Autogenous shrinkage mitigation in UHPC: mechanisms, multiscale regulation, and future perspectives

Abstract

Autogenous shrinkage remains a critical obstacle to the dimensional stability and crack resistance of ultra‑high‑performance concrete (UHPC), owing to its low water‑to‑binder ratio, dense pore structure, and rapid early‑age self‑desiccation. This review critically examines the mechanisms governing autogenous shrinkage in UHPC and establishes a mechanism‑based framework for shrinkage mitigation. The evolution of hydration, chemical shrinkage, internal relative humidity, capillary pressure, stiffness development, and restrained stress is first discussed. Mitigation approaches are then classified into four functional categories: moisture regulation through internal curing, hydration regulation, internal restraint enhancement, and direct shrinkage mitigation using shrinkage‑reducing admixtures and expansive agents. Their effectiveness is compared by considering shrinkage‑control mechanisms, action timing, performance trade‑offs, and application conditions. The review emphasizes that shrinkage reduction should not be treated as an isolated index, because mitigation strategies may simultaneously influence hydration kinetics, pore structure, workability, strength, durability, and cracking resistance. Finally, a future‑oriented design framework is proposed, highlighting time‑matched, performance‑coupled, and sustainability‑aware shrinkage regulation for durable UHPC structures.