Standardized Testing for Determining the Durability of High-Volume Fly Ash Mixtures

Abstract

Fly ash is becoming increasing used in concrete structures for enhanced durability. This research investigated two types of fly ash in conjunction with four cements. The cements were both high and low alkali, with and without blended silica fume. Mortar and concrete mixtures were prepared containing from 0 to 80% fly ash replacement. Standardized tests were performed for compressive strength, as well as sulfate, chloride, and alkali resistance. High replacement levels performed relatively well in sulfate and alkali resistance, but poorly in regards to compressive strength and chloride resistance. From a durability perspective, 40% fly ash replacement was found to have the best overall performance from these mixtures. Standardized test methods are comparative by nature, and as such cannot replicate the complexity of concrete mixtures and their exposure conditions; higher replacements have been successfully used in practice.