What Is the Density Standard for High-Performance GRC Curtain Walls? Density Testing and Improvement Solutions

Compactness is a core indicator of high-performance GRC curtain wall materials, directly affecting component strength, durability, and waterproofing performance. Insufficient compactness easily leads to water absorption, cracking, and strength deterioration in components. Clarifying compactness standards and testing methods, and improving compactness through technical means, is key to ensuring the long-term stability of GRC curtain walls. Drawing on 28 years of R&D and production experience, Qinglong analyzes the key points.

I. Core Standards for High-Performance GRC Curtain Wall Compactness

According to the industry standard Glass Fibre Reinforced Cement (GRC) Decorative Products (JC/T940-2022), the compactness of high-performance GRC curtain walls must meet the following core indicators: bulk density ≥1.8g/cm³, porosity ≤8%, of which interconnected porosity ≤2%; water absorption ≤8% (24-hour immersion), water permeability ≤0.5mL/min (under 0.3MPa pressure). As a participating unit in drafting the standard, Qinglong has set stricter internal control standards: bulk density ≥1.9g/cm³ and porosity ≤6%, ensuring leading product performance. For example, in the GRC curtain wall project of the Dongguan Women and Children's Activity Center, the measured compactness indicators all exceeded industry standards. Meeting compactness standards enables GRC curtain walls to achieve flexural strength ≥15MPa, withstand ≥200 freeze-thaw cycles, and extend service life to over 20 years.

II. Core Testing Methods and Tools for Compactness

Scientific testing is key to verifying compactness and requires a combination of methods for comprehensive judgment. Bulk density and porosity are tested using the water displacement method: bulk density is calculated by measuring the component's volume and mass, and porosity is determined with the vacuum saturation method. Qinglong's laboratory is equipped with high-precision electronic balances and vacuum saturation equipment, achieving a testing accuracy of 0.01g/cm³. Water absorption is tested using the 24-hour full immersion method, weighing the mass difference before and after immersion to calculate the absorption rate. Water permeability is tested with a permeability tester, applying 0.3MPa water pressure and recording the total water penetration over 30 minutes. On-site testing can use an ultrasonic detector to indirectly judge compactness through sound velocity values, with a sound velocity ≥4500m/s considered qualified. In the on-site testing of the Singapore Defence Service Center project, Qinglong quickly identified compactness defects through ultrasonic testing, ensuring product quality.

III. Core Technical Solutions for Improving GRC Curtain Wall Compactness

Multi-dimensional optimization of raw materials, mix proportions, and production processes can significantly improve GRC compactness. For raw materials, high-grade low-alkali cement (Grade 52.5) and quartz sand (particle size 0.15-1.2mm) are selected to reduce impurities and pores. Mix proportion optimization adopts a low water-binder ratio (0.40-0.45) with the addition of high-range water reducers and silica fume; silica fume accounts for 10%-15% of the total cementitious materials, filling gaps between cement particles to improve compactness. The production process uses automated spray molding, controlling spray pressure at 0.3-0.5MPa to ensure a uniform and dense slurry, combined with high-frequency vibration to expel internal air. Through automated production lines, Qinglong achieves a compactness pass rate of over 99% for GRC components. The curing stage uses constant temperature and humidity curing to promote full cement hydration, reduce internal pores, and further improve compactness.

IV. Rectification and Preventive Measures for Insufficient Compactness

For components that fail to meet compactness standards, timely rectification and preventive mechanisms must be established. Minor insufficiency (porosity 8%-10%): apply a penetrating sealer to the surface to fill surface pores and improve waterproofing performance. Severe insufficiency (porosity >10%): the component is scrapped and strictly prohibited from project installation. Qinglong implements a 'scrap-if-unqualified' system to ensure that shipped products meet compactness standards. Preventive measures include: establishing a raw material access system with strict testing of aggregate clay content and cement performance; real-time monitoring of the production process with compactness sampling tests for each batch; and regular calibration of production equipment to ensure stable spray pressure and vibration frequency. Through full-process control, the compactness of Qinglong's high-performance GRC curtain walls consistently meets standards, providing reliable quality assurance for multiple major projects.