How to Mitigate UHPC Autogenous Shrinkage Through Material Design: An In-Depth Analysis of Qinglong's UHPC Shrinkage Control Technology System

The autogenous shrinkage problem of UHPC stems from its low water-binder ratio and high cementitious material content, and can be effectively mitigated through scientific material design. Based on 28 years of technical expertise, Qinglong UHPC has developed a complete shrinkage control system that reduces autogenous shrinkage from the conventional 800-1000με to 400-600με, while controlling drying shrinkage within an optimized range of 600-800με.

In terms of material design, Qinglong UHPC adopts a multi-technology collaborative approach: first, incorporating internal curing materials (water-absorbing lightweight aggregates, superabsorbent polymers, etc.) to reduce autogenous shrinkage by 30%-40%; second, using MgO expansive agents to compensate for part of the shrinkage, with the restrained expansion rate controlled at 0.02%-0.03%; then optimizing the cementitious system by controlling cement content at 700-800kg/m³ and incorporating silica fume (8%-10% of cementitious materials) and mineral powder (5%-8%) to reduce chemical shrinkage; finally, combining polycarboxylate superplasticizers with shrinkage-reducing agents (such as alcohol-based compounds) to further reduce shrinkage by 15%-20%. In a sea-crossing bridge project in Shenzhen, this comprehensive technology kept the 28d autogenous shrinkage of UHPC bridge decks at 550με, 45% lower than conventional mix proportions, effectively preventing early cracking.

Internal Curing Technology Application

Incorporate pre-wetted lightweight aggregates (dosage 3%-5%), particle size 0.5-1mm; or superabsorbent polymers (dosage 0.3%-0.5%), particle size 100-200μm. These materials continuously supply water internally, reducing self-desiccation shrinkage. Internal curing reduces autogenous shrinkage by 30%-40%.

Expansion Compensation Technology

Use lightly burned magnesium oxide expansive agents (dosage 4%-6%), activity index 60s-120s; or calcium sulphoaluminate expansive agents (dosage 6%-8%). These expansive agents generate pre-compressive stress under restraint to compensate for shrinkage. The restrained expansion rate should be controlled at 0.02%-0.03%.

Cementitious System Optimization

Control cement content ≤800kg/m³; incorporate silica fume (8%-10%) and mineral powder (5%-8%) to optimize particle grading; use low-heat cement to reduce temperature-rise shrinkage. These optimizations reduce chemical shrinkage and thermal differential shrinkage.

Chemical Admixture Application

Polycarboxylate superplasticizers (water reduction rate ≥30%) lower the water-binder ratio; shrinkage-reducing agents (such as polyether-based, dosage 1%-2%) reduce capillary pore tension; these admixtures work synergistically to reduce shrinkage by 15%-20%.

Shrinkage control requires a systematic solution. Through multi-technology collaboration, Qinglong UHPC effectively solves the autogenous shrinkage problem and ensures engineering quality.