Determining and optimizing method for concrete winter construction heat preservation covering maintenance conditions
By constructing a correlation model between thermal resistance and curing time, the thermal resistance and coverage thickness of insulation materials are determined, the problem of early frost damage of concrete in winter construction is solved, efficient and efficient insulation coverage and maintenance is achieved, and construction efficiency and cost control are improved.
Patent Information
- Application Number
- CN202311230801.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-22
- Publication Date
- 2025-03-25
AI Technical Summary
In winter construction, concrete is susceptible to early frost damage, which affects its subsequent performance development. The existing technology lacks systematic research on the determination of insulation coverage and maintenance conditions, resulting in uncertainty in construction progress and cost.
Through calculation, convenient and quick use of insulation covering materials to cure the concrete structure, a correlation model between thermal resistance and maintenance time is constructed based on the range of changes in ambient temperature and the actual situation of construction period to determine the required thermal resistance and coverage thickness of the insulation material.
Effectively save the amount of insulation covering materials, improve concrete curing efficiency, simplify construction processes, reduce labor and material costs, is easy to operate, and is suitable for promotion and application.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of building construction, and in particular relates to a method for determining and optimizing the thermal insulation, covering and curing conditions of concrete during winter construction. Background Art
[0002] Concrete is one of the most widely used materials in the construction industry. Besides the quality of the material itself, the construction process also affects the quality and speed of the project. Furthermore, different climates place varying demands on the application of concrete in construction. In areas where low temperatures (below 0°C) persist for five to six months each year, construction companies inevitably conduct concrete construction in winter to expedite project progress. To prevent early freezing damage to concrete during winter construction, which could affect its subsequent performance, it is typically necessary to achieve a certain pre-curing strength (critical freezing strength) before freezing to ensure that the subsequent compressive strength loss after freezing is controlled within 5%.
[0003] To ensure smooth winter concrete construction, scholars at home and abroad have proposed numerous preventative measures and solutions, including raw material heating (using steam / hot air to heat aggregates), concrete thermal storage (leveraging raw material heating and cement hydration heat, along with appropriate insulation measures, to delay concrete cooling), comprehensive thermal storage (after pouring concrete with early-strength agents or early-strength composite admixtures, utilizing raw material heating and cement hydration heat, along with appropriate insulation measures, to delay concrete cooling), greenhouse methods (placing concrete components or structures in a greenhouse with radiators, pipes, electric heaters, or stoves to heat the air within, maintaining a positive temperature environment), and negative temperature curing (adding antifreeze to concrete to enable continuous hardening at negative temperatures, reaching critical freezing strength before the concrete temperature drops below the antifreeze's specified temperature). Currently, the most commonly used method in engineering is a combination of comprehensive thermal storage and negative temperature curing, involving concrete heating, antifreeze, and insulation covering. This approach is simple to implement and offers significant benefits in preventing early frost damage. However, the combustion of materials like coal during the heating process can exacerbate CO2 emissions. The use of covering materials for concrete insulation and curing relies heavily on experience, with a lack of systematic research on curing time, insulation cover thickness, and other conditions (usually based on experience), severely impacting construction progress and costs.
[0004] Therefore, further exploring simple and efficient optimization methods for determining thermal insulation cover maintenance conditions has important research and application significance. Summary of the Invention
[0005] The purpose of the present invention is to provide a method for determining and optimizing the insulation covering and curing conditions for concrete construction in winter. According to the range of ambient temperature changes and the time required by the actual construction period, the concrete structure is cured using insulation covering materials conveniently and quickly by calculating the method, which can effectively save the amount of insulation covering materials, avoid waste in the curing project, and improve the efficiency of concrete curing.
[0006] To achieve the above object, the technical solution adopted by the present invention is:
[0007] A method for determining and optimizing heat preservation and covering curing conditions for concrete construction in winter, comprising the following steps:
[0008] 1) Prepare a concrete mixture with antifreeze, pour and form it, cover it with a film to prevent water evaporation, and then place it in a low-temperature room;
[0009] 2) using a thermal insulation material to perform thermal insulation covering and curing on the test block obtained in step 1), wherein before use, the thermal insulation material is subjected to different thermal resistance values R according to a thermal resistance calculation formula and different designed covering thicknesses;
[0010] 3) Insulation cover curing until the concrete specimen reaches the designed critical strength of freezing, and record the corresponding insulation cover curing time T 覆盖 ;
[0011] 4) Obtain the insulation covering curing time T under different ambient temperatures and covering thicknesses 覆盖 , a chemometric method is used to construct a fitting equation between temperature, thermal resistance value R and thermal insulation covering curing time; the obtained fitting equation is corrected and deformed to obtain the thermal resistance value R determination equation;
[0012] 5) In the actual insulation and maintenance construction, the site is based on the planned insulation and maintenance time, and the equation is determined by the thermal resistance value R to calculate the required thermal resistance value of the insulation material. Then, according to the thermal resistance calculation formula, the coverage thickness of the insulation material is obtained to guide the on-site insulation material construction.
[0013] In the above solution, the temperature of the low-temperature chamber is controlled at 5 to -15°C.
[0014] In the above solution, the antifreeze agent accounts for 2-4% of the total mass of the concrete cementitious material; specifically, one or more of alcohols, alcohol ethers, chlorinated hydrocarbons, inorganic salts and the like can be selected.
[0015] Furthermore, the alcohol antifreeze can be ethylene glycol, etc.; the alcohol ether antifreeze can be one or more of ethylene glycol butyl ether, propylene glycol butyl ether, etc.; the chlorinated hydrocarbon antifreeze can be one or more of 1,1-dichloroethane, 1,2-dichloroethane, etc.; the inorganic salt antifreeze can be one or more of dimethyl sulfoxide, sodium acetate, magnesium chloride, etc.
[0016] In the above scheme, the components and their weight proportions in the concrete mixture include: 130-210 parts of cement, 80-150 parts of fly ash, 50-70 parts of mineral powder, 750-850 parts of sand, 1000-1200 parts of crushed stone, 120-160 parts of water, 3-6 parts of polycarboxylate water reducer, and antifreeze accounting for 2-4% of the total mass of the concrete cementitious material.
[0017] In the above solution, the thermal insulation material may be felt, quilt, straw curtain, etc. commonly used in the art.
[0018] In the above scheme, the thermal resistance calculation formula is: R = δ × λ -1 , where: R—thermal resistance of insulation material (m 2 ·k / w); δ—the thickness of the insulation material (m); λ—the thermal conductivity of the insulation material W / (m·k).
[0019] In the above solution, the critical freezing strength is above 5 MPa, preferably 5 MPa.
[0020] In the above scheme, the fitting equation is: y=a+b×r R ; Where R is thermal resistance, m 2 k / w; y is the curing time to reach 5 MPa coverage, h; a, b, r are constants, and their specific values are shown in Table 1 below.
[0021] Table 1 Values of a, b, and r constants
[0022]
[0023]
[0024] Furthermore, the correction step includes: correcting the fitting equation, and the obtained corrected fitting equation is: y = x / α, where: y is the time (h) for concrete to reach the critical strength of 5 MPa after freezing; x is the expected curing time (h); α is the correction coefficient, and the value of α is shown in Table 2 below.
[0025] Table 2 α changes with environment
[0026]
[0027] The corrected equation is: x=αa+αb×r R .
[0028] In the above solution, the thermal resistance value R after deformation is determined by the equation:
[0029] Compared with the prior art, the present invention has the following beneficial effects:
[0030] 1) This invention proposes, for the first time, a correlation model between thermal resistance and curing time. By leveraging the pattern in which curing time varies with the thermal resistance of insulation materials, this model establishes a mathematical relationship between curing time and the thermal resistance of the material. Furthermore, the required thermal resistance of the insulation material can be calculated based on the pre-curing time, enabling rapid, accurate, and efficient thermal curing of concrete materials.
[0031] 2) The determination method described in the present invention can effectively simplify the construction process of thermal insulation materials for concrete winter construction, further clarify the specific covering method of thermal insulation materials, and promote the diversified use of thermal insulation materials, significantly save labor and material costs, be easy to operate, and be suitable for promotion and application. DETAILED DESCRIPTION
[0032] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. These descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.
[0033] In the following application example, the concrete test block used has the following formula conditions: 200 parts of cement, 130 parts of fly ash, 60 parts of mineral powder, 785 parts of sand, 1085 parts of crushed stone, 150 parts of water, 5 parts of polycarboxylate water reducer, and antifreeze accounting for 4% of the total mass of concrete cementitious materials; the size after molding is 100mm*100mm*100mm.
[0034] The insulation material used is felt, which has a thermal conductivity of 0.06W / (m·K), a specific heat capacity of 1.88kJ / (kg·K), and a single layer thickness of 3mm.
[0035] Example 1
[0036] A method for determining and optimizing heat preservation and covering curing conditions for concrete construction in winter, comprising the following steps:
[0037] 1) A C30 concrete mixture containing an antifreeze agent was prepared according to the formula. After pouring and molding, the resulting concrete specimens were covered with plastic wrap to prevent water evaporation and placed in a low-temperature chamber under different temperature conditions; the temperatures were set to 5°C, 0°C, -5°C, -10°C, and -15°C.
[0038] 2) Use felt, a commonly used thermal insulation material in engineering, to wrap the test blocks for thermal insulation and curing. Adjust the covering thickness to obtain different thermal resistance values. Record the curing time. After the concrete has finally set, take the test blocks out of the low-temperature chamber every 2 to 3 hours according to the hardening status of the test blocks.
[0039] 3) Perform compressive strength tests on the removed specimens. When the concrete specimens reach the critical freezing strength of 5 MPa, record the thermal curing time. Obtain the time and thermal resistance of the concrete specimens at 5 MPa under different temperature conditions. After approximately 3,200 repeated tests, a database of the relationship between curing time and thermal resistance at different ambient temperatures was generated.
[0040] 4) According to the insulation cover curing time under different temperature and cover thickness conditions, the chemometric method is used to construct the fitting equation between temperature, thermal resistance value R and insulation cover curing time, specifically: y = a + b × r R , where R is thermal resistance, y is the coverage curing time to reach 5MPa, a, b, r are constants, and their specific values are shown in Table 1 below;
[0041] 5) Correct the fitting equation to obtain the corrected fitting equation: y = x / α, where α is the correction coefficient and the values of α are shown in Table 2 below;
[0042] 6) Based on the equations in 4) and 5), the corrected equation of thermal resistance and planned curing time is obtained by substitution and transformation: Where R is thermal resistance, α is correction coefficient, x is planned curing time, a, b and r are constants;
[0043] 7) According to the thermal resistance formula R = δ × λ -1 Deformation to obtain the insulation material covering thickness formula This formula can be used to calculate the required insulation coverage thickness within the planned curing time. Insulating concrete at this thickness will ensure that the concrete reaches its critical freezing strength within the planned timeframe.
[0044] Application Example 1
[0045] A C30 concrete mix containing antifreeze was prepared according to the recipe and transported to the construction site by tank truck for pouring. The site ambient temperature was 5°C, the average wind speed was 4.0 m / s, and the concrete surface temperature after pouring was 20°C. Based on the construction site environmental conditions, a table was used to obtain values of 18.47 for a, 36.36 for b, 0.15 for r, and 1.28 for the correction factor α. The construction party planned a thermal insulation curing time x of 40 hours. Using the insulation material cover thickness formula obtained in step 7), the felt cover thickness was calculated to be 33 mm.
[0046] After the concrete hardened, its strength was monitored using a rebound hammer (mushroom head). The timing was stopped when the critical freezing strength of 5 MPa was reached. The actual curing time was finally obtained to be 40.5 h, which was 0.5 h different from the planned curing time, meeting the requirement of an accuracy of less than or equal to 1 h.
[0047] Application Example 2
[0048] A C30 concrete mix containing antifreeze was prepared according to the formula and transported to the construction site for pouring using a tank truck. The on-site ambient temperature was 0°C, the average wind speed was 2.5 m / s, and the concrete surface temperature after pouring was 10°C. Based on the construction site environment, a table was used to obtain a value of 9.37, a value of 31.03, a value of 0.5 for r, and a value of 1.16 for the correction coefficient α. The construction party planned the insulation curing time x to be 30 hours. Using the insulation material coverage thickness formula obtained in step 7), the felt coverage thickness was calculated to be 55 mm. After the concrete hardened, its strength was monitored using a rebound hammer (mushroom head). The timer was stopped when the critical freezing strength of 5 MPa was reached. The actual curing time was finally obtained to be 29.5 hours, which differed by 0.5 hours from the planned curing time, meeting the requirement of an accuracy of less than or equal to 1 hour.
[0049] Application Example 3
[0050] A C30 concrete mix containing antifreeze was prepared according to the formula and transported to the construction site for pouring using a tank truck. The on-site ambient temperature was -5°C, the average wind speed was 5.0 m / s, and the concrete surface temperature after pouring was 10°C. Based on the construction site environment, a table was consulted to obtain a value of 15.2, a value of 45.43, a value of 0.37, and a correction factor α of 1.38. The construction party planned the insulation curing time x to be 45 hours. Using the insulation material cover thickness formula obtained in step 7), the felt cover thickness was calculated to be 58 mm. After the concrete hardened, its strength was monitored using a rebound hammer (mushroom head). The timer was stopped when the critical freezing strength of 5 MPa was reached. The actual curing time was ultimately 46 hours, which differed by 1 hour from the planned curing time, meeting the requirement of an accuracy of less than or equal to 1 hour.
[0051] Application Example 4
[0052] A C30 concrete mix containing antifreeze was prepared according to the formula and transported to the construction site for pouring using a tank truck. The on-site ambient temperature was -10°C, the average wind speed was 3.0 m / s, and the concrete surface temperature after pouring was 20°C. Based on the construction site environment, a table was used to obtain a value of 14.36, b value of 50.99, r value of 0.34, and the correction coefficient α value of 1.59. The construction party planned the insulation curing time x to be 38 hours. Using the insulation material coverage thickness formula obtained in step 7), the felt coverage thickness was calculated to be 92 mm. After the concrete hardened, its strength was monitored using a rebound hammer (mushroom head). The timer was stopped when the critical freezing strength of 5 MPa was reached. The actual curing time was finally obtained to be 37.5 hours, which differed by 0.5 hours from the planned curing time, meeting the requirement of an accuracy of less than or equal to 1 hour.
[0053] Application Example 5
[0054] A C30 concrete mix containing antifreeze was prepared according to the formula and transported to the construction site for pouring using a tank truck. The on-site ambient temperature was -15°C, the average wind speed was 6.0 m / s, and the concrete surface temperature after pouring was 30°C. Based on the construction site environment, a table was used to obtain a value of 12.89, a value of 49.17, a value of 0.4, and a correction factor α of 1.80. The construction party planned the insulation curing time x to be 35 hours. Using the insulation material coverage thickness formula obtained in step 7), the felt coverage thickness was calculated to be 134 mm. After the concrete hardened, its strength was monitored using a rebound hammer (mushroom head). The timer was stopped when the critical freezing strength of 5 MPa was reached. The actual curing time was finally obtained to be 35 hours, which differed from the planned curing time by 0 hours, meeting the requirement of an accuracy of less than or equal to 1 hour.
[0055] Comparative Example 1
[0056] A C30 concrete mixture containing antifreeze was prepared according to the formula and transported to the construction site by tanker for pouring. The on-site ambient temperature was -5°C, with an average wind speed of 5.0 m / s. The concrete surface temperature after pouring was 10°C. Based on previous experience with winter concrete construction, the specimens were insulated and cured, with a planned curing time of 48 hours. After the concrete hardened, its strength was monitored using a rebound hammer (mushroom head). The timer was stopped when the critical freezing strength of 5 MPa was reached, resulting in an actual curing time of 56 hours. The deviation between the planned and actual curing time reached 8 hours, seriously affecting the project progress.
[0057] Comparative Example 2
[0058] Referring to the relational database obtained in Example 1, without considering the concrete surface temperature, the average ambient temperature is -5°C, and the chemometric method is used to construct a fitting equation between the thermal resistance value R and the insulation cover curing time, specifically: y = a + b × r R , where a is 11.46, b is 39.64, and r is 0.39. A C30 concrete mixture mixed with antifreeze was prepared according to the formula and transported to the construction site for pouring using a tank truck. The on-site ambient temperature was -5°C and the average wind speed was 5.0 m / s. According to the environmental conditions of the construction site, the correction coefficient α was found to be 1.38 by looking up the table. The construction party planned the insulation curing time x to be 45h. The insulation material covering thickness formula obtained in step 7) was used to calculate the felt covering thickness to be 40mm. After the concrete hardened, a rebound tester (mushroom head) was used to monitor its strength. The timing was stopped when the critical strength of freezing was reached, 5MPa. The actual curing time was finally obtained to be 52h, which was 7h different from the planned curing time, and did not meet the requirement of an accuracy of less than or equal to 1h.
[0059] Comparative Example 3
[0060] Reference example 1 gained relational database, when not considering construction site wind speed, when ambient average temperature is-10 ℃, actual time and planned time are revised again, and obtaining correction factor is 1.62. According to the C30 concrete mix of antifreeze agent prepared by formula, tanker is used to be transported to construction site and poured, and field environment temperature is-10 ℃, and after pouring, concrete surface temperature is 20 ℃. According to construction site environment situation, table look-up obtains a value 14.36, b value 50.99, r value 0.34, correction factor α value 1.62, construction party plans heat preservation curing time x to be 38h, and using step 7) gained thermal insulation material covering thickness formula calculation obtains felt covering thickness to be 95mm. Use rebound hammer (mushroom head) to monitor its intensity after concrete hardening, stop timing when reaching frozen critical strength 5MPa, and finally obtaining actual curing time is 36.5h, differs 1.5h with planned curing time, does not meet the requirement that precision is less than or equal to 1h.
[0061] The present invention is not limited to the above-described embodiments. Persons skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are deemed to be within the scope of protection of the present invention. Any matters not described in detail in this specification constitute prior art known to those skilled in the art.
Claims
1. A method for determining and optimizing the conditions for heat preservation and covering maintenance of concrete in winter, characterized in that: The steps include: 1) Prepare a concrete mixture with antifreeze, pour and form it, cover it with a film to prevent water evaporation, and then place it in a low-temperature room; 2) using a thermal insulation material to perform thermal insulation covering and curing on the test block obtained in step 1), wherein before the thermal insulation material is used, different thermal resistance values R are obtained according to a thermal resistance calculation formula and different designed covering thicknesses; 3) Insulation cover curing until the concrete specimen reaches the designed critical strength of freezing, and record the corresponding insulation cover curing time T 覆盖 ; 4) Obtain the insulation covering curing time T under different ambient temperatures and covering thicknesses 覆盖 , a chemometric method is used to construct a fitting equation between temperature, thermal resistance value R and thermal insulation covering curing time; the obtained fitting equation is corrected and deformed to obtain a thermal resistance value R determination equation; 5) In the actual insulation maintenance construction, the equation and thermal resistance calculation formula are determined according to the planned insulation maintenance time and thermal resistance value R to obtain the coverage thickness of the insulation material, so as to guide the on-site insulation material construction.
2. The determination optimization method according to claim 1, characterized in that: The low temperature is 5 to -15°C.
3. The determination optimization method according to claim 1, characterized in that: The heat-insulating material is felt, quilt or straw curtain with a thermal conductivity of 0.03-0.06 W / (m·k).
4. The determination optimization method according to claim 1, characterized in that: The thermal resistance calculation formula is: R = δ × λ -1 , where: R is the thermal resistance of the insulation material, m 2 ·k / w; δ is the thickness of the insulation material, m; λ is the thermal conductivity of the insulation material, W / (m·k).
5. The determination optimization method according to claim 1, characterized in that: The critical freezing strength is above 5 MPa.
6. The determination optimization method according to claim 1, characterized in that: The fitting equation is: y = a + b × r R ; Where R is thermal resistance, m 2 k / w; y is the coverage curing time to reach 5MPa, h; a, b, r are constants, and the specific value conditions are as follows: -15℃≤T 环境 <-12.5℃,5℃≤T 表面 When <15℃, a=24.21,b=74.95,r=0.33; -15℃≤T 环境 <-12.5℃,15℃≤T 表面 When <25℃, a=18.46,b=58.53,r=0.38; -15℃≤T 环境 <-12.5℃,25℃≤T 表面 When ≤35℃, a=12.89, b=49.17, r=0.40; -12.5℃≤T 环境 <-7.5℃,5℃≤T 表面 When <15℃, a=17.76,b=55.44,r=0.38; -12.5℃≤T 环境 <-7.5℃,15℃≤T 表面 When <25℃, a=14.36,b=50.99,r=0.34; -12.5℃≤T 环境 <-7.5℃,25℃≤T 表面 When ≤35℃, a=11.07, b=42.42, r=0.29; -7.5℃≤T 环境 <-2.5℃,5℃≤T 表面 When <15℃, a=15.20,b=45.43,r=0.37; -7.5℃≤T 环境 <-2.5℃,15℃≤T 表面 When <25℃, a=13.26,b=41.04,r=0.33; -7.5℃≤T 环境 <-2.5℃,25℃≤T 表面 When ≤35℃, a=9.18, b=38.95, r=0.31; -2.5℃≤T 环境 <2.5℃,5℃≤T 表面 When <15℃, a=9.37,b=31.03,r=0.50; -2.5℃≤T 环境 <2.5℃,25℃≤T 表面 When ≤35℃, a=7.71,b=23.47,r=0.38; 2.5℃≤T 环境 ≤5℃, 5℃≤T 表面 When <15℃, a=25.75,b=39.09,r=0.20; 2.5℃≤T 环境 ≤5℃, 15℃≤T 表面 When <25℃, a=18.47,b=36.36,r=0.15; 2.5℃≤T 环境 ≤5℃, 25℃≤T 表面 When ≤35℃, a=11.97, b=38.54, r=0.
13.
7. The determination optimization method according to claim 1, characterized in that: The correction fitting equation used in the correction step is: y=x / α, where: y is the time for the concrete to reach the critical strength of 5MPa after freezing, h; x is the expected curing time, h; α is the correction coefficient, and the value of α is as follows: 2.5≤T 环境 ≤5, wind speed V<3m / s, α=1.13; 2.5≤T 环境 ≤5, 3≤V≤5, α=1.28; 2.5≤T 环境 ≤5, 5<V≤8, α=1.53; -2.5≤T 环境 <2.5, V<3, α=1.16; -2.5≤T 环境 <2.5, 3≤V≤5, α=1.33; -2.5≤T 环境 <2.5,5<V≤8,α=1.63; -7.5≤T 环境 <-2.5, V<3, α=1.20; 7.5≤T 环境 <-2.5, 3≤V≤5, α=1.38; 7.5≤T 环境 <-2.5, 5<V≤8, α=1.68; -12.5≤T 环境 <-7.5, V<3, α=1.53; -12.5≤T 环境 <-7.5, 3≤V≤5, α=1.59; -12.5≤T 环境 <-7.5, 5<V≤8, α=1.72; -15≤T 环境 <-12.5, V<3, α=1.68; -15≤T 环境 <-12.5, 3≤V≤5, α=1.74; -15≤T 环境 <-12.5, 5<V≤8; 1.
80.
8. The determination optimization method according to claim 1, characterized in that: The obtained correction equation is: x = αa + αb × r R .
9. The determination optimization method according to claim 1, characterized in that: The thermal resistance value R after deformation is determined by the equation: