The influence of spent catalyst from catalytic cracking in fluidized bed (FCC) on the hydration of two kinds of calcium aluminate cements (of about 40 and 70% content of alumina) was studied. Cement pastes were prepared with constant ratio of water/binder = 0.5 and with content of 0, 5 and 25% mass of addition as replacement of cement. The samples were stored at room temperature. Thermal analysis (TG, DTG), infrared absorption (FTIR) and X-ray diffraction methods were applied to investigate changes in various periods of hydration (up to 150 days). The compressive strength of cement mortars was also examined. On the basis of presented results it was affirmed that in studied conditions spent FCC catalyst is a reactive addition in calcium aluminate cement (CAC) pastes, which probably can create a new phase type C-A-S-H. It may be an interesting alternative for limitation of the negative phenomenon of conversion of aluminate hydrates, although the degree of the influence of the mineral additive depends on the composition of CAC and of the quantity of the used waste.

The effect of the composition of industrial concrete designed for radiation shielding structures on the air permeability and the diffusion of moisture was studied. The mix design for heavyweight concrete of bulk density 3168-3317 kg/m 3 was developed using barite and magnetite aggregate and cements blended with fly ash and blastfurnace slag. Structural elements, like columns of a height of 4 m and massive blocks made of mixtures with different cements were manufactured using ready mixed concrete pumped into the formwork. Core specimens were taken from the elements at different locations. The air permeability index was tested using Autoclam device. Evaluation of the quality of concrete on the basis of API results varied from ''very good'' to ''good''. The moisture distribution inside concrete specimens was equilibrated to RH = 60 ± 5%. Observation of RH changes allowed to determine the moisture diffusion coefficient. Significant differences of the permeability and moisture diffusion coefficient depending on the location of the core specimens drilling and mix design of concrete were found. The D coefficient provided a good reflection of the different quality of heavyweight concrete in structural elements.

No abstract

No abstract

No abstract