Durability Testing of Marginal and Unconventional Fly Ash Mortars

Author: Jetsun Ty Thinley, Department of Civil and Environmental Engineering

Mentor: Dr. Christopher Shearer, Department of Civil and Environmental Engineering

Strength and durability properties of emerging sources of fly ash and bottom ash used as a partial replacement for cement are assessed. A suite of off-specification, marginal, reclaimed, and beneficiated ashes with a range of chemical and physical properties are analyzed. Off-specification and marginal ashes have deviations in sulfur trioxide content, carbon content, and fineness. A variety of beneficiation processes are also represented in the data. Testing conducted to assess the cement-fly ash specimens includes compressive strength (ASTM C311), bulk uniaxial resistivity (AASHTO TP-119), sulfate attack (ASTM C1012) and alkali-silica reaction (ASR) (ASTM C1567) resistance capabilities. Results are linked to reactivity testing on pastes. Calcium hydroxide consumption and product formation due to sulfate attack are quantified using thermogravimetric analysis (TGA)’s DTG curves and X-ray diffraction. Results show that strength and durability properties of these emerging sources of ash can be comparable to in-specification ashes depending on their properties. Therefore, ASTM C618 specifications may need to be rewritten to accommodate these types of ashes if they exhibit good performance in concrete applications.