A method for evaluating the anti-icing performance of concrete coatings in water delivery channels

Abstract

The present invention discloses a method for evaluating the anti-icing performance of concrete coatings for water conveyance channels. The present invention evaluates the anti-icing performance of concrete anti-icing coatings for water conveyance channels by the difficulty of icing, and uses the icing speed at a fixed temperature and flow rate per unit time to reflect the difficulty of icing the coating. A rectangular concrete specimen is coated with an anti-icing coating to perform an icing test and calculate the icing speed. The anti-icing performance evaluation method for anti-icing coatings of the present invention can fully reflect the anti-icing performance of concrete anti-icing coatings for water conveyance channels, and provide a basis for solving the problem of water conveyance in the winter ice period for water conveyance channels, ensuring safe operation during the ice period, and improving water supply capacity during the ice period.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic concrete, and in particular to a method for evaluating the anti-icing performance of a concrete coating on a water conveyance channel. Background Art

[0002] Northeast, Northwest and North my country are in seasonal frozen ground areas, and frost damage to buildings is very common, especially channel concrete. At present, researchers have conducted in-depth research on the problem of frost heave damage to channels and have achieved a lot of research results. This problem has also been well solved. For some areas prone to ice disasters, the anti-icing technology of concrete has attracted widespread attention from researchers around the world. There are four main types of anti-icing measures in anti-icing technology: solution anti-icing, mechanical deicing, thermal anti-icing and coating anti-icing. Among them, anti-icing coatings mainly achieve the purpose of anti-icing through the special surface properties and microphase morphology of the material. This type of material needs to have both anti-icing and ice-repelling properties, and reduce or even eliminate ice and snow accumulation by extending the freezing time and reducing the adhesion of ice. There are three main reasons for delaying the ice condensation time: 1. The surface of the anti-icing coating is generally a hydrophobic surface, and the contact area between the surface water droplets and the substrate is very small, which can inhibit the formation of ice with fewer nucleation sites; 2. According to the classical thermodynamic nucleation theory, the nucleation free energy barrier ΔG required for ice nucleation formation and growth is positively correlated with the static water contact angle, that is, the larger the contact angle, the higher the ΔG required for nucleation, and the more difficult it is for water droplets to nucleate; 3. The micro-nano rough structure on the coating surface forms an air layer between the substrate and the water droplets, which has a heat insulation effect to a certain extent and reduces heat transfer, reducing the freezing rate of water droplets. The anti-icing coating can reduce the adhesion strength of ice mainly because the super-hydrophobic surface has excellent waterproof properties, so that water does not penetrate into the concrete, but only condenses on the surface, resulting in less adhesion between the ice layer and the concrete. In principle, coating anti-icing should be said to be an ideal anti-icing method, because it belongs to active protection, low energy consumption, environmental friendliness and a wide range of applications.

[0003] In actual application, the anti-icing performance of the anti-icing coating directly determines the winter anti-icing effect of the water supply channel. However, the current research is more about concrete anti-icing coating technology, and there are fewer methods for testing and evaluating the performance of anti-icing coatings on water supply channel concrete. This is because the complexity of the interaction between ice and coating makes it difficult to establish universal standards. The surface coating modification of water supply channel concrete realizes passive anti-icing of the main channel material. The current performance evaluation of anti-icing coatings is based on the laboratory characterization of hydrophobic surfaces, that is, measuring the contact angle of the coating. A few will conduct icing tests on the coating, which is not targeted enough for the main body of the water supply channel. Summary of the invention

[0004] In view of the above background technology, in order to solve the problem of water delivery during the ice period caused by freezing of water delivery channels in winter, ensure safe operation during the ice period, and improve water supply capacity during the ice period, the present invention designs a method for evaluating the anti-icing performance of concrete coatings of water delivery channels, which fully reflects the anti-icing properties of the channel concrete coatings.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A method for evaluating the anti-icing performance of a water channel concrete coating, comprising:

[0007] (1) Preparation of test specimens: forming a group of rectangular concrete specimens, and coating one side of the group of rectangular concrete specimens with an anti-icing coating as rectangular concrete test specimens;

[0008] (2) Concrete test specimen freezing test: A group of rectangular concrete test specimens prepared in step (1) are immersed in water to make them saturated with water. During the test, the test specimens are taken out, and the surface of the test specimens is wiped dry with a wet cloth to weigh the saturated surface dry mass M0. The test specimens are then placed in a low-temperature box to ensure that half of the anti-icing coating surface of the test specimens is immersed in water. The typical water flow velocity and air temperature of the water channel in the winter ice period are set, and the test is run while maintaining the water flow velocity and temperature. After the test, the surface of the test specimens is wiped dry in the low-temperature box to weigh the mass of the frozen specimens M1, and the freezing velocity is calculated. Where S is the surface area of ​​the anti-icing coating, t is the running time, and the average value of the icing speed of a group of test pieces is taken as the icing speed of the anti-icing coating of the test piece;

[0009] (3) Evaluation of the anti-icing performance of the coating: The anti-icing performance of the concrete coating of the water supply channel is evaluated by the difficulty of icing, that is, the icing speed per unit time at a fixed temperature and flow rate measured in step (2) reflects the icing difficulty of the coating. The lower the icing speed, the more difficult it is for the coating to freeze, that is, the better the anti-icing performance of the coating.

[0010] Furthermore, the number of concrete specimens in a group in step (1) of the present invention is at least 3.

[0011] Furthermore, the rectangular concrete specimen in step (1) of the present invention is a 150×150×300 mm concrete specimen, and an anti-icing coating is coated on the 150×300 mm surface.

[0012] Furthermore, the rectangular concrete test piece in step (2) of the present invention is immersed in water for 4 days.

[0013] Furthermore, in step (2) of the present invention, the typical water flow velocity of the water conveyance channel during the winter ice period is 1 to 1.5 m / s, and the air temperature is -30°C to -20°C. In step (2), different water flow velocities and air temperatures are set to obtain different freezing speeds, and the anti-icing performance of the anti-icing coating at different water flow velocities and air temperatures is evaluated.

[0014] Furthermore, in step (2) of the present invention, the water flow rate and temperature are maintained for at least 4 hours.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] At present, the method of measuring the contact angle to evaluate the anti-icing performance of the coating is inaccurate. When the coating reaches the hydrophobic level (contact angle>90°), the anti-icing performance of the coating is not simply positively correlated with the contact angle. The evaluation method of the present invention determines the icing difficulty of the coating through experiments, and evaluates the anti-icing performance of the anti-icing coating for concrete water delivery channels. DETAILED DESCRIPTION

[0017] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form.

[0018] Example

[0019] The method for evaluating the anti-icing performance of a water conveyance channel concrete coating of the present invention comprises:

[0020] (1) Preparation of test specimens: Form a group of rectangular concrete specimens and a group of "8"-shaped concrete specimens at the same time;

[0021] One side of the rectangular concrete specimen is coated with an anti-icing coating to serve as a rectangular concrete specimen to be tested;

[0022] (2) Concrete test specimen freezing test: A group of rectangular concrete test specimens prepared in step (1) are immersed in water to make them saturated with water. During the test, the test specimens are taken out, and the surface of the test specimens is wiped dry with a wet cloth to weigh the saturated surface dry mass M0. The test specimens are then placed in a low-temperature box to ensure that half of the anti-icing coating surface of the test specimens is immersed in water. The typical water flow velocity and air temperature of the water channel in the winter ice period are set, and the test is run while maintaining the water flow velocity and temperature. After the test, the surface of the test specimens is wiped dry in the low-temperature box to weigh the mass of the frozen specimens M1, and the freezing velocity is calculated. Where S is the surface area of ​​the anti-icing coating, t is the running time, and the average value of the icing speed of a group of test pieces is taken as the icing speed of the anti-icing coating of the test piece;

[0023] (3) Evaluation of anti-icing coating performance: The anti-icing performance of the water supply channel concrete coating is evaluated by the difficulty of icing. The icing speed per unit time at a fixed temperature and flow rate measured in step (2) reflects the icing difficulty of the coating. The lower the icing speed, the more difficult it is for the coating to freeze, that is, the better the anti-icing performance.

[0024] Furthermore, the number of concrete test pieces in step (1) of the present invention is 3.

[0025] Furthermore, the rectangular concrete specimen in step (1) of the present invention is a 150×150×300 mm concrete specimen, and an anti-icing coating is coated on the 150×300 mm surface.

[0026] Furthermore, the rectangular concrete test piece in step (2) of the present invention is immersed in water for 4 days.

[0027] Furthermore, in step (2) of the present invention, the water flow rate and temperature are maintained for 4 hours.

[0028] Polyurea resin (PU), polyfluorosilane (PFS) and polytetrafluoroethylene (PTFE) were used as anti-icing coatings to evaluate the anti-icing performance of the coatings, and compared with the blank group.

[0029] The freezing temperature of the first test was set to -20°C and the water flow rate was 1m / s, and the freezing temperature of the second test was set to -30°C and the water flow rate was 1.5m / s. The freezing test results of the anti-icing coating on concrete specimens are shown in Table 1, and the results of the comparison of the coating contact angle and the freezing difficulty parameter are shown in Table 2.

[0030] Table 1 Icing test results of different anti-icing coatings and blank group

[0031]

[0032] Table 2 Comparison of coating contact angle and icing difficulty parameters

[0033]

[0034]

[0035] It can be seen from the test results in Tables 1 and 2 that the contact angle and the difficulty of icing are not a simple linear relationship, and there are certain differences in the responses of different coatings to changes in freezing temperature and water flow velocity. The anti-icing performance of anti-icing coatings on concrete of water conveyance channels needs to be evaluated through targeted tests, especially the freezing speed under typical climatic conditions of the service project can more fully reflect the anti-icing performance of anti-icing coatings on concrete of water conveyance channels.

Claims

1. A method for evaluating the anti-icing performance of a water channel concrete coating, characterized in that: include: (1) Preparation of test specimens: forming a group of rectangular concrete specimens; coating one side of the rectangular concrete specimens with an anti-icing coating to serve as rectangular concrete test specimens; (2) Concrete test specimen freezing test: A group of rectangular concrete test specimens prepared in step (1) are immersed in water to make them saturated with water. During the test, the test specimens are taken out, and the surface of the test specimens is wiped dry with a wet cloth to weigh the saturated surface dry mass M0. The test specimens are then placed in a low-temperature box to ensure that half of the anti-icing coating surface of the test specimens is immersed in water. The typical water flow velocity and air temperature of the water channel in the winter ice period are set, and the test is run while maintaining the water flow velocity and temperature. After the test, the surface of the test specimens is wiped dry in the low-temperature box to weigh the mass of the frozen specimens M1, and the freezing velocity is calculated. Where S is the surface area of ​​the anti-icing coating, t is the running time, and the average value of the icing speed of a group of test pieces is taken as the icing speed of the anti-icing coating of the test piece; (3) Evaluation of the anti-icing performance of the coating: The anti-icing performance of the anti-icing coating of the water supply channel concrete is evaluated by the difficulty of icing. That is, the icing speed per unit time at a fixed temperature and flow rate measured in step (2) reflects the icing difficulty of the coating. The lower the icing speed, the more difficult it is for the coating to freeze, and the better the anti-icing performance.

2. The method for evaluating the anti-icing performance of a water channel concrete coating according to claim 1, characterized in that: The number of concrete specimens in a group described in step (1) is at least 3.

3. The method for evaluating the anti-icing performance of a water channel concrete coating according to claim 2, characterized in that: The rectangular concrete specimen in step (1) is a 150×150×300 mm concrete specimen, and an anti-icing coating is applied on the 150×300 mm surface.

4. The method for evaluating the anti-icing performance of a water channel concrete coating according to claim 1, characterized in that: The rectangular concrete test piece in step (2) is immersed in water for 4 days.

5. The method for evaluating the anti-icing performance of a water channel concrete coating according to claim 1, characterized in that: The typical water flow velocity of the water conveyance channel in step (2) during the winter ice period is 1 to 1.5 m / s, and the air temperature is -30°C to -20°C.

6. The method for evaluating the anti-icing performance of a water channel concrete coating according to claim 1, characterized in that: In the step (2), the water flow rate and temperature are maintained for at least 4 hours.

Images