On some microstructural aspects of concrete deterioration

Abstract

There are numerous mechanisms that can lead to deterioration of portland-cement concrete in service. The best known are corrosion of reinforcement, freezing-thawing expansion, alkali-silica reaction, acid attack, and sulfate-related problems, including delayed ettringite formation. Additionally, concrete can deteriorate as a consequence of improper processing, including curing. Often, several of the above mechanisms of deterioration are jointly responsible for the observed damage. This paper briefly reviews the light-optical and electronoptical microscopic methods available to study some of the causes of concrete deterioration, and briefly describes selected case studies. Specifically, microstructural features resulting from physical (e.g., freezing-thawing) and chemical (e.g., alkali-silica reaction, delayed ettringite formation) deterioration of concrete are highlighted. Corrosion of reinforcement is not discussed.

Keywords

• concrete durability
• microstructure
• electron microscopy
• alkali-aggregate reaction
• delayed ettringite formation
• hiqh-temperature curinq
• freezinq and thawinq