Some procedures given to the repair of concrete structures is commonly applied to visible surfaces only. Whether elevated or on grade this requires specific engineered waterproofing and durability solutions not always addressing the real problem deeper within.
Concrete deterioration, commonly caused by corrosion of embedded reinforcement resulting in concrete delamination and spalling. Other common causes include freezing- and-thawing deterioration, chemical attack, ASR (Alkali-silica Reaction), DEF (Delayed Ettringite Formation), and other moisture/contaminant induced deterioration.
After proper evaluation of the deterioration, a developed plan should include clear objectives and specifications for the repair. Steps for repairs that include replacement of loose or deteriorated concrete, removals, and curing have included below as a field guide for use by AQURON® factory-trained applicators.
With the entire AQURON® 7000/AQURON®2000 system, you can treat and repair concrete structures at risk by depleting and purging internal chlorides, waterproof internally, and densify with an impermeable, hydrogel barrier. This unique hydrogel barrier system permanently surrounding embedded reinforcing steel from future threat of corrosion, is a momentous change in the future application of concrete durability enhancement and repair.
Accomplishing permanent densification and waterproofing of concrete from capillary reduction (porosity), introduced in the form of Aquron insulating hydrogel-paste (CSH) created by AQURON®7000/AQURON®2000 in repair applications is outlined in the steps below.
Regardless of the repair method, surface preparation is the same. Unsound concrete is removed, and exposed rebar are undercut, and surfaces are cleaned with high-pressure water (3000 psi minimum) and exposed bars are water/ abrasive blasted to remove all visible rust. Follow the steps outlined below:
Step 1: Sound the concrete surfaces to locate delaminated areas. This may be done as described in ASTM D4580 – “Standard Practice for Measuring Delamination in Concrete Bridge Decks by Sounding.”
Step 2: Mark the perimeter of the repair area. Preferable layout will result in simple geometric shapes with as few reentrant, 90 degree-angled corners as possible.
Step 3: Sawcut the perimeter of the repair. To avoid damaging reinforcement, the sawcut should not be deeper than the cover over the reinforcement. If the delamination is caused by corrosion, but the area of corroded reinforcing is not certain, use chipping hammers to expose the reinforcement until areas of uncorroded bars are found. Then sawcut an area that encompasses the boundaries of corrosion that have been established.
Step 4: Concrete surfaces must be prepared by suitable mechanical means, abrasive blasting and/or high-pressure water at sufficient volume and pressure to remove all surface contaminants such as oil, grease, curing membranes, efflorescence, algae, moss, dirt, etc. All loose materials and any existing coatings must be removed to provide a clean, sound, dry, and absorbent surface prior to application of the. Reference ICRI Technical Guidelines 310.2R-2013 – Selecting
and Specifying Concrete Surface Preparation for Sealers, Coatings, Polymer Overlays and Concrete Repair.
Step 5: If exposed bars are corroded, concrete surrounding the bar should be fully removed to expose the corroded bar, regardless of how much of the bar corroded. Removals around the bar should allow the hand to pass under the bar. Clearance around the bar should be approximately 3/4 in. (20 mm). Perform initial concrete removal with 15-lb but not larger than 30-lb air-assisted, chipping- hammers. Chipping hammers larger than 30 lb. may cause damage to reinforcement, reinforcement bond to surrounding concrete, and remaining
concrete. Use 15-lb chipping hammers for final removal and detailing around the reinforcing steel.
NOTE: If corroded bars are found and the bars have loss of cross section, a structural engineer should be consulted.
Step 6: After all bad material is removed and repair area is cleaned, the application of AQURON® 7000 can begin. Apply AQURON® 7000 at a total minimum consumption rate of 175-200 sf/gallon/coat by low-pressure, airless paint sprayer in two cross-hatching coats. AQURON® 7000 is applied to a point of concrete saturation, in a wet-on-wet application.
DO NOT allow first application to dry; second application is applied to surface while still damp from the first application (SSD).
NOTE: Installation requires using an airless paint sprayer with a 3/8” ID fluid hose, with a .017”-.019” spray tip producing 1500 to 2000 psi outbound pressure.
Step 7: Begin the application of the AQURON® CPT 2000 immediately after the AQURON® 7000, undiluted, with the same airless paint sprayer. 2 applications minimum, depending on the porosity of the concrete substrate, back-to-back, in a cross-hatching pattern. Application of the AQURON® 2000 CPT will be applied at a consumption rate of 150-200 sf/gal per coat with a high-pressure, paint sprayer. Allow 30 – 60 minutes to dry and rinse any visible efflorescence (chlorides) purged to the surface of the repair area. Allow to dry 12-24 hours from initial application. Additional purge may continue to come to the surface especially when heavy salt or chloride content exist within the concrete substrate. Continue to rinse away any visible efflorescence as needed. This may take several days on older concrete or concrete in coastal areas, but it will stop when the AQURON® treatments overcome the porosity of the substrate.
NOTE: Installation requires using an airless paint sprayer with a 3/8” ID fluid hose, with a .013” – 25-degree fan tip for steel troweled, smooth concrete surfaces. For more porous or weathered concrete surfaces, us a .015” – .019” – 25 – degree spray tip.
Step 8: Once substrate is properly prepared, begin installation of the AQURON® Steel Penetrating Primer to thoroughly cleaned/de-greased, rust intact, reinforcement. Completely encapsulate all exposed ferrous metals front and back (4mils total). Allow to dry 3 – 4 hours. Once dry, the cementitious repair can begin.
Step 9: Pre-wet concrete substrate before placing repair materials. Concrete surfaces receiving repair materials should be saturated surface-dry (SSD).
Step 10: Certain repair material mixture proportions and placement conditions may not require a separate bonding agent. If a manufactured (bagged) product is used, follow the manufacturer’s instructions. Follow the procedures outlined in the preceding section of this document. This will ensure that the placement methods and materials will result in adequate bond. If ready mixed concrete is used for the larger scaled repairs, AQURON® 300 Mix Water Conditioner (MWC) is recommended. AQURON MWC 300 provides extraordinary filler benefits like silica fume, resulting in denser, more impermeable concrete with less susceptibility to corrosive pollutants, and freeze-thaw damage. Plus, the added benefit of protecting any embedded reinforcing re-bar from future corrosion.
Step 11: Place repair material into the prepared repair area by necessary means and method (bucket, wheelbarrow, concrete buggy, etc.)
Step 12: Consolidate the repair material into the cavity using either a vibrating screed or internal vibrator. Vibration allowsthe repair material to flow around the reinforcing steel and come into intimate contact with the existing concrete substrate. This will promote maximum bond between the new material and the substrate. Also, any entrapped air will also be removed in this step.
Step 13: Screed, float and finish repair materials by acceptable means as outlined by manufacturers.
Step 14: After the repair material has been placed and set, the entire substrate is treated with AQURON® SPT-1200 if, invisible surface repellency and breathable protection is acceptable. (Visible Repair). This added invisible, waterproof, surface protection will allow excess moisture vapor to escape without allowing new moisture to penetrate. If a surface coating is desired to hide repairs, treat the repair only, with two applications of AQURON® CPT-2000(TDS) and proceed with coating(s) once cured.
We decided what repair materials should be used, compressive strength of the cementitious materials should NOT be greater than the original concrete and should not be less than 4000 psi. Prepackaged materials specially designed for the repair of concrete surfaces can also be used. Selection should be based on meeting the specified properties outlined by the owner’s representative. Refer to ICRI Guidelines 110.1-216 – Guide Specifications for Structural Concrete Repair (030130) for more information.
Hearing protection must reduce sound levels reaching the inner ear to limits on these levels that are specified by OSHA.
Respiratory protection is required when airborne dust or vapors are produced.
Protective clothing and gloves should be worn to protect exposed skin against
from chemicals and cement burns
Safety Data Sheets (SDS) should be available for materials on the job site. It is the responsibility of the user of this document to establish health and safety practices appropriate to the specific circumstances involved with its use. The user must determine the applicability of all regulatory limitations before applying the document and must comply with all applicable laws and regulations including, but not limited to, United States Occupational Safety and Health Administration (OSHA) health and safety standards.
Prior to proceeding with the repair, a preconstruction meeting is recommended. The meeting should include representatives from participating parties (owner, engineer, contractor, materials manufacturer), and specifically address the parameters, means,
methods, and materials necessary to achieve the repair objectives.
ASTM D4580 – “Standard Practice for Measuring Delamination in Concrete Bridge Decks by Sounding.”
ICRI, 1997, “Selecting and Specifying Concrete Surface Preparation for Coatings, Sealers, and Polymer Over- lays,” ICRI Technical Guideline No. 310.2-1997
ICRI, 2008, “Guide for Surface Preparation for the Repair of Deteriorated Concrete
Resulting from Reinforcing Steel Corrosion,” ICRI Technical Guideline No. 310.1R-2008.
ICRI, 2009, “Guide for Selecting and Specifying Materials for Repair of Concrete Surfaces,” ICRI Technical Guideline No. 320.2R-2009.