Investigation into the use of macro synthetic fibre reinforced concrete for breakwater armour units

A common form of coastal protection in New South Wales, Australia, is the rubble mound breakwater. This consists of quarried rock or unreinforced concrete armour units. However, increased impact forces on these structures due to greater storm surge levels that are predicted by global warming models, suggest that they will require strengthening. Traditionally steel bar reinforcement is used to strengthen concrete; however, as steel is particularly susceptible to corrosion in aggressive coastal environments, it is not a robust solution. This paper reports on the potential of using macro-synthetic fibre reinforcement in reinforcing of breakwater armour units, in lieu of traditional steel reinforcing bars. To this end, a programme to ascertain the tensile capacity of 0.6 percent and 1.0 percent by volume of concrete reinforced with macro-synthetic fibres was implemented. The behaviour of this synthetic fibre reinforced concrete in Dolos type breakwater armour units was then examined using the finite element analysis software ATENA. The results of the numerical analysis indicate that the addition of synthetic fibres at these volume percentages into concrete armour units improves the post peak response under impact loading by a factor of two to three, compared with unreinforced units. Furthermore, the addition of fibres significantly reduced the maximum crack width for the same number of impact loadings and allows the units to withstand larger crack widths before failure.