Degradation in pavement concretes - Effects of cyclic loading on fluid transport processes and ASR

Abstract

The Alkali-Silica-Reaction (ASR) in concrete pavements has been known for several years. The previous investigations of ASR focused mainly on potentially reactive aggregates and the assessment of the ASR-potential in concrete pavements. A study of the separate influences causing and accelerating an ASR has been missing. The ASR can be greatly affected by externally supplied alkalis such as de-icing agents. These penetrate into the concrete microstructure, which is damaged through traffic. One focus within this extensive research project is the characterization of the degradation in the concrete microstructure caused by cyclic loading. Further focus lies on the determination of the effect of degradation on the transport behavior of fluids into the concrete. These studies show the degradation of the concrete microstructure under a varying number of load-cycles and changing stress levels. A significant increase in penetration depth of alkaline solutions was not only determined for different stages of degradation but also caused by overrolling tires, which increase the pressure on the surface locally. The externally applied alkali-ions then ingress and accelerate an ASR drastically. Thus, the superposition of these effects are greatly relevant for a damaging ASR. These studies are of interest for researchers as well as for practitioners.