Factors Influencing the Strength of Cement Fly Ash Base Courses

Abstract

Fly ash is a waste produced in coal-fired thermal power stations. It has pozzolonic properties and can therefore be stabilized with either cement or lime to achieve the strength required for use as base courses in pavements. Agencies such as the Electric Power Research Institute (EPRI) have specified criteria and guidelines for the determination of the stabilizer content. This requires carrying out unconfined compression tests on stabilized fly ash specimens prepared and cured as per standard procedures. The stabilizer content is the minimum amount of the stabilizer for which the unconfined compressive strength of the specimens complies with the specified values. The actual curing conditions of the stabilized fly ash bases in the field, however, will differ from those of the laboratory specimens. This will affect the strength development of the bases, their durability, and their performance. The paper explains the details and results of a laboratory experimental program carried out to study the influence of curing conditions and other factors on the development of strength. The program comprised compaction tests and unconfined compression tests. Two Indian fly ashes and a commercial portland cement were used in the study. Six different curing conditions, including controlled and ambient conditions, were adopted. The influence of differences in the dry unit weight and water content was also investigated.