As defined by ISO 14040
As defined by ISO 14040 an LCA analysis should consist of the phases illustrated in Figure above. A partial LCA framework is established for this study on the characteristics of construction materials and structural forms, including elements such as the study goal, the system boundary, scope definition, inventory analysis, impact assessment, and interpretation of results (Feifei Fu, 2014).
1.Goal and Scope Definition
The goal and scope definition of an LCA is the most important aspect of the process since they define the intended application and reasons for carrying out the study as well as the intended audience the results will be directed to. Particulars of the project comprise defining the functional units, the product system to be studied, system boundaries and outlining limitations and assumptions.
LCA is relatively a new system process with an iterative technique nature, hence clearly defined goals should be set for the clear distribution of results and for reaching justifiable conclusions. To answer the various questions arising from the scope defined of the assessment, a quantitative functional unit should ensure compatibility and comparability of LCA results.
Functional units are most important when multiple elements of products are compared such an example being a direct comparison of an 80m highway composite bridge with one span 15m footbridge could not be directly achieved for reasons of bridges different purposes of use and different size (ISO14040, 2006) (Feifei Fu, 2014).
The functional unit vastly accepted in practice is the normalised carbon (kgCO2e/m2) for carbon assessment of infrastructure (E.g. Buildings, bridges, etc.)
2.Life cycle inventory analysis (LCI)
This phase of the assessment includes the data collection and calculation procedures to quantify relevant inputs and outputs within the selected system boundaries (ISO14040, 2006). A number of data associated with the inputs and outputs datasets analysed can be obtained from publicly accessible inventory databases such as the Inventory of Carbon and Energy that contains materials embodied carbon factor (ECF) for modules A1-A3.
The LCI analysis inputs include data associated with raw material quantities, embodied carbon factors (ECF), transport emission factors (TEF) and waste generation per functional unit (e.g., kgCO2e/kg).
However, the data inputs range is largely affected by the material process technologies applied, regional or global conditions of the markets and the variations on data from different sources (DU, 2015). For example, an embodied carbon factor for reinforcement bar from UK-based producers could have an ECF of 0.684 kgCO2e/kg, whereas a UAE- produced bar with no recycled content could reach up to 2.13 kgCO2e/kg (O P & J J, 2020).
Furthermore, as seen in Figure below from (O P & J J, 2020), values of EPD (Environmental Product Declaration) data from 1500 specific concrete mixes were plotted showing the extensive range of carbon emissions of different concrete strength classes.