Super slow-setting concrete and preparation method thereof

Abstract

The present application relates to the field of concrete, and specifically discloses a super-slow setting concrete and a preparation method thereof. A super-slow setting concrete, which includes 380-400 parts of cement, 700-800 parts of fine aggregate, 900-1000 parts of coarse aggregate, 60-80 parts of fly ash, 60-80 parts of mineral powder and 8-12 parts of admixtures in parts by weight, wherein the admixture includes sulfide-modified lignin; S1, cement, fine aggregate, coarse aggregate, mineral powder and fly ash are first mixed and stirred to obtain a mixture; S2, polyoxyethylene stearate is dissolved in 80% water and added to the mixture and stirred; S3, sulfide-modified lignin is evenly added to the mixture in 3-5 times and continuously stirred; S4, the remaining 20% ​​of water is added to the mixture 2-3 times and stirred to obtain super-slow setting concrete. The super-slow setting concrete of the present application can be used for occlusal piles, which has the advantages that the concrete strength cannot increase too fast in the early stage and can reach high strength in the later stage.

Description

Technical Field

[0001] The present invention relates to the field of concrete, and more particularly to a super slow-setting concrete and a preparation method thereof. Background Art

[0002] Snap piles are primarily used in civil engineering as a bearing method for deep foundation pits in large bridges, docks, large buildings, and other structures requiring support. Snap piles offer strong suction bearing capacity, wide adaptability, and easy construction. They are often used in building foundation treatment to increase stability and bearing capacity. In urban development, snap piles have become an important means of solving building foundation problems.

[0003] During the manufacturing process of a snap pile, a hole meeting the design specifications is first excavated using an underground drilling machine. Concrete is then poured into the hole. As the concrete begins to flow into the hole, due to its viscosity and initial solidification, friction is generated, allowing it to firmly bond to the inner wall of the hole.

[0004] However, if the concrete possesses high strength early in the pour, it will significantly hinder its flow and filling, potentially preventing the concrete from fully filling the hole, resulting in defects such as voids or cracks. Therefore, when pouring concrete for interlocking piles, it is desirable to maximize the initial setting and hardening time of the concrete to allow it to flow and fill the entire hole. Furthermore, over time, the concrete's strength gradually increases, ultimately reaching the design load-bearing capacity.

[0005] Taking these factors into account, certain measures are generally adopted when pouring concrete in interlocking piles, such as using a low water-cement ratio, a low fly ash content, or adding retarders and anti-cracking agents. These measures ensure that the concrete has good fluidity in the early stages while achieving sufficient strength in the later stages. This can overcome the negative impact of high early concrete strength, thereby ensuring the construction quality and structural stability of the interlocking piles. Summary of the Invention

[0006] In order to prevent the concrete strength from increasing too quickly in the early stage and to achieve high strength in the later stage, the present application provides a super-slow-setting concrete and a preparation method thereof.

[0007] In a first aspect, the present application provides a super-slow-setting concrete, which adopts the following technical solution:

[0008] A super slow-setting concrete comprises, by weight, 380-400 parts of cement, 700-800 parts of fine aggregate, 900-1000 parts of coarse aggregate, 60-80 parts of fly ash, 60-80 parts of mineral powder and 8-12 parts of an admixture, wherein the admixture comprises sulfurized modified lignin.

[0009] By adopting the above technical solution, low cement dosage and high fine aggregate and coarse aggregate dosage, concrete has lower strength in the early stage. Sulfurized modified lignin as an admixture can also slow down the setting time of concrete, so that concrete has better fluidity and filling properties, thereby avoiding local premature hardening due to uneven pouring and other reasons and affecting the overall strength of concrete. As the cement reaction proceeds and the sulfurized modified lignin plays a role, concrete gradually reaches sufficient strength and stability. In addition, the addition of micro-fillers such as fly ash and mineral powder into concrete can effectively densify the concrete structure, improve the density and durability of concrete, thereby improving the strength and long-term stability of concrete. In summary, the present application has the effect of preventing the concrete strength from increasing too fast in the early stage and achieving high strength in the later stage, and has the effect of improving the fluidity and density of concrete.

[0010] Optionally, the mixture comprises 390 parts of cement, 759 parts of fine aggregate, 951 parts of coarse aggregate, 70 parts of fly ash, 70 parts of mineral powder and 10.6 parts of admixture in parts by weight, wherein the admixture comprises sulfurized modified lignin.

[0011] By adopting the above technical solution and adjusting the dosage of each component, the super slow-setting concrete can achieve better results.

[0012] Optionally, the admixture further includes polyoxyethylene stearate, and the ratio of the sulfurized modified lignin to the polyoxyethylene stearate is 3:(1-2).

[0013] By adopting the above technical solution, polyoxyethylene stearate can improve the fluidity and crack resistance of concrete, and can coat cement particles and disperse the sulfide lignin in concrete, so that the sulfide lignin can better play a retarding role, so that the concrete strength does not increase too quickly in the early stage, and can achieve a high strength effect in the later stage.

[0014] Optionally, the fine aggregate is natural sand with a particle size of 0.5mm-0.25mm.

[0015] By adopting the above technical solution, the use of natural sand as a fine aggregate in concrete can increase the fluidity and plasticity of the concrete, while also helping to improve the concrete's compressive strength and durability. Selecting natural sand with a smaller particle size as a fine aggregate can achieve a better blending effect, making the concrete easier to construct, process, and pour, thereby avoiding potential defects such as voids and cracks.

[0016] Optionally, the coarse aggregate is 5-25 mm crushed stone.

[0017] By adopting the above technical solution and selecting 5-25mm crushed stone as coarse aggregate, the concrete structure can be kept tight while ensuring the fluidity of the concrete, thereby adapting to construction needs in different environments.

[0018] Optionally, the fly ash is secondary fly ash, and the mineral powder is S95 grade mineral powder.

[0019] By adopting this technical solution, secondary fly ash can replace a portion of cement, reducing concrete costs while also increasing concrete's fluidity, self-sustaining properties, and durability. Mineral powder, during the concrete manufacturing process, refines the concrete's particle structure, increasing its density and improving its strength.

[0020] In a second aspect, the present application provides a method for preparing super-slow-setting concrete, which adopts the following technical solution:

[0021] A method for preparing super slow-setting concrete comprises the following steps:

[0022] S1. First, add cement, fine aggregate, coarse aggregate, mineral powder and fly ash into a mixing pot and mix for 2 minutes;

[0023] S2. Dissolve polyoxyethylene stearate in 80% water and add to a stirring pot and begin stirring for 8-10 minutes;

[0024] S3, sulfurized modified lignin is added into the pot in 3-5 equal portions and stirred continuously;

[0025] S4. Add the remaining 20% ​​of water into the pot 2-3 times and continue stirring for 10-15 minutes to obtain super-slow concrete.

[0026] By adopting this technical solution, the introduction of sulfurized modified lignin regulates the setting reaction of concrete, enabling it to achieve a super-retarded setting effect, thus better adapting to various construction conditions and requirements. The addition of polyoxyethylene stearate improves the fluidity and plasticity of concrete, making it easier to construct. Furthermore, the appropriate addition of admixtures such as fly ash and mineral powder helps enhance the concrete's crack resistance.

[0027] Preferably, the preparation method of the sulfurized modified lignin is:

[0028] A1. Add 400 ml of ethanol to a 1 L graduated cylinder, then add 100 g of sodium hydroxide and shake well to obtain a pretreatment solution.

[0029] A2. Add 200g of lignin to the pre-treated solution, stir evenly, and heat to about 70-80°C, keeping the temperature constant;

[0030] A3. When the solution becomes clear and transparent, gradually add the crushed sulfiding agent and continue stirring to obtain a reaction solution;

[0031] A4. The reaction solution is filtered to remove impurities, heated, air-dried, and ground to obtain sulfur-modified lignin.

[0032] By adopting the above technical solution, the sulfurized modified lignin has excellent water solubility, can better combine with concrete raw materials such as cement, and will not precipitate in the concrete. The sulfurized modified lignin can improve the crack resistance, durability and compressive strength of concrete by regulating the cement reaction.

[0033] Preferably, the vulcanizing agent is selected from one of ferric sulfate and sodium thiosulfate, the usage amount of the ferric sulfate is 50-60 g / L, and the usage amount of the sodium thiosulfate is 30-40 g / L.

[0034] By adopting the above technical solution, the sulfiding agent is a chemical reagent that can synergistically react and promote the degradation and modification of lignin. Ferric sulfate and sodium thiosulfate can react with lignin at a certain temperature to form a more stable sulfided modified lignin.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. Since the present application adopts low cement dosage and high fine aggregate and coarse aggregate dosage, the concrete has lower strength in the early stage. Sulfurized modified lignin as an admixture can also slow down the setting time of concrete, so that the concrete has better fluidity and filling properties, thereby avoiding local premature hardening due to uneven pouring and other reasons that affect the overall strength of the concrete. As the cement reaction proceeds and the sulfurized modified lignin plays a role, the concrete will gradually reach sufficient strength and stability. In addition, the addition of micro-fillers such as fly ash and mineral powder into the concrete can effectively densify the concrete structure, improve the density and durability of the concrete, thereby improving the strength and long-term stability of the concrete. In summary, the present application has the effect of preventing the concrete strength from increasing too fast in the early stage and achieving high strength in the later stage, and has the effect of improving the fluidity and density of the concrete.

[0037] 2. In this application, polyoxyethylene stearate is preferably used to improve the fluidity and crack resistance of concrete, and can coat cement particles and disperse the sulfide lignin in concrete, so that the sulfide lignin can better play a retarding role, so that the concrete strength does not increase too fast in the early stage, and can achieve high strength in the later stage.

[0038] 3. The method of this application, by introducing sulfurized modified lignin to regulate the setting reaction of concrete, achieves a super-retarded setting effect, thereby better adapting to various construction conditions and requirements. The addition of polyoxyethylene stearate improves the fluidity and plasticity of the concrete, making it easier to construct. Furthermore, the appropriate addition of admixtures such as fly ash and mineral powder helps enhance the concrete's crack resistance. DETAILED DESCRIPTION

[0039] The present application is further described in detail below with reference to the embodiments.

[0040] Preparation example of sulfurized modified lignin

[0041] Preparation Example 1

[0042] The preparation method of sulfurized modified lignin is:

[0043] A1. Add 400 ml of ethanol to a 1 L graduated cylinder, then add 100 g of sodium hydroxide and shake well to obtain a pretreatment solution.

[0044] A2. Add 200g of lignin to the pre-treated solution, stir evenly, and heat to about 75°C and keep the temperature constant;

[0045] A3. When the solution becomes clear and transparent, gradually add the crushed sulfiding agent and continue stirring to obtain a reaction solution. A4. Filter the reaction solution to remove impurities, heat, air-dry, and grind to obtain sulfurized modified lignin.

[0046] Among them, the vulcanizing agent is ferric sulfate, and its usage amount is 55g / L.

[0047] Preparation Example 2

[0048] Preparation method of sulfurized modified lignin: The difference from Preparation Example 1 is that sodium thiosulfate is used as the sulfurizing agent, and its usage is 35g / L

[0049] Example

[0050] Example 1

[0051] A method for preparing super slow-setting concrete comprises the following steps:

[0052] S1. First, add 3800g cement, 7000g fine aggregate, 9000g coarse aggregate, 600g mineral powder, and 600g fly ash into a mixing pot and mix for 2 minutes;

[0053] S2, 80% water was added to the stirring pot and stirred for 10 minutes;

[0054] S3, 80g of sulfurized modified lignin were added into the pot in three equal portions and stirred continuously;

[0055] S4. The remaining 20% ​​of water was added into the pot three times and stirred continuously for 15 minutes to obtain super-retarded concrete.

[0056] Among them, the fine aggregate is natural sand with a particle size of 0.35 mm, the coarse aggregate is crushed stone with a particle size of 15 mm, the fly ash is secondary fly ash, and the mineral powder is S95 grade mineral powder; the sulfurized modified lignin is prepared by Preparation Example 1.

[0057] Example 2

[0058] A method for preparing super slow-setting concrete comprises the following steps:

[0059] S1. First, add 4000g cement, 8000g fine aggregate, 10000g coarse aggregate, 800g mineral powder, and 800g fly ash into a mixing pot and mix for 2 minutes;

[0060] S2. Add 80% water into the stirring pot and start stirring for 10 minutes;

[0061] S3, 120g of sulfurized modified lignin was added into the pot in three equal portions and stirred continuously;

[0062] S4. The remaining 20% ​​of water was added into the pot three times and stirred continuously for 15 minutes to obtain super-retarded concrete.

[0063] Among them, the fine aggregate is natural sand with a particle size of 0.35 mm, the coarse aggregate is crushed stone with a particle size of 15 mm, the fly ash is secondary fly ash, and the mineral powder is S95 grade mineral powder; the sulfurized modified lignin is prepared by Preparation Example 1.

[0064] Example 3

[0065] A method for preparing super slow-setting concrete comprises the following steps:

[0066] S1. First, add 3900g cement, 7590g fine aggregate, 9510g coarse aggregate, 700g mineral powder, and 700g fly ash into a mixing pot and mix for 2 minutes;

[0067] S2. Add 80% water into the stirring pot and start stirring for 10 minutes;

[0068] S3, 106g of sulfurized modified lignin were added into the pot in three equal portions and stirred continuously;

[0069] S4. The remaining 20% ​​of water was added into the pot three times and stirred continuously for 15 minutes to obtain super-retarded concrete.

[0070] Among them, the fine aggregate is natural sand with a particle size of 0.35 mm, the coarse aggregate is crushed stone with a particle size of 15 mm, the fly ash is secondary fly ash, and the mineral powder is S95 grade mineral powder; the sulfurized modified lignin is prepared by Preparation Example 1.

[0071] Example 4

[0072] A method for preparing super slow-setting concrete comprises the following steps:

[0073] S1. First, add 3900g cement, 7590g fine aggregate, 9510g coarse aggregate, 700g mineral powder, and 700g fly ash into a mixing pot and mix for 2 minutes;

[0074] S2, 26.5g polyoxyethylene stearate dissolved in 80% water, added to the stirring pot and stirred for 10 minutes;

[0075] S3, 79.5g of sulfurized modified lignin were added into the pot in three equal portions and stirred continuously;

[0076] S4. The remaining 20% ​​of water was added into the pot three times and stirred continuously for 15 minutes to obtain super-retarded concrete.

[0077] Among them, the fine aggregate is natural sand with a particle size of 0.35 mm, the coarse aggregate is crushed stone with a particle size of 15 mm, the fly ash is secondary fly ash, and the mineral powder is S95 grade mineral powder; the sulfurized modified lignin is prepared by Preparation Example 1.

[0078] Example 5

[0079] A method for preparing super slow-setting concrete comprises the following steps:

[0080] S1. First, add 3900g cement, 7590g fine aggregate, 9510g coarse aggregate, 700g mineral powder, and 700g fly ash into a mixing pot and mix for 2 minutes;

[0081] S2, 42.4g polyoxyethylene stearate dissolved in 80% water, added to the stirring pot and stirred for 10 minutes;

[0082] S3, 63.6 g of sulfurized modified lignin were added into the pot in three equal portions and stirred continuously;

[0083] S4. The remaining 20% ​​of water was added into the pot three times and stirred continuously for 15 minutes to obtain super-retarded concrete.

[0084] Among them, the fine aggregate is natural sand with a particle size of 0.35 mm, the coarse aggregate is crushed stone with a particle size of 15 mm, the fly ash is secondary fly ash, and the mineral powder is S95 grade mineral powder; the sulfurized modified lignin is prepared by Preparation Example 1.

[0085] Example 6

[0086] A method for preparing super-slow-setting concrete, which differs from Example 4 in that the sulfurized modified lignin is prepared by Preparation Example 2.

[0087] Example 7

[0088] A method for preparing super-slow-setting concrete, which differs from Example 4 in that: natural sand with a particle size of 0.25 mm is selected as fine aggregate.

[0089] Example 8

[0090] A method for preparing super-slow-setting concrete, which differs from Example 4 in that: natural sand with a particle size of 0.5 mm is used as fine aggregate.

[0091] Example 9

[0092] A method for preparing super-slow-setting concrete, which differs from Example 4 in that 5 mm crushed stone is used as coarse aggregate.

[0093] Example 10

[0094] A method for preparing super-slow-setting concrete, which differs from Example 4 in that 25 mm crushed stone is used as coarse aggregate.

[0095] Comparative Example

[0096] Comparative Example 1

[0097] A method for preparing super slow-setting concrete comprises the following steps:

[0098] S1. First, add 3900g cement, 7590g fine aggregate, 9510g coarse aggregate, 700g mineral powder, and 700g fly ash into a mixing pot and mix for 2 minutes;

[0099] S2, 26.5g polyoxyethylene stearate dissolved in 80% water, added to the stirring pot and stirred for 10 minutes;

[0100] S3, 79.5g lignin were added into the pot in three equal portions and stirred continuously;

[0101] S4. The remaining 20% ​​of water was added into the pot three times and stirred continuously for 15 minutes to obtain super-retarded concrete.

[0102] Among them, the fine aggregate is natural sand with a particle size of 0.35mm, the coarse aggregate is 15mm crushed stone, the fly ash is secondary fly ash, and the mineral powder is S95 grade mineral powder.

[0103] Comparative Example 2

[0104] A method for preparing super slow-setting concrete comprises the following steps:

[0105] S1. First, add 3900g cement, 7590g fine aggregate, 9510g coarse aggregate, 700g mineral powder, and 700g fly ash into a mixing pot and mix for 2 minutes;

[0106] S2, 26.5g polyoxyethylene stearate dissolved in 80% water, added to the stirring pot and stirred for 10 minutes;

[0107] S3. The remaining 20% ​​of water was added into the pot three times and stirred continuously for 15 minutes to obtain super-slow concrete.

[0108] Among them, the fine aggregate is natural sand with a particle size of 0.35mm, the coarse aggregate is 15mm crushed stone, the fly ash is secondary fly ash, and the mineral powder is S95 grade mineral powder.

[0109] Comparative Example 3

[0110] A method for preparing super slow-setting concrete comprises the following steps:

[0111] S1. First, add 3900g cement, 7590g fine aggregate, 9510g coarse aggregate, 700g mineral powder, and 700g fly ash into a mixing pot and mix for 2 minutes;

[0112] S2. Add 80% water into the stirring pot and start stirring for 10 minutes;

[0113] S3. The remaining 20% ​​of water was added into the pot three times and stirred continuously for 15 minutes to obtain super-slow concrete.

[0114] Among them, the fine aggregate is natural sand with a particle size of 0.35mm, the coarse aggregate is 15mm crushed stone, the fly ash is secondary fly ash, and the mineral powder is S95 grade mineral powder.

[0115] Performance testing

[0116] Detection method

[0117] Concrete test blocks of Examples 1-10 and Comparative Examples 1-3 were made into concrete test blocks and cured for 7 days and 28 days, and then subjected to appearance inspection and mechanical inspection respectively.

[0118] The test data statistics are as follows:

[0119] Table 1 Experimental data of Examples 1-10 and Comparative Examples 1-3

[0120]

[0121]

[0122] Combining Example 4 and Comparative Example 1 with Table 1, it can be seen that after the vulcanization treatment, the benzene ring multiple units on the lignin molecules are chemically cross-linked to form vulcanized modified lignin, which increases the cement reaction rate by promoting contact between cement particles and water. At the same time, it can also inhibit the formation of voids inside the concrete, thereby delaying the setting time of the concrete. The vulcanized lignin also has the characteristics of an oxidant and can participate in the oxidation reaction in the concrete, promoting the improvement of the later strength. Compared with Comparative Example 1, Example 4 has lower initial strength and better fluidity of the concrete, and higher strength and density of the concrete in the later stage.

[0123] Combining Example 4 and Comparative Example 2 with Table 1, it can be seen that when only polyoxyethylene stearate is added, polyoxyethylene stearate can combine with the free calcium ions in the cement to form a stable compound, thereby reducing the adsorption and promotion of calcium ions on the cement paste and delaying the gel time. Although it can play a certain coagulation role, it is significantly different from the effect of compounding the sulfurized modified lignin and polyoxyethylene stearate in Example 4. In Example 4, the concrete has lower strength in the early stage and better fluidity, and the concrete strength and density are higher in the later stage.

[0124] Combining Example 4 and Comparative Example 3 with Table 1, it can be seen that Comparative Example 3 does not add sulfurized modified lignin and polyoxyethylene stearate, and does not achieve a good retarding effect. This proves that the combination of sulfurized modified lignin and polyoxyethylene stearate is the reason why Example 4 achieves an excellent retarding effect. The sulfurized modified lignin and polyoxyethylene stearate make the concrete have low initial strength and good fluidity, and the concrete has higher strength and density in the later stage.

[0125] From Examples 1-3 and Table 1, it can be seen that by adjusting the ratio of the components in the ultra-slow setting concrete, different effects can be achieved. Low cement content and high fine aggregate and coarse aggregate content result in lower strength of the concrete at an early stage. Sulfurized modified lignin as an admixture can also slow down the setting time of the concrete, making the concrete have better fluidity and filling properties. The addition of micro-fillers such as fly ash and mineral powder to the concrete can effectively densify the concrete structure and improve the density and durability of the concrete.

[0126] In combination with Examples 3-4 and Table 1, it can be seen that compared with the addition of sulfurized modified lignin alone, the sulfurized modified lignin and polyoxyethylene stearate are compounded in Example 4. Polyoxyethylene stearate can improve the fluidity and crack resistance of concrete, and can coat cement particles and disperse the sulfurized lignin in concrete, so that the sulfurized lignin can better play a retarding effect. The sulfurized modified lignin and polyoxyethylene stearate make the concrete have low initial strength and good fluidity, and the concrete has higher strength and density in the later stage.

[0127] It can be seen from Example 4 and Example 6 and Table 1 that by using different vulcanizing agents, the sulfurized modified lignin can achieve better effects and form more stable sulfurized modified lignin.

[0128] It can be seen from Examples 4-5 and Table 1 that the retarding effect can be better exerted by changing the ratio of sulfurized modified lignin to polyoxyethylene stearate, among which the ratio of Example 4 is more optimal.

[0129] It can be seen from Example 4 and Examples 6-10 and Table 1 that adjusting the size of coarse aggregate and fine aggregate can increase the fluidity and plasticity of concrete, and also help improve the compressive strength and durability of concrete.

[0130] 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 non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A super slow concrete, characterized in that: The invention relates to a composite material comprising 380-400 parts by weight of cement, 700-800 parts by weight of fine aggregate, 900-1000 parts by weight of coarse aggregate, 60-80 parts by weight of fly ash, 60-80 parts by weight of mineral powder, and 8-12 parts by weight of an admixture, wherein the admixture comprises sulfurized modified lignin, and the admixture further comprises polyoxyethylene stearate, and the ratio of the sulfurized modified lignin to the polyoxyethylene stearate is 3:(1-2). The preparation method of the sulfurized modified lignin is as follows: A1. Add 400 ml of ethanol to a 1 L graduated cylinder, then add 100 g of sodium hydroxide and shake well to obtain a pretreatment solution. A2. Add 200g of lignin to the pre-treated solution, stir evenly, and heat to 70-80°C and keep the temperature constant; A3. When the solution becomes clear and transparent, gradually add the crushed sulfiding agent and continue stirring to obtain a reaction solution; A4, filtering the reaction solution to remove impurities, heating, air-drying and grinding to obtain sulfur-modified lignin; The vulcanizing agent is selected from one of ferric sulfate and sodium thiosulfate. The usage amount of the ferric sulfate is 50-60 g / L, and the usage amount of the sodium thiosulfate is 30-40 g / L.

2. The ultra-slow concrete according to claim 1, characterized in that: The invention comprises 390 parts of cement, 759 parts of fine aggregate, 951 parts of coarse aggregate, 70 parts of fly ash, 70 parts of mineral powder and 10.6 parts of admixture in parts by weight, wherein the admixture comprises sulfurized modified lignin.

3. The ultra-slow concrete according to claim 1, characterized in that: The fine aggregate is natural sand with a particle size of 0.25mm-0.5mm.

4. The ultra-slow concrete according to claim 1, characterized in that: The coarse aggregate is crushed stone with a diameter of 5-25 mm.

5. The ultra-slow concrete according to claim 1, characterized in that: The fly ash is selected from secondary fly ash, and the mineral powder is selected from S95 grade mineral powder.

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