Quantity of Alkali Silica Gel and Its Effect on Concrete Properties

Abstract

A quantitative gel fluorescence technique was used to investigate relationships between the extent of alkali silica reactivity (ASR) and properties of concrete cores of varying ages taken from over 20 bridges or pavements in North Carolina. The cores had varying degrees of ASR and were composed of a wide variety of aggregates and cementitious materials. The technique, combining image processing and analysis with a Strategic Highway Research Program qualitative gel fluorescence method, is described and results are discussed. The effects of lamp intensity, thresholding, video averaging, and color based discrimination to differentiate fluorescing areas are reviewed. Preliminary statistical analysis of the technique is presented. While no useful correlation was found between the mechanical properties of cores and the apparent gel content, a strong correlation was found between the percent area of fluorescing material and the log