Most of the important achievements in architecture during the twentieth century, some of which are now on the World Heritage List, were constructed in reinforced concrete, an artificial material which was expected to maintain the required mechanical properties over the expected lifetime of the structure. However, many decades after their construction under specific environmental conditions, these buildings are now facing a series of preservation challenges as they experience various forms of modification, including deterioration of mechanical concrete properties. Meanwhile, researchers from all over the world are focusing their efforts on material modification in order to improve the properties of both fresh and hardened concrete, to study the effects of different types of mineral admixtures and additives, of fiber-reinforcing, w/c ratio, green concrete, and phase change recycled concrete for use in thermal conditioning. In this context, the compressive properties of concrete building materials are usually evaluated to assess the quality of concrete in its different material composition and application, in order to satisfy the structural design purposes responding to the current needs and to guarantee the future ones. The articles published in this Special Issue will cover different topics on concrete modification and performance, ranging from numerical to experimental studies that includes both fieldwork and laboratory research to evaluate the compressive properties of concrete both in its current form and in cases where it has been retrofitted or upgraded. The issue includes papers on monitoring and nondestructive testing methods, aiming to control material modifications during its service life in order to ensure safety, durability, and functionality, as well as sustainability of the concrete buildings. Finally, papers on matters of safety, uncertainty, preservation, and decision on whether to modify the existing condition or not are welcome.
Keywords: High and ultrahigh performance concrete; Fiber-reinforced concrete; Green concrete; Phase change recycled concrete; Durability; Sustainability; Nondestructive testing (NDT) of concrete structures; Onsite inspection; Structural health monitoring; Design by testing; Material uncertainties; Predictive maintenance.