Assessment of in-situ concrete creep: Cylindrical specimen and prototype nuclear containment structure

• Segregating concrete creep, shrinkage and instantaneous strain.
• Investigation of above strains on large prototype containment structure & small specimens.
• Experimental result comparison with B-3 model.
• Aging effect investigation.

The paper is dedicated to develop an efficient methodology that assess and segregate the creep, instantaneous and shrinkage strains on small scale: concrete cylindrical specimens and large proto type structure: BARC Containment (BARCOM) test model. The evaluation of concrete creep, shrinkage and instantaneous strains helps in analyzing the long term behavior of the most critical safety barrier the concrete containment structure. The main purpose of the nuclear pre-stressed concrete containment is to prevent the radioactive leakage to the environment in the case of an internal design basis and beyond design basis accidents. During the initial design, the concrete creep is most important input parameter to be considered for the performance and safety evaluation of containment structure, and hence this work mainly focuses on creep studies.The creep, instantaneous and shrinkage strain in concrete cylindrical specimens and BARCOM test model is experimentally computed from the installed embedded sensors. BARCOM test model consists of cylindrical wall portion headed with dome. The concrete cylindrical specimens and dome of BARCOM test model was cast with identical concrete mix in similar duration and therefore indistinguishable behavior were expected. The identical instantaneous and shrinkage strains are found in concrete cylindrical specimens and dome of BARCOM test model. However due to the aging effect, the dissimilarity in the experimental creep strain for concrete cylindrical specimen and dome of BARCOM test model is observed. The influence of elevation and boundary effect on creep strains of cylindrical wall portion of BARCOM test model is also investigated in this paper.Further, the experimentally observed creep and instantaneous strain are validated with the famous B-3 model for concrete cylindrical specimens and BARCOM test model. The experimentally observed results and predicted through B-3 model are found to be in excellent agreement. A sufficient realistic data on concrete creep for long-time serviceability, durability, long-time stability, safety against collapse is useful for performing consistent non-linear analysis of BARCOM test model is explored. Thus the present work deals with the in-situ creep behavior of concrete structures to develop understanding of the mechanisms of creep, instantaneous and shrinkage behavior on concrete structures. The present formulated study is limited to linear basic creep in which the influence of humidity, temperature effect on creep parameters and superimposition of the cracking strain are not introduced.