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This paper reports on the generation, properties, and spatial variability of the graded layer in functionally graded concrete (FGC) made using 20, 35, and 50% ground granulated blast furnace slag (GGBFS) as partial replacement of ordinary Portland cement (OPC). Two different layers of concrete, one being OPC based normal concrete and the other being GGBFS blended concrete were used to prepare the FGC specimens. The control concrete specimens were made with a single layer OPC or GGBFS concrete. Excluding the control concrete samples, three types of double-layered cube samples of 150 mm thick were prepared in various combinations of the thickness of constituent layers. These double-layered combinations were 25 mm + 125 mm, 75 mm + 75 mm, and 125 mm + 25 mm thick containing OPC concrete and GGBFS blended concrete respectively. The properties like compressive strength, the interfacial bond between two constituent layers, modulus of elasticity, micro-structure, and graded layer were examined. The formation, thickness, and properties of the graded layer at the interface of constituent layers were evaluated using elastic equations and microstructural studies like scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The investigation was conducted by applying the load parallel and perpendicular to the interface plane between constituent layers. The results showed that the properties of concrete improved in FGC compared to control. Formation of graded layer added value to the FGC. Among the specimens of various thickness combinations, the samples with 75 mm OPC concrete and 75 mm GGBFS concrete showed the best results when the load was applied parallel to the graded layer. Finally, environmental benefit in terms of embodied CO2, energy and cost benefit of the different mix proportion concrete are analysed. Further the effectiveness of FGC is also reported which has huge potential to be used in concrete structure elements.

During the heavy oil hydroprocessing, a decrease in catalytic activity with time-on-stream (TOS), is due to the metal and carbon deposition on the catalysts. In this investigation, spent catalysts were obtained from the Maya heavy crude hydrotreating unit, as the processing conditions were close to the industrial practice. The catalysts were unloaded after considerable activity decrease, considering the initial activity as base activity. The spent catalysts were characterized by pore size distribution, SEM-EDS, TEM and 13C solid state NMR. Results indicate that catalysts were deactivated mainly due to the deposition of metal and carbon. The sources of deactivation were identified along with the location of foreign species by analyzing the deposited species on the spent catalysts. The nature of the coke and its compositions were derived from 13C CP/MAS and CP/MAS with dipolar dephasing NMR experiments. The wide range of analysis of spent catalysts specify that the catalyst pores were plugged during the heavy oil processing. The deactivation of catalysts were not only due to the carbon deposition but also due to the deposited metal sulfide (VxSy, NixSy) over the existing (CoMoS) active sites. It appear from the results that considerable amount of deactivation is irreversible and non-regeneratable (i.e., metal deposition). Hence catalyst deactivation during heavy oil hydrotreating (HDT) is a function of metal and carbon deposition during time-on-stream. The metal deposition on spent catalysts, e.g. vanadium is on the surface, while Ni distributed deeper into the pore of the catalysts. The removal of Ni and V showed different behavior, which was attributed to an oxygen atom presence to vanadium and its influence on the vanadium porphyrin structure.