Super-retarding concrete as well as preparation method and application thereof
By optimizing the combination of formula and admixture, the problems of insufficient strength and large aggregate mud content in the later stage of the ultra-retarded concrete when prolonging the settling time are solved, and the high performance and low cost of ultra-retarded concrete are achieved, and suitable for large-volume concrete is suitable for large-volume concrete. and underground continuous wall construction.
Patent Information
- Application Number
- CN202411385432.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2024-12-27
AI Technical Summary
While extending the settling time, existing ultra-retarded concrete is difficult to maintain its later strength, and the large aggregate mud content causes the concrete performance to not meet the requirements, affecting construction and cost.
By optimizing the formulation design, increasing the amount of cement, adjusting the ratio of fly ash, ore powder and admixtures, combined with the screening and washing process, ultra-retarded concrete with initial set time ≥60h and final set time <120h was prepared, and water reducing agent was used. The admixture of white sugar, sodium gluconate and sodium hexametaphosphate is mixed to extend the stirring time to improve the plasticity and cohesion of the concrete.
The difference in the long initial settling time and short final settling time of concrete was achieved, ensuring that the compressive strength was <3.0MPa in 3 days, and the compressive strength reached the design strength level in 28d, and the mud content of the aggregate was reduced, improving the quality of the project and economic benefits. .
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Figure CN119191793A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of concrete, and in particular relates to a super slow-setting concrete and a preparation method and application thereof. Background Art
[0002] The bite pile combines the economy of bored piles and the safety and reliability of underground continuous walls in water-stopping, anti-seepage and deformation control. It is a new support structure system that has developed rapidly in recent years. It has outstanding competitive advantages and has been increasingly recognized and applied. This process requires concrete to have a long initial setting time to meet the construction process requirements. The preparation of super-slow setting concrete can solve this problem, not only ensuring the smooth progress of construction, but also has the following advantages. First, improve the quality of the project: through reasonable mix design, super-slow setting concrete can maintain plasticity while not affecting its later strength development. This helps to improve the quality and durability of the project. Second, control the construction progress: The application of super-slow setting concrete can extend the operable time of concrete, facilitate construction arrangements and control the construction progress. Third, reduce costs: By optimizing the mix design, the cost of raw materials can be reduced and economic benefits can be improved while meeting performance requirements. Fourth, promote technological innovation: The research and application of super-slow setting concrete will help promote the innovation and development of concrete technology and provide more solutions for construction projects.
[0003] Super slow-setting concrete requires a long setting time and a 28d strength no less than the design strength grade. During its preparation, the amount of retarder is often increased to increase the energy barrier that cement hydration needs to overcome, thereby delaying the setting of concrete and inhibiting the development of early concrete strength. However, this operation will also have a certain impact on the later strength development of concrete. Summary of the invention
[0004] The present invention provides a super slow setting concrete and a preparation method and application thereof. The initial setting time of the concrete can reach more than 60 hours, and the difference between the initial and final setting time can be controlled to be less than 20 hours, the 3-day compressive strength is less than 3.0 MPa, and the concrete has good workability, physical properties and mechanical properties after the mixture is hardened.
[0005] The technical scheme of the present invention is to provide a super slow setting concrete, the 3-day compressive strength of the concrete is less than 3.0MPa, the initial setting time is greater than or equal to 60h, and the final setting time is less than 120h; each cubic meter of concrete contains 308-360kg of cement, 60-64kg of fly ash, 53-63kg of mineral powder, 680-735kg of sand, 1020-1035kg of crushed stone and 160-170kg of water, and the concrete also includes an admixture of 2.0-2.3% of the total weight of cement, fly ash and mineral powder, and the admixture is prepared by mixing a water reducer, white sugar, sodium gluconate, sodium hexametaphosphate and water in a ratio of 200:25:30:60:800.
[0006] In some of the embodiments, the cement is ordinary Portland cement with a strength grade of 42.5 and a clinker ratio of 85-90%, and all performance indicators comply with the provisions of GB 175-2023; the admixture fly ash is secondary fly ash; all performance indicators comply with the provisions of GB / T 1596-2017; the mineral powder is S95 grade mineral powder, and all performance indicators comply with the relevant requirements of JTS 202-2-2011.
[0007] In some of the embodiments, the sand fineness modulus is 2.3-3.0, the mud content is ≤3%, and the mud block content is ≤1%. When the mud content or mud block content in the sand exceeds the limit, a screening and washing process is added or the dosage of cement, fly ash, mineral powder and admixture is adjusted.
[0008] In some of the embodiments, the crushed stone is a continuous particle size of 5~25mm, the mud content is ≤1%, and the mud block content is ≤0.5%. When the mud content or mud block content in the crushed stone exceeds the limit, a screening and washing process is added or the amount of cement, fly ash, mineral powder and admixture is adjusted.
[0009] In some of the embodiments, the water reducer is a collapse-retaining polycarboxylic acid-based high-performance water reducer.
[0010] In a preferred embodiment, the super slow setting concrete contains 308 kg of cement, 64 kg of fly ash, 53 kg of mineral powder, 735 kg of sand, 1035 kg of 5-25 mm crushed stone, 9.35 kg of admixture and 170 kg of water per cubic meter; the initial setting time of the concrete is 61.5 h, the final setting time is 76 h; the 3d compressive strength is 1.6 MPa, the 28d compressive strength is 45.9 MPa, and the impermeability grade reaches P6 or above. In a preferred embodiment, the super slow setting concrete contains 360 kg of cement, 63 kg of fly ash, 63 kg of mineral powder, 689 kg of sand, 1034 kg of 5-25 mm crushed stone, 10.69 kg of admixture and 170 kg of water per cubic meter; the mud content of the sand is 8.4%, and the mud block is 3.3%; the mud content of the 5-25 mm crushed stone is 8.0%; the initial setting time of the concrete is 76 h, and the final setting time is 83 h; the 3d compressive strength is 2.1 MPa, the 28d compressive strength is 46.3 MPa, and the 28d impermeability grade reaches P6 or above. The invention also relates to a method for preparing the ultra-slow setting concrete. The concrete raw materials are weighed according to a proportion and then mixed. The mixing time is 120s-160s.
[0011] In some of the embodiments, the admixture is stirred for more than 40 minutes before use.
[0012] The invention also relates to the application of the super slow setting concrete in large volume concrete construction, underground continuous wall construction and / or interlocking pile construction.
[0013] The present invention has the following beneficial effects: The present invention aims at the problem of large aggregate mud content. In addition to washing and screening to reduce the mud content, the final concrete index can also be adjusted by formula adjustment to meet the requirements. Specifically, the technical difficulty of large aggregate mud content not meeting the requirements can be overcome by controlling the clinker content of ordinary Portland cement, increasing the amount of cement, and adjusting the amount of fly ash, mineral powder and admixtures, so as to achieve local materials for aggregates and reduce costs. At the same time, when preparing super slow setting concrete, the mixing time of concrete in the mixing station is extended, 40 seconds are added for each plate, and the mixing time reaches 120-160s, the material mixing is more uniform, and the water, cementitious material and admixture can be more fully wrapped in the aggregate after mixing.
[0014] The ultra-slow setting concrete provided by the present invention is designed with a mix ratio, fly ash and mineral powder added to improve the plasticity, cohesiveness and water retention of the mixture, and by adding a certain proportion of admixtures, the initial setting time can reach more than 60 hours, the final setting time is less than 120, and the difference between the initial and final setting time is preferably less than 20 hours; the 3d compressive strength of the concrete is less than 3.0MPa, the slump is 160-220mm, and the workability and physical properties of the mixture are excellent. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 It is the particle gradation curve arrangement diagram of the sand used in the comparative example and the embodiment. DETAILED DESCRIPTION
[0016] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.
[0017] Example 1 The raw materials used were tested and analyzed, and the specific details are as follows.
[0018] The cement is PO 42.5 ordinary Portland cement. The physical and mechanical properties of the cement are shown in Table 1, and the chemical analysis is shown in Table 2.
[0019] Table 1. Test results of physical and mechanical properties of cement
[0020] Table 2. Cement chemical analysis test results
[0021] It can be seen from the table that all performance indicators of the cement used in this mix test meet the requirements of GB 175-2023 "General Portland Cement".
[0022] The fly ash is specifically Class F II fly ash, and after testing, all performance indicators meet the requirements of GBT 1596-2017 "Fly ash used in cement and concrete". The mineral powder is S95 grade mineral powder, and after testing, all performance indicators meet the requirements of JTS 202-2-2011 "Concrete Quality Control Standard for Water Transport Engineering".
[0023] Fine aggregate sand: The fine aggregate used for the following mix ratio verification comes from natural aggregate produced by the screening system near the construction site. The test was carried out according to the Technical Specifications for Testing and Inspection of Concrete for Water Transport Engineering JTST 236-2019. The screening test and test results are shown in Tables 3, 4 and Figure 1 .
[0024] Table 3. Sand test results
[0025] Table 4. Sand particle gradation test results
[0026] From Table 3, Table 4 and Figure 1 It can be seen that the sand is medium sand. Judging from the screening curve, it basically meets the sand grading range of Zone II, but the mud content and mud block content exceed the standard through actual measurement. By adding screening and washing processes, it can be made to meet the specification requirements.
[0027] Coarse aggregate crushed stone: The coarse aggregate used for the following mix ratio verification comes from 5-25 mm crushed stone aggregate produced by the screening system near the construction site. The test and inspection are carried out according to the "Technical Specifications for Testing and Inspection of Concrete for Water Transport Engineering" JTST 236-2019. The screening test and inspection results are shown in Tables 5 and 6.
[0028] Table 5. Coarse aggregate test results
[0029] Table 6. Coarse aggregate screening results
[0030] It can be seen from Table 5 and Table 6 that the mud content and mud block content exceeded the standard through actual measurement, and they were made to meet the standard requirements by adding screening and washing processes.
[0031] The water reducing agent in the admixture used in the following examples and comparative examples is a slump-retaining polycarboxylic acid high-performance water reducing agent produced by Shaanxi Baian Admixture Co., Ltd., and is tested according to GB8076-2008 "Concrete Admixtures" and GB / T8077-2012 "Concrete Admixture Homogeneity", and all meet the relevant requirements. In the specific test, the water reduction rate of the water reducing agent is 35%. The admixture is made of a mixture of water reducing agent, white sugar, sodium gluconate, sodium hexametaphosphate and water in a mass ratio of 200:25:30:60:800, and stirred for more than 40 minutes before use.
[0032] The design requirements for a certain super slow setting concrete are shown in Table 7 below.
[0033] Table 7. Main performance technical indicators of concrete
[0034] The above raw materials were used to test the mix ratio of super slow setting concrete. The performance test of the mixture is shown in Table 8, and the performance test of concrete is shown in Table 9.
[0035] Table 8. Mixture workability test results
[0036] Table 9 Analysis of indoor test results of interlocking pile super slow setting concrete mix ratio
[0037] The initial setting time of mix proportions 1, 2, 3, 4, and 6 in the above table does not meet the requirements of the specification, and the 3-day compressive strength of mix proportions 7 and 8 does not meet the requirements of the specification. Mix proportion 5 is preferred.
[0038] The mixture with this mix ratio has good cohesiveness, water retention, workability, physical properties and mechanical properties after hardening.
[0039] Example 2 The sand and gravel aggregates at a construction site have a high mud content. Specifically, the sand sampled and tested have a mud content of 8.4% and a mud block of 3.3%. The 5-25 mm crushed stone has a mud content of 8.0%. The sand and crushed stone are used as aggregates and other raw materials in Example 1 are adapted to provide a mix ratio as shown in Table 10. The concrete strength grade is required to be C30.
[0040] Table 10
[0041] During the specific preparation, the raw materials were weighed according to the proportion and mixed, and the mixing time was 160s; the properties of the obtained concrete are shown in Table 11.
[0042] Table 11
[0043] The performance indicators of this concrete can meet the relevant requirements.
[0044] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.
Claims
1. A super slow setting concrete, characterized in that: The 3-day compressive strength of the concrete is less than 3.0MPa, the initial setting time is ≥60h, and the final setting time is less than 120h; each cubic meter of concrete contains 308~360kg of cement, 60~64kg of fly ash, 53~63kg of mineral powder, 680~735kg of sand, 1020~1035kg of crushed stone and 160~170kg of water. The concrete also includes an admixture accounting for 2.0~2.3% of the total mass of cement, fly ash and mineral powder, and the admixture is a mixture of water reducer, white sugar, sodium gluconate, sodium hexametaphosphate and water in the ratio of 200:25:30:60:
800.
2. The super slow setting concrete according to claim 1, characterized in that: The cement is ordinary Portland cement with a strength grade of 42.5 and a clinker ratio of 85-90%. All performance indicators comply with the provisions of GB 175-2023. The fly ash used as the admixture is secondary fly ash, and all performance indicators comply with the provisions of GB / T 1596-2017. The mineral powder is S95 grade mineral powder, and all performance indicators comply with the relevant requirements of JTS 202-2-2011.
3. The super slow setting concrete according to claim 1, characterized in that: The sand fineness modulus is 2.3-3.0, the mud content is ≤3%, and the mud block content is ≤1%. When the mud content or mud block content in the sand exceeds the limit, a screening and washing process is added or the dosage of cement, fly ash, mineral powder and admixture is adjusted.
4. The super slow setting concrete according to claim 1, characterized in that: The crushed stone has a continuous particle size of 5-25 mm, a mud content of ≤1%, and a mud block content of ≤0.5%. When the mud content or mud block content in the crushed stone exceeds the limit, a screening and washing process is added or the dosage of cement, fly ash, mineral powder and admixture is adjusted.
5. The super slow setting concrete according to claim 1, characterized in that: The water reducing agent is a collapse-retaining polycarboxylic acid-based high-performance water reducing agent.
6. The super slow setting concrete according to any one of claims 1 to 5, characterized in that: Each cubic meter of super slow-setting concrete contains 308kg of cement, 64kg of fly ash, 53kg of mineral powder, 735kg of sand, 1035kg of 5-25mm crushed stone, 9.35kg of admixture and 170kg of water; the initial setting time of this concrete is 61.5h, and the final setting time is 76h; the 3d compressive strength is 1.6MPa, the 28d compressive strength is 45.9MPa, and the water-resistance grade reaches P6 or above.
7. The super slow setting concrete according to any one of claims 1 to 5, characterized in that: Each cubic meter of super slow-setting concrete contains 360kg of cement, 63kg of fly ash, 63kg of mineral powder, 689kg of sand, 1034kg of 5-25mm crushed stone, 10.69kg of admixture and 170kg of water; the mud content of sand is 8.4%, and the mud content is 3.3%; the mud content of 5-25mm crushed stone is 8.0%; the initial setting time of the concrete is 76h, and the final setting time is 83h; the 3d compressive strength is 2.1MPa, the 28d compressive strength is 46.3MPa, and the 28d impermeability grade reaches P6 or above.
8. The method for preparing the super slow setting concrete according to any one of claims 1 to 7, characterized in that: The concrete raw materials are weighed according to the proportion and mixed, and the mixing time is 120s-160s; the concrete is obtained.
9. The preparation method according to claim 8, characterized in that: Stir the admixture for more than 40 minutes before use.
10. Use of the super slow setting concrete according to any one of claims 1 to 7 in large volume concrete construction, underground continuous wall construction and / or interlocking pile construction.