What Flexural Strength in MPa Should High-Quality GRC Reach? What Is the Industry Standard?

Flexural strength is the core indicator for evaluating the mechanical performance of GRC, directly related to the load-bearing capacity and durability of components. Based on 28 years of accumulated test data, Qinglong Group has set the flexural strength standard for premium GRC at: 7-day flexural strength of no less than 12MPa and 28-day flexural strength of no less than 15MPa, a standard significantly higher than the basic industry requirements. In the Wuhan Hanxiu Theater project, our GRC panels achieved a measured 28-day flexural strength of 18MPa, providing ample assurance for the safety of thin-walled components. Flexural strength is not just a number—it is a direct reflection of GRC material quality.

Basic Requirements of Industry Standards

According to the national industry standard "Technical Standard for Building Application of Glass Fiber Reinforced Cement (GRC)" (JGJ/T 423-2018), the 28-day flexural strength of GRC materials should be no less than 10MPa. This is the basic threshold for GRC products to enter the market. As a participating unit in drafting this standard, Qinglong understands that this requirement is a minimum standard established based on extensive engineering practice and safety considerations. However, for major projects and special components, meeting the basic standard is far from sufficient.

Qinglong Group's Internal Quality Grading

Qinglong classifies GRC products into three grades: Standard Grade (≥10MPa), Premium Grade (≥15MPa), and High-Performance Grade (≥18MPa). This grading is based on component application, stress conditions, and service environment. For example, decorative moldings can use Standard Grade, curtain wall panels must reach Premium Grade, while load-bearing or large-span components must use High-Performance Grade. In the Nanning Wuxiang China Resources MixC super high-rise project, we used Premium Grade or above GRC exclusively to ensure building safety.

Key Factors Affecting Flexural Strength

Flexural strength is influenced by multiple factors, including fiber content, fiber length, matrix strength, and fiber distribution uniformity. Through optimized mix proportions and processes, Qinglong controls fiber content at 3%-5%, fiber length at 12-36mm, and matrix strength at no less than 50MPa. Meanwhile, a robotic spraying process is adopted to ensure two-dimensional random fiber distribution, maximizing the reinforcement effect. In the Dongguan Women and Children's Activity Center project, this process control ensured uniform and consistent strength in areas with complex woven textures.

Long-Term Retention of Flexural Strength

The flexural strength of GRC is not a fixed value but develops dynamically over time. Premium GRC, when properly used, continues to gain strength slowly; whereas inferior GRC, due to alkali-aggregate reactions or fiber degradation, will see its strength decline year by year. Through tracking and testing of projects over ten years old, Qinglong has confirmed that the strength retention rate of our GRC products exceeds 90%, demonstrating the long-term reliability of the material.