Category Archives: Technical Reports

The Technical Services Team at KING releases Technical Reports based on lab findings and field experiments.

Reference the reports below, to learn about the technical performance of various KING Construction Products, as observed by our technical experts and Engineers.

SURFACE PREPARATION FOR CONCRETE REPAIR

INTRODUCTION

A concrete substrate must be properly prepared prior to the placement of a concrete repair material, in order to ensure a successful repair that meets the expected service life of the repair. Proper surface preparation requires the selection of the most suitable removal method, patch or profile layout selection, saw-cutting around patches, concrete removal and cleaning and saturating the repair surface with water prior to placing the repair material. The intent of this Technical Report is to establish the recommended procedures for the surface preparation of a concrete substrate prior to the placement of KING Construction Products in a concrete repair application.

The project specification, contract documents or direction of the design professional (Architect or Engineer) responsible for the specific project, should be followed and would supersede any recommendations in this Technical Report. It should be noted that the removal of concrete can affect the structural integrity of the structure, and therefore the design professional (Architect or Engineer) responsible for each specific project should be consulted prior to the removal of concrete.

CONCRETE REMOVAL METHODS

The concrete removal method used for a specific repair will play a major role in the overall success of the repair and therefore the future service life of the structure or element being repaired. While some materials that are applied to concrete substrates only require the use of mild surface treatments (e.g. grinding, acid-etching, needle scaling and low-pressure water cleaning), concrete repair materials require a more aggressive concrete removal method and therefore a much rougher surface in order to achieve adequate bond between the concrete repair material and the concrete substrate.

Bonding between the repair material and the substrate is crucial to the success of the repair, and is often specified by the design professional (Architect or Engineer) to be tested in accordance ASTM C 1583 or CSA A 23.2-6B. Typically, the minimum in-situ bond strength must be achieved at a specific testing date following the installation of the repair material. It should be noted that the bond strength can be affected by the soundness and quality of the parent concrete, and when a successful bond is achieved the bond strength will be governed by the tensile strength of the substrate.

In order to ensure the proper surface roughness and bond strength, KING recommends a Concrete Surface Profile (CSP) ranging from 5 to 10† in accordance with ICRI Guideline No. 310.2R (Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, Polymer Overlays, and Concrete Repair). As indicated in Table 7.1 from ICRI Guideline No. 310.2R, only certain concrete removal methods can be used to achieve a minimum CSP of 5. Therefore, KING recommends the methods of concrete removal and surface preparation indicated in Table 1 prior to the placement of KING Construction Products in a concrete repair application.

TABLE 1: RECOMMENDED CONCRETE REMOVAL AND SURFACE PREPARATION METHODS

TABLE 1: *The indicated concrete removal methods can introduce a moderate to high risk of micro-cracking which can reduce bond strength. It is mandatory to subsequently use abrasive blasting or shotblasting following these concrete removal methods in order to remove any concrete damaged by micro-cracking.

SURFACE PREPARATION

Patch repairs in the concrete substrate should have a layout that minimizes irregular shapes and the number of angles in the patch. Using 90° angles in the patch layout simplifies the saw-cutting operation and limits the high stress points in the patch that can increase the risk of cracking. Following the mapping and layout of the repair areas all loose or delaminated concrete should be removed from the repair section, leaving a minimum of 25 mm (1”) clearance behind any reinforcing steel. The perimeter of the repair should be saw-cut a minimum of 6 mm (1/4”) for shallow repairs using a repair mortar (6 mm-50 mm or 1/4”-2”), or a minimum of 20 mm (3/4”) for deeper repairs using concrete or shotcrete (38 mm or 1/2” to full depth).

If not already performed, any corroded reinforcing steel should be cleaned using abrasive blasting or equivalent in order to remove as much rust as possible††. The substrate must then be cleaned with potable water in order to remove any dust, or any other foreign substances that may interfere with the bond of the applied KING Construction Product. The substrate should be saturated but free of any standing water in a saturated-surface dry (SSD) condition. Mixing and application procedures indicated on the technical data sheet should be followed for the applicable KING Construction Product to be used in the repair.

This report is intended for use as a guide only. Refer to ICRI Guideline No.310.2R or contact your KING Technical Representative for more information regarding concrete removal and surface preparation.
†: In certain situations it is possible to use a CSP lower than 5. Contact your KING Technical Representative for more information.
††: Corrosion of reinforcing steel in concrete is a very complex chemical interaction. An expert in corrosion mitigation and remediation techniques should be consulted for further information.