Title: Quantifying Influence of Off-Spec Fly Ash Characteristics on Concrete Performance

Author(s): Gokul Dev Vasudevan and David Trejo

Publication: Materials Journal

Volume: 120

Issue: 3

Appears on pages(s): 31-44

Keywords: carbon footprint; constituent materials of concrete; degree of reactivity; fresh and hardened characteristics of concrete; greenhouse gas emissions; off-spec fly ash

DOI: 10.14359/51738707

Date: 5/1/2023

Abstract:
Fly ashes that do not meet the ASTM C618 specifications areconsidered “off-spec” and are not used as supplementary cementitious materials (SCMs). In this research, four off-spec fly ashes (OFAs) were sourced from different parts of the United States and the characteristics of these OFA concretes were measured to compare their performance with that of the mixtures containing 0% OFA. The first objective of this study is to assess the influence of OFA reactivity and replacement levels on concrete characteristics. The second objective is to assess the influence of constituent material characteristics such as shape and size of coarse aggregate, fineness modulus of fine aggregate, and cementitious content of the concrete mixture on the fresh and hardened characteristics of concretes containing OFAs. Results indicate that at sufficient degrees of reactivity and replacement levels, OFAs can provide characteristics comparable to that of conventional ordinary portlandcement (OPC) concrete while improving the consistency of theconcrete. Findings from sensitivity analysis reveal that the degree of reactivity (DoR) of the OFA has a high influence on the hardened characteristics of concrete. Finally, the life cycle assessment of concrete mixtures containing OFAs indicate that greenhouse gas emissions can be reduced up to 45% when compared to conventional mixtures.