What Key Risks Should Be Controlled in Mass UHPC Construction?

The core risk control in mass UHPC construction centers on four major challenges: "temperature cracks caused by hydration heat, shrinkage cracks, construction cold joints, and internal quality uniformity." Since UHPC uses an extremely high amount of cementitious materials (typically >800kg/m³), the temperature rise and internal-external temperature difference resulting from the concentrated release of hydration heat are far higher than in ordinary mass concrete. In the construction of a super-large UHPC sculpture foundation in Shenzhen (with a single pour exceeding 150m³), Qinglong Group successfully kept the maximum core temperature below 75°C and the internal-external temperature difference under 20°C, achieving crack-free construction through comprehensive measures including the use of low-heat cement, the addition of ice chips and retarding high-range water reducers to control the placing temperature, pre-embedded cooling water pipes for precise temperature control, and thermal insulation and moisture retention curing for up to 14 days.

Precise Prevention and Control of Temperature Cracks Is the Top Priority

This is the biggest risk. Hydration heat must be controlled at the material source. Qinglong uses moderate-heat or low-heat cement and incorporates large amounts of supplementary cementitious materials such as fly ash and slag powder to replace part of the cement. During production, the discharge temperature is kept below 20°C by cooling the aggregates, using chilled water, and even adding ice chips. Pre-embedding cooling water pipes inside the components and dynamically circulating water for cooling based on temperature monitoring data is a key means of controlling the core temperature.

Comprehensive Management of Shrinkage Stress

In mass UHPC, the combined effect of autogenous shrinkage and drying shrinkage can easily cause surface cracks. In addition to using expansive agents and internal curing agents in the materials, continuous pouring must be ensured during construction to avoid cold joints. After pouring is complete, immediately cover the surface with water-retaining film and insulation layers to prevent rapid evaporation of surface moisture and sudden temperature drops; the curing period should be no less than 14 days.

Ensuring Internal Compaction and Quality Uniformity

During mass pouring, the high viscosity of UHPC may make it difficult for air bubbles at the bottom to escape. The pouring plan must be optimized by adopting layered pouring and reasonably arranging vibration points; if necessary, self-compacting UHPC can be used, supplemented with external form-attached vibration. It is essential to use non-destructive testing methods to monitor internal quality.

Mass UHPC construction is a comprehensive test of material technology, temperature control technology, and construction management. With systematic technical solutions and rigorous project management, Qinglong Group has ensured the complete success of multiple large UHPC projects.