Influence of natural coating type on the frictional and abrasion behaviour of siliciclastic-coated sedimentary sand grains

Influence of Loading History and Soil Type on the Normal Contact Behavior of Natural Sand Grain-Elastomer Composite Interfaces

“…A significant decrease (around four times) in the total displacements required to reach 1.5 N normal load for CDG grains was observed when preloading was applied, indicating an increased contact stiffness. Kasyap et al [ 78 ] also observed similar behavior for silt-coated LBS grains owing to the compression of microparticles in the contact region due to excessive normal load in the preloading cycle. From a comparison between CP and PP classes of tests (subsets in Figure 11 ), a common inference observed for both types of aggregates (LBS and CDG) is that the accumulation of plastic deformations (ratchetting) was higher under the influence of preloading.…”

“…Kasyap et al [ 78 ] defined the fundamental difference between the normal contact response of clay- and silt-coated (artificially coated) LBS grains in terms of the trend of non-linearity in the load–displacement curves, given that both the grain classes show significant compression compared to the uncoated grains. It was demonstrated based on micromechanical experiments and microscopic image observations that grains coated with clay, because of the smaller size and softer behavior of the microparticles compared with silt coating, tend to show smoother normal load–displacement curves without any abrupt drop or fluctuations in the normal load (ascribed to particle rearrangement of the silt microparticles in the study by [ 78 ]). In the present study, the CDG grains with non-uniform natural clay coating on their surfaces showed an intermediate behavior between clay- and silt-coated sand grains with higher compression and slightly irregular load–displacement curves (no abrupt drop in the normal load for the given range of normal loads and displacements for the CP tests).…”

“…In the preloading cycle (cycle-1), where the normal load reached 10 N, a complete hardening behavior was observed for LBS grains, but the CDG grains showed significant brittle damage of the micro-asperities, resulting in fluctuation of the normal load (after reaching approximately 4 N). This behavior is hypothesized to be the result of two major mechanisms: one mechanism is contributed by asperity breakage, which is of a brittle nature, as previous studies would also suggest, on rough interfaces of aggregates or weathered rocks [ 73 , 79 , 93 ], and a second mechanism is associated with the compression behavior of existing microparticles on the surfaces of the aggregates [ 77 , 78 ]. As discussed in Section 3.1 , the CDG grains showed an intermediate behavior of silt- and clay-coated LBS grains (after Kasyap et al [ 78 ]) at 1.5 N normal load.…”

“…BLS grains have formations of lightweight alkali earth metal oxides (Mg, Na, and Ca), most presumably due to the mining of the original basaltic rock. The presence of debris materials on the grain surfaces changes the micro-scale morphology of the aggregates and is expected to have a significant influence on their inter-particle contact behavior, as previous studies would also suggest [ 73 , 76 , 77 , 78 ].…”

“…The SEM images in Figure 1 can provide some qualitative inferences on the surface texture at the meso-scale of the different types of aggregates, whose textural characteristics may have an important influence on their tribological behavior, for example, the presence of debris [ 78 , 79 ] or meso-scale morphology [ 80 ]. However, the surface roughness at the micro-scale (expressed with an RMS value in the present study) is itself an important characteristic that controls the frictional and constitutive behavior of interfaces [ 70 , 81 , 82 ] and also the bulk behavior of granular materials [ 46 , 60 , 61 , 62 , 83 , 84 , 85 ].…”