What are the components of a lime-fly ash macadam base layer?

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Two-fly ash macadam is commonly known as the base layer of asphalt pavements; it serves as the underlying layer that provides leveling. The base layer is the main load-bearing component of the pavement structure, and it must possess sufficient strength and stiffness, as well as the ability to effectively distribute stresses. Lime-fly ash macadam is composed of lime powder, coal ash, and gravel in specific proportions. 1. Lime: Ground quicklime powder or slaked lime should be used; the slaked lime must be sieved to remove any lumps larger than 5 mm. The lime should be of grade III or higher, with a moisture content not exceeding 4%. 2. Fly ash: Fly ash of grade 2 or higher should be used, with the total content of SiO2, Al2O3, and Fe2O3 in it being greater than 70%, and the loss on ignition not exceeding 20%. The specific surface area of the fly ash should be greater than 2500 cm2/g, with no less than 70% passing through sieve holes of 0.075 mm and no less than 90% passing through sieve holes of 0.3 mm. When using wet fly ash, its moisture content should not exceed 35%. 3. Gravel: The crushing value should be less than 30% (and less than 35% for the subbase layer), with the maximum particle size not exceeding 37.5 mm. Article keywords: Composition of lime-fly ash in asphalt pavements