Concrete resistant to spalling made with recycled aggregate from sanitary ceramic wastes - The effect of moisture and porosity on destructive processes occurring in fire conditions

The paper describes a new model of the production of the concrete that is resistant to the conditions of a sudden temperature rise, which simulate a fire. Aluminum cement and aggregate obtained from the sanitary ceramic ware wastes were used for the production of the concrete. The composite was modified by the addition of the polypropylene fibers or by introducing additional porosity into the material. The purpose of the work was to produce a concrete, which would have optimal strength parameters despite the impact of a high temperature equal to 1000 °C. The paper presents the results of the research on the physical properties of the cementitious composites, as well as compressive strength before and after thermal loading. In addition, the microstructure of the heated concretes in various moisture states was investigated using a scanning electron microscope (SEM). On this basis, conclusions were drawn regarding the influence of destructive physical changes within the cement paste on the strength properties of the concretes; the beneficial characteristics of the ceramic aggregate in the aspect of the water vapor diffusion were pointed. In addition, the process of the cracks' propagation in the structure of the cement matrix due to thermal load, and the diffusion of water vapor by the structure of the ceramic aggregate has been schematically modeled in the paper.