6.2.5 End of life

This stage mainly calculates the environmental impact caused by different treatment methods at the end of the life of the pavement. The main disposal methods are classified into two categories: burying and recycling [48].

The disposal method of burying is to crush the pavement material and bury it. The environmental impact of this process is divided into three parts, namely, the consumption of crushing, transportation, and burying. There is little literature on the environmental burden of materials after burying, and further research is needed.

Recycling is to break up the pavement material and use it as aggregate to be added to the new pavement material in a certain proportion. In actual engineering, there are various methods for recycling, which can be divided into thermal regeneration and cold regeneration depending on the regeneration temperature and can also be divided into on-site regeneration and in-plant regeneration according to the regeneration site. Since the recycled material comes from the old pavement system and is used in the new pavement system, how the environmental benefits brought by the circulation are distributed between the two systems is a problem still being studied and discussed. The existing distribution methods include cutoff, loss of quality, closed loop, equalization (50/50), and substitution [44]. But there is still no way to get consistent recognition. Due to the lack of data, the equalization method is the most commonly used method. Although it ignores the quantity and importance of recycled materials, it has the best maneuverability in practice [49].

## 6.3 Independent algorithm of LCCA

### 6.3.1 Labor costs and direct monetary inputs

There will be a large amount of labor input in the process of road construction, maintenance, and recycling. At the same time, some direct monetary input as

indirect fee is inevitable. The economic costs of these inputs are relatively easy to calculate, but their environmental costs are difficult to measure directly, so they are calculated as independent economic costs, regardless of their synchronous environmental costs. In the actual calculation, these costs will be directly incorporated into the total economic costs of the corresponding stage.
