Bitumen is a petroleum-derived binding agent. Bitumen is well-known for its high adhesive strength and resistance to water and oil spills. Because asphalt is often utilized as a surface for roadways, parking lots, and driveways, bitumen is the best binder for asphalt. Bitumen can be made to varying standards depending on how it will be used, but it is always produced by distilling crude oil. This procedure eliminates the lighter liquid, leaving a thick sticky solution that, in the case of asphalt, will hold heavy aggregate like stones and gravel together with sand. Bitumen is the liquid adhesive that holds asphalt together. The term bitumen is frequently used interchangeably with asphalt. A bitumen-sealed road has a layer of bitumen sprayed on top of an aggregate layer. This is then done again to create a two-coat seal. Bitumen is also commonly confused with tar, which is a binding agent that, when mixed with gravel, produces tarmac. BST, sometimes known as a seal coat or chip seal, is a thin protective wearing covering put to a pavement or foundation course. BSTs can provide the following services: 
A layer of waterproofing to protect the underlying pavement. Skid resistance has been improved. A repair material for existing cracks or raveled surfaces. An anti-glare surface in rainy weather, as well as a more reflecting surface for night driving. BSTs have been used since the 1920s, particularly on low-volume gravel roads. BSTs are increasingly being used as a preventative maintenance method on well-structured flexible pavements. A BST provides preventive maintenance against the impacts of the sun and water, which can both degrade the pavement structure. BSTs provide both a fresh wearing course and a waterproof coating for the existing pavement. A BST makes it more difficult for water to enter the base material and prevents freeze-thaw damage in regions when temperatures are below freezing. Because of the addition of the cover aggregate, BSTs additionally enhance the surface friction of the pavement. This prevents raveling, which can make the pavement slick and stop difficult. A BST texture provides a good, gripping texture to the pavement surface. BSTs should be applied to a moderately to severely damaged pavement surface. A two to four-year service life is typical, with a five-year service lifespan possible. BSTs are made up of two major components: asphalt and cover aggregate. Asphalt (asphalt binder, cutback asphalt, or asphalt emulsion) and aggregate (uniformly graded). 
Asphalt is usually an emulsion. The weather on the day of a building must be considered carefully; ideally, a warm day with low humidity is recommended. BSTs should never be built on wet days or when rain is forecast. If the asphalt binder has not yet been set, rain can dilute it, bringing it to the top of the cover aggregate; as the water evaporates, tires can pick up the loose aggregate or track binder across the surface. Cut back asphalt While cutback asphalt has traditionally been used for BSTs, the solvent employed (typically gasoline or kerosene) is costly and sometimes hazardous. A cutback is an asphalt that has been dissolved in a solvent, allowing it to be pumped and sprayed without being heated to high temperatures. The solvent evaporates into the air, leaving the asphalt binder behind. The cutback has cured after the solvent has fully disappeared. Gasoline is utilized for quick setting time reductions, while kerosene is used for extended curing times. Asphalt use has been reduced in recent years due to pollution and health concerns. Emulsion of Asphalt Asphalt emulsions are now more routinely used. An emulsion is made up of oil suspended in water. The oil component in this case is asphalt cement. To make the oil and water combine, a surfactant (also known as an emulsifying agent) must be added. 
Because the asphalt is suspended in water, the laying temperature for a BST is much lower than for a hot mix asphalt. A surfactant has two advantages. First, it causes asphalt to create tiny droplets that will float in water by reducing the surface tension between the asphalt and the water. Two, the electrical charge of the emulsion is determined by a surfactant. Aggregate has an electrical charge, which is usually negative. Because opposite charges attract, it is critical to select an emulsion with the opposite charge to improve the binding of the asphalt to the aggregate. Cationic (positively charged) emulsions are commonly employed. Water is the next most important (by volume) component of an asphalt emulsion. Water accounts for roughly one-third of the emulsion's volume. Asphalt particles will float in the water thanks to the emulsifying agent. It is crucial to remember that if the emulsion splits (when the asphalt and water separate), the emulsion becomes brown to black. Before the emulsion breaks, the aggregate must be applied and rolled. When the emulsion breaks, the water evaporates, leaving only the asphalt on the road. The primary component of a BST is asphalt cement. This asphalt is similar to that used in hot mix paving. To improve early chip retention or BST durability, a latex or polymer-modified asphalt may be applied. Natural gravel or crushed stone are two common types of aggregates. These must be clean and dust-free, as well as rigid and uniform. This is done to offer a long-lasting traffic surface. 
Because excessive dust can be a severe adhesion issue for BSTs, it is typical to limit the percentage of material passing the No. 200 sieve (0.075 mm) to around 1% or less. The aggregate used to build a BST should be only one layer thick. The exceptions are when a choke stone or a second BST layer is added (a two-layer BST is often referred to as a "double shot" treatment). Too much aggregate will produce aggregate pickup, causing well-placed stones to become dislodged and perhaps causing windshield damage. In turning and halting zones, a modest quantity of surplus aggregate, greater than 5% but less than 10%, may be used. This will help to prevent tire scuffing in newly laid BST. Contact us for more information on the different types of bitumen and asphalt. Our sales executives will answer all your questions and guide you through the way.
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