The effect of fines content on force transmission and fabric development of gap-graded mixtures under triaxial compression has been studied using the discrete-element method. Results were used to define load-bearing soil fabrics where the relative contributions of coarse and fine components are explicitly quantified in terms of force transmission. Comparison with previous findings suggests that lower particle size ratios result in higher interaction between components. A potential for instability was detected for underfilled fabrics in agreement with recent findings. It was also found that the threshold fines content provides an accurate macroscopic estimation of the transition between underfilled and overfilled fabrics.

Bitumen is a complex hydrocarbon whose composition-structure-property relationship is not well-understood. In this paper, microphase-separated topographic morphologies of unaged penetration grade 70/100 bitumen binders have been visualized by means of AFM QNM, and the relationship to local mechanical properties has been demonstrated. AFM QNM is a surface force mapping technique which measures parameters such as topography, adhesion and elastic modulus simultaneously. The resulting data can then be presented as images representing individual or overlaid parameters, e. g. topographic images with an adhesion overlay or topographic images with a modulus overlay. AFM QNM results show that the adhesive forces measured in the region surrounding (peri phase) the periodic topographic features resembling 'bees' (catana phase) and the region in the 'bee' areas are lower than the adhesive force measured in the smooth matrix (para phase). Likewise it was observed that Young's moduli in the region surrounding (peri phase) the 'bees' (catana phase) and in the 'bees' are higher than Young's modulus of the smooth matrix (para phase).

The so called "bee phenomenon" in bitumen has been investigated by means of AFM quantitative nanomechanical property mapping. Bees are a phenomenon that can be observed by topography measurements using AFM. The characteristic "bee" appearance comes from regions with alternating higher and lower bands in the surface topography of bitumen, which are surrounded by a flat area. The proposed mechanism for bee formation is phase separation and differential contraction during cooling from melt temperatures leading to wrinkling due to differences in the elastic modulus of the material phases. Using a laminate wrinkling model, the thickness of the bee laminate was calculated from the wavelengths and Young's moduli of the bee laminate and the matrix. It was found to vary between 70 and 140 nm for the five bitumen samples that contained significant amounts of wax.