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The paper presents results of a study on T-shaped composite concrete beams with a variously located interface. Damage to tested beams was caused by shear. The crack patterns and the value of the force causing interface cracking were analysed. Conclusions concerning the failure mechanism were formulated. Moreover, the influence of the interface location and of the difference between the moduli of elasticity of joint materials on stress in the interface was also analysed.

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The study presented constitutes the next step of authors’ investigations on the concrete composite T-shaped beams. The comparison of the failure modes and crack patterns of numerical models and beams tested was performed previously. In this paper, analyses concentrate on determination the proper values of cohesive surface parameters ensuring the high conformity of deformation and strains of the numerical model to the experimental results. In the particular series of beams the interfaces between concrete parts are varied as follows: reinforced joint with normal and tangential interactions only (BZ/S2/A), non-reinforced joint with adhesion (BZ/P), and reinforced joint with adhesion (BZ/P+S). Material properties used in numerical model are based on obtained in the laboratory ones. Furthermore, the ‘traction–separation’ law in the ABAQUS software defining the cohesion surface is used and analysis of the cohesive parameters response to interface roughness is carried out. The results show a strong dependence between the cohesion surface parameters and the response of the composite beam. A very good convergence of the numerical model with the experimental results in terms of ‘force-displacement’ relationship is achieved. Finally the parameters defined in the ABAQUS are determined, which have a key impact on the beams response.

The microstructure of concretes containing ceramic sanitary ware waste and granite aggregates was studied using scanning electron microscopy, mercury intrusion porosimetry and computer microtomography, before and after cyclic heating of the concretes to 1000 °C. All methods showed an increase in porosities in the concretes after heating. The proposed new approach to microtomography data analysis detected a much higher increase in the number of cracks in granite than in ceramic concrete after heating. This new approach to combining mercury intrusion and microtomography data showed that heating led to the narrowing of throats connecting smaller pore voids and a broadening of throats connecting larger pore voids, in both concretes.

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The tests results of composite reinforced concrete T-shaped beams with an interface between the web and the flange are presented. The interface in the beams differed in the degree of the adhesion activity and the joining reinforcement ratio. Five series of beams were tested for deflection, displacement of composite parts in relation to each other, strain of main and transverse reinforcement, and crack pattern. The results were compared with the theoretical forces, at which interface cracks and achieves the bearing capacity, calculated in accordance with fib Model Code 2010.