Early-age performance monitoring of cement-based materials by using optical FBG sensors

With more and more widely used of the cement-based materials such as neat cement paste, cement mortar and concrete in structures, people want to see what their performances like. As is known, the working performances of cement-based materials are affected. very much by their hardening process in the early-age. But the common measuring techniques on the early curing of the cement-based materials are limited for some of their disadvantages, such as: difficulties in embedding sensors inside the concrete, limited measuring points, poor durability and interference of electromagnetic wave. So in this paper, according to the sensing properties of the Fiber Bragg Gratings sensors and self-characters of the cement-based materials, we have successfully finished measuring and monitoring the early-age inner-strain and temperature changes of the neat cement paste, concrete with and without restrictions, mass concrete and negative concrete systematically. We developed three types of FBG sensors suitable for being embedded and monitoring in cement-based materials, while the embedding technology and the embedding requirements of FBG sensors in cement-based materials are also discussed. The results show that FBG sensors are well proper for measuring and monitoring the temperature and strain changes including self-shrinkage, dry shrinkage, plastic shrinkage, temperature expansion, frost heaving and etc inside different cement-based materials during their early-age. This technique provides us a new useful measuring method on early curing monitoring of cement-based materials and greater understanding of details of their hardening process.