Title:
Investigation of Relaxation Behaviour of Irradiated Cement Paste Using Statistical Nanoindentation
Author(s):
Poornima Patil
Publication:
Web Session
Volume:
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
10/23/2022
Abstract:
Concrete offers resistance to neutron and gamma radiation and is popularly used in the containment buildings and bio shield walls of nuclear power plants (NPPs). It is crucial to asses the time-dependent relaxation behavior of the concrete exposed to neutron and gamma radiations to forecast the long-term performance of irradiated concrete. In prestressed concrete structures, the change in length of tendons due to varying load can lead to complicated stress redistributions. Time-dependent deformation in prestressed concrete structures may experience a loss of prestress and should be considered in the design and analyses of containment structures. Such deformation can be characterized by novel relaxation indentation. Thus, in the present work, the effect of ionizing and nonionizing radiation on cement paste is studied to understand the long-term viscoelastic behavior of aging concrete in nuclear containment structures. Three cement paste samples with 0.35, 0.40 and 0.50 water to cement ratio were irradiated in K-State TRIGA Mark II research reactor. The samples were exposed to combined gamma-neutron radiations for one hour of 500 kW thermal power. The study employs statistical nanoindentation to investigate the relaxation behavior of cement paste and the obtained data is analyzed by a closed-form analytical method developed using elastic-viscoelastic correspondence principle. Nanoindentation-based results demonstrate that changes in the viscoelastic properties of cement paste can be observed and correlated to neutron-gamma-induced damage. The preliminary findings highlight the need for developing predictive models accounting for effect of irradiation on relaxation behaviour to successfully assess the damage to irradiated concrete.