Heat reflection type mixture applied to road surface thin layer, preparation method and application

Abstract

The invention discloses a heat reflection type mixture applied to a road surface thin layer and a preparation method and application thereof.The heat reflection type mixture comprises dry components, the dry components comprise, by mass, 50-55% of first coarse aggregate, 18-21% of second coarse aggregate, 15-24% of fine aggregate, 3-4% of rutile type titanium dioxide powder and 1.5-3% of glass beads, the particle size of the first coarse aggregate is 5-8 mm, the particle size of the second coarse aggregate is 5-8 mm, the particle size of the fine aggregate is 5-8 mm, and the particle size of the second coarse aggregate is 5-8 mm. The particle size of the second coarse aggregate is 3-5 mm, the particle size of the fine aggregate is less than or equal to 3 mm, the particle size of the rutile type titanium dioxide powder is less than 0.075 mm, and the particle size of the glass beads is 0.3-0.6 mm; the mass ratio of the cementing material to the dry components is (0.075-0.083): 1. The method has the advantages of being simple in production process and high in operability, and the development of a thin-layer maintenance technology towards green functionalization can be promoted.

Description

Technical Field

[0001] This invention belongs to the field of road engineering technology, specifically relating to heat-reflective mixtures for use in thin road surface layers, their preparation methods, and applications. Background Technology

[0002] Asphalt paving is a common construction method in modern road construction. Roads paved with asphalt have advantages such as smoothness, wear resistance, and low noise. Asphalt is a complex, dark brown mixture composed of hydrocarbons of different molecular weights and their non-metallic derivatives. Due to the properties of asphalt, roads paved with asphalt are generally dark or black in color. It has a high absorption rate of solar radiation and absorbs a large amount of heat under prolonged solar radiation, resulting in a significant increase in road surface temperature. This increases the risk of high-temperature road surface defects such as rutting and shoving, exacerbates the urban heat island effect, and has adverse effects on the surrounding environment and pedestrians.

[0003] To address the problem of high heat accumulation on road surfaces, appropriate cooling measures should be taken. A common road surface cooling technology is the use of heat-reflective coatings. This involves covering the road surface with a heat-reflective coating material to reflect sunlight, thereby reducing radiation absorption and achieving the purpose of cooling. However, the coating reduces the original road surface texture depth and pendulum value, greatly affecting the road surface's anti-skid performance. Furthermore, under the influence of external factors such as wheel wear, it is prone to debonding, cracking, or even failure, resulting in poor road performance and long-term cooling effectiveness.

[0004] Therefore, while improving the thermal reflectivity of the road surface to achieve a cooling effect, it is essential to maintain good road performance, such as skid resistance, to ensure driving safety and comfort. Based on this, this invention proposes a new mixture scheme to improve the heat absorption problem of black asphalt pavements, reduce high-temperature pavement damage, promote the green transformation of highways, and build a green transportation system. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a heat-reflective mixture, its preparation method, and its application for use in thin road surface layers. This invention has the advantages of simple production process and strong operability, and can promote the development of thin-layer maintenance technology towards green and functional directions.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a heat-reflective mixture for use in a thin road surface layer, comprising: The dry component, based on its mass, comprises 50-55% first coarse aggregate, 18-21% second coarse aggregate, 15-24% fine aggregate, 3-4% rutile titanium dioxide powder, and 1.5-3% glass microspheres. The particle size of the first coarse aggregate is 5-8 mm, the particle size of the second coarse aggregate is 3-5 mm, the particle size of the fine aggregate is ≤3 mm, the particle size of the rutile titanium dioxide powder is <0.075 mm, and the particle size of the glass microspheres is 0.3-0.6 mm. Both the rutile titanium dioxide powder and the glass microspheres are functional materials. The binder has a mass ratio of (0.075-0.083):1 to the dry component mass.

[0008] Preferably, the porosity of the heat-reflective mixture is 4.8~5.3%, and the oil film thickness is ≥17μm.

[0009] Preferably, both the first and second coarse aggregates are crushed stone, with a polishing value ≥42, a crushing value ≤20%, and an apparent relative density ≥2.6 g / cm³. 3 Water absorption ≤1%, soundness ≤8%, particle content with a particle size less than 0.075 mm ≤1%, and adhesion to binder ≥5; The fine aggregate is manufactured sand, with a sand equivalent of ≥65%, a soundness of ≤12%, and an apparent relative density of ≥2.5 g / cm³. 3 .

[0010] Preferably, in the dry component, the gradation composition, calculated by mass percentage, is as follows: 100% passing through a 9.5 mm sieve, 40-70% passing through a 4.75 mm sieve, 15-35% passing through a 2.36 mm sieve, 8-25% passing through a 1.18 mm sieve, 6-20% passing through a 0.6 mm sieve, 5-15% passing through a 0.3 mm sieve, 4-12% passing through a 0.15 mm sieve, and 3-8% passing through a 0.075 mm sieve.

[0011] Preferably, the retroreflectance luminance coefficient of the glass microspheres is 300 mcd·m. 2 ·lx -1 , Preferably, the binder has a dynamic viscosity at 60°C > 150,000 Pa·s, a composite shear modulus at 60°C ≥ 12 kPa, and an elastic recovery at 25°C > 95%.

[0012] Preferably, the binder comprises 30-45% C5 petroleum resin, 7-15% star-shaped SBS modifier, and 45-50% solvent oil, calculated by mass percentage.

[0013] In a second aspect, the present invention provides a method for preparing a heat-reflective mixture, comprising the following steps: S1. The first coarse aggregate, the second coarse aggregate, the fine aggregate and the glass microspheres are stirred to obtain the first mixture; S2. Add binder to the first mixture and stir to obtain the second mixture; S3. Add rutile titanium dioxide powder to the second mixture and stir to obtain a heat-reflective mixture.

[0014] Preferably, the total stirring time in steps S1-S3 is ≥60 s.

[0015] More preferably, in step S1, the stirring time is 10-13 s; in step S2, the stirring time is 40-45 s; and in step S3, the stirring time is preferably 10-13 s.

[0016] In a third aspect of the invention, the invention proposes the application of heat-reflective mixtures, wherein the aforementioned heat-reflective mixtures are laid as a thin layer on the road surface.

[0017] Beneficial effects

[0018] This invention uses a bright-colored, high-viscosity, and high-elasticity binder to improve the brightness of the mixture. It incorporates rutile titanium dioxide powder and glass microspheres to replace the original aggregate components within the corresponding particle size range. This minimizes the impact of the improved dry components on the asphalt concrete gradation and maximizes the improvement of radiation reflectivity. Through modification, it comprehensively improves the reflectivity of the road surface thin layer to solar radiation. The mixture of this invention acts as an asphalt mixture and can be used to pave the road surface thin layer, reducing the absorption of solar radiation by the road surface, effectively lowering the road surface temperature, improving the high-temperature service conditions of the road surface, and realizing the development of thin-layer maintenance technology towards greening and functional diversification.

[0019] This invention employs a dense skeleton structure, which greatly enhances the interlocking and bonding ability between aggregates, effectively improving the pavement's anti-skid, anti-shear, and anti-rutting capabilities. Simultaneously, based on the thick oil film design concept, the oil film thickness reaches over 17μm. The thick binder film fully encapsulates the aggregate skeleton, significantly improving crack resistance and aging resistance. The binder in this invention effectively improves the interfacial adhesion between aggregates and binder, exhibiting high mechanical strength and excellent deformation recovery. The high viscosity of the binder and the coarse aggregate skeleton structure further enhance the high-temperature stability and deformation resistance of the thin-layer material. This comprehensive improvement in road performance helps the heat-reflective thin layer maintain its long-term cooling function.

[0020] This invention reduces the absorption of solar radiation by the road surface at the source. Compared with traditional heat-reflective coatings, this invention endows the asphalt thin-layer structure with heat-reflective function, fundamentally solving the problems of non-slip and cracking failure of traditional heat-reflective coatings. While ensuring the anti-slip effect of the road surface, it effectively prolongs its cooling effect. Detailed Implementation

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, specific implementation methods of the present invention will be described below. Obviously, the following description is merely some embodiments of the present invention. For those skilled in the art, other implementation methods can be obtained based on these embodiments without creative effort.

[0022] This invention proposes a heat-reflective mixture for use in road surface thin layers, comprising a binder and dry components. The dry components include aggregates, rutile titanium dioxide powder, and glass microspheres. The mixture prepared by mixing the binder and the dry components has heat-reflective properties. When the road surface is paved with the mixture of this invention, the road surface temperature can be reduced to a certain extent, the problem of high road surface temperature can be improved, high-temperature road surface damage can be reduced, the urban heat island effect can be alleviated, and the green functional attributes of the maintenance thin layer can be fully utilized.

[0023] The aggregates in the dry component are graded aggregates, including first coarse aggregate, second coarse aggregate, and fine aggregate. Specifically, in the dry component, the particle size of the first coarse aggregate is 5-8 mm, the particle size of the second coarse aggregate is 3-5 mm, the particle size of the fine aggregate is ≤3 mm, the particle size of the rutile titanium dioxide powder is <0.075 mm, and the particle size of the glass microspheres is 0.3-0.6 mm. Both the rutile titanium dioxide powder and the glass microspheres are functional materials. More preferably, the particle size of the rutile titanium dioxide powder is 0.2-1 μm. Compared with existing graded aggregates, this invention uses small-particle-size rutile titanium dioxide powder and glass microspheres to replace aggregates of the same particle size, allowing the dry component to still function normally in asphalt concrete. Preferably, based on the mass of the dry components, the dry components include 50-55% of the first coarse aggregate, 18-21% of the second coarse aggregate, 15-24% of the fine aggregate, 3-4% of the rutile titanium dioxide powder, and 1.5-3% of the glass microspheres. The ratio of the mass of the binder to the mass of the dry components is (0.075-0.083):1.

[0024] This invention uses binders and functional fillers (i.e., dry components) with solar radiation reflectivity to form a novel asphalt-like thin-layer material with heat reflectivity. It reduces pavement temperature within a certain range, improves pavement high-temperature service conditions, reduces pavement high-temperature damage, and achieves the purpose of reducing pavement temperature without the need for additional coating, thus alleviating the urban heat island effect and fully leveraging the green functional attributes of the maintenance thin layer.

[0025] Preferably, both the first and second coarse aggregates are crushed stone, and the fine aggregate is manufactured sand.

[0026] More preferably, the crushed stone includes one or more of diabase, basalt, and limestone. Even more preferably, the crushed stone has a polishing value ≥42, a crushing value ≤20%, and an apparent relative density ≥2.6 g / cm³. 3 Water absorption ≤1%, soundness ≤8%, particle content with a particle size less than 0.075 mm ≤1%, and adhesion to binder ≥5.

[0027] In the thin pavement layer formed by the mixture, the coarse aggregate plays an important role in bearing vehicle loads and wear, providing the majority of the mechanical strength of the concrete. Its physical properties such as polishing value and strength are related to the road performance and actual service life of the road surface wearing layer, such as skid resistance and wear resistance. The first and second coarse aggregates of this invention are preferably 5-8mm and 3-5mm crushed stone with high compressive strength and good wear resistance, ensuring that the pavement thin layer has good mechanical properties such as compressive strength, wear resistance and skid resistance after construction, compaction and opening to traffic.

[0028] More preferably, the manufactured sand has a sand equivalent of ≥65%, a soundness of ≤12%, and an apparent relative density of ≥2.5 g / cm³. 3 .

[0029] Fine aggregates, by adhering to the binder to form asphalt-like mortar, serve to fill the gaps in the coarse aggregate skeleton and transfer loads. Their angularity, strength, and mud content all affect the road performance of the mixture. Manufactured sand is characterized by its cleanliness, lack of impurities, good angularity, and high roughness. It adheres strongly to the binder, forming mortar effectively and improving the cohesion of the mixture. This invention preferably uses dry, clean, unweathered, and impurity-free manufactured sand as the fine aggregate.

[0030] More preferably, in the dry component, the gradation composition, calculated by mass percentage, is as follows: 100% passing through a 9.5 mm sieve, 40-70% passing through a 4.75 mm sieve, 15-35% passing through a 2.36 mm sieve, 8-25% passing through a 1.18 mm sieve, 6-20% passing through a 0.6 mm sieve, 5-15% passing through a 0.3 mm sieve, 4-12% passing through a 0.15 mm sieve, and 3-8% passing through a 0.075 mm sieve.

[0031] This invention employs a specific ratio of first and second coarse aggregates to form a rigid coarse aggregate skeleton. The fine aggregate content is controlled using a 2.36mm sieve as the key aperture, and a design with more coarse aggregate and less fine aggregate is adopted to construct a dense skeleton gradation structure, while ensuring that the fine aggregate can fully fill the gaps in the skeleton. The design of the dry component composition and content of this invention not only improves the anti-skid performance of the heat-reflective mixture forming a thin layer, solving the problem of non-anti-skid properties of traditional heat-reflective coating materials, but also ensures that the thin layer has good crack resistance and water loss resistance. Furthermore, the interlocking and bonding effect of the dense skeleton structure of the heat-reflective mixture can significantly improve the shear slip resistance of asphalt concrete and enhance the high-temperature stability of the thin layer.

[0032] Preferably, the heat-reflective mixture has a porosity of 4.8–5.3%, employing a dense skeleton structure and a thick oil film design with an oil film thickness ≥17 μm. The thick oil film effectively encapsulates the coarse aggregate skeleton, significantly improving the mixture's low-temperature crack resistance and fatigue resistance. Because solar radiation exhibits a gradient aging characteristic from the outside to the inside along the asphalt film thickness direction, the thick oil film design enhances the mixture's resistance to UV aging. The optimization of low-temperature performance and anti-aging properties helps extend the long-term cooling effect of the heat-reflective mixture.

[0033] Preferably, the refractive index of the rutile titanium dioxide powder is 2.7. For rutile titanium dioxide, titanium ions are located at the center of the oxygen octahedron, and the octahedrons are connected by sharing vertices and edges to form a dense and stable three-dimensional network. The present invention uses titanium dioxide powder with a particle size of 0.2~1μm, which can maximize the reflectivity of visible and infrared light bands and has excellent thermal reflectivity.

[0034] Preferably, the retroreflectance luminance coefficient of the glass microspheres is 300 mcd·m. 2 ·lx -1 The present invention uses glass microspheres with a particle size of 0.3~0.6 mm to further enhance the reflectivity of sunlight. Moreover, the glass microspheres in this particle size range are consistent with the specific grade of aggregate particle size used in asphalt concrete aggregates. The present invention replaces aggregates of the same grade with glass microspheres in a specific particle size range, minimizing interference with the aggregate skeleton, while also filling the gaps in the skeleton.

[0035] In this invention, the maximum content of rutile titanium dioxide powder is 4%, and the maximum content of glass microspheres is 3%. Adding excessive amounts of rutile titanium dioxide powder and glass microspheres has limited effect on improving the heat reflectivity of the heat-reflective mixture. This invention avoids material waste, improves the overall economy of the heat-reflective mixture, and also achieves a good cooling effect. Preferably, in this invention, the content of rutile titanium dioxide powder is 4%, and the content of glass microspheres is 1.5%.

[0036] It should be noted that in this invention, rutile titanium dioxide powder and glass microspheres serve to replace aggregates of the same particle size range, minimizing their impact on the aggregate skeleton while fulfilling their functional properties. This does not conflict with the requirement that the fine aggregate particle size be ≤3 mm, as fine aggregates may contain even smaller particles, and limiting the particle size of fine aggregates to ≤3 mm is reasonable. Compared to existing technologies, the content of aggregates with a particle size ≤3 mm is higher, but since this invention uses rutile titanium dioxide powder and glass microspheres to replace aggregates of the same particle size range, the content of fine aggregates in this invention is correspondingly lower.

[0037] Preferably, the binder has a dynamic viscosity at 60℃ > 150,000 Pa·s, a composite shear modulus at 60℃ ≥ 12 kPa, and an elastic recovery at 25℃ > 95%. The dynamic viscosity at 60℃ and the composite shear modulus at 60℃ are corresponding indicators characterizing the high viscosity and high elasticity of the binder, reflecting the flow resistance of the binder at high temperatures and affecting the high-temperature stability and resistance to permanent deformation of heat-reflective mixtures made from the binder, such as resistance to rutting and shoving. The elastic recovery at 25℃ reflects the binder's ability to return to its original state after being deformed by external force at room temperature, reducing the accumulation of damage from plastic deformation, releasing stress through elastic deformation, and avoiding stress concentration leading to cracking. This is related to the low-temperature crack resistance and fatigue resistance of heat-reflective mixtures.

[0038] The binder of this invention is a high-viscosity, high-elasticity modified asphalt-like material, functioning as asphalt. This binder is characterized by its bright, high-gloss color, significantly improving the high-temperature stability and deformation resistance of heat-reflective mixtures. It effectively constrains the relative slippage between aggregate particles, providing better resistance to high-temperature rutting and shoving. The high-viscosity, high-elasticity binder forms a high-strength bond with the dry components, reducing cracking at the binder-dry component interface, preventing moisture penetration, effectively improving the low-temperature crack resistance of the mixture, and reducing the risk of subsequent water damage. Furthermore, the high viscosity of the binder enhances the adhesion of the binder to rutile titanium dioxide powder and glass microspheres, preventing the loss of heat-reflective performance due to the loosening and debonding of functional filler particles (i.e., rutile titanium dioxide powder and glass microspheres), thus maintaining the cooling function of the heat-reflective thin layer for a long time. With an elastic recovery of >95% at 25℃, the binder can maintain a stronger elastic deformation capacity at low temperatures. When the mixture undergoes low-temperature shrinkage displacement, the binder can release stress through elastic recovery, preventing plastic deformation and ensuring that the shrinkage tensile stress is always below the tensile strength threshold of the mixture. This avoids brittle cracking caused by stress concentration and reduces the risk of pavement cracking.

[0039] Traditional black asphalt has a high absorption rate of solar radiation, generally over 90%. Compared to traditional black asphalt, the heat-reflective mixture of this invention enhances brightness and light transmittance, which can reduce the total heat absorption of asphalt to a certain extent and better reflect solar radiation.

[0040] Furthermore, the binder is preferably a modified asphalt material. Calculated by the mass percentage of the binder, the modified asphalt includes 30-45% C5 petroleum resin, 7-15% star-shaped SBS modifier, and 45-50% solvent oil. C5 petroleum resin, star-shaped SBS modifier, and solvent oil are commonly used substances in the asphalt industry.

[0041] Preferably, the molecular weight of the star-shaped SBS modifier is >300,000. SBS modifiers with higher molecular weights have more physical crosslinking points and higher cohesive strength, which is beneficial to the binder in terms of high temperature stability, high elastic modulus, viscosity, low temperature performance and aging resistance, thereby improving the relevant properties of the mixture.

[0042] Furthermore, the present invention also proposes a method for preparing the binder, as follows: The solvent oil is heated to 135~145℃, and then C5 petroleum resin is added to the solvent oil and stirred evenly to obtain the first mixture; Add the star-shaped SBS modifier to the first mixture and allow it to swell for 30-40 minutes. During the swelling process, raise the temperature to 180-195℃ to obtain the second mixture. The second mixture is sheared for 60-70 minutes and then stirred for 20-30 minutes to obtain a highly viscous and elastic binder.

[0043] Based on the above-mentioned heat-reflective mixture, the present invention also proposes a method for preparing a heat-reflective mixture applicable to a thin road surface layer, comprising the following steps: S1. The first coarse aggregate, the second coarse aggregate, the fine aggregate and the glass microspheres are stirred to obtain the first mixture; S2. Add binder to the first mixture and stir to obtain the second mixture; S3. Add rutile titanium dioxide powder to the second mixture and stir to obtain a heat-reflective mixture.

[0044] In step S1, the stirring time is preferably 10-13 s. In step S2, the stirring time is preferably 40-45 s. In step S3, the stirring time is preferably 10-13 s.

[0045] Preferably, the total stirring time in steps S1-S3 is ≥60 s.

[0046] The heat-reflective mixture prepared by this invention is used for laying thin road surface layers with a thickness of 1.5~2.0 cm. Based on a reasonable dense skeleton structure, a unique thick oil film design, and high molecular weight modification technology, the heat-reflective mixture of this invention can reduce the thickness of the road surface layer to 1.5~2.0 cm, greatly reducing construction costs.

[0047] The technical solution of the present invention will be described in detail below with specific embodiments.

[0048] Example 1

[0049] The heat-reflective mixture in this embodiment includes a binder and dry components.

[0050] Based on the mass of the dry components, the gradation of the dry components is as follows: 100% passing through a 9.5 mm sieve, 45.1% passing through a 4.75 mm sieve, 24.1% passing through a 2.36 mm sieve, 17.5% passing through a 1.18 mm sieve, 12.1% passing through a 0.6 mm sieve, 9.3% passing through a 0.3 mm sieve, 7.1% passing through a 0.15 mm sieve, and 4.0% passing through a 0.075 mm sieve.

[0051] Based on the mass of the dry components, the dry components consist of 53% 5-8mm crushed stone (first coarse aggregate), 19% 3-5mm crushed stone (second coarse aggregate), 22.5% 0-3mm manufactured sand (fine aggregate), 4% rutile titanium dioxide powder, and 1.5% glass microspheres. The crushed stone is diabase, with a crushing value of 15%, an abrasion value of 17%, and an apparent relative density of 2.7 g / cm³. 3 The water absorption rate is 0.5%, the soundness is 5%, and the adhesion to the binder is grade 5; the manufactured sand is diabase, and the apparent relative density of the manufactured sand is 2.7 g / cm³. 3 The strength is 10%, and the sand equivalent is 69%.

[0052] The binder accounts for 8.2% of the dry component mass, has a dynamic viscosity of 150,000 Pa·s at 60℃, a composite shear modulus of 12.1 kPa at 60℃, and an elastic recovery of 95% at 25℃. Based on the mass of the binder, it comprises 42% C5 petroleum resin, 13% star-shaped SBS modifier with a molecular weight of 300,000, and 45% solvent oil.

[0053] The preparation method of the heat-reflective mixture in this embodiment is as follows: S1. Mix the first coarse aggregate, the second coarse aggregate, the fine aggregate, the rutile titanium dioxide powder and the glass microspheres according to the formula and stir for 10 seconds to obtain the first mixture. S2. Add the specified amount of binder to the first mixture and stir for 40 seconds to obtain the second mixture; S3. Add the prescribed amount of rutile titanium dioxide powder to the second mixture and stir for 10 seconds to obtain a heat-reflective mixture.

[0054] Example 2

[0055] The heat-reflective mixture in this embodiment includes a binder and dry components.

[0056] Based on the mass of the dry components, the gradation of the dry components is as follows: 100% passing through a 9.5 mm sieve, 45.3% passing through a 4.75 mm sieve, 24.1% passing through a 2.36 mm sieve, 17.7% passing through a 1.18 mm sieve, 12.0% passing through a 0.6 mm sieve, 9.1% passing through a 0.3 mm sieve, 7.1% passing through a 0.15 mm sieve, and 4.0% passing through a 0.075 mm sieve.

[0057] Based on the mass of the dry components, the dry components consist of 51% 5-8mm crushed stone (first coarse aggregate), 20% 3-5mm crushed stone (second coarse aggregate), 23.5% 0-3mm manufactured sand (fine aggregate), 4% rutile titanium dioxide powder, and 1.5% glass microspheres. The crushed stone is diabase, with a crushing value of 15%, an abrasion value of 15%, and an apparent relative density of 2.7 g / cm³. 3 The water absorption rate is 0.7%, the soundness is 7%, and the adhesion to the binder is grade 5; the manufactured sand is diabase, and the apparent relative density of the manufactured sand is 2.7 g / cm³. 3 The strength is 9%, and the sand equivalent is 65%.

[0058] The binder accounts for 8.1% of the dry component mass, has a dynamic viscosity of 160,000 Pa·s at 60℃, a composite shear modulus of 12.0 kPa at 60℃, and an elastic recovery of 95% at 25℃. Based on the mass of the binder, it comprises 40% C5 petroleum resin, 13% star-shaped SBS modifier with a molecular weight of 350,000, and 47% solvent oil.

[0059] The preparation method of the heat-reflective mixture in this embodiment is as follows: S1. Mix the first coarse aggregate, the second coarse aggregate, the fine aggregate, the rutile titanium dioxide powder and the glass microspheres according to the formula and stir for 11 seconds to obtain the first mixture. S2. Add the specified amount of binder to the first mixture and stir for 41 seconds to obtain the second mixture; S3. Add the prescribed amount of rutile titanium dioxide powder to the second mixture and stir for 10 seconds to obtain a heat-reflective mixture.

[0060] Example 3

[0061] The heat-reflective mixture in this embodiment includes a binder and dry components.

[0062] Based on the mass of the dry components, the gradation of the dry components is as follows: 100% passing through a 9.5 mm sieve, 45.5% passing through a 4.75 mm sieve, 23.9% passing through a 2.36 mm sieve, 17.3% passing through a 1.18 mm sieve, 12.1% passing through a 0.6 mm sieve, 9.5% passing through a 0.3 mm sieve, 7.1% passing through a 0.15 mm sieve, and 4.0% passing through a 0.075 mm sieve.

[0063] Based on the mass of the dry components, the dry components consist of 51% 5-8mm crushed stone (first coarse aggregate), 19% 3-5mm crushed stone (second coarse aggregate), 24.5% 0-3mm manufactured sand (fine aggregate), 4% rutile titanium dioxide powder, and 1.5% glass microspheres. The crushed stone is limestone, with a crushing value of 17%, an abrasion value of 15%, and an apparent relative density of 2.6 g / cm³. 3 It has a water absorption rate of 0.7%, a soundness of 7%, and an adhesion grade of 5 with the binder; the manufactured sand is quartz sand, and its apparent relative density is 2.6 g / cm³. 3 The strength is 9%, and the sand equivalent is 67%.

[0064] The binder accounts for 8.1% of the dry component mass, has a dynamic viscosity of 170,000 Pa·s at 60℃, a composite shear modulus of 12.5 kPa at 60℃, and an elastic recovery of 97% at 25℃. Based on the mass of the binder, it comprises 39% C5 petroleum resin, 15% star-shaped SBS modifier with a molecular weight of 400,000, and 46% solvent oil.

[0065] The preparation method of the heat-reflective mixture in this embodiment is as follows: S1. Mix the first coarse aggregate, the second coarse aggregate, the fine aggregate, the rutile titanium dioxide powder and the glass microspheres according to the formula and stir for 13 seconds to obtain the first mixture; S2. Add the specified amount of binder to the first mixture and stir for 43 seconds to obtain the second mixture; S3. Add the prescribed amount of rutile titanium dioxide powder to the second mixture and stir for 13 seconds to obtain a heat-reflective mixture.

[0066] The road performance tests of the heat-reflective mixtures prepared in Examples 1-3 are as follows: The heat-reflective mixtures obtained in Examples 1-3 were subjected to relevant road performance tests in accordance with the standards specified in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011).

[0067] Regarding the cooling effect test, the following steps should be followed:

[0068] A. The heat-reflective mixtures obtained in Examples 1-3 were made into standard Marshall specimens with a height of 63.5 mm and a diameter of 101.6 mm. Insulation cotton was wrapped around the sides and bottom of the specimens to prevent heat loss. Meanwhile, conventional black asphalt mixtures were used as a control group. Standard Marshall specimens with a height of 63.5 mm and a diameter of 101.6 mm were made and insulation cotton was wrapped around the sides and bottom of the specimens to prevent heat loss.

[0069] B. Embed three high-precision temperature sensors with an accuracy of ±0.15℃ on the surface, 2 cm depth and bottom of a single specimen. Place the single specimen vertically under a xenon lamp light source to fully expose its surface.

[0070] C. Turn on the xenon lamp light source; the radiation intensity is 1000 W / m². 2 Each specimen was irradiated for 70 minutes, and the final temperature was recorded afterward. The temperature difference between the heat-reflective mixture specimen obtained in the example and the black asphalt mixture control group at the surface, 2 cm depth, and bottom surface was calculated. The temperature difference was used as the cooling range. The road performance and cooling effect test results are shown in Table 1.

[0071] Table 1. Road performance data and cooling effect of Examples 1-3

[0072]

[0073] Based on the data in Table 1, it can be seen that the heat-reflective mixture prepared by this invention exhibits significantly higher performance in high-temperature stability, water stability, and skid resistance than the technical standards specified in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). Furthermore, this invention effectively addresses the fundamental problem of traditional heat-reflective coatings lacking skid resistance, possessing excellent texture depth and pendulum value, ensuring driving safety and comfort. In addition, compared with conventional black asphalt mixtures, this invention achieved better cooling under these specific test conditions, with a maximum temperature reduction of 7.0℃ on the specimen surface. This effectively alleviates the problem of heat accumulation on the road surface under solar radiation and the urban heat island effect, improves the high-temperature service conditions of the road surface, and reduces high-temperature road damage. It represents a green, functional asphalt thin-layer maintenance solution with excellent road performance and application prospects.

[0074] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A heat-reflective mixture for use in thin road surface layers, characterized in that, include: The dry component, based on its mass, comprises 50-55% first coarse aggregate, 18-21% second coarse aggregate, 15-24% fine aggregate, 3-4% rutile titanium dioxide powder, and 1.5-3% glass microspheres. The particle size of the first coarse aggregate is 5-8 mm, the particle size of the second coarse aggregate is 3-5 mm, the particle size of the fine aggregate is ≤3 mm, the particle size of the rutile titanium dioxide powder is <0.075 mm, and the particle size of the glass microspheres is 0.3-0.6 mm. Both the rutile titanium dioxide powder and the glass microspheres are functional materials. The binder has a mass ratio of (0.075-0.083):1 to the dry component mass.

2. The heat-reflective mixture according to claim 1, characterized in that, The porosity is 4.8~5.3%, and the oil film thickness is ≥17μm.

3. The heat-reflective mixture according to claim 1, characterized in that, Both the first and second coarse aggregates are crushed stone, with a polished stone value ≥42, a crushing value ≤20%, and an apparent relative density ≥2.6 g / cm³. 3 Water absorption ≤1%, soundness ≤8%, particle content with a particle size less than 0.075 mm ≤1%, and adhesion to binder ≥5; The fine aggregate is manufactured sand, with a sand equivalent of ≥65%, a soundness of ≤12%, and an apparent relative density of ≥2.5 g / cm³. 3 .

4. The heat-reflective mixture according to any one of claims 1-3, characterized in that, In the dry component, the gradation composition by mass percentage is as follows: 100% passes through a 9.5 mm sieve, 40-70% through a 4.75 mm sieve, 15-35% through a 2.36 mm sieve, 8-25% through a 1.18 mm sieve, 6-20% through a 0.6 mm sieve, 5-15% through a 0.3 mm sieve, 4-12% through a 0.15 mm sieve, and 3-8% through a 0.075 mm sieve.

5. The heat-reflective mixture according to claim 1, characterized in that, The binder has a dynamic viscosity of >150,000 Pa·s at 60℃, a composite shear modulus of ≥12 kPa at 60℃, and an elastic recovery of >95% at 25℃.

6. The heat-reflective mixture according to claim 1 or 5, characterized in that, The binder, calculated by mass percentage, comprises 30-45% C5 petroleum resin, 7-15% star-shaped SBS modifier, and 45-50% solvent oil.

7. A method for preparing a heat-reflective mixture, characterized in that, The preparation of the heat-reflective mixture as described in any one of claims 1-6 comprises the following steps: S1. The first coarse aggregate, the second coarse aggregate, the fine aggregate and the glass microspheres are stirred to obtain the first mixture; S2. Add binder to the first mixture and stir to obtain the second mixture; S3. Add rutile titanium dioxide powder to the second mixture and stir to obtain a heat-reflective mixture.

8. The preparation method according to claim 7, characterized in that, The total stirring time for steps S1-S3 is ≥60 s.

9. The preparation method according to claim 8, characterized in that, In step S1, the stirring time is 10-13 s; in step S2, the stirring time is 40-45 s; in step S3, the stirring time is preferably 10-13 s.

10. An application of a heat-reflective mixture, characterized in that, The heat-reflective mixture according to any one of claims 1-6 is used to lay a thin layer on the road surface.

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