Classification and Research Status of the Principles of Smart Concrete

Traditional construction materials not only have problems such as environmental pollution, poor durability, and high repair costs, but also various large-volume hydraulic concrete structures are often damaged and cracked during service due to the effects of alternating loads and material aging. The occurrence and further expansion of cracks will affect the integrity, impermeability, and durability of dam concrete, posing potential safety hazards. To ensure the safe operation of the structure, timely diagnosis in the early stage of crack appearance can significantly extend the service life of the structure.In order to make full use of raw materials, improve the various inherent properties of concrete, and achieve the long-term sustainable development of concrete, "smart materials" are incorporated into concrete. This enables concrete to accurately receive stimuli from the external environment and make corresponding responses, thereby achieving functions such as self-diagnosis, self-adjustment, and self-healing. Applying this modified concrete to monitor and repair crack changes in hydraulic concrete structures is of great significance for hydraulic engineering health services. For example, the 4.5-magnitude earthquake that struck the Italian region in October 1996 caused severe damage to the bell tower of the San Giorgio Church. Indirli et al. carried out structural restoration using four superelastic SMA rods. After the San Francesco Church in Assisi, Italy, was damaged by an earthquake in 1997, SMA devices were also adopted and installed on the gable triangles and roof areas for structural restoration. Based on smart materials, Such as Steel Fiber (SF-A), Milled Steel Fiber (SF-B), Copper-Plated Steel Fiber (SF-C), End-Hooked Steel Fiber (SF-D), and Nano-Carbon Black (NC). This study deeply investigates the influence of self-sensing concrete on mechanical properties and crack repair effects, reviews the principles and properties of smart conductive cement-based composites, discusses the main potential application fields of smart materials, and finally summarizes the current research status of smart materials as well as the challenges they need to face.