Cementation is the principal method for long-term conditioning of intermediate- and low-level nuclear waste (ILW/LLW). During hydration, cementitious matrices are exposed to ionizing radiation - primarily gamma rays - raising the question of the potential effect of irradiation on hydration reactions and, ultimately, on material properties. The available literature presents contradictory results, partly attributable to experimental biases related to temperature, drying, and carbonation under irradiation conditions.

This study aims to evaluate the impact of gamma irradiation on the hydration of C₃S, CEM I, CEM III/A, and CEM III/C pastes under controlled experimental conditions (constant temperature, autogenous environment, sealed systems). The mineralogical and microstructural properties of irradiated materials were systematically compared to those of non-irradiated control samples and mature pastes irradiated under analogous conditions. The results show an absence of significant alteration in mineralogy at the mesoscale, and in mechanical properties, with the methodology considered. Only slight modifications in pore size distribution were observed.

These observations indicate the absence of a direct coupling between gamma irradiation and hydration. They confirm that cementitious matrices retain their properties under conditions representative of the immobilization process for ILW/LLW waste packages by cementation. Thus, the assumptions of safety studies, based on data obtained from mature materials, remain fully valid.

The mineralogical quantification of cementitious materials can be performed using the Rietveld method, provided that suitable crystallographic data is available. X-ray amorphous phases, such as C-(A-)S-H, restrict the use of the Rietveld method because only very little crystallographic information is available. It is possible to get around this shortcoming using the PONKCS method (acronym for Partial Or No Known Crystal Structure) or employing the crystallographic data theorized by Richardson for C-S-H. This study examines the practical application of these two approaches to quantify the C-S-H phase of mature cement paste and the hydration monitoring of CEM I and C₃S pastes. The quantifications obtained were compared to the TGA and hydration modeling results. It was shown that the two methods yield comparable and interchangeable results, each achieving an accuracy within 5% of the expected values.

Evaluating the responses of cementitious materials with complex microstructures through experiments alone requires substantial time and effort. To address this, a comprehensive multiscale analysis framework combining experiments and simulations was adopted to identify correlations between microstructural features and mechanical properties. The framework comprises four modules: fitting/normalization, phase identification, virtual specimen generation, and finite element method (FEM) simulation. X-ray computed tomography (CT) and nanoindentation data were normalized, and their correlation was established using cumulative distribution functions (CDF). Based on this relationship, mechanical properties were inferred from CT data, and virtual specimens were generated for subsequent FEM simulation. The FEM module was calibrated by comparing simulated results with experimental splitting tensile tests. High-resolution micro-CT enabled detailed microstructural characterization for virtual specimen generation. The results demonstrated that porosity and pore connectivity are strongly correlated with the mechanical behavior of cement paste. Overall, the proposed multiscale analysis framework offers a robust and scalable approach for microstructural analysis and is expected to enhance the efficiency of material characterization and development process.

While local in its usage, concrete carries global implications due to the sheer demand for concrete worldwide. Previous work has laid out the general principles and directions for improving the sustainability of concrete, but there is a need to understand and evaluate the relative importance of these issues at the regional and local levels to formulate effective and issue-specific solutions. This study applies hierarchical clustering on principal components, a machine learning technique, to characterize the regionality of concrete sustainability among the 47 prefectures of Japan using a set of eight regional variables that describe pressing sustainability issues for concrete construction. The analysis identified and quantitatively described five distinct clusters of prefectures using statistical metrics, then examined these patterns in the context of the socio-economic characteristics of the prefectures in each cluster. The need to effectively utilize concrete waste or increase utilization of blended cements were found to be critical issues in some prefectures, while other prefectures should aim to reduce cement consumption or water and energy consumption and CO₂ emissions. The results may be used to inform more sustainable decision-making by revealing local sustainability issues that should be prioritized. Furthermore, although the regional patterns found in this study are unique to Japan, the analytical approach serves as a demonstration of how regional differences in concrete sustainability may be investigated, and it is expected that future studies will build on this study to develop a more comprehensive understanding of the regionality of concrete sustainability.

Despite the recognized potential of limestone calcined clay cement (LC³) as a sustainable alternative to Portland cement, a comprehensive analysis of the role of its primary reactive component—clay—remains absent from the literature. This review systematically addresses this gap by analyzing clay mineralogy (kaolinite, illite, montmorillonite), activation methods (thermal, mechanical, chemical), and reactivity assessment to expose their direct impact on LC³ performance. Furthermore, scientometric analysis of the LC³ research landscape is presented, quantifying its evolution and objectively highlighting the centrality of clay to the field's trends and advancements. By integrating a detailed technical review with data-driven bibliometric insights, this work provides an absolute foundation for optimizing LC³ formulations through tailored clay selection and processing, guiding future research toward more sustainable cement production.