Why Concrete Fails and How to Restore It
Concrete is and has been one of if not the most widely used building materials in world history, from the Romans to modern-day and well into the future. It is a mixture of cement, water, and aggregate with many positive attributes. It is durable and resilient, can be made to be decorative, and is extremely strong when used in a compressive application. Sounds like it is the perfect construction material, and for the most part, it is. Where concrete has a weakness is in its tensile strength. Tensile strength is considered its ability to stretch, and concrete does not stretch. If it is stretched, it will fail and crack. To combat this drawback, steel rebar is used to reinforce the concrete. The rebar is added to the concrete to act much like a skeletal reinforcement of the structure, thereby adding additional strength to the construction.
Rebar is necessary to strengthen a concrete structure, but if not installed properly, it can be the Achilles’ heel of the structure. Any steel reinforcement added to the concrete, no matter what thickness, should be encapsulated by a minimum of 2” of concrete. This 2” envelope will help keep moisture from penetrating to the rebar, which over time if allowed, will result in the deterioration of the rebar and therefore the concrete itself. Many times, the failure of structural concrete is due to the improper installation of the rebar cage. If the rebar is too close to the outside edges of the concrete, it is almost inevitable that the moisture will penetrate to the rebar, which will begin the rusting process. As the rebar rusts, it expands, exerting pressures as high as 36,000 P.S.I., which in most cases is somewhere between 6 and 10 times the tensile strength of the concrete itself.
As in the picture of an underground vault used to house underground wires, you can see how the rebar has rusted and the pressure has forced the concrete to crack, separate, and fall to the vault floor. This failure could cause extensive damage to the extremely high voltage wires and or fiber optic lines being housed within the vault. If these lines are damaged, your area of town may experience electrical outages and or loss of communications for several days as expensive repairs or replacements are made.
When vaults reach this level of decay, they can still be repaired and should be. These vaults are a danger to the systems within them, as well as the structures above them. Sidewalks, roads, walls, and other structures are in danger if the walls and ceiling of the vaults completely fail. A vault could implode, allowing the materials above to fall into the newly created void.
How do we make lasting repairs on such damaged rebar and concrete structures? We do so with the use of new innovative products that are proprietary to JES Supply Company based in Las Vegas. JES Supply has identified the problem and developed a system to combat the rusting rebar issue, as well as the tensile strength of the concrete walls and ceilings.
What is the JES Supply Vault Repair System?
It is a combination of state-of-the-art materials and installation procedures of those materials. To begin, we remove all loose concrete from the vault and thoroughly clean the rusted rebar with wire wheels and brushes. Once cleaned, the rebar and concrete is coated with our JES Primer 100 system, which is a two-part Primer that encapsulates the rebar, making it impossible for moisture and oxygen to penetrate the surface of the rebar. This will stop any further deterioration of the rebar.
Our Primer will wick into the pores of the concrete and as it cures, it will expand, creating an extremely strong mechanical bond between the Primer and the concrete. This bond has proven over time to be stronger than the concrete itself. Our next installation is of our quick curing base material, FLEXKIT 5, which is exclusive to JES Supply Company. FLEXKIT 5 is applied to the primed concrete anywhere the concrete was removed, further encapsulating the rebar, giving an extra layer of protection from moisture, as well as filling in all voids where the broken or removed concrete was removed. FLEXKIT 5 is applied to the JES Prime 100; together they bond on a molecular level, creating a bond which in every test was to concrete failure. FLEXKIT 5 will cure up to compression strengths of as high as 12,000 P.S.I., giving an extremely strong wall and or ceiling. This high P.S.I. value could eliminate the need for rebar altogether. We have additives that will allow our product to cure in as little as 15 minutes for cold weather operations.
If you would like further information on our materials and system, please contact JES Supply Company.
Author: Ed McSwain
Ed has been involved in the underground utilities industry for the past 41 years, 28 years as a General Contractor specializing in the installation of all underground systems throughout the Southwest United States. In the last 8 years, Mr. McSwain has ventured into the concrete coatings industry, supplying contractors with products used to repair and preserve concrete both above and below ground.