Texas Tech University

Project 0-1365-1F

Guidelines for Using Hydrated Fly Ash as a Flexible Base


The cost of transporting granular materials for flexible bases can be a major factor in pavement construction costs. Sources of adequate construction aggregates are scarce in some areas of Texas, and pavement construction requires transporting significant amounts of aggregate to the construction site. High transportation costs create the need for alternative sources of material that are available locally. Hydrated fly ash – a stiff material produced by allowing powdered fly ash from coal power plants to cure with moisture – may be used to make aggregate for flexible bases. Hydrated (cured) fly ash is so stiff that it can attain compressive strengths as high as 15,000 kPa. With its natural reactivity, fly ash will set in stockpiles, even in the absence of organized curing. This study included a comprehensive literature search on fly ash characteristics, selection and monitoring of a TxDOT pavement construction project, laboratory characterization of hydrated fly ash material, documentation and presentation of findings to TxDOT, and the development of specifications for fly ash as flexible base.

Project PI: Phillip T. Nash, P.E

Project Researchers:

Priyantha Jayawickrama
Sanjaya Senadheera

Full Project Report