In this paper, particle damage of three test sands with different mineralogical compositions is studied using stress–displacement response measured in ring shear tests, particle-size distributions of the original sand prior to shear and from the shear band after shear, and by examining particle shape changes determined by scanning electron microscope. Particle damage during shearing produced a wider particle-size distribution, and damage typically continued until the normal stress was small (about 28 kPa) in constant volume ring shear tests and the internal stresses were distributed among sufficient particle contacts such that damage practically ceased. The dominant damage mechanism (typically either particle abrasion and shearing-off asperities or particle splitting) depended strongly on the soil response (i.e., contraction or dilation), particle hardness, and particle-size distribution, but both mechanisms produced particles that were more angular and rougher than the original sand particles. The magnitude of particle damage observed in the ring shear tests was influenced by the consolidation normal stress, shear displacement, particle mineralogy, particle-size distribution, drainage conditions, and soil fabric (in constant volume tests). Lastly, the influence of particle damage on engineering properties including hydraulic conductivity, liquefaction resistance, stress–strain response, friction angle, and critical state are briefly discussed.

Reactive Powder Concrete (RPC) is an ultra-high-strength, high ductility and low porosity cementitious material. RPC properties are improved by pressing fresh RPC samples, which can increase its specific weight as high as 3000 kg/m 3. However, high specific weight may be a shortcoming, where weight saving is important. Following to this review, a set of tests on RPC samples with high silica fume contents were carried out in a laboratory. The results show that although high silica fume content increases the compressive strength, however it decreases the density. It is concluded that by means of silica fume it is possible to produce high strength RPC with a specific weight as low as 1900 kg/m 3. This Light Weight Reactive Powder Concrete (LWRPC) could be used in areas where substantial weight savings can be realized and where some of the remarkable characteristics of the material can be fully utilized.

The friction angle is the most important parameter used for analysing the response of sands to loading. However, its variation with stress level, fabric and particle damage has been debated. This study examines the yield and critical state friction angles of three sands using triaxial compression and ring shear tests. Only contractive responses were used to define the yield friction angles and the critical state friction angles from the triaxial tests. However, both contractive and dilative (through particle damage) specimens reached a critical state in the ring shear tests, and therefore critical state friction angles were defined from both dense and loose specimens. The yield friction angle was affected by the initial sand fabric, decreasing as the pre-shear void ratio increased. In contrast, the critical state friction angle from the ring shear tests was independent of stress paths analysed in this paper, independent of initial sand fabric, and decreased only slightly with stress level, becoming essentially constant at stresses larger than about 200 kPa. Its value depended primarily on particle mineralogy and shape (angularity). Particle damage induced in the ring shear tests increased the critical state friction angle by a few degrees, as a wider range of particle sizes and more angular particles were produced.

No abstract