The United States Environmental Protection Agency estimates that there are approximately 26 million manholes in the U.S. The majority of these structures are precast concrete manholes, cast in place concrete manholes and concrete block manholes, however, clay fired brick was a popular material used in the construction of manholes prior to the 1950s.
A quick history lesson on precast concrete manholes
In the post-World War II suburbia, young families in search of homes created a housing boom. Along with new homes, the rapid growth of communities began to make infrastructure a priority. Schools, community centers, churches, supermarkets, office buildings, industrial plants and shopping centers all required proper water and wastewater systems.
In 1954, the Precast Concrete Institute was formed and precast manhole structures became the most cost-effective method for manhole construction. The high cost of labor and installation for brick manholes quickly made them a thing of the past. Not entirely obsolete, brick manholes were still installed in remote locations and industrial sewer systems where the discharge is highly corrosive.
An aging infrastructure leads to manhole rehabilitation priorities
For discussion purposes, let’s say that 1/3 of all manholes in the U.S. are made from clay fired brick prior to the 1950s. That is roughly 9 million brick manholes that range in age from 60 to 100 years old. In the nation’s oldest municipal areas, these structures likely exceed 100 years old.
The most common problems confronting precast manholes are sewer system inflow and infiltration. Clean groundwater infiltration must be processed at the wastewater treatment plant and corrosive structure deterioration compounds the problem.
Brick manholes have similar issues, with one significant exception. Clay fired brick itself is mostly unaffected by corrosive sewer processes that detrimentally affect concrete structures. Typical clay used in common brick manhole construction consists of silica and alumina in the majority, both of which are highly corrosion resistant. The Portland cement mortar joint used to anchor the bricks in place, however, is susceptible to the corrosive atmosphere. As a result, the most common rehabilitation issue found in brick manholes is missing mortar joints. This leads to structural issues that include missing bricks, which facilitates an easy path for groundwater infiltration.
OBIC manhole rehabilitation stops infiltration
OBIC’s Armor System, consisting of OBIC 1000 and OBIC Guard 1306, is the ideal solution for brick manhole rehabilitation.
The polyurethane OBIC Guard 1306 is spray applied to the first layer of OBIC 1000 to provide a level and smooth surface on the brick substrate, where it expands by six times. This expansion allows it to penetrate deep into the mortar joint voids where it anchors the brick, fills the empty space and effectively blocks infiltration. The top coat of OBIC Armor 1000 is then applied to seal the monolithic system and prevent groundwater infiltration. This protects the manhole from future corrosion.
Unlike OBIC’s unique manhole rehabilitation lining system, alternative products will utilize cement to fill the mortar joints. Applied either by trowel application or spraying, these products never achieve the same level of penetration as OBIC’s lining system.
Manhole rehabilitation that stands the test of time
Over the years, OBIC installers have rehabilitated thousands of brick manholes. Some of our favorite stories come from our European installers. They have been faced with rehabilitating ancient structures that are perhaps hundreds of years old. Although the lime-based mortar is long gone on these structures, the meticulous, almost artistic like fitting and construction work produced manholes that are still functional and structurally sound. With the OBIC lining system and proper maintenance, these structures can continue to function for another 100 years.
Thousands of configurations all with one solution
There are thousands of different configurations, sizes, shapes and materials of construction when it comes to manhole rehabilitation. That is why OBIC products were designed with the understanding that no two jobs are the same.
Every product that OBIC offers is backed by our commitment to providing high quality, cost-effective water and wastewater rehabilitation solutions. Our products are backed by a team of chemists who employ rigorous testing that ensures consistency and quality. Additionally, third-party testing has proven that OBIC products are physically stronger than many products available on the market.