Sustainability applied to prefabrication

Prefabrication has evolved in depth and breadth from its beginnings, bringing many of the advantages of industrialisation to construction, while solving some of the problems that arose in the early years. Today prefabrication, compared to traditional construction methods, and concrete as a material, feature a number of beneficial characteristics. Precast elements are factory made products. The only way to industrialise the construction industry is to shift work from temporary construction sites to modern permanent facilities. Factory production entails rational and efficient manufacturing processes, skilled workers, systematisation of repetitive tasks, and lower labour costs per m² as a result of automated production. Factory products are process-based and lean manufacturing principles are deployed. Automation is gradually being implemented in factories and is already in place in areas such as the preparation of reinforcing steel, mould assembly, concrete casting, and surface finishing on architectural concrete. And other stages in the process are sure to follow. As prefabrication makes optimal use of materials, its potential for savings is much greater than in cast-in-situ construction. Structural performance and durability are also enhanced through design, modern manufacturing equipment and carefully planned working procedures. The environmental burden of prefabrication is mainly the burden caused by the raw materials of concrete (especially production of cement and steel). The environmental burden caused by raw materials is approximately three times larger than that caused by the production process of the elements, as indicated by the examples of environmental product declarations. Also thermal inertia of heavy materials is well known for both in warm and cold climates. Most people have experienced the comfort of coming into a comparatively cool stone building on a hot day in a warm climate. In precast structures several systems have been developed using this characteristic. As there is a Fib Bulletin under preparation in Commission 6 Prefabrication, by the Task Group 6.3 Sustainability, in which both authors are members, the conclusions of this document will be presented including a proposal for an evaluation model that can be applied to precast structures