Quantification of the degree of reaction of alkali activated fly ash by image analysis

Alkali activated fly ash (AAF) is one of the promising cementious materials in recent years. The durability of AAF, which has a significant influence on the service life design and safety, is closely related to its chemical composition and microstructure. In order to better understand the compositional change and microstructure development under different condition, and further evaluate the durability of AAF, the quantification of reaction degree is an important parameter. In this study, image analysis of backscattered electron (BSE) images was proposed to quantify the reaction degree of alkali activated fly ash. A combination of filters and grey level thresholding was applied to distinguish the boundary between the unreacted FA and the reaxtion products. Based on the volume fraction of unreacted fly ash, the reaction degree of AAF can be calculated. The results indicate that the reaction degree derived from image analysis is reliable and consistent, which correspond well with the compressive strength of AAF.