High content of fly ash (Class F) in extruded cementitious composites

This paper presents mechanical properties and durability of extruded fiber- reinforced cement composites that contain a high percentage of Class F fly ash. The fly ash was examined as a replacement for cement in a plain cement matrix and composites containing polyvinyl alcohol (PVA), glass, acrylic ( PAN), polypropylene (PP), or cellulose fibers. Accelerated aging was used t o study the effect of fly ash on the durability of the different systems. I t is shown that fly ash improves the flexural performance of the extruded c omposite. The extent of this improvement varies with fiber type. PAN, glass , and cellulose fibers were most affected by the use of fly ash. The greate st improvement in both flexural strength and ductility was obtained for 28- day moist-cured composites containing PAN fibers when as much as 70%, by vo lume, of the cement was replaced with fly ash. In this case, a five-fold in crease in toughness and an approximately 20% improvement in strength were o bserved for steam-cured composites.