Bridges

The standard Super-T bridge girders used in Australia were developed to provide optimum performance at a time when the maximum concrete grade covered by the bridge design code was 50 MPa. This paper examines the opportunities for improved sustainability through the use of high performance concrete, considering the use of existing standard sections, modified sections optimised for higher strength grades, and the use of techniques such as hybrid pre-tensioned and post-tensioned girders, and precast girders used in continuous structures. These alternatives are compared for impact on CO ₂emissions within the context of current Australian precast and bridge construction practice. In addition, the designs of the sections are reviewed based on a series of alternative concrete mix designs covering a reference Portland cement concrete mix and a series of concretes incorporating a range of supplementary cementitious materials included at different levels of cement replacement to determine efficiencies in design and impacts on the embodied energy required to manufacture the elements.