Which Risks Require Key Control in Mass UHPC Construction?

Mass UHPC construction (single pour volume >10m³) requires focused control of four core risks: "temperature cracking, autogenous shrinkage cracking, internal defects, and uneven curing." These risks stem from its low water-binder ratio and high cementitious material content, which result in high hydration heat and shrinkage characteristics. During the continuous roof pouring covering 120,000 m² at the Hainan International Convention and Exhibition Center, Qinglong Group developed a systematic prevention and control plan: using a low-heat cement system (blended with 40% slag powder), pre-cooling aggregates (temperature ≤20°C), layered pouring (each layer ≤0.5m thick), embedding cooling water pipes (controlling temperature rise ≤40°C), and strengthening thermal and moisture curing (film covering with water spraying ≥14 days). Through thermal calculations and temperature monitoring, the core temperature was successfully kept within 65°C with no through cracks. Mass UHPC construction is a combination of materials science and engineering management.

Temperature Control and Crack Prevention Is the Top Priority

UHPC hydration heat is concentrated, with temperature rise reaching 70-80°C; an internal-external temperature difference >25°C easily causes temperature cracks. Qinglong Group uses ice water for mixing and adds crushed ice to keep the placement temperature ≤25°C; embedded temperature sensors adjust cooling water flow in real time to flatten the temperature rise curve.

Shrinkage Management Ensures Volume Stability

Shrinkage stress accumulates even more severely in mass concrete, requiring expansion agents (such as magnesium oxide) for compensation and post-cast strips to release stress. In a foundation project in Nanning, we set post-cast strips at 20m intervals and delayed pouring by 14 days, effectively avoiding shrinkage cracks.

Pouring and Vibrating Ensure Internal Compactness

Pour in layers with intervals between layers ≤ the initial setting time, and use high-frequency vibrators to compact point by point to avoid cold joints. Qinglong Group uses self-compacting UHPC to reduce reliance on vibration, but fluidity loss still needs to be monitored.

Curing Regimen Determines Long-Term Performance

Cover with film immediately after pouring to retain moisture; after final setting, apply ponding curing or continuous spraying for a curing period ≥14 days. For mass components, prevent rapid surface moisture loss with the aid of curing agents. Qinglong Group ensures humidity ≥95% through an automatic spraying system.

Mass UHPC construction requires meticulous planning and full-process monitoring. With extensive experience, Qinglong Group helps clients mitigate risks and achieve high-quality pours.