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This research reports the investigations of threshold reactivity limit of blends of pegmatite with different calcined clays as well as the influence of calcined clay source on the geopolymerization kinetic, microstructural, and physicomechanical properties of feldspathic mineral-based inorganic polymer composites. These composites were designed from 85 to 94 wt% of the solid solution of pegmatite and calcined clay. The three-point flexural and compressive strengths, porosity, and microstructure as well as heat evolution rate of geopolymerization reactions of resulting composites were affected by the type of calcined clay. The four calcined clays provided the highest mechanical properties of the composites when added in the range of 12-15 wt%. Specifically, the values of flexural and compressive strengths ranged from 32 to 34 MPa and 101 to 105 MPa, respectively, for geopolymer composites with 15 wt% of metakolin added, while they ranged from 38 to 42 MPa and 106 to 107 MPa with 12 wt% of meta-hallosyte added. The polycondensation/polymerization process of calcined clay developed sufficient amounts of N-A-S-H and polysialate geopolymer to cover the incongruently dissolved fine particles of pegmatite. The resulting microstructure was dense and compact with the lower cumulative pore volume at about 91 mm3/g. It was concluded that designing the pegmatite/clay-based geopolymer composites with high mechanical strengths and low porosity resulted in sustainable, low energy consumption and environmental-friendly materials for civil engineering. [ABSTRACT FROM AUTHOR]

Since the arrival of lapped porcelain stoneware tiles on the market, several studies have been focused on the improvement of the technical characteristics of the surfaces of these products. Surface lapping induces aesthetical improvements, but can at the same time deteriorate the performance of porcelain stoneware tiles. To overcome this problem, it is possible to protect the lapped surface with commercial waterproofing materials. In this work, lapped commercial porcelain stoneware tiles with protective stain proofing agents (FILA PD15 and FILA 1239 Plus) were evaluated. The stain resistance and chemical resistance results were correlated to the morphological surface characteristics of the products with and without protection. A systematic study of the surface porosity of the tiles was carried out. Results showed that unprotected surface pores tend to fill with dirt that is hardly removable by ordinary maintenance. If the pores are protected, the dirt from foot traffic is deposited only superficially and can be removed.

Recent work on the elastic constants of plagioclase feldspars is reviewed. Based on the 21 elastic constants (stiffnesses) reported in the literature for triclinic plagioclase monocrystals of different composition, the effective elastic constants of dense, single-phase, polycrystalline plagioclase aggregates with isotropic microstructure are calculated via standard VoigtReuss-Hill averaging. Master curves show the good agreement of the constants obtained via the two approaches (experiment and simulation) and recall the fact that values reported in the older literature have been underestimated. Fit relations are given for the calculation of Young modulus, shear modulus, bulk modulus, Poisson ratio and density in dependence of the composition. These fit relations may serve as handy tools for obtaining relevant input information for the calculation of effective elastic constants of multiphase ceramics produced with Ca and Na containing raw materials.

Ceramic tile manufacturing is a highly energy-intensive process. Concerns about carbon emissions and energy costs make energy management crucial for this sector, which holds a leading role in Italian industry. The paper discusses the energetic and environmental performance of cogeneration (CHP) in the ceramic industry, where prime mover exhaust heat is supplied to a spray-dryer system, contributing to the satisfaction of the thermal demand and decreasing natural gas consumption. A thermodynamic model of a dryer unit, validated against real data, has been set-up to provide a detailed representation of the thermal fluxes involved in the process. Then, the thermal integration with two types of CHP prime movers of similar electric size (4 MW) is investigated. Energetic results show that the gas turbine can contribute up to 81% of dryer thermal consumption, whilst internal combustion engine contribution is limited to 26%. A methodology was ad-hoc defined for the environmental assessment of CHP, accounting for global (CO2) and local (CO and NOX) emissions. Results confirm that CHP units guarantee reduction of CO2 and NOX compared to separate generation, with maximum values equal to 81 g/kWhth and 173 mg/kWhth, respectively; CO emission is decreased only in the case of gas turbine operation, with savings equal to 185 mg/kWhth. [ABSTRACT FROM AUTHOR]