The majority of the world's railways are on ballasted track, which consists of rails attached to sleepers, supported by a granular layer (ballast) lying on the natural ground. The repeated passing of trains results in a gradual deterioration of track alignment, leading to the need for periodic maintenance of the ballast. Following a number of maintenance cycles, the ballast is considered degraded, and the track is renewed. Conventional track renewal is costly and potentially unsustainable, as it requires quarrying of fresh ballast, increasing the railway's carbon footprint. A better understanding of the mechanical properties of used ballast, particularly how its stiffness compares to that of fresh ballast, could inform more extensive reuse of ballast. Previous research has demonstrated that the stiffness of granular materials is greatly influenced by their particle shape, size and surface characteristics. This project investigates the difference in stiffness in the vertical and horizontal directions between fresh and used ballast using advanced triaxial tests of 1/3rd scaled material. Fresh-scaled ballast can be readily sourced. Used scaled ballast was created by abrading fresh scaled ballast using a previously established procedure, which resulted in grain characteristics that closely mimic those of ballast recovered during track renewals after 30 years of use. The results from the advanced triaxial tests show that the used scaled ballast in this project had a greater stiffness in the vertical direction than the fresh scaled ballast. Additionally, the horizontal stiffness generally also remained higher for used ballast compared to fresh, suggesting that life-expired ballast has the potential to be reused.

The application of fiber-reinforced polymer (FRP) composites as piling materials in harsh environments has gained popularity due to their high corrosion resistance. FRP composites can be fabricated using different types of epoxy resin matrices and fibers. This study aims to investigate the interface behavior between sand and FRP materials with varying levels of hardness, with a particular emphasis on the abrasive surface wear of FRP. Monotonic interface shear tests (under normal stresses of 50, 100, 200, and 400 kPa) and interface shear tests repeated 20 times (under normal stresses of 200 and 400 kPa) are performed. The local surface roughness of the FRP plates is measured for tested samples under both monotonic and repeated loadings using laser scanning to evaluate the accumulated abrasion effect. The results of monotonic tests indicate that under a given shear displacement and normal stress, the samples with softer FRP plates exhibit higher interface friction angles and more pronounced dilative behavior. Following repeated tests, the interface friction angles of softer FRP specimens decrease, while the surface roughness of the FRP plates gradually increases. However, for the softest FRP plate, its surface is severely damaged after repeated tests under high normal stress levels, leading to unstable changes in the test results.

Fibre-reinforced polymer (FRP) is a promising composite to be used in construction in coastal and marine environments to resist seawater corrosion that deteriorates the properties of conventional civil engineering materials. A classical ground or seabed- structure interaction problem that is involved in the design of FRP structures, is however less understood when the soft nature of FRP is in subjection to the cyclic loadings from traffic, wind, wave and currents, causing penetration and abrasion at the soft FRP- soil interface. This study has downscaled the preceding problem into a micromechanical study at a benchmark sand grain- FRP interface. A large number of cyclic loading is applied, for the first time, at the sand- FRP composite interface, focusing on the development of the elastoplastic behaviour in the normal direction and the evolution of friction and energy dissipation in the tangential direction. The study combines the understanding from the tribology with the knowledge of civil engineering involved in the sand- FRP interaction, suggesting that a larger stick zone at the contact subjected to cyclic shearing is a key triggering of the simultaneous occurrence of the increased coefficient of friction and reduced damping ratio.

External contamination (soiling) of the incident surface is a major limiting factor for solar technologies. A 5year field glass coupon study was conducted to better understand external contamination and its effects; compare cleaning methods and the use of preventative coatings; and explore the abrasion resulting from cleaning to advise on accelerated abrasion testing. Test sites included the cities of Dubai (UAE), Kuwait City (Kuwait), Mesa (AZ), Mumbai (India), and Sacramento (CA). Through the 5-year cumulative study, dry brush, water spray, and wet sponge and squeegee cleaning methods were compared to no cleaning. Optical microscopy was used to obtain images, including representative color images, grayscale images for object analysis, and oblique images for coating integrity assessment. A thresholding protocol was developed to analyze and distinguish specimens using the ImageJ software. Optical performance was quantified using a spectrophotometer, including comprehensive optical characterization (transmittance, reflectance, and absorptance in addition to forward- and back- scattering). Atomic force microscopy was used to verify the abrasion damage morphology, including the width and depth of surface scratches. Analysis of the results included correlation of optical performance and particle area coverage, rank order (by coating or location), and the acceleration factor for abrasion damage. The efficacy of external cleaning was more readily distinguished from the effectiveness of antisoiling coatings. The acceleration factor for dry brush cleaning of a porous silica coating was found to be on the order of unity.

This study introduces a novel method for particle abrasion derived from fundamental natural phenomena and mechanical principles, allowing precise control over the degree of abrasion and more accurately mimicking natural processes. The method's validity is confirmed using a specific shape index. Through conventional triaxial tests, the mechanical behavior of granular aggregates with varying degrees of abrasion was analyzed. The findings indicate that increased particle abrasion leads to a decrease in the average coordination number and sliding amount, while the rotation amount increases. This suggests an inverse relationship between the degree of abrasion and the structural stability and interlocking of the particle aggregate. The fabric anisotropy of the system is mainly attributed to the anisotropy of the contact normal force, which decreases as particle abrasion increases. The partial stress ratio of the particle system is influenced by fabric anisotropy and remains independent of particle shape. Additionally, the internal friction angle may be overestimated in conventional triaxial tests.

In outdoor environment, the exterior walls surface of buildings always suffers from damages caused by ultraviolet radiations, temperature variation, abrasion and erosion phenomenon, dust pollution, and microbial adhesion: Thereby reducing their durability over time. In order to overcome these obstacles, the superhydrophobic coatings can be an advantageous solution to ensure long-term stable use by improving the exterior concrete walls durability. In this line, a fluorine-free water-repellent coating was developed through sol-gel method and successfully applied to concrete substrates by dip-coating technique. The coating was formulated with low surface energy polydimethylsiloxane (PDMS) and polymeric silica (PS) to simultaneously modify the microstructure and chemical properties of concrete substrate surface. The coated concrete substrate showed super-hydrophobicity with high water contact angle (WCA) over than 150 degrees. Besides, the self-cleaning property, mechanical robustness, stability under UV irradiations, resistance to temperature and humidity were investigated. The results indicated that the coated concrete substrate cannot be soiled by dust and can resist over than 300 cycles of abrasion test. It also presents resistance to temperature of 45 degrees C associated with a humidity of 80% during 720 hours and showed excellent resistance to prolonged exposure to UV irradiations during 1440 hours. Natural out-door aging tests have shown that the superhydrophobic coating is weather resistant.