How to Mitigate UHPC Autogenous Shrinkage Through Material Design: Mechanism Analysis and Optimization Strategy Research

How to Mitigate UHPC Autogenous Shrinkage Through Material Design: Mechanism Analysis and Optimization Strategy Research

In the field of construction materials, ultra-high performance concrete (UHPC) is becoming the material of choice for exterior wall cladding panels and irregularly shaped components of high-end buildings such as grand theaters and commercial complexes, thanks to its outstanding mechanical properties and durability. However, the early-age cracking caused by autogenous shrinkage has always been a technical bottleneck restricting its large-scale application. As an industry leader with 28 years of full-chain experience in UHPC/GRC/GRG/GRP materials, Qinglong Group has built a systematic autogenous shrinkage mitigation solution—ranging from material component optimization and microstructure regulation to process innovation—drawing on deep expertise in detailed design, manufacturing, and engineering practice, providing designers and owners with solutions that combine safety and economy.

Formation Mechanism and Engineering Challenges of UHPC Autogenous Shrinkage

UHPC autogenous shrinkage originates from the drop in internal relative humidity triggered by the hydration reaction of cement-based materials, resulting in volumetric shrinkage under the restraint of a dense microstructure. Compared with ordinary concrete, the use of high dosages of ultra-fine powders (such as silica fume and ultra-fine slag powder) in UHPC significantly increases strength but also intensifies autogenous shrinkage stress—the 7-day autogenous shrinkage of typical UHPC can exceed 400με, 3-5 times that of conventional concrete. If not effectively controlled, such shrinkage tends to cause surface cracking of components, which not only compromises the aesthetic effect of the building facade but may also weaken structural durability. In a landmark project in Nanning, the Qinglong technical team found through comparative tests that unoptimized UHPC specimens developed 28-day shrinkage cracks up to 0.15mm wide under standard curing conditions, whereas with optimized material design, crack width could be kept below 0.03mm, meeting the stringent requirements of the "General Technical Conditions for Ultra-High Performance Concrete (UHPC) Non-Load-Bearing Components."

Material Design Optimization: From Component Regulation to Microstructure Improvement

The core strategy of Qinglong Group lies in breaking the "seesaw effect" between autogenous shrinkage and strength through multi-dimensional material design. In cementitious system optimization, a ternary composite system of "cement–silica fume–slag powder" is adopted; by adjusting powder particle gradation (with D50 controlled at 5-8μm), paste packing density is increased by 15%, effectively reducing porosity; nano calcium carbonate (at a dosage of 3%-5%) is innovatively introduced, leveraging its nucleation effect to accelerate the formation of hydration products and reduce the early shrinkage rate. In fiber blending technology, a hybrid system of specially developed modified steel fibers (aspect ratio 20-30) and PVA fibers disperses shrinkage stress through fiber bridging; when the volume dosage reaches 2%, the ultimate tensile strain of UHPC can be raised above 0.8%. In addition, the self-developed internal curing agent (containing pre-wetted lightweight aggregates) continuously releases moisture, keeping internal relative humidity above 85% and significantly delaying autogenous shrinkage development—in a commercial complex project in Guangzhou, UHPC sunshade panels using this technology showed 40% less shrinkage than the conventional solution, and the first-pass installation qualification rate rose to 98%.

Full-Chain Process Coordination: Quality Control from Laboratory to Construction Site

As a national high-tech enterprise integrating detailed design, manufacturing, and construction installation, Qinglong deeply integrates material optimization with engineering practice. In the detailed design stage, BIM technology is used to simulate shrinkage deformation under different ambient temperature and humidity conditions, allowing component reinforcement schemes to be optimized in advance; in production, a "gradient curing" process is adopted—60°C steam curing first to accelerate early strength development, followed by transfer to a 20°C constant-temperature, constant-humidity environment to slowly release shrinkage stress; during on-site installation, an innovative combination of adjustable supports and elastic sealant is used, reserving 3-5mm of shrinkage allowance for components. This full-chain control system enabled Qinglong's translucent concrete project at Nanjing East Road Century Plaza to be delivered with zero cracking; the project won the Silver Award of the inaugural AALBORG WHITE Cup UHPC Construction Engineering Innovation Award, confirming the reliability of the technical solution.

Autogenous shrinkage control is a key topic in the application of UHPC materials, requiring collaborative innovation between material science and engineering practice. As a vice-chairman unit of the China GRC Association and a participant in drafting the "Ultra-High Performance Concrete (UHPC) Exterior Wall Panels" standard, Qinglong Group has always upheld the mission of "creating beautiful architecture," and the material design system built on 28 years of technical accumulation is continually expanding the application boundaries of UHPC. Whether for complex curved components of landmark buildings or the durability requirements of municipal engineering, Qinglong always works with a "meticulous and excellence-driven" attitude, providing clients with full-cycle solutions from material R&D to project implementation, and promoting the high-quality development of UHPC/GRC/GRG/GRP materials in the field of architectural decoration.