Underwater non-shrinkage concrete and preparation method thereof

Abstract

The present application discloses an underwater non-shrinkage concrete and a preparation method thereof, wherein the concrete comprises the following raw materials in parts by weight: 130-200 parts of cementitious material; 450-650 parts of crushed stone; 300-500 parts of sand; 50-90 parts of water; 3-6 parts of water reducer; 2-4 parts of UEA expansion agent; 15-30 parts of modified spherical alumina; the modified spherical alumina is prepared by grafting and modifying spherical alumina and modifier in anhydrous ethanol in a weight ratio of 100:(3-6); the modifier is prepared by using liquid isomeric tridecanol polyoxyethylene ether and dimethyl dimethoxysilane in a molar ratio of 1:1 as raw materials, and heating reaction under the catalysis of dodecylbenzene sulfonic acid. The underwater concrete of the present application has good anti-shrinkage performance and self-compacting performance.

Description

Technical Field

[0001] The present application relates to the field of concrete, and in particular to an underwater non-shrinkage concrete and a preparation method thereof. Background Art

[0002] Underwater concrete is concrete that is poured and hardened under the water surface, and is usually used for the underwater construction of buildings. Due to the special construction environment, underwater concrete needs to have excellent underwater non-separation, self-compactness and shrinkage resistance.

[0003] Underwater shrinkage-free concrete refers to a concrete system with relatively small shrinkage damage. Expansion agents are usually added to its raw materials. The pre-compression stress generated by the expansion of the expansive agent is used to compensate for the tensile stress generated by drying shrinkage, effectively reducing the shrinkage phenomenon. However, the use of expansive agents will increase the viscosity of the concrete slurry, reducing its workability and self-compacting properties. Summary of the invention

[0004] The present application provides an underwater non-shrinkage concrete and a preparation method thereof, which can effectively balance the anti-shrinkage performance and self-compacting performance of the underwater concrete.

[0005] In a first aspect, the present application provides an underwater non-shrinkage concrete, which includes the following raw materials in parts by weight:

[0006] Cementitious material: 130-200 parts;

[0007] Crushed stone: 450-650 parts;

[0008] Sand: 300-500 parts;

[0009] Water: 50-90 parts;

[0010] Water reducing agent: 3-6 parts;

[0011] UEA expansion agent: 2-4 parts;

[0012] Modified spherical alumina: 15-30 parts;

[0013] The modified spherical alumina is prepared by grafting and modifying spherical alumina and a modifier in anhydrous ethanol in a weight ratio of 100:(3-6); the modifier is prepared by using liquid isomeric tridecanol polyoxyethylene ether and dimethyldimethoxysilane in a molar ratio of 1:1 as raw materials and heating reaction under the catalysis of dodecylbenzenesulfonic acid.

[0014] The addition of UEA expansion agent can certainly reduce the shrinkage rate of concrete, but it also increases the viscosity of the concrete slurry, which is not conducive to the fluidity of the concrete, thereby reducing its self-compacting performance. To overcome this problem, the present application adds spherical alumina, which can effectively reduce the friction resistance between materials, improve the fluidity of the concrete slurry, and thus help improve the self-compacting performance of the concrete.

[0015] However, spherical alumina has poor dispersibility and is prone to agglomeration, so the present application uses a modifier to modify its surface to suppress its agglomeration tendency. Specifically, dimethyldimethoxysilane is a difunctional silane in the above-mentioned modifier, which has two terminal hydroxyl groups after hydrolysis or hydrolysis polycondensation, one of which condenses with the hydroxyl group of tridecanol polyoxyethylene ether, thereby obtaining a modifier with a silanol group and a long chain of polyoxyethylene ether. Its silanol group can bond with the active groups on the surface of spherical alumina, and the long chain of tridecanol polyoxyethylene ether stretches outward to form a steric hindrance to suppress its agglomeration. In addition, the two methyl side chains make it difficult to form a dense film layer that wraps the spherical alumina, which is conducive to maintaining the thermal conductivity of the spherical alumina.

[0016] The cementitious material in this application refers to a concrete raw material with hydration activity, including one or more of cement, fly ash, and mineral powder. The cement is preferably ordinary Portland cement; the crushed stone is preferably 5-25mm continuous graded crushed stone and 5-16mm continuous graded crushed stone with a mass ratio of 6 to 7:1; the sand is preferably medium sand in zone II; the water reducer is preferably polycarboxylate water reducer.

[0017] In the modification reaction of spherical alumina, the amount of anhydrous ethanol is preferably 20-30% of the weight of the spherical alumina, the reaction temperature is preferably 50-60°C, and the reaction time is preferably 2-4h; the drying temperature after the reaction is 100-130°C, and the drying time is preferably 1-2h.

[0018] Preferably, the temperature of the heating reaction is 70-80°C.

[0019] Preferably, the particle size of the spherical alumina is 100-300 μm.

[0020] Spherical alumina of appropriate size is beneficial to optimize the fluidity of concrete slurry, improve the thermal conductivity of concrete during curing, and reduce drying shrinkage.

[0021] Preferably, the cementitious material is cement and fly ash in a weight ratio of 65-70: (30-35).

[0022] Fly ash has lower activity than cement. It does not participate in early hydration, thus filling the pores of concrete and reducing shrinkage. At the same time, it generates solid gel substances in the secondary hydration reaction, thus compensating for shrinkage. Therefore, using an appropriate amount of fly ash to replace cement as a gel material has a good anti-shrinkage effect.

[0023] Preferably, the fly ash is Class I or Class II fly ash.

[0024] Preferably, the raw materials of the concrete further include 2 to 5 parts of sodium polyacrylate with a molecular weight of 1000 to 3000.

[0025] While fly ash improves the shrinkage resistance of concrete, due to its strong adsorption, it adsorbs a large amount of water and water reducing agent, which easily reduces the fluidity of concrete slurry and is not conducive to the self-compacting of concrete. To overcome this problem, this application uses small-molecule sodium polyacrylate, which has high permeability and can be quickly adsorbed on the surface of fly ash, playing a good dispersing and compensating role, preventing the water reducing agent from being consumed in large quantities, and effectively ensuring the fluidity and self-compacting effect of concrete slurry.

[0026] Preferably, the raw materials of the concrete also include 20 to 40 parts of steel fibers.

[0027] Steel fibers can effectively cooperate with modified alumina to form a heat-conducting network in concrete, reduce the temperature difference between inside and outside, and thus reduce shrinkage caused by temperature difference stress.

[0028] The length of the steel fiber is preferably 10 to 35 mm, more preferably 10 to 20 mm, and most preferably 15 to 20 mm.

[0029] Preferably, the steel fiber is modified according to the following method:

[0030] Methyl orthosilicate and mercaptosilane coupling agent are dissolved in ethanol, and then a mixed solution of ethanol, water and glacial acetic acid in a weight ratio of 10-12:3-5:1 is dropped, heated to 50-60°C, and after 0.5-1h, the temperature is raised to 100-120°C to continue the reaction, and after 2-4h, steel fiber and silver nitrate solution are added and mixed evenly to obtain modified steel fiber; the weight ratio of the steel fiber, methyl orthosilicate and mercaptosilane coupling agent is 100:(0.5-1.5):(2-5).

[0031] The modified steel fiber can reduce the probability of electrical corrosion caused by the attachment of chloride ions. Specifically, after the hydrolysis and polycondensation of methyl orthosilicate and mercaptosilane coupling agent, the obtained silane polymer can be firmly adsorbed on the surface of the steel fiber through the silanol group and complexed with the silver ion through the mercapto group. The silver ion can absorb the chloride ions that penetrate into the concrete with the external water and form precipitation to destroy its electrical corrosion, thereby playing the role of resisting chloride ion corrosion.

[0032] Preferably, the molar ratio of the mercaptosilane coupling agent to the silver ions is 1:(1.5-2).

[0033] Typically but not limiting, the concentration of the silver nitrate solution is 20-40 wt % silver nitrate aqueous solution.

[0034] In a second aspect, the present application provides a method for preparing underwater shrinkage-free concrete, which comprises uniformly mixing the raw materials such as the cementitious material, crushed stone, sand, water, UEA expansion agent, modified spherical alumina and water according to a proportion.

[0035] Preferably, the raw materials further include 2 to 5 parts of sodium polyacrylate with a molecular weight of 1000 to 3000 and 20 to 40 parts of steel fiber.

[0036] In summary, this application has the following beneficial effects:

[0037] 1. By using UEA expansion agent and modified spherical alumina, a balance between the shrinkage resistance and fluidity of concrete can be achieved, thereby effectively reducing the shrinkage rate of concrete while ensuring the self-compacting effect of concrete.

[0038] 2. This application uses fly ash and sodium polyacrylate to further improve the shrinkage resistance of concrete while ensuring the fluidity and self-compacting effect of concrete.

[0039] 3. The present application adopts modified steel fiber and modified spherical alumina together to form a heat conduction network in concrete, reduce the temperature difference between the inside and outside of the concrete, thereby reducing shrinkage stress and reducing the shrinkage rate of concrete. DETAILED DESCRIPTION

[0040] Preparation example of modified spherical alumina

[0041] Preparation Example 1-1, a modified spherical alumina is prepared according to the following method:

[0042] Preparation of modifier: Take 470g (1mol) of liquid isomeric tridecanol polyoxyethylene ether and 120g (1mol) of dimethyldimethoxysilane and add them into a reaction kettle, stir evenly, add 11.5g of dodecylbenzenesulfonic acid, heat to 75°C, react for 2h, and obtain the modifier.

[0043] Modification of spherical alumina: Take 250g of anhydrous ethanol and add it into another reactor, add 1000g of spherical alumina (D50 particle size is 200μm) and 5g of the above-obtained modifier, stir evenly, heat to 50℃, continue stirring and react for 2h, release the material after the reaction is completed, remove the upper layer of anhydrous ethanol after standing for 1.5h, and then dry at 120℃ for 1h to obtain modified spherical alumina.

[0044] Preparation Example 1-2, a modified spherical alumina is prepared according to the following method:

[0045] Preparation of modifier: 500 g (1 mol) of liquid isomeric tridecanol polyoxyethylene ether and 120 g (1 mol) of dimethyldimethoxysilane were added to a reaction kettle, stirred evenly, 12.5 g of dodecylbenzenesulfonic acid was added, heated to 70°C, reacted for 2 h, and the modifier was obtained.

[0046] Modification of spherical alumina: Take 200g of anhydrous ethanol and add it into another reactor, add 1000g of spherical alumina (D50 particle size is 300μm) and 3g of the above-mentioned modifier, stir evenly, heat to 60℃, continue stirring and react for 3h, release the material after the reaction is completed, remove the upper layer of anhydrous ethanol after standing for 1h, and then dry at 130℃ for 1h to obtain modified spherical alumina.

[0047] Preparation Example 1-3, a modified spherical alumina, is prepared according to the following method:

[0048] Preparation of modifier: 500 g (1 mol) of liquid isomeric tridecanol polyoxyethylene ether and 120 g (1 mol) of dimethyldimethoxysilane were added to a reaction kettle, stirred evenly, 12.5 g of dodecylbenzenesulfonic acid was added, heated to 80°C, reacted for 2 hours, and the modifier was obtained.

[0049] Modification of spherical alumina: Take 300g of anhydrous ethanol and add it into another reactor, add 1000g of spherical alumina (D50 particle size is 100μm) and 6g of the above-obtained modifier, stir evenly, heat to 55°C, continue stirring and react for 4h, release the material after the reaction is completed, remove the upper layer of anhydrous ethanol after standing for 2h, and then dry at 110°C for 3h to obtain modified spherical alumina.

[0050] Preparation Example 1-4, a modified spherical alumina, differs from Preparation Example 1-1 in that no modifier preparation step is performed, and an equal amount of liquid isomeric tridecanol polyoxyethylene ether is used as the modifier.

[0051] Preparation Example 1-5, a modified spherical alumina, differs from Preparation Example 1-1 in that the modifier preparation step is not performed and an equal amount of dimethyldimethoxysilane is used as the modifier.

[0052] Modified steel fiber preparation example

[0053] Preparation Example 2-1, a modified steel fiber is prepared according to the following steps:

[0054] 0.1 kg of methyl orthosilicate and 0.3 kg of mercaptopropyl triethoxysilane (1.26 mol) were dissolved in 0.15 kg of ethanol, and then 60 g of a mixed solution of ethanol, water and glacial acetic acid in a weight ratio of 10:4:1 was added, heated to 60 ° C, and heated to 110 ° C for 1 hour to continue the reaction. After 3 hours, 10 kg of steel fiber (average length of 18 ± 2 mm) and 855.7 g of 50 wt% silver nitrate aqueous solution (2.51 mol) were added and stirred for 2 hours. The steel fiber was filtered and taken out, and dried at 110 ° C for 1.5 hours to obtain the modified steel fiber.

[0055] Preparation Example 2-2, a modified steel fiber is prepared according to the following steps:

[0056] 0.05 kg of methyl orthosilicate and 0.2 kg of mercaptopropyl triethoxysilane (0.84 mol) were dissolved in 0.1 kg of ethanol, and then 40 g of a mixed solution of ethanol, water and glacial acetic acid in a weight ratio of 11:3:1 was dripped in. After the dripping was completed, the mixture was heated to 50 ° C, and then heated to 120 ° C for 0.5 h to continue the reaction. After 2 h, 10 kg of steel fiber (average length of 15 ± 2 mm) and 535.5 g of 40 wt% silver nitrate aqueous solution (1.26 mol) were added and stirred for 2 h. The steel fiber was filtered and taken out, and dried at 100 ° C for 2 h to obtain the modified steel fiber.

[0057] Preparation Example 2-3, a modified steel fiber is prepared according to the following steps:

[0058] 0.15 kg of methyl orthosilicate and 0.5 kg of mercaptopropyl triethoxysilane (2.1 mol) were dissolved in 0.2 kg of ethanol, and then 90 g of a mixed solution of ethanol, water and glacial acetic acid with a weight ratio of 12:5:1 was dripped in. After the dripping was completed, it was heated to 50 ° C, and then heated to 100 ° C for 1 hour to continue the reaction. After 4 hours, 10 kg of steel fiber (average length of 30 ± 2 mm) and 892.5 g of 60 wt% silver nitrate aqueous solution (3.15 mol) were added and stirred for 3 hours. The steel fiber was filtered and taken out, and dried at 120 ° C for 2 hours to obtain the modified steel fiber.

[0059] Preparation Example 2-4, a modified steel fiber, differs from Preparation Example 2-1 in that an equal amount of mercaptosilane coupling agent is used instead of methyl orthosilicate, and the weight of the added silver nitrate aqueous solution (50wt%) is 1141g.

[0060] Preparation Example 2-5, a modified steel fiber, differs from Preparation Example 2-1 in that an equal amount of methyl orthosilicate is used to replace the mercaptosilane coupling agent.

[0061] Preparation Example 2-6, a modified steel fiber, differs from Preparation Example 2-1 in that no silver nitrate solution is added during the modification process.

[0062] Example

[0063] Example 1, an underwater non-shrinkage concrete, is prepared according to the following method:

[0064] The obtained product is prepared by uniformly mixing 120 kg PO42.5 cement, 64.5 kg fly ash, 550 kg crushed stone, 400 kg sand, 23.5 kg modified spherical alumina obtained in Preparation Example 1-1, 30 kg modified steel fiber obtained in Preparation Example 2-1, 4.5 kg polycarboxylic acid water reducer, 3.6 kg sodium polyacrylate (molecular weight 2000), 3 kg UEA expansion agent and 78 kg water.

[0065] Example 2, an underwater non-shrinkage concrete, is prepared according to the following method:

[0066] The obtained product is prepared by uniformly mixing 90 kg PO42.5 cement, 38.5 kg fly ash, 450 kg crushed stone, 300 kg sand, 15 kg modified spherical alumina obtained in Preparation Example 1-2, 20 kg modified steel fiber obtained in Preparation Example 2-2, 3 kg polycarboxylic acid water reducer, 2 kg sodium polyacrylate (molecular weight 1000), 2 kg UEA expansion agent and 50 kg water.

[0067] Example 3, an underwater non-shrinkage concrete, is prepared according to the following method:

[0068] The obtained product is prepared by uniformly mixing 130 kg PO42.5 cement, 70 kg fly ash, 650 kg crushed stone, 500 kg sand, 30 kg modified spherical alumina obtained in Preparation Example 1-3, 40 kg modified steel fiber obtained in Preparation Example 2-3, 6 kg polycarboxylic acid water reducer, 4 kg sodium polyacrylate (molecular weight 3000), 4 kg UEA expansion agent and 90 kg water.

[0069] Example 4 is an underwater non-shrinkage concrete, which differs from Example 1 in that no modified steel fiber is added.

[0070] Example 5, an underwater shrinkage-free concrete, differs from Example 1 in that an equal amount of modified steel fibers obtained in Preparation Example 2-4 are used to replace the modified steel fibers obtained in Preparation Example 2-1.

[0071] Example 6, an underwater shrinkage-free concrete, differs from Example 1 in that an equal amount of modified steel fibers obtained in Preparation Example 2-5 are used to replace the modified steel fibers obtained in Preparation Example 2-1.

[0072] Example 7, an underwater shrinkage-free concrete, differs from Example 1 in that an equal amount of modified steel fibers obtained in Preparation Example 2-6 are used to replace the modified steel fibers obtained in Preparation Example 2-1.

[0073] Example 8, an underwater shrinkage-free concrete, differs from Example 1 in that an equal amount of unmodified steel fibers (average length of 18±2 mm) are used to replace the modified steel fibers obtained in Preparation Example 2-1.

[0074] Example 9, an underwater shrinkage-free concrete, differs from Example 1 in that sodium polyacrylate with a molecular weight of 5000 is used.

[0075] Example 10, an underwater non-shrinkage concrete, differs from Example 1 in that sodium polyacrylate is not added.

[0076] Example 11 is an underwater shrinkage-free concrete, which differs from Example 12 in that an equal amount of cement is used to replace fly ash.

[0077] Comparative Example

[0078] Comparative Example 1 is an underwater shrinkage-free concrete, which differs from Example 4 in that an equal amount of the modified spherical alumina obtained in Preparation Example 1-4 is used to replace the modified spherical alumina obtained in Preparation Example 1-1.

[0079] Comparative Example 2 is an underwater shrinkage-free concrete, which differs from Example 4 in that an equal amount of the modified spherical alumina obtained in Preparation Example 1-5 is used to replace the modified spherical alumina obtained in Preparation Example 1-1.

[0080] Comparative Example 3, an underwater shrinkage-free concrete, differs from Example 4 in that an equal amount of unmodified spherical alumina (D50 particle size of 200 μm) is used to replace the modified spherical alumina obtained in Preparation Example 1-1.

[0081] Comparative Example 4 is an underwater shrinkage-free concrete, which differs from Example 4 in that an equal amount of amorphous alumina (D50 particle size is 200 μm) is used to replace the modified spherical alumina obtained in Preparation Example 1-1.

[0082] Comparative Example 5 is an underwater non-shrinkage concrete, which differs from Comparative Example 4 in that no UEA expansion agent is added.

[0083] Performance testing

[0084] 1. According to GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete", the compressive strength of concrete is tested. The size of the compressive strength specimen is a standard specimen of 150mm×150mm×150mm.

[0085] 2. Test the shrinkage rate of concrete using the non-contact method specified in GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete".

[0086] 3. According to GB / T50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures", the slump and water seepage rate of fresh concrete are tested, and the slump value is used to characterize its self-compacting performance.

[0087] 4. According to the rapid chloride ion migration coefficient method in GB / T50082-2009 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete", the anti-oxygen ion penetration performance of the standard test block is tested.

[0088] Table 1. Experimental results

[0089]

[0090]

[0091] Experimental results analysis:

[0092] (1) It can be seen from Examples 1 to 11 and Comparative Examples 1 to 5 and Table 1 that the present application can achieve a balance between the anti-shrinkage performance and self-compacting performance of concrete by using modified spherical alumina and UEA expansion agent in synergy, so that the concrete can meet the use requirements of slump ≥ 230 mm while having a lower shrinkage rate.

[0093] The reason for the above phenomenon may be that UEA expansion agent can resist shrinkage stress and reduce shrinkage rate, but at the same time it will increase the viscosity of concrete slurry, reduce its fluidity and slump, and thus reduce the self-compacting performance of concrete. Modified spherical alumina can significantly compensate for the fluidity of slurry due to its good friction reduction properties. At the same time, the thermal conductivity of modified spherical alumina has the effect of reducing shrinkage stress, which can further reduce shrinkage rate.

[0094] (2) It can be seen from Example 1 and Examples 4 to 8 and Table 1 that the present application can effectively reduce the shrinkage rate of concrete by using steel fibers; and the use of modified steel fibers can further improve the concrete's resistance to chloride ion penetration. The reason may be that steel fibers and spherical alumina can synergistically form a multi-dimensional heat-conducting network in concrete, reduce the temperature difference between the inside and outside, and thus reduce the shrinkage phenomenon caused by temperature stress. After polymer modification with methyl orthosilicate and mercaptosilane coupling agent, a large number of mercapto groups are attached to the surface of the steel fibers, and form complexes with silver ions, which can then react with chloride ions that penetrate into the concrete to resist their penetration.

[0095] (3) Combining Example 1 and Examples 9 to 11 with Table 1, it can be seen that the present application can effectively reduce the shrinkage of concrete by replacing part of the cement (30 to 35%) with fly ash, but at the same time, the fluidity of the concrete slurry will also decrease. The present application effectively compensates for its fluidity by using sodium polyacrylate with a molecular weight of 1000 to 3000.

[0096] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed. However, as long as it is within the scope of the claims of the present application, it shall be protected by the patent law.

Claims

1. An underwater non-shrinkage concrete, characterized in that: The invention comprises the following raw materials in parts by weight: Cementitious material: 130-200 parts; Crushed stone: 450-650 parts; Sand: 300-500 parts; Water: 50-90 parts; Water reducing agent: 3-6 parts; UEA expansion agent: 2-4 parts; Modified spherical alumina: 15-30 parts; The modified spherical alumina is prepared by grafting and modifying spherical alumina and a modifier in anhydrous ethanol in a weight ratio of 100:(3-6); the modifier is prepared by using liquid isomeric tridecanol polyoxyethylene ether and dimethyldimethoxysilane in a molar ratio of 1:1 as raw materials and heating reaction under the catalysis of dodecylbenzenesulfonic acid; the temperature of the heating reaction is 70-80°C.

2. The underwater non-shrinkage concrete according to claim 1, characterized in that: The particle size of the spherical alumina is 100-300 μm.

3. The underwater non-shrinkage concrete according to claim 1, characterized in that: The cementitious material is cement and fly ash in a weight ratio of 65-70: (30-35).

4. The underwater non-shrinkage concrete according to claim 3, characterized in that: The raw materials of the concrete also include 2 to 5 parts of sodium polyacrylate with a molecular weight of 1000 to 3000.

5. The underwater non-shrinkage concrete according to claim 1, characterized in that: The raw materials of the concrete also include 20 to 40 parts of steel fibers.

6. The underwater non-shrinkage concrete according to claim 5, characterized in that: The steel fiber is modified according to the following method: Methyl orthosilicate and mercaptosilane coupling agent are dissolved in ethanol, and then a mixed solution of ethanol, water and glacial acetic acid in a weight ratio of 10 to 12:3 to 5:1 is added dropwise, heated to 50 to 60°C, and heated to 100 to 120°C after 0.5 to 1 hour to continue the reaction, and steel fiber and silver nitrate solution are added after 2 to 4 hours, and mixed evenly to obtain modified steel fiber; the steel fiber, methyl orthosilicate, mercaptosilane coupling agent are added dropwise to a mixed solution of ethanol, water and glacial acetic acid in a weight ratio of 10 to 12:3 to 5:1, and heated to 50 to 60°C, and heated to 100 to 120°C after 0.5 to 1 hour to continue the reaction, and steel fiber and silver nitrate solution are added after 2 to 4 hours, and mixed evenly to The weight ratio of silane coupling agent is 100: (0.5-1.5): (2-5).

7. The underwater non-shrinkage concrete according to claim 6, characterized in that: The molar ratio of the mercaptosilane coupling agent to the silver ions is 1:(1.5-2).

8. The method for preparing underwater non-shrinkage concrete according to any one of claims 1 to 7, characterized in that: The raw materials are mixed evenly according to the proportions.

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