MONITORING OF THE HARDENING OF CONCRETE/MORTAR USING PLASTIC OPTICAL FIBER SENSORS: FUNDAMENTAL EXPERIMENT AND DATA INTERPRETATION

In the New Austrian Tunneling Method (NATM) of tunnel design and construction, it is important to know actual compressive strength lining concrete at early ages, which determines time demolding its future durability. The degree hydration reaction in-place regarded as a useful reference estimate development concrete. Based on concept On-Site Visualization, this paper presents new approach monitoring hardening progress fresh concrete/mortar using plastic optical fiber (POF) sensors. principle sensing illustrated conceptually. fundamental experiments were carried out investigate change in visible light intensity reflected from plane POF sensor during ages. typical influence factors also studied. process ages was well observed by direction installation had significant effect pattern change. When installed pointing downwards, dropped first but increased rapidly few hours, indicated phase evolution when free water disappeared concrete/mortar. While set up upwards, stage then grew slowly with time. Furthermore, characterized introducing nominal refractive index (NRI), could be calculated measured intensity. Thus, divided into three stages approximately according curve NRI (when upwards), coincided common knowledge process. Finally, work discussed briefly.