Xie, Ning; Cui, Na
U.S. Department of Transportation; Western Transportation Institute, Montana State University; Center for Environmentally Sustainable Transportation in Cold Climates, University of Alaska, Fairbanks
Admixtures; Binders; Deicing chemicals; Durability; Environmental impacts; Fly ash; Hydration; Mechanical properties; Recycled materials; Environment; Highways; Materials
From the economic and social perspectives, the use of waste materials would not be attractive until their costs and quality can satisfy the construction requirements. In this study, a pure fly ash paste (PFAP) was developed in place of ordinary Portland cement paste (OPCP). This PFAP was prepared at room temperature and without direct alkali activation. The samples were prepared using only the as-received class C coal fly ash (CFA), water, and a very small amount of borax (Na₂B₄O₇). On average, the PFAP featured 28-d compressive strength of about 36 MPa, and micro-nano hardness and elastic modulus 29% and 5%, higher than the OPCP, respectively. These mechanical and other properties of the PFAP make it a viable “green” construction binder suitable for a host of structural and non-structural applications. Advanced characterization of the raw material and PFAP pastes was employed to elucidate the hydration mechanisms of this “green” binder. The obtained knowledge sheds light on the role of class C CFA in the hydration process and may benefit the expanded use of various CFAs in cementitious materials.