A brief on high-volume Class F fly ash as cement replacement – A guide for Civil Engineer

TLDR

Fly ash from coal power plants poses a major environmental challenge as its disposal volume rises while landfill capacity shrinks. This paper reviews prior studies on using high‑volume Class F fly ash as a partial cement replacement in Portland cement paste, mortar, and concrete. The review compiles data on mix designs, replacement levels, and performance metrics from existing literature on HVFA systems. The review summarizes that HVFA (≥45 %) affects fresh and mechanical properties, durability, and electrical resistivity, and identifies additives that mitigate performance deficits.

Abstract

Disposal of fly ash (FA) resulting from the combustion of coal-fired electric power stations is one of the major environmental challenges. This challenge continues to increase with increasing the amount of FA and decreasing the capacity of landfill space. Therefore, studies have been carried out to re-use high-volumes of fly ash (HVFA) as cement replacement in building materials. This paper presents an overview of the previous studies carried out on the use of high volume Class F FA as a partial replacement of cement in traditional paste/mortar/concrete mixtures based on Portland cement (PC). Fresh properties, mechanical properties, abrasion resistance, thermal properties, drying shrinkage, porosity, water absorption, sorptivity, chemical resistance, carbonation resistance and electrical resistivity of paste/mortar/concrete mixtures containing HVFA (⩾45%) as cement replacement have been reviewed. Furthermore, additives used to improve some properties of HVFA system have been reviewed.