Chimney Rust Repair Fundamentals


Arresting Column Expansion Wall Cracks From Rust:

As chimneys age they experience changes from weather: moisture, freeze and thaw cycles, temperature changes on the inside and outside, changes in wind direction and changes in wind speeds. It is principally these factors that essentially move the chimney in every direction. Over time the natural results are cracks, spalling and column expansion. As a chimney cracks water can then get into the rebar more easily and cause rust all along any piece of steel in the concrete or brickwork vertically and horizontally.

Rusting steel inside a chimney column is best arrested by following the following plan.


  1. Identify where the cracks are.
  2. Find out how extensive the rust is rust by using rust detecting meters.
  3. Come up with a repair plan.
  4. Expose rusted steel with chipping and cutting tooling. Either introducing new steel into concrete or repairs to old steel, both need to be properly treated and painted.
  5. Cleaning the steel of rust.
  6. Apply a rust reversing coating to the steel.
  7. After this step the brickwork or concrete can be restored and re-sealed.
  8. Additionally, considering the age of the chimney, new bands should be set on the chimney column ever 5’ typically.


Information on concrete crack repair is found in literature which has to do with structures that have steel reinforcement:

  1. Repair and Strengthening of Bridge Substructures
  2. American Concrete Institute ACI 562 Assessment, Repair, and Rehabilitation of Existing Concrete Structures: The ACI Code Requirements for Assessment, Repair, and Rehabilitation of Existing Concrete Structures (ACI 562) and Commentaryis the first code specifically for repairing reinforced concrete: Providing clearly defined, uniform requirements aimed at extending the service life of existing structures, chapters cover all aspects of concrete repair, from conception to completion, including the basis for compliance, evaluation and analysis, design of structural repairs, durability, and construction.
  3. ACI 562 Public Seminar: A seminar titled Guide to the Code for Assessment, Repair, and Rehabilitation of Existing Concrete Buildings has two components that work together to provide additional information on how to apply the performance requirements in ACI 562 and how the requirements may be applied to a broad range of projects.
  4. 562 Repair Code Related Articles:
  5. Defining Concrete Repair, as published in Concrete Construction, April 2016
  6. New Code Sets Standards for Concrete Repair, as published in NACE International, March 2016 Rethinking Concrete Repair, as published in Concrete Contractor, December 2015
  7. Taking a New Approach to Concrete, as published in Construction Specifier, March 2016
  8. The Fix is In, as published in Concrete Surfaces, November-December 2015
  9. Free Online Presentations from ACI:
  10. History and Background of the ACI 562 Code
  11. Chapter 1—The ACI 562 Code
  12. The Building Official’s Perspective
  13. Evaluation of Existing Concrete Structures
  14. Structural Design Requirements for Concrete Repair
  15. Durability Requirements in ACI 562 Chapters 9 and 10—Construction and Quality Assurance

ACI 563—Specifications for Repair.

  1. Concrete Repair Manual – 4th Edition : 2-Volume Set  $ 269.00
  2. 1R-07 Causes, Evaluation, and Repair of Cracks in Concrete Structures.
  3. 7-07 Specification for Crack Repair by Epoxy Injection.
  4. 53R-14 Guide to Materials Selection for Concrete Repair.


Finding Rust In Concrete Rebar:

An Elcometer cover meter [See 800-444-1508 ] must be used in concrete evaluation to examine the extent of rusted rebar prior to any repairs.


Arresting Moisture Penetration to the chimney façade:

Throughout the life of a chimney, when there is no regular maintenance the shell will become compromised and moisture will enter the structure. When this happenings rebar within concrete chimneys will form hairline, and then ever larger cracks due to movement and rusting steel.


Arresting Moisture Penetration to the chimney base:

Moisture can also enter the chimney at the chimney base when it is below grade, or else moisture can enter the structure because of poor drainage making the ground wet near the chimney. The use of a Concrete Moisture Meter is therefore necessary to determine if water is trapped in a concrete structure. See for their concrete moisture meters.


Coating Maintenance:

Concrete industrial chimney columns are sometimes painted. Sometimes these coatings become damaged and cracked. As a result, these coating that have been designed to keep moisture out, then trap moisture in. This will quickly lead to devastating problems within the chimney structure with rusting re-bar and cracked bricks.  When a chimney is coated that coating needs to be maintained regularly or if cannot be maintained, it should be immediately removed.


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