To evaluate the radiation-induced degradation of concrete, a rigid-body spring network model is introduced that takes into account the three phases in concrete: mortar, aggregate, and the interfacial transition zone. The proposed model enables evaluation of the change in the physical properties of concrete affected by aggregate expansion under the free restraint condition. Good agreement with previous experimental data is found for the linear expansion of the concrete specimen and the compressive strength, Young’s modulus, and splitting tensile strength. Based on the numerical results, it is concluded that, to reproduce the physical property changes in concrete, the expansion of mortar due to the radiation-induced expansion of fine aggregate and/or creep behavior must be considered. In addition, it is clarified that an isolated expansion of mortar with a lack of expansion in the coarse aggregate also degrades the concrete and, consequently, analysis of the type of aggregate used is critical for predicting the properties of concrete under neutron irradiation. Furthermore, the impact of inhomogeneous expansion of rock-forming minerals in coarse aggregates on physical property changes is studied, showing that such a partial expansion in the aggregates and the resultant cracks in aggregates greatly influences the reduction of the Young’s modulus, with minimal impact on the reduction of compressive strength. The proposed model can be used to evaluate concrete degradation due to radiation-induced volumetric expansion of aggregate caused by the metamictization of rock-forming minerals.
As the nuclear fleet in the United States ages and subsequent license renewal applications grow, the prediction of concrete durability at extended operation becomes more important. To address this issue, a Fast-Fourier Transform (FFT) method is utilized to simulate aging-related degradation of concrete within the Microstructure Oriented Scientific Analysis of Irradiated Concrete (MOSAIC) software. MOSAIC utilizes compositional phase maps to simulate damage from radiation-induced volumetric expansion (RIVE), applied force, creep, and thermal expansion. This compositional detail allows each mineral in the microstructure to be assigned specific material properties, allowing the simulation to be as accurate and representative as possible. The principal goal of MOSAIC is to simulate the effects of nonlinear aging mechanisms occurring in nuclear concrete on the macroscopic mechanical properties, using only the aggregate microstructure compositional information as a starting point. Several realistic example simulations are shown to demonstrate the utility and uniqueness of the MOSAIC software.
Lateral loading tests using reduced reinforced concrete (RC) walls affected by alkali-silica reactions (ASR) and their simulation analyses were performed in order to evaluate the influence of ASR on the structural performance of shear walls that act as seismic resistant members in nuclear power facilities. The state of RC walls was also measured by several techniques to assess applicable monitoring methods during ASR expansion. The transition of the elastic wave velocity of the walls by the ultrasonic method has a good co-relationship with the transition of the static elastic modulus of the cylindrical specimens, indicating that non-destructive testing could capture the degradation trend of concrete due to ASR expansion. The initial stiffness of the ASR specimens became slightly smaller than that without ASR, but the maximum strength remained at the same level with or without ASR. Based on the results of experiments and analyses, a practically appropriate structural performance evaluation method and a monitoring method of ASR affected RC members were proposed.
This special issue includes 12 pertinent manuscripts addressing the varied technical issues associated with the long-term operation of nuclear power plants (NPPs). Five manuscripts focus on the effects of gamma and neutron irradiation on concrete and its constituents, bridging the gap between the fundamental understanding of the effect of gamma irradiation and the advanced modeling techniques using lattice-based models that are applied at varied scales to provide predictive simulation of the physical and engineering properties of concrete-forming aggregates, concrete, and the concrete biological shield. Two papers complement this research by presenting - a novel petrographic x-ray‒based characterization method, and - a method to implement advanced characterization of the aggregate forming mineral phases into a FFT based simulation framework. Notably, this pathology is addressed in this issue in two papers focused on the modeling and monitoring of the structural performance of ASR-affected shear walls. The effects of chemical attacks caused either by sulfate ingress or carbonation are presented in this special issue, with a focus on the effects of the actual operating conditions in NPPs. A discussion of the structural performance of concrete structures that support vibrating equipment such as that found in a turbine building of an NPP is also included.
Improvement in Long-term Strength and Flow of Mortar Containing Reed Ash and Powder
Released on J-STAGE: April 05, 2022 | Volume 20 Issue 4 Pages 267-276
Masahiro Hyodo, Shinya Shibahara, Hidehiko Ogata, Daiki Atarashi, Yuma Kawasaki, Takahisa Okamoto
Views: 402
Measurement Method for Macrocell Corrosion in Concrete Specimen using a Segmented Steel Bar
Released on J-STAGE: March 17, 2022 | Volume 20 Issue 3 Pages 222-235
Shinichi Miyazato, Nobuaki Otsuki
Views: 326
Effects of Solid Activator and Fly Ash on Rheology and Thixotropy of One-Part Alkali-Activated Pastes
Released on J-STAGE: March 12, 2022 | Volume 20 Issue 3 Pages 139-151
Yazan Alrefaei, Yan-Shuai Wang, Ye Qian, Jian-Guo Dai
Views: 325
Hardened Mechanical Properties of Self Compacting Geopolymer Mortar
Released on J-STAGE: April 14, 2022 | Volume 20 Issue 4 Pages 287-299
Muhammad Talha Ghafoor, Chikako Fujiyama, Koichi Maekawa
Views: 319
A New Three-dimensional Fractal Dimension Model to Describe the Complexity of Concrete Pores
Released on J-STAGE: March 11, 2022 | Volume 20 Issue 3 Pages 127-138
Haonan Liu, Zhao Xie, Ruixue Yu, Ning Zhang
Views: 315