Simultaneous measurement of shrinkage and coefficient of thermal expansion of mortar based on EFPI sensors with nanometer resolution

Abstract

Sliding and displacement instruments based on extrinsic Fabry-Perot interferometer (EFPI) are proposed to simultaneously monitor shrinkage and the coefficient of thermal expansion (CTE) of mortar specimens at early stages. Mortar specimens with three water cement ratios are tested. The effect of surface roughness on the shrinkage of mortar specimen is considered by using grooved stainless steel molds. The shrinkage from displacement sensors are compared with that from traditional linear variable differential transformer (LVDT). The CTE of mortar specimens is also measured with EFPI displacement sensor. Results indicate that both EFPI sliding and displacement sensors are capable of measuring shrinkage of mortar beam with nanometer resolution, which is higher than micrometer resolution from LVDT. The shrinkage of mortar is dependent on water cement ratio, curing age and surface roughness. The evolution of the CTE of mortar specimens over curing time is successfully measured with EFPI displacement sensor.