Customarily, retarders serve as the setting time regulators of cement-based composites to meet the demands of various construction environments. However, the limited ability to adjust the setting time restricts the application of polysaccharides in special environments. In this study, we reported a naturally high-efficiency retarder, konjac glucomannan (KGM), and studied the mechanism of its effect on the hydration of ordinary Portland cement. Incorporating KGM could significantly prolong cement hydration without strength damage. Furthermore, the active hydroxyl group (−OH, rich in KGM) could chelate with Ca²⁺ (released from cement hydration) to form a cross-linking network, which is adsorbed on the surface of cement clinker, thereby being conducive to delaying the process of cement hydration and reducing the heat of hydration. The findings of this study are critical to the ongoing efforts to develop polysaccharide-cement-based composite materials for application in various special environments.

The cordierite–belite core-shell lightweight aggregate (CSLWA) effectively improves the performance of the interfacial transition zone (ITZ) in lightweight aggregate concrete; however, the underlying fracture behavior still needs to be revealed. This study characterized the reinforced mechanical properties of ITZ by CSLWA through nanoindentation and interfacial fracture tests and the reinforcement mechanism was further explained using finite element analysis. The results showed that the continuous hydration of the belite shell of CSLWA enhanced the yield stress and improved the failure strain during fracture. Energy dissipation was observed during the fracture of CSLWA concrete, improving the brittleness of the lightweight aggregate concrete. Finite element analysis showed that the core strength of CSLWA changed the energy dissipation model and affected the toughness of CSLWA concrete, and a suitable composition of 6:4 was proposed for the “cordierite–anorthite” core constitution in CSLWA depending on the strength order between the cement matrix and core of the CSLWA.

In order to address the issues of energy depletion, more resources are being searched for in the deep sea. Therefore, research into how the deep-sea environment affects cement-based materials for underwater infrastructure is required. This paper examines the impact of ocean depth (0, 500, 1000, and 1500 m) on the ion interaction processes in concrete nanopores using molecular dynamics simulations. At the portlandite interface, the local structural and kinetic characteristics of ions and water molecules are examined. The findings show that the portlandite surface hydrophilicity is unaffected by increasing depth. The density profile and coordination number of ions alter as depth increases, and the diffusion speed noticeably decreases. The main cause of the ions’ reduced diffusion velocity is expected to be the low temperature. This work offers a thorough understanding of the cement hydration products’ microstructure in deep sea, which may help explain why cement-based underwater infrastructure deteriorates over time.