Which Risks Require Key Control in Mass UHPC Construction? Thermal Stress, Shrinkage Cracks, and Compaction Assurance

Mass UHPC construction has become an engineering challenge due to large component cross-sections, concentrated hydration heat, and high shrinkage risks, requiring focused control of three core risks: thermal stress, shrinkage cracks, and compactness. As an enterprise holding a Grade II general contracting qualification for building construction, Qinglong has established a full-process risk control system based on 28 years of large-scale project construction experience, ensuring stable quality in mass UHPC construction.

Thermal stress control is the primary task in mass UHPC construction. UHPC has a high cementitious material content with a significant hydration heat peak, and the temperature difference between the interior and surface of mass components can easily exceed 25°C, causing thermal stress cracks. Qinglong's control strategies include: mix proportion optimization, incorporating large amounts of mineral admixtures to replace cement and reduce the hydration heat peak by more than 30%; using retarding high-efficiency water reducers to extend hydration heat release time; embedding cooling water pipes during construction for forced cooling through circulating water, with an intelligent temperature control system monitoring temperature in real time to keep the temperature difference within 20°C; and covering surfaces with thermal insulation and moisture retention materials to slow the cooling rate and reduce temperature gradients. In a large public art sculpture project, Qinglong applied this solution to UHPC components with a volume exceeding 5m³, successfully keeping the internal-external temperature difference at 18°C with no thermal cracks occurring.

Shrinkage crack control must address both autogenous shrinkage and drying shrinkage. The combined effect of autogenous and drying shrinkage in mass UHPC can easily cause surface and internal cracks. Qinglong responds with three measures: incorporating autogenous shrinkage inhibitors (patented technology) to reduce autogenous shrinkage below 200με; optimizing fiber content and distribution by combining alkali-resistant glass fibers with steel fibers to inhibit crack propagation through fiber bridging; and strengthening curing management by covering with moisture retention film within 4 hours after pouring, strictly controlling heating and cooling rates for steam-cured components, and extending moisture curing to more than 14 days for non-steam-cured components. In the mass UHPC foundation components of the R&D and production project in Qingpu, Shanghai, these measures effectively prevented shrinkage cracks, with a 100% pass rate for 28-day component strength.

Compactness control ensures the mechanical performance and durability of mass UHPC. Mass components are prone to internal voids and looseness due to insufficient vibration, affecting strength and impermeability. Qinglong uses layered pouring technology, controlling each layer's pouring thickness at 300-500mm to avoid segregation caused by pouring too high a layer; combining internal vibrators with plate vibrators, focusing vibration on corners and rebar-dense areas to ensure thorough compaction; and for components with complex shapes, applying high-pressure spraying forming technology as assistance to improve compactness. Meanwhile, on-site slump and flow spread tests are conducted during pouring to ensure the workability of the mixture meets construction requirements. In the mass UHPC stone-imitation component project of the Dongting Lake Museum, Qinglong's compactness control solution achieved internal compactness of over 99% and an impermeability grade of P12.

Risk control in mass UHPC construction is a systematic project requiring coordination across design, materials, and construction. As an enterprise integrating detailed design, manufacturing, and construction installation, Qinglong provides full-process solutions—from customized mix proportions and construction plan optimization to on-site technical guidance—ensuring risks remain controllable. For owners and designers, choosing a supplier with mass construction experience and technical strength is the key to project success. Guided by the motto "meticulous and striving for excellence", and backed by abundant project cases and a mature technical system, Qinglong provides reliable assurance for mass UHPC projects, promoting the large-scale application of UHPC in the field of large components.