We investigate the band structure of elastic waves propagating in carbon nanostructure phononic crystals with square, rectangular, triangular, honeycomb and Kagomé lattices. We also study the influence of carbon nanostructure cross section geometry - circular, hollow circular, square and rotated square with a 45° angle of rotation with respect to the x and y axes. Plane wave expansion method is used to solve the governing equations of motion of a isotropic solid based on classical elasticity theory, ignoring nanoscopic size effects, considering two-dimensional periodicity and wave propagation in the xy plane. Complete band gaps between XY and Z modes are observed for all types of carbon nanostructures. The best performance is for nanophononic crystal with circular carbon nanostructures in a triangular lattice with high band gap width in a broad range of filling fraction. We suggest that carbon nanostructure phononic crystals are feasible for elastic vibration management in GHz.

This paper analyzes the compressive strength of Portland cement concrete in response to the incorporation of 5%, 10% and 20% of flat glass powder in place of sand, at w/c (water/cement) ratios of 0.50, 0.55 and 0.58. A statistical analysis of variance (ANOVA) was performed after 7, 14 and 28 days of curing. The compressive strength test results indicate that the concrete containing a w/c ratio of 0.50 can be used for structural applications, regardless of the waste glass content, as can that with a w/c ratio of 0.55 containing 20% of waste glass. We suggest that the use of flat glass powder in place of sand in the abovementioned percentages is feasible for the production of an environmentally appropriate and structurally applicable concrete. However, the concrete's fluidity and void content must be taken into account.