Waste fishing nets were utilized as recycled nylon (RN) short fiber to improve the mechanical properties of cement mortar. RN and manufactured polyethylene (PE) fibers were added to polymer cement mortar (PCM) as a reinforcement, and fiber-reinforced PCM was sprayed on the section of reinforced concrete (RC) beams. Normal RC beams and the upgraded RC beams were placed in the tidal zone for 14 months to induce rebar corrosion. Consequently, a repair operation took place by the removal of the concrete cover then spraying fiber-reinforced PCM. The tested RC beams were subjected to four-point flexural tests to study their load-carrying capacity. It was found that the fibers helped transfer stresses through cracks and distribute stresses by transforming a single wide crack into many small cracks. Overall, the experimental results showed that recycled nylon fibers from waste fishing nets have great potential to be used as a strengthening fiber in cementitious material.

Granular surfaces subjected to repeated passage often spontaneously develop a corrugated pattern. In this study, we scrutinized the growth dynamics of surface corrugation in a self-rotating sand bed that is traced by the edge of a vertically oscillating arm. We found that both the rotation velocity and the frequency of the oscillator strongly affect the occurrence rate of corrugation as well as the time evolution in the corrugation pattern, due to the intermittent collision between the oscillator and sand bed. We also discovered that the growth dynamics involves two distinct collective modes that describe the translational motion of the corrugation pattern on the sand bed.

No abstract

On unpaved or snowy icy roads, it is known that corrugation pattern on road surface spontaneously emerges due to the repetition of loading by vehicle, and this phenomenon is named washboard road. Washboard road on snowy icy road causes serious problem on the driving of vehicles because the braking performance deteriorates due to lack of friction between road surface and tires. The authors developed an indoor experimental device to reproduce similar phenomenon in a laboratory. As the first step of the study, we chose fine dry sand as a surface material and we successfully reproduced the corrugation on the track. After scrutinizing the growing process of corrugation, we found that the running velocity of the track and the natural frequency of the oscillator are the most important factors for the growth. However, the frequencies of the corrugation converge to some specific value which is different from the natural frequency of the oscillator. Further, we adopted different road materials such as saturated sand, artificial snow and natural snow. This paper introduces interesting findings on formation process of washboard road.

No abstract