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High calcium cementless fly ash binder with low environmental footprint: Optimum Taguchi design
Author(s) -
Hwang Sung H.,
Shahsavari Rouzbeh
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15873
Subject(s) - fly ash , portland cement , taguchi methods , compressive strength , portlandite , materials science , footprint , calcium oxide , cement , composite number , chemical engineering , waste management , pulp and paper industry , composite material , metallurgy , engineering , geology , paleontology
Despite the myriad of research efforts on exploiting fly ash as an alternative binder, its current role in industry is largely restricted to the supplementary use, which enables only partial replacement of conventional portland cement. Herein, we propose an unprecedented binder composite with the promising early‐age strength, which is cost‐effective and reduces the CO 2 footprint compared with portland cement. The major constituent is fly ash occupying 76.4%‐80.3% by the total mass of the constituents, while calcium oxide, nanosilica, and the minimum amounts of sodium‐based activators are added to induce the early‐age strength development. Optimization of the composition via the Taguchi design of experiments produced the early (7‐day) compressive strength of 16.18 MP a. This value is encouraging considering that it is comparable to that of conventional portland cement and that a cementless composition with the minimum amounts of sodium‐based activators was employed. The extensive materials analysis demonstrates that the starting Ca/Na molar ratio and the amount of nanosilica play instrumental roles in strength development by influencing the formation of key reaction products, which include the sodium‐substituted AF m phase (the U‐phase), katoite and portlandite. Overall, the promising early‐age strength coupled with the significantly decreased amount of sodium‐based chemicals and the reduced CO 2 footprint will lay a foundation for development of low‐cost, environmentally friendly binder in diverse industries.