Impact resistance of concrete produced with plain and reinforced cold-bonded fly ash aggregates

In this paper, the impact resistance of concrete produced with cold-bonded fly ash aggregates (FAAs) in partial or full replacement, by volume, of crushed limestone coarse aggregates was investigated. Fly ash aggregates were produced as plain (PFAA), with 0.1% crumb rubber (CRRFAA) and with 0.1% polypropylene fibers (PPFRFAA), by weight, as reinforcement. Nine concretes are produced at w/c of 0.40 by replacing crushed stone coarse aggregate at 4-8 mm, 8-16 mm and 4-16 mm size fractions with fly ash aggregate together with the control concrete having a target compressive strength of 50 MPa. While use of different types of FAAs resulted in slight to substantial decrease of compressive and splitting tensile strengths and impact resistance of concretes, higher values are obtained in concretes with FAAs replacing 8-16 mm size group of crushed stone coarse aggregate. Polypropylene fiber and crumb rubber addition into the fly ash pellets increased the ability of the aggregates to absorb energy and thus the impact resistance of concrete. The polypropylene fibers protruding from the surface of FAAs might have caused better adherence of the FAAs to the cement paste to result in higher impact resistance.