DETERIORATION PREVENTION IN REINFORCED CONCRETE STRUCTURES SUBJECT TO HOSTILE ENVIRONMENTS

Objective

Corrosion of steel in concrete is a worldwide problem of enormous proportions. The 2 main causes of corrosion are carbonation and chloride contamination. This project aimed at identifying cementitious materials, admixtures, and surface treatments which reduced corrosion. It also focused on developing a design life prediction model for new and existing structures.
Materials were evaluated at exposure sites in the United Kingdom, Bahrain and Greece using a range of nondestructive tests (NDT), including half cell potentials on the reinforcement resistivity of the concrete, chloride ingress, carbonation depth, and corrosion current. Laboratory tests were then used to measure compressive strength, oxygen diffusion, water permeability, chloride diffusion, and absorption properties.
Based on 24 months of observation, this project led to a number of significant observations and improvements in the modelling of reinforcement corrosion. It was observed that chloride ingress in the first 6 months is mainly absorption. Also, it was found that the rate limiting factor for carbonation is more likely to be chemical than physical.
Half cell potentials have increased progressively with increasing chloride concentration. Therefore, the concept of a chloride threshold level for corrosion activation must be reconsidered.
It was found that, for a given grade of adequately cured concrete, the only transport property which varies significantly between mix types is chloride diffusivity.
It was observed that absorption decreases with depth into the concrete. The work in Greece appears to show that an increase in the lime content enhances passivation and retards carbonation.
THE PROJECT AIMS ARE TO IDENTIFY MATERIALS WHICH CAN BE USED TO DIMINISH THE RATE OF CORROSION OF REINFORCEMENT IN STRUCTURES EXPOSED TO HOSTILE ENVIRONMENTS.
CHEMICAL ADMIXTURES, ALTERNATIVE CEMENTS AND SURFACE COATINGS ARE BEING EXAMINED.
PERFORMANCE IS BEING ASSESSED BOTH ON EXPOSURE SITES AND BY ACCELERATED TESTING IN THE LABORATORY. THE RESULTS WILL BE USED TO DEVELOP A LIFE PREDICTION MODEL FOR REINFORCED CONCRETE STRUCTURES.

Programme(s)

• FP1-BRITE - Multiannual research and development programme (EEC) in the fields of basic technological research and the applications of new technologies (BRITE), 1985-1988

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Taylor Woodrow Construction Ltd

Address

Taywood House 345 Ruislip Road
UB1 2QX Southall
United Kingdom

Participants (2)

British Rail Research

United Kingdom

Address

London Road
DE2 8YB Derby

HERACLES GENERAL CEMENT COMPANY SA

Greece

Address

Soph. Venizelou Street 49-51Ph&
14123 Nea Ionia,atikis