Behaviour of steel-reinforced concrete armour units used in coastal defences

Abstract

This paper reports on the use of steel reinforcement in slender-section concrete armour units used to protect the North Wirral coastline from storm erosion. The novel use of steel reinforcement has permitted the design of armour units that are both structurally and hydraulically more efficient than either natural stone armour or plain concrete armour units. However there is a risk that the steel reinforcement may suffer from corrosion attack within the design lifetime of the units. A programme of monitoring a sample of units on an annual basis has been established to assess their hydraulic, structural and durability performance. Electrical potential and resistivity methods are used to assess the level of corrosion activity in the steel reinforcement. A number of armour units have made use of cement replacements and admixtures in the mix design to enhance the durability characteristics of the concrete. The results of the initial four years of this study have shown that the armour units are behaving very well in all aspects of their performance. Furthermore, the use of steel reinforcement has permitted the full repair of accidental damage that would not have been possible with unreinforced concrete units.