P3 Polymers uses next generation polymer science to solve centuries old problems. We design and manufacture cost-effective, environmentally friendly, and long-lasting polymer concrete structures to modernize our crumbling infrastructure and eliminate the need for costly maintenance and rehabilitation.

The threats to Concrete Manholes

Biogenic Sulfide Corrosion, also referred to more broadly as Microbial Induced Corrosion (MIC), is likely the most severe threat to concrete manholes. It is caused by certain bacteria that thrive in sewer lines and manholes. This bacteria feeds on the untreated sewage and produces hydrogen sulfide gas as a byproduct. The hydrogen sulfide gas is what causes the characteristic rotten egg smell that often emanates from manholes. This gas reacts with moisture inside the manhole to form sulfuric acid, which steadily corrodes the concrete surface.

It is estimated that Biogenic Sulfide Corrosion causes the average concrete manhole to lose over an inch and a half of wall thickness from corrosion over the course of one decade. The United States spends $14 billion a year combatting the effects of Biogenic Sulfide Corrosion.

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Sulfate attack occurs when sulfate ions from soil or groundwater penetrate concrete and react with calcium compounds in the mix, resulting in the formation of gypsum crystals. These crystals grow and expand over time, straining the surrounding concrete and ultimately resulting in a network of cracks.

Sulfate Attack is especially dangerous in manholes, as the corrosion begins on the outside of the manhole, which is not visible. Sulfate Attack can cause severe cracking, spalling, and surface deterioration, that might remain undetected even with routine inspection until it results in massive infiltration issues or catastrophic structural failure.

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Ion penetration has two different methods of damaging a concrete manhole depending on which ions are involved. The most concerning type is chloride ion penetration. Chloride ions are prevalent in coastal regions as well as anywhere that deicing salts. The chloride ions easily penetrate the porous concrete and begin rusting the steel rebar. Rust, or iron oxide, is less dense than steel and begins pushing outward on the surrounding concrete as it forms. This ultimately leads to spalling and cracking which allows for infiltration and inflow issues as well as the possibility of structural failure.

Calcium and magnesium ions are also a threat to manholes. They are less likely to interact directly with the rebar, and more prone to reacting with the cement paste. This reaction weakens the binding agent in the concrete, thereby reducing strength, and also expands as it does so, causing similar issues as sulfate attack. However, this process is slower than sulfate attack or chloride ion penetration, so it is unlikely to be the primary concern.

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Freeze-thaw is a common threat to concrete structures exposed to freeze-thaw cycles, such as manholes located in areas with a cold climate. When water freezes inside the pores of concrete, it expands and exerts pressure on the surrounding material. When the ice thaws, the pressure is released, and the concrete may crack or spall. The impacts of freeze thaw are obvious on the roadways in the form of potholes, but the effects on the manholes just below the street are less likely to be seen.

Even in areas with a relatively shallow frost line of around 36”, the cone of the manhole, which bears much of the surface load, will be significantly impacted.

If a manhole has cracked even slightly from any of the before mentioned threats, it will be susceptible to tree root intrusion. Tree roots will actively seek out the manhole as a source of water and nutrients. The roots are able to enter though very small cracks and grow overtime causing further cracking, joint separation, and even collapse of the manhole. In addition, the presence of tree roots can create channels for water and other contaminants to enter the manhole, leading to further deterioration.

If left unaddressed, the impact of tree root intrusion can be severe. The roots can result in serious blockages, structural damage, reduced flow capacity, and contamination of the surrounding soil and groundwater.

Use our Concrete Manhole Lifespan Calculator to estimate how long a manhole can withstand these threats, and how much it will cost to keep operational.

The Polymer Concrete Solution

Polymer Concrete Manholes and Wet Wells have excellent resistance to all chemical and physical threats. P3 Polymers uses a custom formulated vinyl ester resin and a carefully designed blend of inert mineral fillers so that our polymer concrete is as resilient as possible. We back all of this up with our 50-year corrosion warranty.

The vinyl ester resin we use has a significantly higher resistance to chemical attack than the industry standard polyester, and our aggregate blend features grains with the optimal size and shape for an interlocking, high-strength matrix. Our polymer concrete is completely non-porous to eliminate the risks of freeze-thaw or ion penetration, and the chemical resistance of the resin entirely prevents biogenic sulfide corrosion.

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Our unique resin formula and aggregate blend gives our polymer concrete unrivaled strength and durability. In compression, our polymer concrete exceeds 12,000 psi. That's roughly twice the strength of a high-quality Portland cement concrete. We also achieve upwards of 4,000 psi in flexural strength and 1,500 psi in tensile strength.

Unlike other polymer concrete manufacturers, the styrene-free vinyl ester resin we use also allows us to use and fully benefit from steel reinforcement. We face no bonding or cracking issues from the steel that would force us to use FRP reinforcement or significantly increase our wall thickness. That means we can build the the well established standards of ASTM C478.

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The polymer concrete P3 uses has a very similar density as standard Portland cement concrete. However, the material's high strength and steel reinforcement makes it possible to manufacture structures with much thinner walls, while still remaining far stronger than standard concrete structures.

That means contractors are able to use lighter equipment, install faster, and have fewer safety concerns.

We are also able to provide materials, expertise, and assistance for cast-in-place operations. That opens up significant flexibility during the design stage and allows for doghouse manholes or even complicated box structures.

Nearly all vinyl ester or polyester thermosetting resins use styrene monomer, or a styrene derivative such as vinyl toluene, as a reactive diluent. The styrene monomer in the resin improves the viscosity, lowers the reaction temperature, and leads to better curing all together. Without those improvements, polymer concrete production would be nearly impossible.

However, styrene carries with it some significant issues and concerns, and for that reason, P3 Polymers only uses a custom formulated vinyl ester resin that contains no styrene or vinyl toluene.

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