of claims 1-4, characterized in that, It includes the following steps: (1) Mix the portland cement, mineral admixture, tetracalcium ferroaluminate powder, crushed stone, and medium sand to obtain dry materials; mix the water and the polycarboxylate water reducer to obtain a water reducer solution; (2) Dry-mix the dry materials, and then add the water reducer solution to the dry materials during the dry-mixing process, and continue stirring to obtain the concrete mixture; (3) Subject the concrete mixture to in-mold curing to obtain high-strength concrete.

Images