A method of mass concrete construction
By using low-heat-of-hydration, low-shrinkage, and high-durability concrete and temperature control technology, the problem of shrinkage cracking in large-volume concrete construction across seasons has been solved, achieving efficient construction and durability of concrete.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA WEST CONSTR GRP
- Filing Date
- 2023-08-21
- Publication Date
- 2026-06-23
AI Technical Summary
In the construction of large-volume concrete, the heat of hydration and shrinkage caused by cross-seasonal construction are significant, which can easily lead to shrinkage cracking. In particular, it is difficult to effectively control the temperature difference in the high temperature of summer and the cold temperature of winter.
Low-heat-of-hydration, low-shrinkage, and high-durability concrete is used as the construction substrate. Temperature differences are regulated during transportation, pouring, and curing by temperature control. Reflective insulation materials and hot water pipe lubrication technology are used to control the temperature difference between the inside and outside of the concrete. Modified almond shell powder-starch composite powder and composite capsules are added to alleviate heat of hydration and shrinkage deformation.
It effectively reduces the heat of hydration and shrinkage deformation of concrete, reduces the risk of cracking, improves the tensile strength and crack resistance of concrete, and ensures construction performance and no cracks after hardening.
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Abstract
Description
Technical Field
[0001] This application relates to the field of concrete construction technology, and more specifically, to a method for constructing large-volume concrete. Background Technology
[0002] With the rapid development of society and economy, my country's civil engineering construction is developing at an increasingly fast pace. Large-volume concrete has been widely used in hydraulic structures, such as dams, ports, and wharves. In recent years, large-volume concrete has been increasingly applied to the field of building construction, such as large equipment foundations in industrial buildings, monolithic foundations for high-rise civil buildings, box foundation slabs, pile caps, and raft foundations. The foundation volume of general large industrial and civil buildings can reach several thousand cubic meters, while the concrete volume of some large equipment foundations and raft foundations for super high-rise civil buildings can reach tens of thousands of cubic meters, with a thickness of over 2 meters and a length exceeding 100 meters. The scale of large-volume concrete projects is expanding daily, and the structural forms are becoming increasingly complex.
[0003] This also means that the construction of large-volume concrete often spans from summer to winter. This leads to several problems associated with cross-seasonal construction of large-volume concrete: firstly, the large volume of concrete results in significant heat of hydration and substantial shrinkage; secondly, the significant environmental differences between the high temperatures of summer and the cold temperatures of winter make the concrete prone to shrinkage cracking. Controlling the temperature and maintaining the performance of the concrete are major challenges. Therefore, it is crucial to study and manage cross-seasonal construction of large-volume concrete to reduce the risk of shrinkage cracking. Summary of the Invention
[0004] To reduce the risk of concrete shrinkage cracking, this application provides a method for constructing large-volume concrete.
[0005] This application provides a method for constructing large-volume concrete using the following technical solution:
[0006] A method for constructing large-volume concrete includes the following steps:
[0007] S1. Prepare large-volume concrete with low heat of hydration, low shrinkage, and high durability.
[0008] S2. Concrete transportation, pouring, and vibration. When pouring concrete, in winter construction, the pipe should be lubricated with hot water and mortar with a temperature not lower than 15℃ before pumping. In summer construction, the concrete pumping pipe should be wrapped with reflective insulation material to keep the temperature difference between the inside and outside of the pump pipe between 1-1.5℃.
[0009] The temperature of large-volume concrete placed in the formwork should be controlled to be less than 30°C in high-temperature summer environments and higher than 10°C in cold winter environments.
[0010] S3. Concrete curing: During the concrete curing process, the temperature difference between the center and surface of the concrete should not exceed 25℃ during summer curing. If the temperature difference between the center and surface of the concrete is too large or the temperature difference between the inside and outside exceeds 25℃ during summer construction, cover it with insulation material. If the temperature difference between the inside and outside of the concrete does not decrease after 24 hours, continue to add more insulation material until the temperature difference is less than 25℃.
[0011] By adopting the above technical solutions, this application first uses low-heat-of-hydration, low-shrinkage, and high-durability mass concrete as the construction substrate, reducing the heat of hydration and shrinkage deformation of mass concrete, thereby reducing the risk of concrete shrinkage cracking. Through research on temperature control throughout the entire process of concrete transportation, pouring, and curing, the temperature of mass concrete entering the formwork is less than 30℃ in the high-temperature environment of summer and higher than 10℃ in the cold environment of winter. This allows for timely monitoring of the internal and external temperature differences and temperature stress of the concrete, thus better controlling the internal and external temperature differences of the concrete during the curing stage to not exceed 25℃, ultimately resulting in a significant improvement in concrete cracking. During the pouring process, reflective insulation material is wrapped around the concrete pumping pipes to effectively reduce the impact of ambient temperature on the concrete during pumping. In winter construction, hot water and mortar are used to lubricate the pump pipes and increase their temperature, reducing temperature loss during pumping of concrete under cold conditions and ensuring the workability and entry temperature of the concrete. During concrete curing, the temperature difference between the center and surface of the concrete is controlled to reduce the internal and external temperature difference of the mass concrete block, preventing cracking caused by temperature pressure due to excessive temperature difference. Ultimately, by controlling the temperature conditions from transportation to curing during the construction of large-volume concrete, the phenomenon of surface cracking after the concrete has hardened can be greatly alleviated.
[0012] Optionally, in step S1, mixing water is added to the raw materials when preparing low-heat-of-hydration, low-shrinkage, durable mass concrete, and the mixing water is added after cooling. Specifically,
[0013] When the highest ambient temperature is between 30℃ and 35℃, add ice cubes to the mixing water. When the highest ambient temperature is above 35℃, in addition to using the ice cubes normally, add urea and dry ice to the mixing water to make the temperature of the mixing water below 15℃.
[0014] By adopting the above technical solutions, and by controlling the temperature of the raw materials for large-volume concrete, combined with temperature control during transportation and pouring, the requirement for regulating the temperature of large-volume concrete when it is poured into the formwork during the high temperatures of summer can be finally achieved.
[0015] Optionally, in step S1, when preparing low-heat-of-hydration, low-shrinkage, high-durability mass concrete, it is prepared from raw materials comprising the following parts by weight:
[0016] 100-150 parts low-heat cement, 150-230 parts fly ash, 230-340 parts mineral powder, 1800-2000 parts coarse aggregate, 1000-1300 parts fine aggregate, 1-3 parts water-reducing agent, 80-120 parts modified almond shell powder-starch composite powder, 20-35 parts composite capsules, 10-15 parts n-hexyl acrylate, and 120-150 parts mixing water;
[0017] The composite capsule is made with acryloyl chloride, boron nitride, acrylamide and an initiator as core materials.
[0018] By adopting the above technical solutions, this application adds low-heat cement to reduce its heat of hydration, and also adds fly ash and mineral powder to replace part of the cement. Fly ash has low water requirement, and mineral powder has high activity, reducing cement usage, reducing carbon dioxide emissions, and also reducing the heat of hydration of cement, thus resulting in low carbon, low heat of hydration, and low shrinkage. In addition, this application adds modified almond shell powder-starch composite powder. Almond shells have high surface hardness, and combined with starch, they have certain water absorption and expansion properties. On the one hand, this can alleviate the bleeding phenomenon of cement hardening, thereby improving the early strength and elastic modulus of concrete and alleviating subsequent cracking. On the other hand, its water absorption and expansion can also reduce the heat of hydration of cement, reduce the internal and external temperature difference formed during hydration, and reduce the temperature difference between the core temperature and the surface temperature of concrete, thus reducing shrinkage and cracking. The almond shells are added in powder form to enhance the density and tensile strength of concrete, further reducing shrinkage deformation.
[0019] In addition, this application also adds a composite capsule with beneficial acryloyl chloride, boron nitride, acrylamide, and an initiator as the core material. When the composite capsule comes into contact with water, it releases the core material. Acryloyl chloride in the core material dissolves in water to form carboxylic acid. Carboxylic acid can reduce the cement hydration rate, thereby reducing the heat of hydration of concrete and playing a role in reducing shrinkage and heat of hydration. Moreover, acryloyl chloride reacts with hydroxyl-containing starch and almond shell powder to generate acrylate, which then undergoes free radical polymerization with n-hexyl acrylate under the action of an initiator to form a macromolecular network structure, thereby further improving the tensile strength of concrete and its crack resistance, alleviating cracking problems. The addition of boron nitride particles plays an excellent role in thermal conductivity, enabling timely heat conduction and alleviating the large temperature difference between the inside and outside caused by the slow dissipation of heat of hydration, which leads to a greater internal heating rate than the surface. This further improves its crack resistance, ultimately resulting in low heat of hydration, low shrinkage, and high durability concrete. No cracks appear on the surface of the hardened concrete, reducing the risk of shrinkage cracking.
[0020] Optionally, the composite capsule uses ethyl cellulose and hydroxypropyl methyl cellulose in a mass ratio of 1:(1.2-1.5) as coating materials.
[0021] By adopting the above technical solution, when the coating of the composite capsule is made of ethyl cellulose and hydroxypropyl methylcellulose, hydroxypropyl methylcellulose is easily soluble in water and dissolves in water when the composite capsule is added, releasing the core material. At the same time, ethyl cellulose is insoluble in water. By controlling the ratio of the two, a sustained-release effect is achieved.
[0022] Optionally, the mass ratio of acryloyl chloride, boron nitride and acrylamide is 1:(1-1.2):(0.5-0.8), and the amount of initiator added is 0.3-0.5 wt% of acryloyl chloride.
[0023] Optionally, the modified almond shell powder-starch composite powder is prepared by the following method:
[0024] Almond shells are crushed and ground to obtain almond shell powder. Then, almond shell powder and starch are mixed to obtain a mixed powder. The mixed powder is heated under anaerobic conditions at 220-250℃ for 1-2 hours. After cooling, it is soaked in phosphoric acid solution, washed with water, and dried to obtain modified almond shell powder-starch composite powder.
[0025] By adopting the above technical solution, almond shell powder and starch are mixed and then semi-carbonized under specific conditions, and then activated by soaking in phosphoric acid solution to obtain a composite powder with a porous structure, which has better water absorption and release properties, thereby reducing the probability of concrete shrinkage cracks.
[0026] Optionally, the mass ratio of almond shell powder to starch is 1:(0.6-0.8).
[0027] By adopting the above technical solution, almond shell powder can make use of almond shell waste. Moreover, by compounding with less starch with a porous structure for modification, the resulting composite powder has better water absorption and release properties.
[0028] Optionally, the preparation of low-heat-of-hydration, low-shrinkage, and high-durability mass concrete in step S1 includes the following steps:
[0029] Half of the low-heat cement, mineral powder, fly ash, coarse aggregate, fine aggregate, and modified almond shell powder-starch composite powder are mixed to obtain the first mixture;
[0030] The water-reducing agent and mixing water are mixed, then the first mixture is added, followed by n-hexyl acrylate and composite capsules. The mixture is stirred, and then the remaining low-heat cement is added to obtain low-heat hydration, low-shrinkage, and high-durability mass concrete.
[0031] By adopting the above technical solution, the preparation method of this application is simple and convenient, and easy to industrialize. Moreover, by adding low-heat cement in two stages, its heat of hydration is further reduced.
[0032] Optionally, 3-5 parts by weight of FEA expanding agent may be added when fly ash is added.
[0033] By adopting the above technical solution, the addition of FEA expansion agent helps to compensate for shrinkage, reduce shrinkage value, and improve crack resistance.
[0034] Optionally, the low-heat cement is P.LH42.5 low-heat cement;
[0035] The fly ash used is Class I, Grade F fly ash;
[0036] The coarse aggregate is selected from crushed stone with a continuous gradation of 5-40mm;
[0037] The fine aggregate is sand with a fineness modulus of 2.5-3.0;
[0038] The water-reducing agent used is a high-performance polycarboxylate water-reducing agent.
[0039] In summary, this application has the following beneficial effects:
[0040] 1. This application first uses low-heat-of-hydration, low-shrinkage, and high-durability mass concrete as the construction substrate to reduce the heat of hydration and shrinkage deformation of mass concrete, thereby reducing the risk of concrete shrinkage cracking; through research on temperature control throughout the entire process of concrete transportation, pouring, and curing, it has been achieved that the temperature of mass concrete entering the formwork is less than 30℃ in the high-temperature environment of summer and higher than 10℃ in the cold environment of winter, so as to timely grasp the temperature difference and temperature stress between the inside and outside of the concrete, thereby better controlling the temperature difference between the inside and outside of the concrete during the curing stage to not exceed 25℃, and finally greatly improving the phenomenon of concrete cracking.
[0041] 2. In this application, reflective insulation material is wrapped around the concrete pumping pipeline during the pouring process, effectively reducing the impact of ambient temperature on the concrete during pumping. In winter construction, hot water and mortar are used to lubricate the pump pipes and increase their temperature, reducing temperature loss during pumping in cold conditions and ensuring the concrete's workability and placement temperature. During concrete curing, the temperature difference between the center and surface of the concrete is controlled to reduce the internal and external temperature difference of large-volume concrete blocks, preventing cracking caused by excessive temperature stress. Ultimately, by controlling the temperature conditions from transportation to curing of large-volume concrete, the phenomenon of surface cracking after concrete hardening is greatly alleviated.
[0042] 3. The low heat of hydration, low shrinkage, and high durability mass concrete raw material of this application contains modified almond shell powder-starch composite powder. Almond shells have high surface hardness, and when combined with starch, they have certain water absorption and expansion properties. On the one hand, this can alleviate the bleeding phenomenon of cement hardening, thereby improving the early strength and elastic modulus of concrete and alleviating subsequent cracking. On the other hand, its water absorption and expansion can also reduce the heat of cement hydration, reduce the internal and external temperature difference formed during hydration, and reduce the temperature difference between the core temperature and the surface temperature of the concrete, thereby reducing shrinkage and cracking. The almond shells are added in powder form to enhance the density and tensile strength of the concrete, further reducing shrinkage deformation.
[0043] 4. The low heat of hydration, low shrinkage, and high durability mass concrete raw material of this application incorporates a composite capsule with beneficial acryloyl chloride, boron nitride, acrylamide, and an initiator as the core material. Upon contact with water, the composite capsule releases the core material. The acryloyl chloride in the core material dissolves in water to form a carboxylic acid. This carboxylic acid can reduce the cement hydration rate, thereby reducing the heat of hydration in the concrete, thus reducing shrinkage and heat of hydration. Furthermore, the acryloyl chloride reacts with hydroxyl-containing starch and almond shell powder to generate acrylate, which then undergoes free radical polymerization with n-hexyl acrylate under the action of an initiator to form a macromolecular network structure, further improving the tensile strength and crack resistance of the concrete, alleviating cracking problems. The addition of boron nitride particles provides excellent thermal conductivity, enabling timely heat conduction and mitigating the large internal and external temperature difference caused by the slow dissipation of heat of hydration leading to a greater internal heating rate than the surface, further improving crack resistance. Ultimately, this results in low heat of hydration, low shrinkage, and high durability concrete. After hardening, no cracks appear on the surface of the concrete, reducing the risk of shrinkage cracking. Detailed Implementation
[0044] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.
[0045] In the following preparation examples and embodiments, P.LH42.5 low-heat cement was selected;
[0046] The fly ash selected is Class I, Grade F fly ash;
[0047] The water-reducing agent selected is the retarded PCA-1 polycarboxylate high-performance water-reducing agent;
[0048] The coarse aggregate is crushed stone, and the crushed stone is selected from small stone and medium stone with a mass ratio of 1:0.8. The continuous gradation of small stone is 5-20mm, and the continuous gradation of medium stone is 20-40mm.
[0049] The fine aggregate should be sand with a fineness modulus of 2.5-3.0.
[0050] The following preparation examples are for compound capsules.
[0051] Preparation Example 1
[0052] A method for preparing a compound capsule includes the following steps:
[0053] Core material preparation: Acryloyl chloride is dissolved in water, then boron nitride, acrylamide, and sodium persulfate initiator are added, mixed and stirred, granulated, and dried to obtain core material particles;
[0054] The mass ratio of acryloyl chloride to water is 2:4, the mass ratio of acryloyl chloride, boron nitride, and acrylamide added is 1:1.1:0.6, and the amount of initiator added is 0.4 wt% of acryloyl chloride.
[0055] Coating: An ethyl cellulose solution was prepared by dissolving ethyl cellulose in anhydrous ethanol at a mass ratio of 1:2. Hydroxypropyl methylcellulose was then added to the ethyl cellulose solution to obtain a coating solution at a mass ratio of 1:1.3. The total mass ratio of ethyl cellulose and hydroxypropyl methylcellulose to the core material particles was 50:50. The coating solution was then sprayed onto the surface of the prepared core material particles and dried to obtain a composite capsule.
[0056] Preparation Example 2
[0057] A method for preparing a compound capsule includes the following steps:
[0058] Core material preparation: Acryloyl chloride is dissolved in water, then boron nitride, acrylamide, and sodium persulfate initiator are added, mixed and stirred, granulated, and dried to obtain core material particles;
[0059] The mass ratio of acryloyl chloride to water is 2:3, the mass ratio of acryloyl chloride, boron nitride, and acrylamide added is 1:1:0.5, and the amount of initiator added is 0.3 wt% of acryloyl chloride.
[0060] Coating: An ethyl cellulose solution was prepared by dissolving ethyl cellulose in anhydrous ethanol at a mass ratio of 1:1.5. Hydroxypropyl methylcellulose was then added to the ethyl cellulose solution to obtain a coating solution at a mass ratio of 1:1.2. The total mass ratio of ethyl cellulose to hydroxypropyl methylcellulose to the core material particles was 40:60. The coating solution was then sprayed onto the surface of the prepared core material particles and dried to obtain a composite capsule.
[0061] Preparation Example 3
[0062] A method for preparing a compound capsule includes the following steps:
[0063] Core material preparation: Acryloyl chloride is dissolved in water, then boron nitride, acrylamide, and sodium persulfate initiator are added, mixed and stirred, granulated, and dried to obtain core material particles;
[0064] The mass ratio of acryloyl chloride to water is 2:5, the mass ratio of acryloyl chloride, boron nitride, and acrylamide added is 1:1.2:0.8, and the amount of initiator added is 0.5 wt% of acryloyl chloride.
[0065] Coating: An ethyl cellulose solution was prepared by dissolving ethyl cellulose in anhydrous ethanol at a mass ratio of 1:2.5. Hydroxypropyl methylcellulose was then added to the ethyl cellulose solution to obtain a coating solution at a mass ratio of 1:1.5. The total mass ratio of ethyl cellulose to hydroxypropyl methylcellulose to the core material particles was 60:40. The coating solution was then sprayed onto the surface of the prepared core material particles and dried to obtain a composite capsule.
[0066] Preparation Example 4
[0067] A method for preparing a composite capsule is carried out according to the method in Preparation Example 1, except that in the coating step, ethyl cellulose is not added, and only hydroxypropyl methylcellulose is used as the coating material, with a mass ratio of hydroxypropyl methylcellulose to core material particles of 50:50.
[0068] Comparative Preparation Example 1
[0069] A method for preparing a composite capsule is carried out according to the method in Preparation Example 1, except that boron nitride is not added to the raw materials.
[0070] Comparative Preparation Example 2
[0071] A method for preparing a composite capsule is carried out according to the method in Preparation Example 1, except that no initiator is added to the raw materials.
[0072] Comparative preparation example 3
[0073] A method for preparing a composite capsule is carried out according to the method in Preparation Example 1, except that acryloyl chloride is not added to the raw materials.
[0074] Example 1
[0075] A method for preparing large-volume concrete with low heat of hydration, low shrinkage, and high durability includes the following steps:
[0076] Half of 120kg low-heat cement, 280kg mineral powder, 190kg fly ash, 4kg FEA expansion agent, 1900kg coarse aggregate, 1150kg fine aggregate and 100kg modified almond shell powder-starch composite powder are mixed to obtain the first mixture.
[0077] The modified almond shell powder-starch composite powder is prepared by the following method:
[0078] Almond shells are crushed and ground to obtain almond shell powder of 800-1000 mesh. Then, almond shell powder and starch are mixed at a mass ratio of 1:0.7 to obtain mixed powder. The mixed powder is heated at 240℃ for 1.5 hours under anaerobic conditions. After cooling, it is soaked in 35wt% phosphoric acid solution, washed with water, and dried to obtain modified almond shell powder-starch composite powder.
[0079] Mix 2 kg of water-reducing agent and 130 kg of mixing water, then add the first mixture, 12 kg of n-hexyl acrylate and 25 kg of the composite capsules prepared in Preparation Example 1, stir, and then add the remaining low-heat cement to obtain low-heat hydration, low-shrinkage, and high-durability large-volume concrete.
[0080] Example 2
[0081] A method for preparing large-volume concrete with low heat of hydration, low shrinkage, and high durability includes the following steps:
[0082] Half of 100kg low-heat cement, 230kg mineral powder, 150kg fly ash, 3kg FEA expansion agent, 1800kg coarse aggregate, 1000kg fine aggregate, and 80kg modified almond shell powder-starch composite powder are mixed to obtain the first mixture.
[0083] The modified almond shell powder-starch composite powder is prepared by the following method:
[0084] Almond shells are crushed and ground to obtain almond shell powder of 800-1000 mesh. Then, almond shell powder and starch are mixed at a mass ratio of 1:0.6 to obtain mixed powder. The mixed powder is heated at 220℃ for 2 hours under anaerobic conditions. After cooling, it is soaked in 35wt% phosphoric acid solution, washed with water, and dried to obtain modified almond shell powder-starch composite powder.
[0085] Mix 1 kg of water-reducing agent with 120 kg of mixing water, then add the first mixture, 10 kg of n-hexyl acrylate and 20 kg of the composite capsules prepared in Preparation Example 2, stir, and then add the remaining low-heat cement to obtain low-heat hydration, low-shrinkage, and high-durability large-volume concrete.
[0086] Example 3
[0087] A method for preparing large-volume concrete with low heat of hydration, low shrinkage, and high durability includes the following steps:
[0088] Half of 150kg low-heat cement, 340kg mineral powder, 230kg fly ash, 5kg FEA expansion agent, 2000kg coarse aggregate, 1300kg fine aggregate and 120kg modified almond shell powder-starch composite powder are mixed to obtain the first mixture.
[0089] The modified almond shell powder-starch composite powder is prepared by the following method:
[0090] Almond shells are crushed and ground to obtain almond shell powder of 800-1000 mesh. Then, almond shell powder and starch are mixed at a mass ratio of 1:0.8 to obtain mixed powder. The mixed powder is heated at 250°C for 1 hour under anaerobic conditions. After cooling, it is soaked in 35wt% phosphoric acid solution, washed with water, and dried to obtain modified almond shell powder-starch composite powder.
[0091] Mix 3 kg of water-reducing agent and 150 kg of mixing water, then add the first mixture, 15 kg of n-hexyl acrylate and 35 kg of the composite capsules prepared in Preparation Example 3, stir, and then add the remaining low-heat cement to obtain low-heat hydration, low-shrinkage, and high-durability large-volume concrete.
[0092] Example 4
[0093] A method for preparing large-volume concrete with low heat of hydration, low shrinkage, and high durability is carried out according to the method in Example 1, except that FEA expansion agent is not added to the raw materials.
[0094] Example 5
[0095] A method for preparing large-volume concrete with low heat of hydration, low shrinkage, and high durability is carried out according to the method in Example 1, except that the composite capsule is selected from the composite capsule prepared in Preparation Example 4.
[0096] Example 6
[0097] A method for preparing large-volume concrete with low heat of hydration, low shrinkage, and high durability is carried out according to the method in Example 1, except that almond shell powder and starch are mixed and added directly.
[0098] Example 7
[0099] A method for preparing low-heat-of-hydration, low-shrinkage, and high-durability mass concrete is carried out according to the method in Example 1, except that the modified almond shell powder-starch composite powder is prepared by the following method:
[0100] The almond shells were crushed and ground to obtain almond shell powder of 800-1000 mesh. The almond shell powder was heated at 240℃ for 1.5 hours under anaerobic conditions, then cooled and soaked in 35wt% phosphoric acid solution, washed with water, dried, and then mixed with starch at a mass ratio of 1:0.7 to obtain modified almond shell powder-starch composite powder.
[0101] Comparative Example 1
[0102] A method for preparing large-volume concrete with low heat of hydration, low shrinkage, and high durability is carried out according to the method in Example 1, except that no composite capsules are added to the raw materials.
[0103] Comparative Examples 2-4
[0104] A method for preparing large-volume concrete with low heat of hydration, low shrinkage, and high durability is carried out according to the method in Example 1, except that the composite capsules are selected from the composite capsules prepared in Comparative Preparation Examples 1-3.
[0105] Comparative Example 5
[0106] A method for preparing large-volume concrete with low heat of hydration, low shrinkage, and high durability is carried out according to the method in Example 1, except that modified almond shell powder-starch composite powder is not added to the raw materials.
[0107] Comparative Example 6
[0108] A method for preparing low-heat hydration, low-shrinkage, high-durability large-volume concrete is carried out according to the method in Example 1, except that hexyl acrylate is not added to the raw materials.
[0109] Performance testing
[0110] First, the concrete prepared in the above embodiments and comparative examples was subjected to shrinkage tests and early crack resistance tests according to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The total shrinkage after 28 days and the total crack area per unit area are shown in Table 1 below:
[0111] Table 1:
[0112]
[0113] As can be seen from Table 1 above, the concrete prepared in the embodiments of this application has a smaller shrinkage value and better crack resistance. Referring to Examples 1 and 4, it can be seen that when no expansive agent is added to the raw materials, the shrinkage value of the concrete increases and its crack resistance decreases. Referring to the test results of Examples 1 and 5, it can be seen that when ethyl cellulose is not added to the composite capsule coating, its shrinkage value also increases and its crack resistance decreases. This may be because the addition of ethyl cellulose enables the slow release of the core material particles in the composite capsule, thereby slowly releasing carboxylic acid to reduce hydration and shrinkage, and is more conducive to forming a network structure to improve tensile strength, thereby improving its crack resistance. Referring to the test results of Examples 1, 6, and 7, in Example 6, almond shell powder and starch were mixed and added directly without modification, resulting in a significant increase in shrinkage value and a decrease in crack resistance. In Example 7, almond shell powder was semi-carbonized and modified before being mixed with starch and added, resulting in an increase in shrinkage value and a decrease in crack resistance, but the performance was better than that in Example 6.
[0114] Referring to the test results of Example 1 and Comparative Example 1, when no composite capsules were added to the concrete raw materials, the shrinkage value was significantly increased and the crack resistance was significantly reduced. Combining the test results of Comparative Examples 2-4, when no boron nitride, initiator, or acryloyl chloride was added to the composite capsules, the shrinkage value was also increased and the crack resistance was reduced. Combining the test results of Comparative Example 6, when no n-hexyl acrylate was added to the raw materials, the shrinkage value was increased and the crack resistance was significantly reduced. When initiators, acryloyl chloride, and n-hexyl acrylate were added to the concrete at the same time, it helped to form a macromolecular network structure and improve its crack resistance. Combining the test results of Comparative Example 5, the addition of modified almond shell powder-starch composite powder helped to further improve its crack resistance.
[0115] The concrete prepared in Example 1 was used for large-volume concrete construction across seasons.
[0116] Application Example 1
[0117] A method for constructing large-volume concrete includes the following steps:
[0118] S1. Prepare low-heat-of-hydration, low-shrinkage, high-durability mass concrete according to the method in Example 1;
[0119] The mixing water for concrete raw materials is added after being cooled, specifically:
[0120] When the highest ambient temperature is between 30℃ and 35℃, add ice cubes to the mixing water. When the highest ambient temperature is greater than 35℃, in addition to using the ice cubes normally, add urea and dry ice to the mixing water so that the temperature of the mixing water is below 15℃ when it is added.
[0121] S2. Concrete transportation, pouring, and vibration. When pouring concrete, in winter construction, the pipes are lubricated with hot water and 20℃ mortar before pumping. In summer construction, the concrete pumping pipes are wrapped with reflective insulation material to keep the temperature difference between the inside and outside of the pump pipes between 1-1.5℃.
[0122] The temperature of large-volume concrete placed in the formwork should be controlled to be less than 30°C in high-temperature summer environments and higher than 10°C in cold winter environments.
[0123] S3. Concrete curing: During the concrete curing process, the temperature difference between the center and surface of the concrete should not exceed 25℃ during summer curing. If the temperature difference between the center and surface of the concrete is too large or the temperature difference between the inside and outside exceeds 25℃ during summer construction, cover with thermal insulation material. If the temperature difference between the inside and outside of the concrete does not decrease after 24 hours, continue to add thermal insulation material until the temperature difference is less than 25℃. Control the concrete to be cured with water for no less than 7 days and the moist curing time for no less than 14 days.
[0124] During winter curing, after the pouring is completed, the surface should be manually leveled and smoothed, and then immediately covered with insulation material.
[0125] The above construction method achieves a synergistic improvement in the strength, workability, and heat of hydration of concrete. The concrete exhibits low shrinkage, no cracking, and high durability. It effectively solves technical problems such as high temperature at the discharge point and high risk of shrinkage cracking in large-volume concrete. After hardening, no cracks are generated on the concrete surface, resulting in significant economic and social benefits.
[0126] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. A method for constructing large-volume concrete, characterized in that, Includes the following steps: S1. Prepare large-volume concrete with low heat of hydration, low shrinkage, and high durability. S2. Concrete transportation, pouring, and vibration. When pouring concrete, in winter construction, the pipe should be lubricated with hot water and mortar with a temperature not lower than 15℃ before pumping. In summer construction, the concrete pumping pipe should be wrapped with reflective insulation material to keep the temperature difference between the inside and outside of the pump pipe between 1-1.5℃. The temperature of large-volume concrete placed in the formwork should be controlled to be less than 30°C in high-temperature summer environments and higher than 10°C in cold winter environments. S3. Concrete curing: During the concrete curing process, the temperature difference between the center and surface of the concrete should not exceed 25℃ during summer curing. If the temperature difference between the center and surface of the concrete is too large or the temperature difference between the inside and outside exceeds 25℃ during summer construction, cover it with insulation material. If the temperature difference between the inside and outside of the concrete does not decrease after 24 hours, continue to add more insulation material until the temperature difference is less than 25℃. In step S1, when preparing low-heat-of-hydration, low-shrinkage, and high-durability mass concrete, it is prepared from raw materials comprising the following parts by weight: 100-150 parts low-heat cement, 150-230 parts fly ash, 230-340 parts mineral powder, 1800-2000 parts coarse aggregate, 1000-1300 parts fine aggregate, 1-3 parts water-reducing agent, 80-120 parts modified almond shell powder-starch composite powder, 20-35 parts composite capsules, 10-15 parts n-hexyl acrylate, and 120-150 parts mixing water; The composite capsule is made with acryloyl chloride, boron nitride, acrylamide and an initiator as core materials.
2. The method for constructing large-volume concrete according to claim 1, characterized in that: In step S1, mixing water is added to the raw materials when preparing low-heat-of-hydration, low-shrinkage, durable mass concrete. This mixing water is added after being cooled. Specifically... When the highest ambient temperature is between 30℃ and 35℃, add ice cubes to the mixing water. When the highest ambient temperature is above 35℃, in addition to using the ice cubes normally, add urea and dry ice to the mixing water to make the temperature of the mixing water below 15℃.
3. The method for constructing large-volume concrete according to claim 1, characterized in that: The composite capsules use ethyl cellulose and hydroxypropyl methyl cellulose in a mass ratio of 1:(1.2-1.5) as coating materials.
4. The method for constructing large-volume concrete according to claim 1, characterized in that: The mass ratio of acryloyl chloride, boron nitride and acrylamide is 1:(1-1.2):(0.5-0.8), and the amount of initiator added is 0.3-0.5 wt% of acryloyl chloride.
5. The method for constructing large-volume concrete according to claim 1, characterized in that: The modified almond shell powder-starch composite powder is prepared by the following method: Almond shells are crushed and ground to obtain almond shell powder. Then, almond shell powder and starch are mixed to obtain a mixed powder. The mixed powder is heated under anaerobic conditions at 220-250℃ for 1-2 hours. After cooling, it is soaked in phosphoric acid solution, washed with water, and dried to obtain modified almond shell powder-starch composite powder.
6. A method for constructing large-volume concrete according to claim 5, characterized in that: The mass ratio of almond shell powder to starch is 1:(0.6-0.8).
7. The method for constructing large-volume concrete according to claim 1, characterized in that: Step S1, preparing low-heat-of-hydration, low-shrinkage, and high-durability mass concrete, includes the following steps: Half of the low-heat cement, mineral powder, fly ash, coarse aggregate, fine aggregate, and modified almond shell powder-starch composite powder are mixed to obtain the first mixture; The water-reducing agent and mixing water are mixed, then the first mixture is added, followed by n-hexyl acrylate and composite capsules. The mixture is stirred, and then the remaining low-heat cement is added to obtain low-heat hydration, low-shrinkage, and high-durability mass concrete.
8. A method for constructing large-volume concrete according to claim 7, characterized in that: When fly ash is added, 3-5 parts by weight of FEA expanding agent are also added.
9. A method for constructing large-volume concrete according to claim 1, characterized in that: The low-heat cement used is P.LH42.5 low-heat cement; The fly ash used is Class I, Grade F fly ash; The coarse aggregate is selected from crushed stone with a continuous gradation of 5-40mm; The fine aggregate is sand with a fineness modulus of 2.5-3.0; The water-reducing agent used is a high-performance polycarboxylate water-reducing agent.