Young's modulus and poisson's ratio of hardened cement paste under different relative humidity

easured by ultrasonic method as well as direct tensile loading test. It was experimentally confirmed that Young's modulus, Poisson's ratio, and bulk modulus of hardened cement paste decreased as decrease in equilibrium relative humidity especially inthe range above 40%RH. And in the range below 40%RH, experimental results of direct tensile loading test showed the decrease in Young's modulus and Poisson's ratio while the experimental results of ultrasonic test showed slight increase of Young's modulusand almost constant behavior of Poisson's ratio. For the decrease of Young's modulus and Poisson's ratio can be explained by thereduction of load-bearing water in the hardened cement paste due to drying, and slight increase under 40%RH by ultrasonic test can be explained by the increase of Si-O network of C-S-H due to drying, and slight increase under 40%RH by ultrasonic test can be explained by the increase of Si-O network of C-S-H due to drying.