A method for rapid determination of the resistance of concrete to sulphates based on a composite immersion solution

Abstract

The application relates to the field of civil engineering materials, in particular to a method for rapidly determining the sulfate resistance grade of concrete, and specifically comprises the following steps: (1) preparing a concrete test piece; (2) performing a dry-wet cycle test by using a 5% sodium sulfate+2.5% magnesium sulfate composite solution; (3) test result calculation: using a function K f2 = exp ( a+b × t+c × t^ 2) to perform regression analysis and obtain the values of parameters a 、 b 、 c in a regression equation; (4) sulfate resistance grade calculation: according to a calculation formula: K f1 = exp ( a+ ( b / 1.0810)× t+ ( c / 1.1686)× t^ 2), letting K f1 =75% in the above formula, solving the value of t and rounding down to thirty, that is, the sulfate resistance grade of the concrete to be measured. The application can rapidly determine the sulfate resistance grade of concrete under the premise of ensuring the accuracy.

Description

Technical Field

[0001] This application relates to the field of civil engineering materials, and more specifically, it relates to a method for rapidly determining the sulfate resistance grade of concrete based on a composite soaking solution. Background Technology

[0002] Concrete is the most widely used structural material in civil engineering. In recent years, the service life of concrete structures has received increasing attention. The durability of concrete is closely related to its surrounding environment. When the concentration of sulfate ions in the environment reaches a certain level, and the concrete structure is not protected, external sulfate ions can easily penetrate into the concrete, react, and cause expansion, ultimately leading to structural damage. In severe cases, it may even threaten people's lives and property.

[0003] According to the test method for sulfate resistance grade in the "Standard for Test Methods of Long-Term Performance and Durability of Concrete" (GB / T 50082-2024), concrete specimens need to be cured under standard conditions for 28 days or at the age specified in the design (which should be stated in the test report). Then, they need to be placed in a 5% sodium sulfate solution for wet-dry cycle test. After reaching the required number of cycles, the compressive strength of the wet-dry cycle specimens and the control specimens should be measured, the compressive strength corrosion resistance coefficient of the specimens should be calculated, and then the sulfate resistance grade of the concrete should be determined. The test cycle is relatively long. Summary of the Invention

[0004] To determine the sulfate resistance grade of concrete more quickly, accurately, and conveniently, this application provides a method for rapidly determining the sulfate resistance grade of concrete based on a composite soaking solution.

[0005] This application provides a method for rapidly determining the sulfate resistance grade of concrete based on a composite soaking solution, employing the following technical solution: A method for rapidly determining the sulfate resistance grade of concrete includes the following steps: (1) Prepare concrete specimens; (2) Wet-dry cycle test: testing concrete specimens under different conditions. t In the wet-dry cycle test, the solution underwent a process in a 5% sodium sulfate + 2.5% magnesium sulfate composite solution. N Coefficient of compressive strength and corrosion resistance after two wet-dry cycles K f2 ; (3) Calculation of test results: Based on the test results of step (2), and using the function on them... K f2 = exp ( a+b × t+c × t^2) Perform regression analysis to obtain the parameters in the regression equation. a , b , c The possible values ​​of ; (4) Calculation of sulfate resistance grade: According to the calculation formula: K f1 = exp(a+(b / 1.0810 ） × t+(c / 1.1686 ) × t ^2) Let the above formula be K f1 =75%, solve. t The value is then rounded down to the nearest thirty, which gives the sulfate resistance grade of the concrete being tested.

[0006] In one specific implementation, in step (2), K f2 =f 2 / f 0, where, f 2 represents the concrete specimens of group A in... N Compressive strength (MPa) after one wet-dry cycle; f 0 represents the compressive strength (MPa) of the standard-cured concrete specimens from Group B, which were cured at the same age as the Group A concrete specimens; additionally, time... t The unit is days.

[0007] Furthermore, f 2 and f During the 0 test, the arithmetic mean of three specimens was used as the measured value for each test age.

[0008] In one specific embodiment, in step (2), the concrete specimens of group A are cured under standard conditions for 2 days before the 28-day curing period. They are then taken out of the standard curing room, their surface moisture is wiped off, and they are placed in an oven at (80±5)℃ to dry. After drying, they are cooled to room temperature in a dry environment. They are then immediately immersed in a 5% sodium sulfate + 2.5% magnesium sulfate composite solution, with the temperature of the immersion solution controlled at (25~30)℃. They are then taken out and dried, with the drying temperature controlled at (80±5)℃, which is one wet-dry cycle. The time from the start of immersion in the composite solution to the end of the immersion process is (15±0.5)h, and the time of one wet-dry cycle is (24±2)h. N After several wet-dry cycles, the compressive strength (MPa) of the concrete specimens in group A was measured. f 2.

[0009] Furthermore, the process begins with immersing the test block in the composite solution and then removing and drying it, constituting one complete wet-dry cycle.

[0010] In one specific embodiment, in step (1), the concrete specimen is a cubic specimen with dimensions of 100mm×100mm×100mm; the water-cement ratio of the concrete specimen is in the range of 0.38~0.50, and the fly ash content is in the range of 0~30%.

[0011] In summary, this application has the following beneficial effects: This application provides a method for rapidly determining the sulfate resistance grade of concrete and proposes a calculation formula: K f1 = exp ( a+ ( b / 1.0810)× t+ ( c / 1.1686)× t^ 2), let the above formula... K f1 =75%, solve. t The value is then rounded down to the nearest thirty, which gives the sulfate resistance grade of the concrete being tested. This application can significantly shorten the testing cycle and has high accuracy. Detailed Implementation

[0012] The present application will be further described in detail below with reference to the embodiments.

[0013] Example This application provides a method for rapidly determining the sulfate resistance grade of concrete, including the following steps: (1) Prepare concrete specimens; The concrete specimens were cubic blocks with dimensions of 100mm×100mm×100mm; the water-cement ratio of the concrete specimens was in the range of 0.38 to 0.50, and the fly ash content was in the range of 0 to 30%.

[0014] (2) Wet-dry cycle test: testing concrete specimens under different conditions. t Within a certain time period, it underwent a reaction in a 5% sodium sulfate + 2.5% magnesium sulfate composite solution. N Compressive corrosion resistance coefficient after wet-dry cycle test K f2 ; in, K f2 =f 2 / f 0, where, f 2 represents the concrete specimens of group A in... N The compressive strength (MPa) after each wet-dry cycle was measured, and the arithmetic mean of three specimens was used as the measured value for each test age. f0 represents the compressive strength (MPa) of the standard-cured concrete specimens from Group B, which are at the same age as the three concrete specimens from Group A. The arithmetic mean of the three specimens at each test age is used as the measured value. Additionally, time... t The unit is days.

[0015] Specifically, in step (2), the concrete specimens of group A were cured under standard conditions for 2 days before reaching the 28-day age. They were taken out of the standard curing room, their surface moisture was wiped off, and they were placed in an oven at (80±5)℃ to dry. After drying, they were cooled to room temperature in a dry environment and immediately immersed in a 5% sodium sulfate + 2.5% magnesium sulfate composite solution. After that, they were taken out and dried, which was one dry-wet cycle. The time from the start of immersion in the composite solution to the end of the immersion process was (15±0.5)h, and the time for one dry-wet cycle was (24±2)h. The temperature of the immersion solution was controlled at (25~30)℃. The drying temperature after immersion was controlled at (80±5)℃. N After one wet-dry cycle, the compressive strength (MPa) of the three concrete specimens in group A was measured. f 2.

[0016] (3) Calculation of test results: Based on the test results of step (2), and using the function on them... K f2 = exp ( a+b × t+c × t^ 2) Perform regression analysis to obtain the parameters in the regression equation. a , b , c The possible values ​​of ; (4) Calculation of sulfate resistance grade: According to the calculation formula: K f1 = exp ( a+ ( b / 1.0810)× t+ ( c / 1.1686)× t ^ 2), let the above formula... K f1 =75%, solve. t The value is then rounded down to the nearest thirty, which gives the sulfate resistance grade of the concrete being tested.

[0017] It should also be noted that in this application, time... t The smallest unit is 1 day, which is the number of cycles. N The smallest unit is 1 time, and the corresponding time for 1 dry-wet cycle is (24±2h).

[0018] The following is an illustration through specific examples.

[0019] Example 1 Example 1 provides a method for rapidly determining the sulfate resistance grade of concrete, comprising the following steps: (1) Preparation of concrete specimens: The concrete specimens are cubic blocks with dimensions of 100mm×100mm×100mm; the concrete specimens are made of P·MSR 42.5 medium sulfur-resistant cement, Class F II fly ash, water-cement ratio of 0.41, fly ash content of 25%, and cement content of 208kg / m³. 3 Fly ash usage: 89 kg / m³ 3 The sand content is 34%.

[0020] (2) Wet and dry cycle test: Concrete specimens from Group A were cured for 26 days under standard conditions of indoor temperature (20±2)℃ and relative humidity above 95%. After being removed from the standard curing room, the surface moisture was wiped off, and the specimens were placed in an oven at (80±5)℃ for 24 hours. After drying, they were cooled to room temperature in a dry environment and immediately immersed in a 5% sodium sulfate + 2.5% magnesium sulfate composite solution, followed by further drying. This constituted one wet-dry cycle. The time from the start of immersion in the composite solution to the end of the immersion process was (15±0.5) hours, and the time for one wet-dry cycle was (24±2) hours. After 10, 20, 30, and 40 wet-dry cycles, the compressive strength (MPa) values ​​of the Group A concrete specimens at different test ages were obtained. f 2; The compressive strength (MPa) of concrete specimens from group B at the same age was obtained. f 0.

[0021] Testing concrete specimens at t In the wet-dry cycle test, the compressive corrosion resistance coefficient in a 5% sodium sulfate + 2.5% magnesium sulfate composite solution was measured. K f2 ; K f2 =f 2 / f 0, where, f 2 represents the concrete of Group A in N Compressive strength (MPa) after one wet-dry cycle; f 0 represents the compressive strength (MPa) of the standard-cured concrete specimens of Group B at the same age as the concrete specimens of Group A; 0 represents the compressive strength at different test ages after 10, 20, 30, and 40 wet-dry cycles. f 2. f 0 and K f2 The values ​​are shown in Table 2.

[0022] (3) Calculation of test results: Based on the test results of step (2), and using the function on them...K f2 = exp ( a+b × t+c × t^ 2) Perform regression analysis to obtain the parameters in the regression equation. a , b , c The value of ; in this embodiment a , b , c See Table 2.

[0023] (4) Calculation of sulfate resistance grade: According to the calculation formula: Kf 1= exp ( a+ ( b / 1.0810)× t+ ( c / 1.1686)× t^ 2), let the above formula... Kf 1 = 75%, solve. t The value is rounded down to 30, which gives the sulfate resistance grade of the concrete to be tested, as shown in Table 2.

[0024] Examples 2-5 The difference between Examples 2-5 and Example 1 is that the mix proportion parameters and the values ​​of parameters in each step of the concrete specimen are different, as shown in Tables 1 and 2.

[0025] Table 1. Raw material list for concrete specimens in the examples. Table 2 Correlation coefficient table of the embodiments Accuracy verification and evaluation of test cycle Concrete specimens from Examples 1-5 were taken and their sulfate resistance was tested according to the current national standard "Standard for Test Methods of Long-Term Performance and Durability of Concrete" (GB / T 50082-2024). The deviation of the test results from the test results of this invention and the evaluation of the test cycle are shown in Table 3.

[0026] Table 3 Performance Deviation and Test Cycle Evaluation Table of Examples As shown in Table 3, the calculation formula provided in this application... K f1 = exp ( a+ ( b / 1.0810 )× t+ ( c / 1.1686 )× t^2), and the corresponding calculation method, can not only greatly save the test cycle of the sulfate resistance grade of concrete, but also ensure a high accuracy rate.

[0027] 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 rapidly determining the sulfate resistance grade of concrete, characterized in that, Includes the following steps: (1) Prepare concrete specimens; (2) Wet-dry cycle test: testing concrete specimens under different conditions. t Within a certain time period, it underwent a reaction in a 5% sodium sulfate + 2.5% magnesium sulfate composite solution. N Coefficient of compressive corrosion resistance after wet-dry cycle test K f2 ; (3) Calculation of test results: Based on the test results of step (2), and using the function on them... K f2 = exp ( a+b × t+c × t^ 2) Perform regression analysis to obtain the parameters in the regression equation. a , b , c The possible values ​​of ; (4) Calculation of sulfate resistance grade: According to the calculation formula: K f1 = exp(a+(b / 1.0810 ） × t+(c / 1.1686 ) × t^2) Let the above formula be K f1 =75%, solve. t The value is then rounded down to the nearest thirty, which gives the sulfate resistance grade of the concrete being tested.

2. The method for rapidly determining the sulfate resistance grade of concrete according to claim 1, characterized in that, In step (2), K f2 =f 2 / f 0, where, f 2 represents the concrete specimens of group A in... N Compressive strength (MPa) after one wet-dry cycle; f 0 represents the compressive strength (MPa) of the standard-cured concrete specimens from Group B, which were cured at the same age as the Group A concrete specimens; additionally, time... t The unit is days.

3. The method for rapidly determining the sulfate resistance grade of concrete according to claim 2, characterized in that, In step (2), the concrete specimens of group A were cured under standard conditions for 2 days before the 28-day age. They were taken out of the standard curing room, wiped dry, and placed in an oven at (80±5)℃ to dry. After drying, they were cooled to room temperature in a dry environment and immediately immersed in a 5% sodium sulfate + 2.5% magnesium sulfate composite solution. The temperature of the immersion solution was controlled at (25~30)℃. They were then taken out and dried again at (80±5)℃. This was one wet-dry cycle. The time from the start of immersion in the composite solution to the end of the immersion process was (15±0.5)h, and the time for one wet-dry cycle was (24±2)h. N After several wet-dry cycles, the compressive strength (MPa) of the concrete specimens in group A was measured. f 2.

4. The method for rapidly determining the sulfate resistance grade of concrete according to claim 1, characterized in that, In step (1), the concrete specimen is a cubic specimen with dimensions of 100mm×100mm×100mm; the water-cement ratio of the concrete specimen is in the range of 0.38~0.50, and the fly ash content is in the range of 0~30%.

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