Why Is Sea Sand Prohibited in GRC? What Are the Standards for Qualified Silica Sand?

The core reason sea sand is prohibited in GRC is that sea sand contains high levels of chloride ions and impurities, which severely compromise product durability and safety. Qualified silica sand must meet strict standards for purity, particle size, and cleanliness. Qinglong implements a "three-level inspection" system to ensure aggregate quality compliance.

1. Core Reasons for Prohibiting the Use of Sea Sand

The characteristics of sea sand fundamentally conflict with the performance requirements of GRC, posing three major hazards. Extremely high chloride ion content: sea sand typically contains 0.1%-1.0% chloride ions, far exceeding the ≤0.02% allowed in GRC, causing corrosion of metal connectors and GRC strength deterioration. Qinglong's tests show that in GRC made with sea sand, the corrosion rate of steel connectors reaches 50% within 3 years, with 30% strength loss. High impurity content: sea sand contains impurities such as shells, salts, and mud lumps. Shells reduce GRC density, while mud lumps form weak points in strength, leading to component cracking. Traditional cement components made with sea sand are prone to surface pitting and spalling. Extremely poor durability: chloride ions and impurities accelerate the decomposition of GRC hydration products, reducing freeze-thaw resistance and impermeability. Sea sand GRC used in coastal projects showed chalking after only 5 years. Qinglong strictly prohibits sea sand from entering the plant, avoiding risks at the source.

2. Core Technical Standards for Qualified Silica Sand

Qualified silica sand must meet four major standards to ensure suitability for GRC production. Purity requirement: silicon dioxide (SiO₂) content ≥98%; the higher the purity, the lower the aggregate activity, preventing alkali-aggregate reaction. The quartz sand selected by Qinglong has a SiO₂ content above 99%. Particle size requirement: particle size range of 0.15-0.6mm, graded in 3-4 size classes (e.g., 0.3-0.6mm at 50%, 0.15-0.3mm at 35%) to achieve the tightest packing. Qinglong enhances GRC density through particle gradation optimization. Cleanliness requirement: mud content ≤0.3%, mud lump content ≤0.1%, chloride ion content ≤0.02%, free of shells, organic matter, and other impurities. Qinglong's silica sand is washed, sieved, and dried to meet cleanliness standards. Appearance requirement: uniform particles, round or sub-round in shape, with smooth surfaces and no sharp edges, reducing damage to alkali-resistant fibers. Qinglong's silica sand has a particle roundness of ≥0.8, ensuring fiber dispersion.

3. Corporate Practices in Aggregate Control and Standards Compliance

Qinglong has established a full-process aggregate control system to ensure silica sand quality. Procurement control: partnering with reputable quartz sand mines and requiring test reports on SiO₂ content, chloride ion content, mud content, and other indicators; all of Qinglong's strategic partner mines are ISO quality system certified. Incoming inspection: each batch of silica sand undergoes visual inspection upon arrival, followed by laboratory testing of key indicators; non-conforming products are returned immediately, and Qinglong achieves a 100% acceptance rate for incoming aggregates. Production control: silica sand is re-sieved before use to remove oversized particles; Qinglong's production bases are equipped with vibrating screens to ensure precise particle size. Standards compliance: fully complying with the aggregate requirements of the Technical Standard for Glass Fiber Reinforced Cement (GRC) Building Applications (JGJ/T423-2018). Projects such as the Dongting Lake Museum and the Hainan International Convention and Exhibition Center all used qualified silica sand meeting this standard, with no quality issues after years of use.