The effect of fly ash additive on the resistance of concrete to alkali silica reaction

Abstract

Concrete is the most widely used construction material obtained after the setting of the mix composed course and fine aggregates, cement and water. The main properties of concrete are determined by the quality and characteristics of aggregates, w/c ratio, and the uniformity of mix compaction. Materials used: Portland cement CEM I 42.5 R, 0/4 fraction sand, 4/16 fraction gravel, fly ash, superplasticizer, and water. 7 batches of specimens were made with different fly ash content: 0%, 15%, 25%, 35%, 45%, 55%, 65% (replacing cement in the mix, %). Compressive strength and flexural strength, water absorption, density, ultrasonic pulse velocity, and alkali silica reaction resistance were tested in modified concretes against the expansion of the specimens. Concrete, where 65% of cement is replaced by fly ash, has higher density, ultrasonic pulse velocity, and lower water absorption rate. Subsequently, the expansion of modified specimens is lower. All these characteristics improve the alkali silica reaction resistance of concrete. The obtained relationship between the fly ash content in concrete mix, the change of ultrasonic pulse velocity and expansion of the specimen is used to evaluate the alkali silica reaction effect on concrete. The tests revealed that concrete modified with 65% of fly ash has better durability and alkali silica reaction resistance characteristics and can be used in construction works.