Effectiveness of Class C Fly Ash on Mitigating Alkali-Silica Reaction in Concrete Pavement

Throughout the state of Nebraska, Portland cement concrete pavements (PCCP) use Platte River sand and gravel exclusively as a fine aggregate. It has been well established that this aggregate is a reactive aggregate that can potentially lead to alkali-silica reaction (ASR). Fly ash has been used as an economic and effective way for ASR mitigation. However, Class C fly ash produced by Nebraska power plants has been identified as a major contributor to the premature deterioration of PCCP. This paper presents the experimental work performed to assess the effect of using Class C fly ash in PCCP to control ASR. The ASTM C 1567 test method was adopted to evaluate the expansion in 16 different mixes that contain different proportions of Class C fly ash, Class F fly ash, slag, and cement. Four mixes have been chosen for overall performance testing based on the ASTM C 1567 test results and material cost. These mixes, which contain at least 15% Class C fly ash in addition to Class F fly ash and/or slag, showed better performance over the current standard mix.