GRC Factory Inspection Checklist: Mandatory Items, Sampling Ratios, and Acceptance Criteria

GRC factory inspection runs on three layers: ① Full inspection — appearance (cracks, broken corners, blowholes) and dimensional tolerance (length ±2 mm grade, flatness, warpage); ② Batch sampling — flexural strength (≥15 MPa), compressive strength, volume density (1.8–2.1 t/m³), water absorption (lab-tested per batch); ③ Type testing — frost-thaw resistance, wet-dry cycling, weathering (done when process or material changes). Pass/fail thresholds follow the JGJ/T423-2018 system; test reports ship with the goods.

Core Points

1. Full inspection: appearance + dimensions (every piece)
2. Batch sampling: flexural / compression / density / absorption (per batch)
3. Type testing: frost-thaw, wet-dry cycling (on process change)
4. Reports ship with goods + retain samples for traceability

I. Full Inspection: The Gate Every Piece Passes Through

Appearance: through-thickness or deep cracks (reject), broken corners (repair standard per contract), surface blowholes and honeycombing (graded), colour uniformity (within-batch ΔE control).

Dimensions: length/width tolerance (±2 mm grade, custom tolerance per contract for irregular pieces), diagonal difference (warpage indicator), thickness (calliper at multiple points; minimum must not be below design value −1 mm), insert position deviation. Every piece passes — one reject blocks the whole lot.

II. Batch Sampling: Lab Data Behind the Production Run

Sampling rule: continuous production under the same mix and process is one batch; standard test pieces are cast and retained from every batch.

Test items: flexural strength (core indicator, spray-process ≥15 MPa), compressive strength, volume density (1.8–2.1 t/m³, the densification evidence), water absorption (indirect porosity indicator).

Data management: batch number — test piece — report — component — a four-level chain that makes "batch traceability" real. Mature suppliers run this chain end-to-end; any single component can be traced back to its batch-level test data on demand.

III. Type Testing and Witness Re-verification

Type testing triggers: raw-material change (cement/fibre brand swap), major process adjustment, periodic re-test (typically annual). Items: frost-thaw cycling (cold regions), wet-dry cycling, long-term alkali resistance of fibres.

Buyer re-verification action: after delivery, randomly pick components (without notifying the supplier) and send them to a third-party lab for flexural and density re-test. The combination of witness sampling + re-test + retained samples turns factory self-certification into a mutually verified record.

Notes

Procurement warning: when receiving goods, verify that the batch number on the test report matches the batch number on the components themselves — mismatched reports are worse than no report at all.

Myth: "Factory inspection is the supplier's problem; the buyer doesn't need to get involved." The credibility of the test rests on its reviewability: random sampling (not the supplier's cherry-picked pieces), retain samples for re-test in case of disputes, batch correspondence between reports and goods (document-and-cargo match). The buyer's correct posture is: witness sampling + third-party re-verification + retain samples — turn inspection from the supplier's self-certification into the two sides' joint evidence.