Knowles Applies Principles of Air-Entrained Concrete to Dry-Mix Shotcrete

Knowles Industrial Services is proud to announce the successful application of air-entrained dry-mix shotcrete. While air-entrained concrete has been an industry standard since its conception more than 80 years ago, the process of introducing porosity to dry-mix shotcrete is a newer development that Knowles has been closely following. As customer demand for freeze-thaw resistant shotcrete has increased over recent years, we saw an opportunity to expand our client portfolio.

What is Air-Entrained Concrete?

Air-entrained concrete is concrete that has been chemically altered to contain small, controlled, and evenly-spaced air bubbles throughout the material’s structure. The process is achieved by mixing a surfactant into plastic concrete which in turn creates air bubbles while mixing. These air entraining admixtures are useful in harsh environments that have frequent freeze-thaw cycles, as the air bubbles help make concrete significantly more crack resistant. These air bubbles provide a controlled space for water to occupy and permit the expansion of freezing water without creating internal stresses that can eventually cause cracking within the concrete.

Air-Entrained Shotcrete in Action

Air Entrained Shotcrete ApplicationOne of our key hydro-electric/utility clients recently requested a concrete application that could withstand the extreme winter weather cycles in New England. The Owner and Design Engineer mandated a minimum of 4% air entrainment by volume to resist damage caused by freeze/thaw cycles. Due to difficult site access requirements for conventional cast-in-place concrete application, this project was a strong candidate for dry-mix shotcrete (pneumatically-applied mortar). Knowles had never before been tasked with air-entraining shotcrete. The contract award was contingent upon successfully proving the ability to air-entrain dry-mix shotcrete prior to commencing construction.

Knowles has been following this relatively new dry-mix air entrainment concept for some time as it affects our core business and is just now starting to take hold in the industry with meaningful data. Dry-mix shotcrete, by the nature of the process, typically contains up to 4% air. Dry-mix has been documented to provide a very durable material up to .012 inch air spacing. In an effort to bring this technology to the project, Knowles performed a series of test panels at our Portland, Maine office on June 19th, 2015, and had cores tested by the country’s foremost authority on ASTM C457. We have obtained outstanding air void system results with the proposed air entrainment admixture used for these tests.


Read more about the testing process in our full report on air-entraining shotcrete

Repairing Structures: Knowles Saves Wastewater Plant Control Building

East Windsor WPCA Concrete Repairs & Coatings

In January of 2016, Woodard & Curran Inc. contacted management at Knowles Industrial Services Corporation and requested their professional opinion on wastewater concrete repair during a job site inspection at a plant in Northern Connecticut. The intent of this inspection was to identify structural issues and varying types of concrete and steel deterioration in the Control Building at the Water Pollution & Control Authority. Woodard & Curran then authored a structural condition assessment memorandum to the owner with repair suggestions and called upon Knowles Industrial Services to supply a cost estimation and work plan for a concrete repair service. The reinforced concrete floors in the Control Building had severely compromised structural integrity due to contamination and repeated exposure to sodium hypochlorite; an acidic chemical compound commonly used in the wastewater disinfection process.

Dealing with Concrete Contamination Safely and Efficiently

The concrete slabs on the ground floor had been heavily saturated with disinfectants. Much of the contaminant had migrated through spalls and cracks in the slab, reaching down to the underlying structural steel reinforcement and allowing the corrosion process to take place. The corrosion caused the embedded steel to expand and spall the concrete through a process known in the industry as “rust jacking”. This process also reduced the overall tensile strength of the reinforcement itself.

The WPCA contracted with Knowles Industrial Services to perform the repair work per specifications laid out by Woodard & Curran. The work items included demolition and replacement of over 400 SF of concrete floors and ceilings, secondary containment modifications/waterproofing/and chemical lining, structural steel surface preparation and coatings in the basement, urethane injection and coatings of leaking cold joints in the sump pit, and surface preparation and painting of the concrete basement walls.

I often strongly recommend to Owners that they work with Knowles, in my opinion one of the best and most reputable repair contractors in New England… They always get the job done right and at a fair price, and I have found their project management staff and field crews to be an absolute pleasure to work with.”  

-Jim Sturgis (Sr. Structural Engineer at Woodard & Curran)

Knowles Senior Foreman Dan Tardif and crew quickly had to overcome some difficult site conditions. The contamination reached a level of severity that required all concrete demolition be performed with strict adherence to respiratory and skin protection programs. The demolition dust was harmful and measures were taken to ensure workers could properly demolish and dispose of the contaminated without being exposed to harmful chemicals. Prolonged sodium hypochlorite contact with skin, eyes, or lungs can lead to irritation, rash, or acidic burns.

Meeting Important Concrete Repair Deadlines

The project schedule was a concern for the owner as they would only permit 7 working weeks to the contractor so that the disinfection season could start as normally scheduled in the Spring months. Knowles had to staff the project with a highly-experienced crew in order to meet the customer’s needs. All East Windsor plant operators and maintenance personnel were extremely knowledgeable and helpful throughout the construction process. The project’s success was highly attributed to the team effort put forth by all parties involved in the project.

Knowles completed all work scopes on schedule and were able to provide some additional repairs to the owner within the same timeline. Woodard & Curran and Knowles Industrial Services once again successfully worked together to provide the customer with high-value repairs at a fair price.

“Due to the great work of Dan Tardif and crew the building was able to be brought back into structural integrity. Dan went above and beyond what I expected. The building is now in better shape than when new… It was a real pleasure working with you and Knowles on this very difficult project and we are very pleased with the result.”

-E. Arthur Enderle III (Superintendent at WPCF)

Knowles Industrial Services Launches New Website

Knowles invites valued customers and new visitors alike to explore their new website which has been designed with a fresh new interface and more intuitive and simplified user experience. The new site features streamlined navigation and improved functionality throughout, allowing users to easily locate product information as well as access helpful resources like case studies and project details. Continue reading

Completion of Penstock Rehabilitation for Major Northeast Power Generation Firm

KnowlesGORHAM, MAINE, USA — February 24, 2015 – Knowles Industrial Services Corporation (KISC), a New England-based industry leader in concrete repair and masonry restoration, is proud to announce the completion of an in-house designed rehabilitation project involving two 5,500 sq. ft. penstocks. KISC served as the contractor for the project’s Owner, a wholesale power generator and marketer based in the Northeast United States.
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The Economical and Sustainable Advantages of Using Shotcrete

Worker SafetyOne of the driving factors in deciding construction materials and placement strategies has moved towards a desire for sustainability. The shotcrete method of applying concrete offers both sustainable and economical benefits. Dry-mix shotcrete is a way to apply concrete material to new or existing structures, and when properly applied by a professional, is a sound and durable option for a variety of projects. Using shotcrete allows the same composition as concrete, but a much lower water-cement ratio. Its high compressive strength, low absorption, low permeability, and resistance to weathering or chemicals make dry-mix shotcrete comparable, perhaps even superior, to conventional concrete applications.
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Knowles Industrial Featured in US Builders Review

Knowles Industrial Services, expert concrete contruction contractors, have been featured in the Summer 2013 Edition of the US Builders Review as an industry leader of restoration projects in the New England region. As a third-generation business with fifty years of experience our longevity has been essential to our success. Over the years we have “grown from repairing industrial stack and chimneys to fixing large-scale structures such as dams and parking garages.” We pride ourselves on having a strong core of employees that have been with us for many years. Together we strive to continue learning as technology within our industry evolves. Our goal, as skillful craftsmen, is to provide a trusting relationship that encourages our clients to return. To read our full article, see the images below or check out the Us Builders Review website for the digital edition.

Knowles Industrial

Knowles Industrial

Knowles Industrial

Knowles Industrial

Knowles Industrial Wins AGC Safety Awards

Knowles IndustrialKnowles Industrial Services is proud to announce that they are the winners of two AGC Safety Awards. Since 1924, Knowles has been a leader in specialty concrete repair and restoration projects in Maine, New England, and around the country. This third generation, family owned business delivers innovative methods to repair, protect, and strengthen concrete and masonry structures. It is their mission to provide 100% customer satisfaction to their clients, as well as remain committed to the safety and efficiency of their skilled workforce.
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Knowles Industrial Launches New Website for 2013

Today Knowles Industrial Services is proud to announce the unveiling of their new website. Since 1924, Knowles has been a leader in specialty repair and restoration projects around Maine, New England and around the country. A third generation family owned business, Knowles strives to provide 100% customer satisfaction with their skilled workforce, dedication to safety and efficiency, and now their fresh new website.

The new Knowles offers an enhanced user experience, allowing current and potential customers to learn more about the past projects Knowles has completed, as well as delve more in depth into the markets served.
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