Colored asphalt pigments, colored asphalt mixtures and colored asphalt pavement cases

Colored Asphalt Pigment , that is a specialized high-performance pigment used for coloring colored asphalt mixtures. Colored asphalt pigment is a major material for colored asphalt concrete pavement, which determines the success or failure of the project of paving colored asphalt concrete pavement. Colored asphalt concrete pavement special pigments should not fade or decompose under long-term sunlight exposure, be insoluble in water, have good heat and cold resistance, be easily dispersed in asphalt binder, not react within the construction temperature range, and have excellent outdoor weather resistance.

Oxide Pigments have a significant impact on the cost of colored asphalt pavement, and low-cost pigments should be selected as much as possible. Organic pigments are generally not used, but inorganic pigments are used, which have stable color, good durability, acid resistance, alkali resistance, UV resistance, good durability, chemical stability, insolubility in water, and are non-toxic and harmless.

The commonly used inorganic pigments for colored asphalt concrete pavement include iron oxide red (iron based pigment), light chromium yellow (chromium based pigment), cobalt blue (cobalt based pigment), titanium chromium green (titanium chromium metal blend oxide pigment), titanium dioxide (titanium based pigment), composite chromium green, composite iron blue, composite chromium red and composite chromium yellow, etc. Among them, iron oxide red has a red tone, light chromium yellow and composite chromium yellow have a yellow tone, cobalt blue and composite iron blue have a blue tone, titanium chromium green and composite chromium green have a green tone, titanium dioxide has a light gray tone, and composite iron gray has a gray tone.

Customized Asphalt Pigment Blending Design : According to the requirements of end clients, our ZHEJIANG GREEFIELD factory's technical experts can provide precise color matching services for colored asphalt pigments based on client projects requirements. For example, using single or several pigments such as iron oxide red, iron oxide yellow, titanium dioxide white, cobalt blue, chrome oxide red, chrome oxide yellow, chrome green ( Chromium Oxide Green ) etc as the basis, unique single color colored asphalt pigments can be formulated through stable verification formulas and synthesis methods.

The term " Colored Asphalt " can be expressed as Colored Bitumen (EN) or Colored Asphalt (US) in English clients in different countries, such as colored bitumen, colored asphalt, colorless bitumen, colorless asphalt, decolorized asphalt, synthetic decolorized asphalt binder etc. The more accurate types of expressions are : 

Ordinary Colored Asphalt: A light colored bonding material with road petroleum asphalt properties, mainly processed from petroleum resin and other raw materials. This is a reprocessed asphalt material based on black asphalt after removing some carbon elements (in the form of carbon black). 

Modified Colored Asphalt Polymer (synthetic decolorized asphalt binder) that Colorable light colored polymer bonding materials with polymer modified asphalt properties are processed from petroleum resin, polymer modifiers, and other main raw materials. This polymer modified colored asphalt can also be expressed as a synthetic decolorized asphalt binder. There are three mainstream polymer modified asphalt material modification pathways with stable quality: SBS modified blend polymers, SBR modified blend polymers, and EVA mixture PE modified blend polymers.

Definition of Colored Asphalt Mixture : The colored asphalt mixture is a product that uses ordinary colored asphalt or modified colored asphalt as a binder, and is heated and mixed with mineral aggregates and coloring agents in a certain proportion. After transportation to the target construction site, it is used for laying colored asphalt pavement. 

The Definition of Colored Asphalt Concrete Pavement : The so-called colored asphalt concrete pavement refers to the mixture of decolorized asphalt with various colored stones, special pigments, additives and other materials at a specific temperature, which can be configured into various colored asphalt mixtures. After paving and rolling, it forms a colored asphalt concrete pavement with certain strength and road performance. 
As a standardized construction of colored asphalt pavement engineering, there are two mature industrial scale production methods for colored asphalt binder :

The First Method is to use an appropriate solvent to remove the black asphaltene from petroleum asphalt, leaving behind lighter colored components, and adding modified materials and special pigments of a certain color to make the asphalt turn into different colors such as red, yellow, blue, green, camel, purple, etc. as needed. However, the production process is complex, requiring a large amount of capital and equipment investment, and the pollution is severe, which is not conducive to promotion. However, due to the low price of asphalt abroad, there are so-called "environmentally friendly asphalt or colorless asphalt " materials. However, in actual colored asphalt pavement projects, the selection of this unsuitable decolorized asphalt material results in a lack of brightness and a darker color, such as chocolate dark reddish or dark wine reddish.

The Second Method is to use modern petrochemical products to manually mix light colored binders with properties equivalent to asphalt. The adhesion, elasticity, and toughness indicators of the light colored binder produced by this technology are much better than those of ordinary asphalt. This light colored binder is mixed with light colored aggregates with a certain gradation, added with pigments of a certain color, and then spread and rolled to form a colored asphalt pavement with a certain strength. The colored asphalt binder developed in China is produced using this artificial synthesis technology.

Optimal Selection of Suitable Aggregates : The implementation of a good colored asphalt pavement construction project requires not only suitable colored asphalt binders and pigments, but also suitable aggregates that match the geographical and environmental conditions of the construction. In addition to meeting the general requirements as a pavement material, the color of colored asphalt aggregates is also an important selection criterion. The effect of color reflected by different base colors of aggregates varies. Generally, black or dark brown aggregates are not suitable for use, and it is advisable to choose aggregates that are similar in color to the pavement or light in color. Generally, red, yellow, and green are the main colors, and colored fine stones such as limestone, basalt, diabase, granite, etc. are often used as aggregates. The priority purpose of this aggregate is to achieve the pH balance of the final colored asphalt concrete material, preferably neutral with a pH value of 7.0, so that the colored pavement can continue to maintain good performance and long-term service life in sunny and rainy weather environments. 

Performance characteristics of colored asphalt pavement :
1). Traffic signs, guidance, and safety functions 

In recent years, with the rapid increase in vehicle ownership, the guiding function of colored asphalt roads towards traffic has received increasing attention from traffic managers. Asphalt pavements of different colors can provide better warning effects than traffic signs, effectively improve drivers' recognition, attract their attention, keep their minds clear, alleviate driving fatigue, and play a positive role in inducing traffic flow, safe driving, and reducing traffic accidents. 

The large pore low-noise permeable pavement ( colored OGFC pavement, OGFC = Open-grade Friction Courses ) paved with colored asphalt concrete significantly improves the friction coefficient and significantly enhances the driving safety performance. 

The use of yellow asphalt pavement for tunnel pavement can significantly improve the lighting effect inside the tunnel and enhance the safety of tunnel driving. Reasonable road color design and matching make the road surface rich in layers, even if the straight section is too long, it will not affect the driver's safe driving effect. 

2). Reduce environmental pollution function 

The black asphalt on traditional road surfaces contains high volatile light fractions, which cause significant pollution to the surrounding environment of the road. The light fraction of colored asphalt mixture evaporates very little, greatly reducing environmental pollution compared to black asphalt. 

Traditional black road surfaces are prone to heat absorption and generate the "heat island effect". According to actual measurements and statistics, in the hot summer, the temperature of black asphalt concrete road surfaces after absorbing heat is beyond imagination, and the surface temperature can reach over 60 ℃. Colored aggregate, as its color mainly comes from the color of the stone itself, will also reduce the significant harm it causes to the surrounding environment after the road surface is built. Colored asphalt concrete pavement has a certain positive significance in eliminating the "heat island effect". 

The permeable pavement paved with colored asphalt concrete not only has a higher friction coefficient for safer driving, but also reduces noise by 6db~ 9db compared to ordinary pavement. It mainly eliminates noise pollution caused by tire compressed air through large pores, and can also absorb other external noise to a certain extent. 

3). Humanistic care and convenience for the lives of the people

As a new type of pavement material, colored asphalt concrete has the same road performance as ordinary hot mix petroleum asphalt concrete, with good road performance. Under different temperatures and external environments, its high temperature stability, water damage resistance, and durability are all very good, and there is no deformation, asphalt film peeling, or other phenomena. It has good adhesion with the base layer.

Colorful building materials can play an important role in modern infrastructure projects. The advantages of colored asphalt go beyond its aesthetic appeal, and it can be widely used in pedestrian streets, scenic areas, building roofs, school playgrounds, sports fields, residential areas' corridors and slow lanes, park tour roads, and some special roads. It can change the single color tone of the road surface and beautify the environment; It can also be used in pedestrian crossings, intersections, accident prone areas, hospitals, elementary school gates, and other scenarios to standardize the significant identification of road categories, facilitate operation and management, and maintain traffic safety; At the same time, using colored asphalt concrete to pave the road surface has good elasticity and flexibility, providing a comfortable walking experience. It is most suitable for elderly people to take a walk and can also prevent slipping in winter. In addition, the color mainly comes from the color of the aggregate itself, which will not cause significant harm to the surrounding environment. 

Overview For the Development of Colored Asphalt Abroad : 

The technology of colored asphalt concrete pavement has been widely promoted in developed countries abroad, not only for its good economic benefits, but more importantly, based on the international trend of environmental protection and sustainable development. 
The research on colored asphalt pavement in foreign countries started earlier, and the technology is now relatively mature, with the application scale continuously expanding. As early as the 1950s, countries such as Europe and America began researching colored asphalt concrete pavement and gradually expanded its application scope; In the 1960s, the Soviet Institute of Road Science and the Kharkiv Highway Academy also conducted research on the laying of colored asphalt pavement, and subsequently laid tens of thousands of square meters of colored asphalt concrete pavement in cities such as Moscow, Kharkiv, and Tbilisi; Japan (maritime cold regions) has also conducted a lot of research on colored asphalt concrete pavement technology and has received some applications.

The most typical projects for the application of colored asphalt concrete pavement in foreign countries include: National Highway 199 (street section) in Kitakyushu City, Japan, with iron red pavement on both sides of the roadside lanes, grass green pavement on the middle parking lane of the Nagata Minami Nippo Line in downtown Kobe, yellow pavement on the main section of the Osaka Prefectural Expressway, yellow pavement on the main bend of National Highway 50 in Mito City for large passenger vehicles, a thin layer of yellow pavement on cement concrete pavement in Nagoya, and blue pavement on the northeast road of Paris, France, which is about 30km long; European Austrian highway tunnels and entrance and exit tunnel surfaces, etc.

At present, there are various types of colored asphalt concrete pavement technologies, including hot mix colored asphalt concrete pavement, emulsified colored asphalt slurry sealing layer, and colored anti-skid wear layer, which are widely used. Experimental research is mainly conducted from these directions.

Overview For the Development of Colored Asphalt Concrete in China : 
In the 1980s, China began research on colored pavement technology, but its application on roads was still limited. In recent years, with the improvement of national economic strength and engineering technology level, the application of colored asphalt concrete technology has made significant progress. For our country, with the rapid development of economic construction, various provinces and cities are trying to beautify the environment, showcase the city's style, improve citizens' living taste, and reflect the pace of urban modernization by making the urban environment "green", urban roads "bright", and urban transportation "fast" in urban infrastructure construction.. In recent years, with the improvement of the country's economic strength and engineering technology level, multiple domestic companies or research institutions have cooperated to conduct research on the application of colored asphalt concrete technology, reaching a new level of technology, some even leading domestically or internationally. The use of non motorized vehicle lanes and sports and leisure trails is gradually increasing in areas such as squares, parks, urban roads, and key highways.

The most typical successful cases of the application of colored asphalt concrete pavement in China include: the non motorized vehicle lanes on both sides of Xiamen Avenue, about 4km long, and the iron red tourist observation road on Huandao Road, about 3.4km long; Beijing Chang'an Avenue Extension, Luxin Dacheng Colorful Basketball Court, and Shijingshan Amusement Park; Shenyang Botanical Garden Color Tour Road, Botanical Garden Color Tour Road (Phase II), Luda Color Roof, Huaxing Middle School Color Playground, and Shenyang Beijing Street and Beiling Street Color Viewing Road; The slow lanes of Zhaojiabang Road and Taiyuan Road in Shanghai, the leisure and cultural street of several hundred meters in Chengdu, and the bus only lane on Yan'an West Road; Huangpu Avenue Project in Guangzhou, etc.

In recent years, with the implementation of the Western Development Plan in China, colored asphalt concrete pavement has also begun to take off in economically underdeveloped areas (cold regions) in northwest China. The non-stop toll lane of the Xi'an Xianyang Airport Expressway in Shaanxi, the non motorized vehicle lane of the Lanzhou North Exit Project in Gansu, and the colored asphalt concrete pavement of the Jiefang Street bus lane in Yinchuan, Ningxia, as well as the colored asphalt pavement of Binhai Avenue in Ningbo, Zhejiang Province, were successively built and put into use from 2007 to 2016, indicating the wide application prospects of this new pavement technology in China.

In summary, the application of colored asphalt pigment technology and new technologies for colored asphalt concrete pavement is becoming increasingly widespread, and their applications in various scenarios at inland and abroad will be numerous. 

Classic Colour Asphalt Pavement Hot Mixed Material Formulation Sheet :

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