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Superpozzolanic Concrete for Sustainable Construction and CO2 Emissions Reduction
University of Kentucky Ultra fine fly ash, derived from coal combustion waste ash ponds, can potentially be used to produce "superpozzolanic concretes" at competitive costs. Superpozzolanic concretes take full advantage of the capacity of Portland cement to produce cementitious gels from the hydraulic reaction of the primary components of Portland cement, as well through pozzolanic reactions between the ultra fine fly ash and aqueous calcium hydroxide. Superpozzolans such as silica fume and air-classified fly ash have been used for years but their high cost and limited supply has kept usage relatively low. Ongoing research at the University of Kentucky has found that ultra fine fly ash can be produced from ponded coal ash using a hydraulic classification technology. However in the case of ponded fly ash, there is a need for fundamental research into its pozzolanic reactivity. In fact, some marketers and users of fly ash believe that ponded fly ash has a low reactivity in concrete. In this study it is proposed to examine the pozzolanic properties of ultra-fine fly ash that is produced from ponded fly ash, with the objective of maximizing the proportion of Portland cement in concrete that is replaced with fly ash. To accomplish this, the engineering properties of mortar and concrete, both in the fresh and hardened state, will be tested. In addition, crystalline phase composition and morphology, and pore solution chemistry of mortar will be studied in order to better understand the pozzolanic reactivity of the ultra fine fly ash. The enormous supply of stored ash in Kentucky and elsewhere, combined with a relatively simple technology, could result in much lower cost superpozzolans if the demand develops. However, for superpozzolanic concrete to be widely accepted, formulations and performance will have to be carefully investigated and characterized. Furthermore, organizations that specify and produce concrete must be involved from the outset. Therefore, stakeholders in this technology, such as the Kentucky Transportation Cabinet and the Kentucky Ready Mixed Concrete Association, will be consulted over the course of the project.
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