How to Prevent GRC Component Cracking During Setting: Key Techniques and Practical Measures

In the field of architectural decoration, GRC components are widely used in high-end projects such as grand theaters, commercial complexes, and landmark buildings thanks to their lightweight, high-strength, and richly varied forms. However, cracking during the setting process has long been an industry pain point, affecting not only aesthetics and structural safety but also potentially increasing later maintenance costs. As an industry leader with 28 years of full-chain experience in UHPC/GRC/GRG/GRP materials, Qinglong Group—drawing on practical expertise in detailed design, manufacturing, and construction installation—has developed a systematic cracking prevention solution covering material formulation, process control, and environmental management, providing professional technical support for designers and owners.

Analysis of the Core Causes of Cracking in GRC Components During Setting

Setting cracks in GRC components mainly stem from the imbalance between internal material stress and the external environment. In terms of material properties, the chemical shrinkage and drying shrinkage generated during cement hydration are the primary internal causes, and poor bonding at the interface between glass fibers and the cement matrix can easily lead to stress concentration. In terms of production processes, problems such as uneven mixing, poor fiber dispersion, and insufficient molding pressure weaken component density. In terms of environmental factors, sudden changes in temperature and humidity as well as untimely curing exacerbate shrinkage cracks. During its participation in drafting the Technical Standard for Building Application of Glass Fibre Reinforced Cement (GRC) (JGJ/T423-2018), Qinglong Group analyzed data from over a thousand project cases and summarized a 'material-process-environment' trinity cracking risk model, providing a theoretical basis for preventive measures.

Material Optimization: Controlling Cracking Risk at the Source

As a custom GRC product manufacturer, Qinglong Group has carried out targeted innovations in material formulation. First, it adopts a composite system of high-purity quartz sand and specialty cement to reduce the peak hydration heat. Second, by incorporating modified polypropylene fibers and alkali-resistant glass fibers (content ≥5%), it forms a three-dimensional randomly oriented supporting structure that enhances crack resistance. Meanwhile, mineral admixtures such as nano-grade silica fume are introduced to optimize the interfacial transition zone and reduce porosity. Testing shows that Qinglong GRC components achieve flexural strength above 20MPa and keep drying shrinkage within 0.04%, exceeding industry standards. In addition, for projects in different climate zones, Qinglong offers 'climate-adaptive formulations'—for example, adding antifreeze components for cold regions and raising the impermeability grade for humid regions—to precisely match material performance with the environment.

Process Upgrading: Refined Full-Process Control

In manufacturing, Qinglong Group relies on intelligent production lines with an annual capacity of 600,000 square meters and has built a full-process quality control system from batching to forming. A computerized automatic metering system (error ≤±1%) ensures precise proportions, while twin-shaft forced mixers combined with ultrasonic dispersion technology achieve uniform fiber distribution. During the forming stage, a vacuum high-pressure grouting process (pressure ≥0.6MPa) improves component density, and a second troweling before initial setting eliminates early surface cracks. For complex-shaped components such as double-curved facade panels and openwork reliefs, BIM technology is used to simulate shrinkage deformation and set stress-relief joints in advance. Taking the Century Square renovation project on Nanjing East Road as an example, Qinglong adopted a composite process of light-transmitting concrete and GRC, and through segmental pouring and gradient curing, successfully solved the cracking problem of long-span components, winning the AALBORG WHITE Cup UHPC Construction Engineering Innovation Award.

Environment and Curing: Scientific Management to Reduce External Stress

Ambient temperature and humidity are key external factors affecting setting cracks in GRC. At its production base in Nanning, Guangxi, Qinglong Group has established constant temperature and humidity curing workshops (temperature 20±2℃, humidity ≥90%), combining steam curing with spray curing to ensure full cement hydration. For construction sites, it provides a 'three-stage curing plan': moisture-retentive covering during initial setting (4-6 hours), mist spraying for moisture retention during final setting (7 days), and sealed protection before handover (14 days). For construction in high-temperature seasons, an innovative 'night pouring + shading canopy' process avoids rapid surface water loss caused by direct sunlight; in winter, electric heat tracing curing keeps the temperature difference between interior and exterior at ≤25℃. These measures have been verified in overseas projects such as the Qatar World Cup venues, effectively adapting to extreme climatic conditions.

Preventing setting cracks in GRC components requires coordinated control of materials, processes, and environment. As a National High-Tech Enterprise, Qinglong Group transforms its 28 years of full-chain experience into replicable technical solutions, providing customers with one-stop services from detailed design to after-sales maintenance through 'customized formulations + refined production + intelligent curing.' Looking ahead, Qinglong will continue to promote innovation in the composite application of GRC with UHPC, GRG, and other materials. With the mission of 'creating beautiful architecture,' it aims to help more landmark projects achieve a perfect unity of safety and aesthetics.