Lightly cemented rubber tire chips as highway pavement sub-base and the use of fiber Bragg's grating (FBG) as instrumentation sensors

Recently, Earth-Link Technology Enterprises Ltd. (a start-up company from HKUST) developed a high performance geo-material called "Rubbersoil", which is made from recycled wire-free rubber chips derived from scarp rubber tires and bonded together by rubberized cementitious material. Experimental investigations have indicated that the dynamic properties of the material are very good. One potential application of the cemented rubber chips would be the use as a sub-base material underneath the asphaltic concrete pavement structure. The combined structural effect of the asphaltic pavement and the Rubbersoil could potentially reduce the long-term maintenance requirement of the pavement, increase riding comfort and reduce traffic noise. More importantly, it can decrease the required thickness of the bituminous road-base layer, therefore, significantly reducing the construction cost of the entire pavement system. In order to study the dynamic behavior and long-term performance of this innovative material in pavement sub-base applications, it is necessary to make clear the characteristics of pavement behavior during traffic loads. However, the relationship between the dynamic characteristics and the strain of asphalt and Rubbersoil is not completely studied, because there is no device to measure the strain of asphalt and Rubbersoil directly. Therefore, this thesis presents a system to measure the pavement strain, using the fiber Bragg's grating (FBG) sensors. Using optical fiber sensor makes the devices simple in mechanism and highly durable. The feasibility study of this testing method will also be performed in a full-scale field test. The results in the field test indicated that it is possible to measure the asphalt and Rubbersoil strain with a higher level of accuracy than conventional strain measuring devices such as strain gauge (STG). Keywords: flexible pavement, fiber Bragg's grating (FBG), field test, elastic analysis, multi-layer system, dynamic response, Rubbersoil, sensor, sensing technique, instrumentation, sub-base, non-destructive test