# Study on the Carbon Emissions in the Whole Construction Process of Prefabricated Floor Slab
## 2 Research Methods  
### Life Cycle Framework of the Whole Construction Process of Prefabricated Buildings  
As a comprehensive environmental impact assessment method, the LCA method is widely used to evaluate the effect of energy consumption reduction in the construction industry [23; 24; 25]. The specific assessment method involves evaluating the potential environmental impact by compiling an inventory of inputs and outputs related to the product system, and then the results of the inventory analysis and impact assessment are evaluated [26]. The evaluation process can be summarized into four stages: (1) goal definition and scope, (2) inventory analysis, (3) impact assessment, and (4) interpretation. Due to the various scopes and theories of different product systems, LCA can be divided into three parts: process LCA, input-output LCA, and mixed LCA [27]. The life cycle of the building is a process from cradle to demolition [28], and its specific details are shown in Table 1.  
As can be seen from Table 1, the whole process of the life cycle of a building goes through four phases, namely building materials production phase, construction phase, use phase, as well as end of life phase. Among them, the use phase is the main part of the building life cycle, lasting 50 years. Thus, the study of carbon emissions in building life cycle is a long-term issue involving complex uncontrollable factors. However, the construction life cycle of building materials production phase and construction phase usually lasts relatively short time span, involving simple factors controlled by the professional construction production team management. Therefore, this paper take the material production phase and construction phase as example to study the carbon emission in the whole construction process of PFS.  
The whole PFS construction process is the beginning of the life cycle of the building, and its LCA framework is shown in Figure 1. The materials required for the production stage are obtained by collecting raw materials and processing them in the corresponding factories.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Phase** & **Activity** \\ \hline Building material production phase & Raw material extraction, Main production process, Arrow indicating transportation, Packing and storage \\ Construction phase & Construction, Assembly onsite, Prefabrication off site, Transportation on site and off site, Administration \\ Use phase & Operating building appliances, Renovation, Maintenance \\ End of life phase & Disposal recycle \\ \hline \hline \end{tabular}
\end{table}
Table 1: Life cycle stages of a building.  
The LCA framework of PFS in the construction stage is shown in Figure 1. The production stage includes: (1) preparation of building materials, converting raw materials (stone, metal ore, and wood) into building materials, including rebar, concrete, embedded parts, etc. and (2) the prefabrication of floor slabs, where the manufactured building materials are used to prefabricate specific components of each floor slab. The transportation stage refers to the transportation of PFS and premixed concrete to the construction site by a transport vehicle. The construction stages include the installation of PFS and concrete pouring on-site for connecting PFS with other prefabricated components.