Durable Steel-Reinforced Concrete Structures for Marine Environments

Igor A Chaves,Robert E Melchers

doi:10.3390/su132413695

Abstract

Even in harsh marine environments, concrete structures reinforced with steel can show excellent long-term durability, with little or no reinforcement corrosion. Very few actual reinforced concrete (RC) structures have been closely scrutinized over many years and subject to interpretation using recent state-of-the-art understanding gained from detailed laboratory observations. Such a case is described for an 80-year-old RC structure observed annually over about 30 years in what is essentially an extraordinary long experiment. Despite very high chloride concentrations, field excavation evidence showed that reinforcement corrosion overall remains minimal, except where insufficient concrete compaction permitted air-voids to initiate quite severe, very localized corrosion even with still high concrete pH. It is possible that the use of blast furnace slag as aggregate may have assisted the observed durability. The case study supports other studies that show that it is possible to achieve long-term durable and therefore sustainable RC structures without additives and using only conventional reinforcement steels and conventional cements and aggregates. However, the potential dangers of deep narrow cracking extending to the reinforcement and the potentially deleterious effects of alkali–aggregate reactivity of some aggregates needs to be considered.

Highlights

It seems to have been forgotten that there is a long history of very successful reinforced concrete (RC) structures made with conventional reinforcement steels and without additives of any kind and that these have performed, and in some cases still are performing, remarkably well after many decades of exposure in severe marine environments and elsewhere [2,3]
The ‘concretes’ such as those used in reinforced concrete (RC) structures have a very long history and owe their durability to the types of aggregates and pozzolans used in the mix
Other cases and examples have become available, including the more than 150 Phoenix caissons placed during WW2 on the coast of Normandy to form breakwaters for the Mulberry B harbor as part of the Allied invasion in 1944. These were intended as temporary structures, yet after more than 75 years of exposure to the harsh marine environment of the English Channel, they show remarkably little evidence of reinforcement corrosion [7]

Summary

Introduction

The effects of such corrosion include the possibly serious impairment of structural capacity, unacceptable visual impact, high repair and maintenance costs and associated undesirable environmental impacts. These findings depart considerably from the conventional wisdom but, importantly, are based on detailed observations and investigations for multiple actual RC structures, supplemented with careful observations of the extended performance (14 years) of a large set of laboratory model concretes. The observations support recent conclusions from laboratory observations that construction practices and quality of construction can have considerable influence on the rate of progression and severity of steel reinforcement corrosion [6] and, on durability and sustainability of RC structures in marine environments

Background

Field Observations

Location

Analysis of Observations

Discussion

Conclusions