Mechanical properties of geopolymer-based ultra-high performance concrete with ceramic ball coarse aggregates

This research reported the mechanical properties of geopolymer-based ultra-high performance concrete containing ceramic ball coarse aggregates. 10 mm straight steel fibres with various contents (0, 0.6 vol-%, 1.2 vol-% and 1.8 vol-%), medium-aluminium ceramic balls with various sizes (3 mm, 6 mm and 10 mm) and contents (0, 10 vol-%, 20 vol-% and 30 vol-%) were utilised. Mechanical properties, including the slump flow, uniaxial compressive, splitting tensile and flexural strengths, were investigated via a series of material tests. Fundamental contributions arisen from the steel fibre content, ceramic ball size and content towards the mechanical properties were analysed and discussed. In the light of the flexural load-midspan deflection curves, a constitutive flexural model was established, and the flexural toughness characteristics were quantitatively assessed using two indexes. Also, empirical equations to evaluate the strength relationships were proposed. Scanning electron microscope observation was carried out on the steel fibre-matrix interface to further explain the influencing mechanism of ceramic balls on the fibre reinforcement efficiency.