"Ballast" has been renamed as "ballast", which refers to the gravel used to support the track sleepers. This is a common ballast bed structure in the early days. Before laying the track, the project will lay a layer of gravel on the subgrade, then compact it, and then lay the sleepers and tracks. As an attempt of highway subgrade filling, ballast has no operational construction technical specifications and quality evaluation standards. It is of great practical significance to study the construction technology and quality control method of ballasted subgrade. First of all, we must determine two standards. The selection of ballast materials and the determination of ballast particle size are determined by engineers and technicians according to the situation of ballast raw materials and combined with engineering practice after repeated research.

Water-stable layer

Water-stabilized layer is the abbreviation of cement stabilized macadam layer, that is, cement solidified graded macadam is completed by compaction and maintenance. The water-stable mixture ratio should be mixed in the laboratory in advance to determine the cement content and the proportion of coarse and fine aggregate, and at the same time determine the maximum dry density. A large amount can be mixed in a water-stable mixing station.

Lime-fly ash macadam

Lime-fly ash macadam, also known as lime-fly ash stabilized macadam, is a semi-rigid structure with strength, which is made of inorganic binder lime, fly ash and graded macadam mixed with a certain amount of water, rolled and maintained.