Environmental analysis of concrete deep foundations: Influence of prefabrication, concrete strength, and design codes

There is great potential to reduce the environmental impact of the building sector, which is now an area of immense importance, through the optimisation of construction materials and components. This study assesses both the design and the construction of Concrete Deep Foundations (CDFs), which are widely used in construction, from an environmental perspective considering the following variables: (i) grade of prefabrication, i.e., fully cast in situ, partly prefabricated, and fully prefabricated; (ii) compressive strength of cast-in-situ concrete; and (iii) building design codes, i.e., current Spanish codes (EHE-08 and CTE), Eurocode with the Spanish annexes, and Eurocode with the United Kingdom annexes. In addition, the results of Dynamic Load Tests (DLTs) and the economic cost of several CDFs are evaluated. Geotechnical and structural designs of CDFs are carried out along with their life-cycle assessment. Some of the main findings include: (i) partially and fully prefabricated CDFs and conducting DLTs reduced the environmental impact in most categories (by up to 44% for global warming emissions) compared to the fully cast-in-situ CDFs, although they were 12–37% more expensive; (ii) changing the compressive strength of the concrete (in piles and cap) in fully cast-in-situ CDFs from 25 to 35 MPa reduced the environmental impact by up to 14–17% in all categories and economic costs by up to 12%; and, (iii) CDFs with bored piles resulted in the lowest environmental burden when designed with Eurocode and UK annexes (11–31% less impact), as did CDFs with driven piles designed with current Spanish codes (11–18% less impact). The study variables and sensitivity analysis showed a significant effect on the results and should be considered in future construction, research, and building codes.