Modeling of granular material's packing: Equivalence between vibrated solicitations and consolidation

Effects of humidity and glidants on the flowability of pharmaceutical excipients. An experimental energetical approach during granular compaction

Granular materials are part of the design, production and final products of different industrial sectors. Powder flowability is a major topic in manufacturing and transport as it is closely related to process feasibility. Nonetheless, the flows of granular materials are not easy to describe or quantify, even in the simple case of dry monodisperse cohesionless particles. Flowability assessment is not a standard or normalized issue; still, no test is able predict powder flow behavior in all the different mechanical situations encountered during processing. This study aims (1) to evaluate flowability, as device-related, through the force or the energy supplied to the powder bed and (2) to study the effect of glidants and moisture content on flowability. To illustrate these aims, the flowability of two well-known pharmaceutical excipients, Avicel® PH-102 and Retalac® mixed with four different types of precipitated nano-silica (SIPERNAT® D10, D17, 50 S and 500 LS), was assessed using two granular compaction devices: Densitap® and FT4® compaction cell. Our results show that the hydrophilicity of colloidal silica affects surface coverage, ranging from 6% to over 80%. Binary mixtures with hydrophobic additives, D10 and D17, generated smaller silica aggregates with a wider spread on the surface of host particles. For Retalac® conditioned at 20% RH, HR values changed from 1.30 (acceptable flow) to 1.17 (good flow). For Avicel® PH-102, conditioned at 60% RH, HR values changed from 1.22 (fair flow) to less than 1.10 (excellent flow).

Feasibility of manufacturing ultra-high performance cement-based composites (UHPCCs) with recycled sand: A preliminary study

Due to the excellent mechanical and durability properties, ultra-high performance cement-based composites (UHPCCs) have attracted a lot of attention during the past decades. It is noted that most existing UHPCCs are manufactured from raw materials with high quality, for instance, well-graded river sands. However, the huge consumption of river sands as construction materials has inevitably resulted in some serious ecological impacts, as reported around the world. In this regard, it shall be much beneficial if some substitutes, such as recycled sands produced through processing of construction and demolition waste (CDW), could be used to replace natural sands to manufacture the qualified UHPCCs. This paper presents such a preliminary study on the feasibility of manufacturing UHPCCs with recycled sands. A total of five UHPCCs are designed and cast with different replacement percentages of recycled sand, i.e., 0%, 30% 50%, 70% and 100% (in mass). The associated packing density of the mixed sands is estimated based on the linear packing model. The fresh and hardened properties of the UHPCCs, including the workability, strength and shrinkage, are experimentally examined. The test results indicate that it is possible to use recycled sand to replace natural river sand in the manufacture of UHPCCs; however, the amount of the recycled sand needs to be limited. In the case when the replacement percentage of the recycled sand is lower than 50% (in mass), the properties of the UHPCCs with the recycled sand are comparable with those containing river sand only.