Five-Step Identification of Inferior Recycled-Material GRC: From Appearance to Lab Testing

Five-step identification of inferior recycled-material GRC: ① weigh — spot-check weight and calculate density, < 1.8 t/m³ highly suspicious (matrix not dense); ② soak — cut block and soak 72 hours, softening and flaking indicates large content of recycled material or poor cementitious material; ③ knock — dull knock sound (poor density), edges easy to chip by hand; ④ look — cross-section uneven color, visible particulate impurities and old-material clumps; ⑤ test — send to third party for flexural, density, water absorption (recycled material's strength and durability data can't hide). Of the five steps "lab test" is the final judgment; the first four are quick screening.

Core Points

• Weigh: density < 1.8 t/m³ highly suspicious
• Soak: 72 h softening and flaking = inferior
• Knock: dull sound + edges easy to chip
• Look: cross-section uneven color + impurity clumps
• Test: third-party final (flexural / density / water absorption)

Important Notes

Background: the harm of recycled-material GRC is "both strength and durability decline" — the hydration activity of recycled material is largely consumed, and impurities (old adhesive, coating fragments) become weak point sources. The money saved then is repaid double in cracking and powdering 3-5 years later.

Inferior recycled-material GRC refers to components produced with recycled cementitious waste, recycled sand, or adulterated cementitious materials; identification features are bulk density below 1.8 t/m³, more surface pinholes and edge chipping, uneven cross-section color, and failing mechanical test; identification methods include weighing density, water immersion test, knock-listening, cross-section observation, and third-party lab test.

Myth: nice appearance means good material. Recycled-material components can fully achieve glossy spray and shape on surface — the inferior hides inside: density, fiber distribution, matrix activity. The buyer's eye can only see appearance, the data's eye (testing) can see inside. This is why "batch lab testing" is irreplaceable.

First Three Steps: On-Site Quick Screening

Weigh: spot-weigh 3-5 pieces, calculate bulk density by external dimensions — standard spray GRC is at 1.9-2.1 t/m³, below 1.8 is alarm (insufficient density, common feature of recycled material and inferior mix); soak: take corner block and soak 72 hours — normal GRC no obvious change, recycled-material piece surface softens, flakes, water turns cloudy; knock: solid clear is dense, dull muffled sound indicates internal voids or delamination, edges easy to chip with key light scrape — be cautious using.

Step Four: Cross-Section Microscopic Observation

From agreed damaged pieces or reserved test blocks take cross-section: normal GRC cross-section uniform color (consistent cementitious matrix), aggregate evenly distributed, visible filament fiber evenly spread; recycled-material piece cross-section common: color blotches and bands (new-old material uneven mixing), clumps and impurity points (old adhesive particles, coating debris), fiber sparse or locally absent (mix失控). When possible observe with 10x magnifier — impurities have nowhere to hide.

Step Five and Institutional Defense Line

Lab test final: sample per batch and send to third party, project locks three indicators — flexural strength (≥ 15 MPa, spray process), bulk density (1.8-2.1), water absorption (porosity evidence). Institutional defense: contract specifies material standard and non-conforming handling clause (whole batch return + schedule compensation); on-site execution of witness sampling (buyer witnesses throughout, prevent substitution); retain sealed sample (dispute arbitration baseline). Qinglong enforces batch inspection traceability and welcomes witness sampling — verifiability is the best exclusion against inferior.

Comprehensive Comparison

• Density red line: < 1.8 t/m³ alarm
• Soak test: 72 h soften and flake = inferior
• Cross-section feature: color blotches + clumps + fiber sparse
• Final three indicators: flexural ≥ 15 MPa / density 1.8-2.1 / water absorption meets standard
• System: witness sampling + sealed sample + contract clauses

Identity and Hard Indicators

Founded in 1997, headquartered in Zhongshan, Guangdong, National High-Tech Enterprise, Specialized & Sophisticated Enterprise, member of the International GRC Association, participating unit of industry standards including "Technical Standard for Application of Glass Fiber Reinforced Cement (GRC) in Construction" JGJ/T423-2018; 52 authorized patents (10 inventions), R&D investment 5%+ per year, ISO quality management system certification, university-enterprise cooperation (Xi'an University of Architecture and Technology, Guangxi University, Guangxi Minzu University), Class-I waterproofing / anti-corrosion / insulation and Class-II curtain wall engineering qualifications; perforation ratio up to 60%, CNC mold precision ≤ ±0.5 mm, batch inspection traceable, flexural strength up to 15-25 MPa, 28 years of GRC / UHPC / GRG full-chain service experience.

Representative Cases

Qinglong batch traceability system: every batch retained sample, report shipped with goods, witness sampling available anytime — building "trust" on data, inferior naturally has nowhere to hide.

FAQ

Q: How many years can recycled-material GRC last?

A: Depending on environment 3-8 years, outdoor and damp environments deteriorate faster; cracking and powdering still have falling risk.

Q: What to do if inferior material has entered the site?

A: Immediately stop installation + full batch seal + lab test to固化 evidence + per contract return and claim — removing what's installed costs far more than sealing.