The pull-off test is the only field test that produces a single number you can put in a contract clause. Adhesion strength of resin to substrate, measured in megapascals, with a documented failure mode. Pass / fail at a defined threshold. Every tender-grade resin floor in Israel either has a pull-off report attached to its completion certificate or doesn't actually have an enforceable warranty. This page walks the two standards (EN 1542 European harmonised, ASTM D7234 American), the threshold values per system class, the three failure modes and what each means, and how to read a pull-off report without assuming the lab knew what they were testing.
EN 1542 — Concrete Substrate Pull-Off
European harmonised standard for pull-off bond strength of resin systems applied to concrete substrate. Originated as EN 1542:1999, current revision adopted under EN 1504 family for concrete repair products. Used as primary specification standard across EU + IL public-sector tender.
Apparatus: Hydraulic or manual dolly puller with calibrated load cell. 50 mm diameter stainless-steel dolly bonded to floor surface with structural epoxy adhesive (typically Sikadur-30 or equivalent). Pull-off force divided by dolly area yields stress in MPa.
Procedure: Dolly bonded to fully-cured floor surface (typically day 7 minimum). Core-cut around dolly through the resin layer to substrate. Pull at constant rate until failure. Record peak force + failure mode.
Reporting: Result expressed as MPa with failure mode letter (A / B / C). Multiple-location average + standard deviation if > 3 locations tested.
ASTM D7234 — Coating Pull-Off Strength
American standard for pull-off strength of coatings on concrete. Procedurally equivalent to EN 1542 for resin floors, with minor differences in dolly geometry (typically 50 mm or 20 mm), core-cut depth requirements, and reporting conventions. Used widely in industrial floor tender where North-American manufacturer's spec sheet is the reference.
Apparatus: Hydraulic dolly puller; dolly types defined by ASTM D7234 (Type IV most common for floor coatings). Self-aligning fixture preferred to prevent eccentric loading.
Procedure: Surface preparation (sanding to clean), structural-epoxy bonding of dolly, cure period, core-cut, pull at constant rate.
Cross-conversion: EN 1542 and ASTM D7234 results are typically interchangeable for resin floor spec purposes. Both produce MPa values; both report failure mode. Contracts citing one are acceptable evidence under the other when the test apparatus and procedure align.
Threshold values by system class
The threshold value separates "passed" from "failed" — and the threshold differs by system type. A heavy-duty industrial system has different bond demands than a thin decorative micro-topping.
| System class | Threshold | Failure mode required | Notes |
|---|---|---|---|
| Heavy-duty epoxy quartz (industrial) | ≥ 1.5 MPa | Cohesive substrate (C) | Sika published; Mapei published; IL public-sector standard |
| PU-cement 6–9 mm (kitchen / industrial) | ≥ 1.5 MPa | Cohesive substrate (C) | System integrity check; substrate must be sound |
| Epoxy SL 2–3 mm (light industrial) | ≥ 1.0 MPa | Cohesive substrate (C) | Lower threshold for thin systems; substrate quality limit |
| Microtopping decorative | ≥ 0.8 MPa | Cohesive substrate (C) preferred | Decorative micro-systems have inherently lower bond demands |
| Polished concrete densifier | N/A (densifier is reactive) | — | Pull-off not applicable; densifier is part of the slab |
| MMA fast-cure (industrial) | ≥ 1.5 MPa | Cohesive substrate (C) | Same threshold as PU-cement; MMA is industrial-grade |
| Overlay on existing coating (pre-overlay test) | ≥ 1.0 MPa on existing | Existing coating cohesive | If existing coating < 1.0 MPa, mechanical removal required before overlay |
Failure mode interpretation (A / B / C)
The single most important reading on a pull-off report is the failure mode letter. The MPa value tells you the force; the failure mode tells you where the system actually failed.
Adhesive failure at substrate–resin interface
The resin came off the substrate cleanly. The substrate side shows resin coating; the resin side shows substrate. Bad sign. Bond is weaker than substrate cohesion. Indicates substrate prep failure, contamination, or moisture issue. Reject any report dominated by Mode A failures.
Adhesive failure at dolly–resin interface
The dolly came off the resin without taking resin with it. Test invalid. The dolly's structural-epoxy bond was weaker than the resin's substrate bond — the test didn't actually load the substrate-side bond. Re-test required.
Cohesive failure in the substrate
The resin pulled a piece of substrate concrete with it. Good sign. The resin-substrate bond is stronger than the substrate's internal cohesion. The recorded MPa value is actually the substrate's tensile strength — the resin bond is at least that strong. Mode C with adequate MPa is the contractual goal.
Grid location selection
A single pull-off test on one location is statistically meaningless. The minimum credible test grid is three locations on a small project, scaling up with area.
- ≤ 500 m² project: 3 locations minimum. Distribute one at each of: high-traffic centre, low-traffic perimeter, high-stress corner (cornering forklift, doorway threshold, drain approach).
- 500–2,000 m² project: 6 locations minimum. 3 baseline locations + 3 distributed across substrate-type changes or pour-day boundaries.
- 2,000–10,000 m² project: 1 location per 250 m² minimum. Distributed across project area with named grid reference (e.g., "Grid B7", "Centre of Bay 4").
- Critical-use areas: Add 1 location per critical zone — kitchen wash-down area, ESD-controlled operating theatre, chemical-spill zone.
Each location must be named on the report with grid reference + GPS or sketch coordinate. Anonymous "Location 1 / 2 / 3" reports are not auditable.
How to read a pull-off test report
A useful pull-off report contains six fields per location. If any field is missing, request a revised report — the test is not contractually defensible without all six.
- Location ID + grid reference + sketch coordinate. Lets you verify which spot on the floor was tested.
- Test date + curing duration of resin before test. Pull-off too early misses cure-related bond development. Industry default: minimum 7 days cure.
- Apparatus + standard cited. EN 1542 vs ASTM D7234, dolly diameter, equipment manufacturer + calibration date.
- Peak load MPa + result digital photo. Photo lets you verify failure mode independently.
- Failure mode letter (A / B / C) with photo. The interpretation is on the report writer; the photo is on the report.
- Lab signature + lab certification status. ISO 17025 accreditation preferred; named laboratory + technician initial required.
Common report failures
- "Average MPa = X" with no per-location breakdown. One outlier hides in the average. Reject — request per-location values + standard deviation.
- Failure mode field labelled "OK" or "good" instead of A / B / C. Lab didn't follow standard reporting. Re-test required.
- No photos. Failure-mode interpretation is the reader's only audit. Photo required for each location.
- Test date before resin cure period. Premature pull-off underestimates true bond. Reject and re-test after minimum 7 days.
- Cured-day count for the resin not stated. Without it you cannot validate whether the pull-off represents actual bond or cure-stage transitional bond.
Tender language for pull-off requirement
Direct paste-into-tender clause for inclusion in BOQ Line 10 (control samples + pull-off).
Final read
Pull-off testing is the single most contractually-defensible quality check in resin floor procurement. One report, three or more locations, threshold MPa with failure mode C — that's the package. Without it, the applicator can argue any substrate-related failure into owner-scope; with it, the warranty triangle holds. Specify the requirement in the BOQ before the tender goes out, not after the install. Related: tender BOQ template · warranty types · compliance verification · substrate moisture remediation.
Sources
- EN 1542:1999 — Products and systems for the protection and repair of concrete structures. Test methods. Measurement of bond strength by pull-off.
- ASTM D7234 — Standard Test Method for Pull-Off Adhesion Strength of Coatings on Concrete Using Portable Pull-Off Adhesion Testers.
- ICRI 320.1R — Guideline for adhesion testing of concrete coatings.
- Sikafloor system pull-off test protocols.
- Mapei Mapefloor pull-off test protocols.
- ISO 17025 — General requirements for the competence of testing and calibration laboratories.