LAUSR

Abstract This paper presents a comprehensive study of the cracking processes of concrete specimens containing fly ash (FA). Concrete composites with the additives of: 0%, 20% and 30% FA were analysed. In the paper we analysed failure processes in the concrete specimens subjected to torsion. The studies examined effect of the FA additive on the work of fracture W f . Furthermore values of critical torsion moment T c and dissipated energy Δ w , at the fracture initiation point were assessed. During tests all stages of the crack growth, starting from initiation to specimen failure, were analysed (Fig. 6). It can be concluded that the FA additive changes the behaviour of the concrete during cracking process. 20% FA additive causes a small increase of the W f , while 30% FA additive causes a significant decrease in the work of fracture. On the other hand value of Δ w is the smallest in concrete containing 20% FA while the greatest in composites with the addition of 30% FA.