Effect of thermo-solid cooked lime powder coating on the cooling of asphalt pavement

Liu Jifa, Lai Feng, Wei Wei
Tai'an City Road Planning and Design Institute, Shandong Province
Chang'an University Special Area Road Engineering Ministry of Education Key Laboratory
Summary: In order to reduce the temperature of the asphalt road surface, this paper developed a thermo-solid cooked lime powder coating. First, polyester resin and cooked lime as the main raw materials, prepared three light-color system thermo-solid cooked lime powder coating, and test reflectivity, and then, through cooling, anti-slip, wear-resistant and adhesive tests to analyze the color of the coating, the amount of cloth on the cooling effect and road performance. The results show that the reflectivity of polyester light gray and polyester light orange is high in the 400 to 2000nm band, and can reach 76%

. As the amount of cloth increases, the cooling effect and adhesion increase, while the anti-slip and wear-resistant performance decreases. Further, polyester light gray is 44.45% higher than polyester sea gray, indicating that the cooling effect of powder coating is related to color. Taking into account the cooling effect and road performance, the optimal spread is 100-150g/m2.
Investment
thermoso-solid powder coating refers to a thermo-solid powder sprayed on a hot-mixed asphalt surface, which uses the adhesion of asphalt at high temperatures and the curing reaction of powder coating to make the powder firmly adhere to the surface of the asphalt mixture to form a coating. Thermoo-solid powder coating has the following advantages:
(1) powder coating is a solid powder, free of any solvents, and is non-volatile during preparation, transportation and construction.
(2) light-colored thermoso-solid powder reflectivity is high, which can reduce the temperature of the road surface and delay the production of rut disease.
(3) powder coating can be mechanized production, storage stability, easy to transport, high degree of modular process, improve production efficiency.
(4) powder coating enters the void of asphalt pavement without affecting the anti-slip performance of the road surface.
research on powder coatings abroad began earlier, and in 1958, the experiment of the thermo-solid powder process of fluidized bed coating was successful, and the powder coating has been of practical value ever since. In 1971, SCADOBV of the Netherlands developed polyester epoxy mixed powder coatings and TGIC powder coatings. The research and production of powder coatings in China started late, since 1990, China's powder coatings industry has developed rapidly. Powder coatings are widely used in the home appliance shell market because of their environmental protection, color and durability. The research on the application of thermoso-solid powder to the thermal reflection coating of asphalt pavement in China is still in the exploration stage. Emery uses a specific process to heat cooked lime on the surface of hot-mixed asphalt concrete, forming a gray asphalt pavement, which significantly improves the backlight of the road surface, can effectively reduce the road surface temperature, improve the road surface anti-rutting performance. Tests such as Timm have shown that the surface of hot-pressed lime can be effectively reduced by 5 degrees C during the summer high temperature season. Tang Yu prepares a thermostosteroid coating with resin, titanium dioxide and carbon black as the main raw materials, which can reduce the road surface temperature by 12.5 degrees C. Zheng Mulian and other epoxy resin, titanium dioxide as raw materials for the preparation of thermal reflection coating, the results show that the white thermal coating indoor cooling limit of up to 18 to 25 degrees C.
, the cooked lime sprinkled on the surface of the asphalt road can reduce the temperature of the road surface, but the resistance to wear and consumption is poor. And the cooling effect of thermo-solid cooked lime coating is not yet known. In this paper, cooked lime is applied to the asphalt pavement surface with the help of more viscous resin material to improve the anti-wear performance of the coating material, and then, with polyester resin, curing agent and pigment as the main raw material, the thermoclytic cooked lime powder coating of different colors is prepared, and the cooling effect of the thermosolytic cooked lime powder coating of different colors is discussed by using the homemade heat radiation device, and its road performance is tested.
coating composition
1.1 polyester resin
thermo-solid powder coating is generally composed of resins, curing agents, pigments and additives. Resin is the main film-forming substance of thermoosteroid powder coating, and it is the main component that determines the properties of the coating and the properties of the coating. In this paper, the performance, price and suitability of resins are considered, and polyester resins are selected as the main raw materials, and their technical indicators are shown in Table 1. Polyester resins are generally called polymer compounds made up of binary alcohols or binary acids or polyols and polyic acids. Polyester resin in the powder rate, weather resistance, UV glare and other performance is superior, and in the construction, storage stability and price have advantages. Low and medium acid values (25 to 45 mg KOH/g) polyester resins are cured with isocyanuric acid triglycerides (TGICs) to prepare polyester powder coatings with excellent weather resistance.
1.2 curing agent
the resin in thermostate powder coating must cross-link with the curing agent in order to form insoluble, non-melting 3D mesh polymer. Polyester powder coatings use isocyanuric acid triglycerides (TGICs) as curing agents. TGIC can be combined with low-acid polyester resins to create a high weather-resistant polyester powder coating, which has excellent weather resistance, electrometic properties, heat resistance, chemical resistance.
1.3 Pigments
Pigments are designed to color the coating and improve the reflectivity of the coating, and fillers are designed to improve the physical, mechanical properties and reduce coating costs. In this article, three colors are provisioned, and the recipe is shown in Table 2.
reflectivity
the reflectivity of the three colors was tested with an UV-visible near-infrared spectrograph, and the results are shown in Figure 1.
As can be seen from Figure 1, polyester light gray and polyester light orange have high reflectivity in both visible and near-infrared segments, with a reflectivity of 76% in the 400 to 2000 nm band and 70% in polyester light gray and polyester light orange. Therefore, polyester light gray paint and polyester light orange paint have a high reflectivity.
preparation process
3.1 powder coating preparation process
This experiment uses melt extrusion method to prepare powder coating, melt extrusion method laboratory preparation process is as follows:
(1) premix. Use a cylinder mixer to mix resins, pigments, and additives evenly.
(2) melt out. The mixture undergoes thermal melting and uses high shear force to distribute curing agents, leveling agents, pigments, etc. evenly in the resin, with the tool being a double helix extruder.
(3) Smash. Break the squeezed material to the particle size required for the coating using a mechanical crusher at room temperature.
(4) filter. Filter out the particle size required for the test.
3.2 Thermoso-solid powder coating test part preparation
asphalt mixture rutting plate after crushing, the use of 0.075mm standard sieve will be evenly spread on the surface of the mixture, the spread temperature should not be less than 105 degrees C. After the test piece is unmodulated, wash the surface of the mixture with a water cannon to verify the firmness of the bonding of the powder to the asphalt. The preparation process can be summarized as: (a) preparation of hot-pressed rutting plates, (b) spraying powder coating, (c) cooling and curing into film, and (d) molding. The procedure is shown in Figure 2. Paints of light gray, light orange and sea gray are applied to the surface of the rut plate in accordance with the above process, as shown in Figure 3.
the cooling effect
this experiment uses the self-developed indoor simulated radiation experimental system to test the cooling effect of the coating. One group of uncooled black rutting plate as the standard test piece, the rest of the coating three different colors of thermo-solid powder, paint spray volume of 50g/m2, 100g/m2, 150g/m2, 200g/m2, the test piece in the device for testing, compared with the application of different colors and amounts of testware and standard test parts between the cooling situation. The results of the experiment are shown in Figure 4.
by Figure 4, as the amount of cloth increased, the powder coating cooling range increased. When from 50g/m2 to 100g/m2, the cooling range is larger, and the cooling range from 100g/m2 to 200g/m2 is gradually smaller. Because the coating is small, the coating is thin, thermal radiation is easy to pass through the coating, as the amount of scattering increases, the coating gradually thickens, the thermal radiation transmission rate decreases, and when the thickness of the coating continues to increase, the thicker coating will form a build-up layer, weakening the cooling effect. And when the amount of cloth is too large, not only reduce its anti-slip performance, but also increase the economic costs. Therefore, it is recommended to spread the amount of 100g / m2 - 150g / m2.
figure 4, the cooling range is in the order of polyester light gray > polyester light orange> polyester sea gray. At 200g/m2, the maximum cooling range of polyester light gray and polyester sea gray was 13 degrees C and 9 degrees C, respectively, and the cooling range of polyester light gray was 44.45 percent higher than that of polyester sea gray, because the reflectivity of polyester light gray was slightly higher than that of polyester sea gray. Explain that color systems are property of cooling.
road performance study
5.1 anti-slip performance
thermoo-solid powder coating will change the vehicle tire and road surface contact status, in this section will explore the impact of the amount of cloth on the road surface anti-slip performance. Using the BPN of the swing friction device to test the test piece, the experimental results are shown in Table 3.
as can be known from Table 3, BPN decreases with the increase in the amount of scattering, which is 200g/m2, which is lower than the specification requirement. This is because when the coating is thicker, it not only reduces the depth of construction of the asphalt surface, but also forms a smooth resin film, so BPN is reduced. In order to reduce the effect of coating on the anti-slip performance of the road surface, the appropriate amount of sprinkling should be used to not only make the anti-slip performance meet the specification requirements (BPN>45), but also the cooling performance can also meet the requirements of road cooling. Taking into account anti-slip and cooling properties, it is recommended that the optimum spread is 100-150g/m.
in terms of formulation, pure polyester light orange BPN is the largest, indicating that the addition of orange peel agent, can make the surface appear micro-fine texture, improve anti-slip performance.
5.2 grinding test
thermoso-solid powder coating will be repeatedly crushed by driving load, this paper uses an accelerated wearer to test the thermo-solid powder coating. The results of the experiment are shown in Figure 5, and the mass loss before and after wear and tear is shown in Table 4.
is known from the data in Table 4, and the quality loss increases gradually as the amount of scattering increases. This is because when the amount of cloth is small, the sprayed powder can all adhere to the surface of the asphalt mixture, it is difficult to wear out. As the amount of powder spread increases gradually, the coating not only covers the surface of the asphalt mixture, but also forms a thicker film. This layer film has limited anti-wear capacity and is easy to wear. Therefore, with the increase of the amount of cloth, the quality loss of the test pieces gradually increased. In addition, different formulations have little effect on wear and tear.
5.3 Pull Test
Asphalt mixture surface thermosolystical powder needs to have a high bonding strength, so as to have the ability to resist shedding, this paper uses pull test material adhesion performance. The results of the experiment are shown in Table 3.
is known by Table 5, and as the amount of cloth increases, so does the pull strength. From 50g/m2 to 100g/m2, the increase in pull strength increased, and from 150g/m2 to 200g/m2, the increase in pull strength decreased and tended to remain unchanged. The reason may be that when the amount of cloth is small, the powder does not completely cover the surface of the asphalt mixture, and the surface area in contact with the asphalt is small, so the pull strength increases gradually with the increase of the amount of the cloth. When reaching 150g/m2, the powder coating has completely covered the surface of the asphalt mixture, and the contact surface area of the asphalt mixture reached the maximum, so increase the amount of cloth, pull strength increase tends to remain unchanged. Comprehensive Table 3 to Table 5 data can be found that the amount of clothing is 100g/m2-150g/m2, BPN and pull strength values are larger, and the wear loss is moderate, so the recommended amount of thermoclyclycic powder coating is 100g/m2-150g/m2. In terms of formulations, different formulations have a certain effect on BPN, and have no effect on the amount of wear loss and pull strength.
conclusion
in order to reduce the production of rutting diseases in hot weather, different colors of coated thermoo-solid cooked lime coating materials have been developed. This coating material improves the reflectivity of the asphalt pavement and reduces the efficiency of the road surface in absorbing heat. Through the study of the construction process, cooling effect and road performance of the applied thermo-solid cooked lime coating, the conclusion is as follows:
(1) According to the curing characteristics of polyester resin, the preparation process of the thermoo-solid cooked lime coating material in the laboratory is developed, i.e. (a) the preparation of thermo-pressed rutting plate, (b) spraying powder coating, (c) cooling-curing film, (d) molding.
(2) In the thermosocarbon powder coating reflectivity and cooling performance test, polyester light gray powder coating cooling range of 13 degrees C, polyester light orange powder coating of 12.5 degrees C, polyester sea gray powder coating of 9 degrees C. Polyester light gray than polyester sea gray cooling range increased by 44.45 percent, indicating that the color system has a certain effect on cooling.
(3) in road performance test, with the increase of the amount of cloth, wear resistance slightly reduced, adhesion performance, pull strength is increased. Taking into account cooling performance and road performance, different formulations have a certain impact on BPN in terms of formulations. Combined cooling effect and road performance, it is recommended that its optimal spread volume is 100-150g/m2.