Abstract

Alkali silica reaction has been discovered over 75 years ago as a deleterious reaction in concrete, but the mechanism is not yet fully understood. Although there have been thousands of studies over the years, most of these studies have focused mostly on accessing aggregates that are susceptible alkali silica reaction so as to avoid it in new structures. In this study, focus is placed on understanding how moisture affects the progression of alkali silica reaction, as moisture cannot be affect the internal relative humidity inside concrete eliminated in concrete compared to other prerequisites for alkali silica reaction in concrete.Understanding how various forms of moisture will affect the reaction will help to understand the reaction more and how to sustain structures already affected by ASR.

This study employs the use of relative humidity as a measure of moisture in concrete, four sensors were assessed and internal relative humidity in concrete samples was measured at different depths to see how the external conditions affect the internal moisture of the concrete. Also, the effects of the initial water added to concrete, i.e. the water to cement ratio, and external relative humidity was studied to see how they affect expansion due to ASR. The overall objective of this thesis is to observe how moisture in various ways affects progression of alkali silica reaction in terms of primarily expansions observed and visual inspection of samples under an optical microscope. It was observed that the external relative humidity has an effect on the internal moisture in concrete.

Also, it was observed that the initial water to cement ratio has a slight increase on ASR as expansion of samples increase in water to cement ratio. It was also noted that fly ash and coatings affect the internal relative humidity inside concrete