High-density geopolymer concrete for Port Kembla breakwater upgrade

Abstract

Marine environments can pose continuous threats to coastal infrastructure, especially during episodic storm events. Thus, monitoring and maintenance of rock or concrete units-armoured coastal breakwaters are required, especially under present climate change scenarios, where changes in wave behaviour are anticipated and coastal structures are likely to be exposed to even greater wave energy resulting in higher rates of damage. A possible pathway towards the upgrading of existing breakwaters is to introduce high-density armour units, suggested by theoretical estimates and physical model test findings. In this project, a unique, sustainable high-density geopolymer concrete (GPC) mix was developed and trialled in fabricating armour units for upgrading existing coastal breakwaters. The system developed in laboratories was upscaled for field applications and is being tested at the Northern breakwater of NSW Ports’ Port Kembla Harbour. The concrete uses steel furnace slag (SFS) aggregate in an alkali-activated blended fly ash-blast furnace slag binder proportioned to facilitate the elimination of delayed expansion of the aggregate. The concrete properties were measured and microstructural analyses undertaken. The results show that SFS aggregate offers higher bulk density to the concrete alongside satisfactory strength in on-site curing and can reduce armour mass requirements at the same level of structural stability. Microstructural analyses confirm the elimination of SFS aggregate free-lime expansion. This important result provides a novel approach to both repair of existing structures and construction of new structures with reductions to both cost and carbon footprint.