Is the Shrinkage Rate of UHPC High? Volume Stability and Qinglong Group's Deformation Control Technology

The shrinkage rate is a core indicator of UHPC's volume stability, encompassing "plastic shrinkage, drying shrinkage, autogenous shrinkage, and carbonation shrinkage." Due to its low water-binder ratio and high cementitious material content, UHPC exhibits relatively large early autogenous shrinkage, but by optimizing the mix proportion and curing process, its total shrinkage rate can be kept at a low level. Qinglong Group, by adding shrinkage compensating agents and internal curing agents and optimizing curing regimes, has stabilized the final drying shrinkage of UHPC at 600–800 microstrain (i.e., 0.06%–0.08%), far lower than that of ordinary concrete (typically 300–600 microstrain, but on a much larger base). In the large-size panel application for the Shenzhen Yirui Biotechnology Building, we successfully eliminated the risk of shrinkage cracking through prestressing technology and joint design. Controlling shrinkage is the prerequisite for ensuring the dimensional stability and durability of UHPC components.

Autogenous Shrinkage Is a Distinctive Feature of UHPC

With an extremely low water-binder ratio (below 0.2), UHPC's internal water is heavily consumed by hydration during early hardening (1–3 days), producing significant autogenous shrinkage (up to 200–400 microstrain). This is the main risk of early-age cracking. We ensure workability and reduce water demand by adding high-performance water reducers; at the same time, magnesium oxide-based expansive agents or saturated lightweight aggregates are added for internal compensation, effectively suppressing autogenous shrinkage.

Long-Term Control of Drying Shrinkage

The drying shrinkage of UHPC mainly occurs at later ages. Due to its dense structure, moisture evaporates slowly and drying shrinkage develops over a long period, yet the total shrinkage is not high. We use steam curing (80°C × 24h) to promote early strength development and form a dense surface layer, reducing internal moisture loss and thereby lowering drying shrinkage. In the Nanning New Media Center project, this process kept panel joint width variations within the design-allowed range.

Engineering Response Strategies

For large-size components, we proactively address shrinkage through measures such as post-cast strips, sectional casting, and prestressing. In mix design, we control cement content and use large proportions of inert supplementary materials such as fly ash and slag powder, reducing shrinkage sources at the origin. Through long-term observation, Qinglong Group's UHPC mix proportions have demonstrated excellent volume stability.

Only through scientific understanding and proactive control of shrinkage can UHPC deliver its maximum value. Backed by in-depth materials research, Qinglong Group provides you with dimensionally stable, reliable products.