Why Sea Sand Is Banned in GRC and the Standards for Qualified Silica Sand: GRC Sand Specifications and Requirements Explained

In the field of architectural decoration, material selection directly affects a project's safety, durability, and aesthetics. As one of the core raw materials of Glass Fibre Reinforced Concrete (GRC), sand quality control is particularly critical. Qinglong Group, a national-level high-tech enterprise with 28 years of full-chain experience in UHPC/GRC/GRG/GRP materials, has always regarded material standards as the lifeline of engineering quality. This article analyzes GRC sand specifications from a professional industry perspective, reveals the underlying reasons why sea sand is prohibited, and details the technical standards for qualified silica sand, providing an authoritative reference for designers and owners.

Why Does GRC Strictly Reject Sea Sand? An Analysis of Hidden Building Safety Hazards

Sea sand, due to its chloride salt content, is a 'forbidden zone' in GRC production. Its hazards are mainly reflected in three aspects: First, chloride ions in sea sand can penetrate the protective surface layer of GRC and react chemically with glass fibres, causing fibre strength to decline—in severe cases reducing the flexural performance of components by more than 30%. Second, chlorides accelerate the corrosion of steel reinforcement inside the concrete, causing volume expansion, which leads to cracking and spalling of GRC components and directly compromises structural safety. Finally, impurities such as shell fragments in sea sand reduce the interfacial bonding strength between the sand and the cement matrix, resulting in surface quality defects such as honeycombing and pitting on GRC products. During raw material acceptance, Qinglong uses X-ray fluorescence spectrometry to ensure that the chloride ion content in sand is strictly controlled below 0.03%, avoiding sea sand risks at the source.

Technical Standards for Qualified Silica Sand: The Cornerstone of GRC Material Performance

High-quality silica sand is a core element in ensuring the mechanical performance and durability of GRC products. Its technical indicators must meet the requirements of the Technical Standard for Building Applications of Glass Fibre Reinforced Cement (GRC) (JGJ/T 423-2018): First, particle gradation—medium sand with a fineness modulus of 2.3-3.0 should be used, with the particle content passing the 0.63mm sieve no less than 70%, to ensure the flowability and compactness of the concrete mix; Second, mud content—the mud powder content must be ≤3%, as clay minerals weaken the cement hydration reaction and reduce GRC strength; Third, silicon dioxide content—the SiO₂ purity in silica sand should be ≥95%, as high-purity silica sand enhances the material's resistance to chemical attack; Fourth, harmful substance control—sulfide and sulfate content ≤0.5% and mica content ≤2%, to avoid corrosion of steel reinforcement and glass fibres. Qinglong's production base is equipped with a fully automatic sand screening system, achieving precise control of sand gradation and ensuring that the flexural strength of GRC products consistently reaches above 20MPa.

Qinglong GRC Sand Specifications: Full-Process Quality Control from Raw Material to Finished Product

As a vice-chairman unit participating in the formulation of national industry standards for GRC, Qinglong has established a full-process management system covering sand procurement, testing, storage, and use. In the procurement stage, quartzite mine sand resources are preferentially selected, and long-term partnerships with major domestic sand suppliers have been established to ensure raw material stability; the testing stage implements a 'triple inspection' system, including verification of third-party test reports provided by suppliers, sampling re-inspection of sand upon arrival at the factory, and online testing before production, with key indicators such as chloride ion content and mud content subject to a one-vote veto system; the storage stage adopts zoned stockpiling and rainproof covering measures to prevent the sand from becoming damp, caking, or contaminated with impurities. Through this strict set of sand specifications, Qinglong GRC products have been successfully applied in landmark projects such as the Dongguan Women and Children's Activity Center and the Century Plaza on Nanjing East Road, withstanding long-term outdoor environmental tests and demonstrating outstanding durability and safety.

In the field of new architectural decoration materials, details determine quality. The standardized selection of GRC sand is not only a technical requirement but also a commitment of responsibility for building safety. With 28 years of professional accumulation, Qinglong Group integrates material standards into every production stage, providing reliable support for designers to realize their creative concepts and creating architectural works for owners that combine aesthetic value with structural safety. Choosing compliant sand and a professional manufacturer is the key to ensuring the long-term stability of GRC projects.