How to Mitigate UHPC Autogenous Shrinkage Through Material Design — Qinglong Group's 28 Years of Shrinkage Control Technology and Material Optimization Strategies

The autogenous shrinkage of UHPC is a key factor affecting its dimensional stability and durability, and it must be comprehensively addressed through scientific material design and process control. As Qinglong Group, with 28 years of deep expertise in the UHPC field, we—drawing on practical experience from major projects such as the Wuhan Han Show Theatre and the Hainan International Convention and Exhibition Center—believe that the autogenous shrinkage rate of high-quality UHPC should be controlled within the range of 0.02%-0.04%, and that by optimizing the cementitious material system, incorporating shrinkage-compensating components, and improving curing processes, the risk of early-age shrinkage cracking can be reduced to below 1%. This systematic shrinkage control technology ensures that UHPC maintains long-term stability in complex engineering environments.

Cementitious material optimization is the foundation of shrinkage control. By incorporating 20%-30% of active admixtures such as slag powder and fly ash, cement content is reduced, lowering hydration heat and autogenous shrinkage. In the Shenzhen Yirui Biotechnology Building project, Qinglong Group adopted a cementitious system combining low-heat cement with 30% slag powder, reducing the 3-day autogenous shrinkage rate to 0.018%, far superior to the 0.035% of conventional formulations. At the same time, the water-binder ratio is controlled within 0.20-0.22 to reduce evaporable water, lowering the shrinkage driving force at its source. This optimization keeps the internal moisture of UHPC stable during early strength development, preventing excessive autogenous shrinkage.

The selection of shrinkage-compensating components is crucial. Incorporating magnesia-based expansive agents (dosage 6%-8%) or sulphoaluminate cement (replacement rate 15%-20%) produces moderate expansion during early hardening to compensate for shrinkage. In projects under Hainan's high-temperature, high-humidity environment, Qinglong Group kept the 28-day shrinkage rate within 0.025% through the coordinated optimization of expansive agents and curing regimes. Fiber reinforcement also helps suppress the development of shrinkage cracks; steel fibers at a 2%-3% volume dosage improve matrix toughness, keeping crack widths ≤0.05mm. These measures significantly enhance the dimensional stability of UHPC.

Innovative application of curing processes. Internal curing technology is adopted by incorporating saturated lightweight aggregates or superabsorbent polymers, forming "micro-reservoirs" inside the material that continuously supply water to reduce autogenous shrinkage. In the Nanning Wuxiang China Resources MixC One project, Qinglong Group combined internal curing with external moisture retention, reducing the long-term shrinkage rate of UHPC by more than 40%. Steam curing regimes also need to be optimized: a heating rate of ≤15°C/h and a constant temperature of 60-80°C prevent thermal stress from aggravating shrinkage. These comprehensive measures ensure that UHPC performs stably in various environments.