Influence of concrete mix design on CO2 emissions for large wind turbine foundations

Large capacity wind turbines require sizeable foundations. Onshore turbines are commonly supported by massive spread foundations involving hundreds of cubic metres of concrete and tonnes of steel reinforcement. Concrete gravity base foundations for offshore wind turbines also employ significant quantities of concrete and reinforcement. The CO2 emissions associated with concrete foundations has been analysed to examine means of reducing the materials-related impact on the carbon footprint of wind power. The effects of strength class, cement content, partial replacement of cement and use of recycled concrete aggregate were investigated. It was determined that use of 32 MPa class concrete rather than 40 MPa can reduce the concrete generated emissions by at least 11%. The greatest decrease in emissions for the studied mixes was found for concrete with 65% replacement of cement with blast furnace slag and the reductions were 42.7-44.8%, depending on strength class. The use of recycled concrete aggregate resulted in moderate reductions in emissions and would have other environmental benefits. The study has shown that selection of concrete constituents and appropriate mix design can be used to minimise CO2 emissions associated with large wind turbine foundations without compromising strength and performance requirements.