USE OF ARAMIS SYSTEM FOR TESTING FRACTURE TOUGHNESS OF CONCRETE COMPOSITES MODIFIED WITH FLY-ASH ADDITIVES

Nowadays, structural concretes containing additives of fly-ash are quite commonly used in the construction industry. This is mainly due to economic reasons connected with the possibility of utilizing this industrial waste (fly-ash) as an effective substitute for cement. The analysis of the defects occurring inside the composite structure plays a significant role in concrete mechanics. If we know the parameters of fracture mechanics or the levels of critical compressive stresses, we can estimate at what load level a defect will develop in an uncontrolled manner in the material. The ARAMIS system is a useful tool for research on the processes of crack propagation in concrete elements. The system is designed for the optical analysis of deformations occurring in test specimens and constructional elements. Significant advantages of the system make it possible, for example, to analyse the development of initial cracks in a specimen in the course of a load application as well as to observe the propagation of cracks in a successive manner. The system provides the possibility of recording the crack propagation process in the form of a film (wmp file). The study presents the research on the fracture toughness of concretes containing 0, 20 and 30% additives of fly-ash. The composites containing a 20% additive of fly-ash were characterized by the best fracture toughness. Initial cracks propagated in the specimen at the angles from 0 to 15 degrees. The research results demonstrate the possibilities of the practical application of the ARAMIS system for analysing the development of defects in the structure of concretes containing fly-ash additives. This system can be useful for the macroscopic estimation of crack propagation as well as for determining concrete fracture mechanics that are convergent with the results obtained with the use of traditional methods based on the estimation of press displacement.