Standards for Testing the Bond Strength between Dry-Spread Materials and Concrete Substrates

In anti-corrosion flooring construction, the bond strength between dry-spread materials (such as corundum and acid-resistant aggregates) and the concrete substrate directly determines whether the flooring will peel, flake, or allow anti-corrosion media to penetrate.

For this type of "composite structure," the main testing standards and methods are as follows:

1. Core Testing Standard: Pull-off Strength Test

Currently, the most directly recognized indicator in the industry is tensile strength.

Implementation Standard

International Standard: ASTM D4541 (Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers)

Domestic Standard: GB/T 5210 "Paints and Varnishes - Pull-Off Adhesion Test" or JGJ/T 70 "Basic Performance Test Methods for Building Mortar".

Corrosion Protection Standard: GB 50212 "Code for Construction of Corrosion Protection Engineering for Buildings".

Testing Procedure

Core Drilling/Kernel Cutting: Using a hollow drill bit, cut a ring, typically 50mm in diameter, into the hardened floor surface. The kerf depth should penetrate the dry-spread layer and reach the concrete base layer by approximately 5mm-10mm.

Steel Ingot Adhesion: Adhere a standard steel ingot (Dolly) to the surface of the ring using high-strength epoxy resin adhesive.

Pressure Pull-Out: Apply tension at a constant rate using a fully automatic or manual pull-out tester until the specimen detaches.

2. Result Judgment and Failure Mode Analysis

Bond strength is not only determined by its numerical value (MPa), but also by the location of fracture, which is crucial for diagnosing construction quality:

Location of failure	Judgment Result	Cause Analysis
Concrete base layer failure	Pass	The adhesion strength is greater than the substrate strength, which is the ideal state.
Bond interface failure	Fail/Risk	This indicates that the material was applied too late, and the aggregate did not enter the concrete hydration system.
Dry-spread layer internal failure	Requires Evaluation	This indicates that the dry-applied material itself lacks strength or the surface was not properly smoothed.
Adhesive layer failure	Invalid Test	The adhesive did not adhere well or the surface was not cleaned properly; retesting is required.

Specifications: For high-performance anti-corrosion flooring, a tensile strength of ≥ 1.5 MPa is typically required. For environments subjected to heavy loads and strong chemical corrosion, a strength of ≥ 2.0 MPa is recommended.

3. Other Auxiliary Testing Standards

Besides direct pull-out testing, the following physical indicators indirectly reflect the bonding quality:

GB/T 16925 (Indentation Hardness/Impact Test): Tests whether the dry-spread layer will delaminate and detach from the substrate under heavy impact.

Hollow Zone Test (Tapping Method): According to GB 50209 "Code for Acceptance of Construction Quality of Building Ground Engineering", tap with a 0.5kg drumstick; there should be no hollow sound.

Imperibility Test (ISAT): Measures the amount of water that permeates per unit time. If the bond is not dense, the permeability will be significantly increased.

Next Steps Recommendations

If you are preparing to outsource laboratory testing, it is recommended to reserve at least three representative test sites.

 

Do you need to prepare inspection and certification documents, or is there a localized detachment at the construction site? If it's the latter, I can help you analyze the specific fracture surface characteristics to find the cause.

 

Note: The parameters provided in this document are for reference only and are not mandatory. Due to differences in technical characteristics between different brands and models of laser levelers, please consult the manufacturer for a suitable solution before actual operation. This reference document assumes no responsibility for any issues arising from failure to follow the manufacturer's instructions.

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