In developed areas, underground stormwater systems are sized to channels large discharges in case of heavy rain to nearby bodies of water. The material that makes up the components of these systems must withstand not only the volumes of water flowing inside them, but extreme loading conditions on the outside as well. And in both cases, they much stand up to corrosive elements. Precast concrete steps up to these challenges. Stormwater treatment systems consist of manholes, catch basins and pipes structures that are manufactured by precast concrete plants every day and are readily available throughout North America.
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Superior Strength and Durability
The strength of precast concrete gradually increases over time. Other materials can deteriorate, experiencing creep and stress relaxation, lose strength and⁄or deflect over time. The load–carrying capacity of precast concrete is derived from its own structural qualities and does not rely on the strength or quality of the surrounding backfill materials. Studies have shown that precast concrete products can provide a service life in excess of 100 years. In severe conditions, additional design options are available to extend the life of precast concrete products.
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High Degree of Quality Control
With a specific gravity of 2.40, precast concrete on–site wastewater tanks resist buoyant forces better than tanks made from other materials. In comparison, fiberglass has a specific gravity of 1.86, while high-density polyethylene (HDPE) has a specific gravity of 0.97. Additionally labor–intensive and time–consuming on–site preparation is often required to anchor structures made from more buoyant materials.
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Ease of Installation
Because precast concrete products typically are produced in a controlled plant environment, they exhibit high quality and uniformity. Problems affecting quality typically found on a job site – temperature, curing conditions, poor craftsmanship and material quality – are nearly eliminated in plant environment. Precast concrete products manufactured in a quality–controlled environment and installed with high–quality sealants offer a superior solution to watertightness requirements. Standard watertight sealants are specially formulated to adhere to precast concrete, making watertight multiple–seam precast concrete structures possible.
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Reduced Weather Dependency
Setting precast concrete structures into place is easier because they do not require special rigging (such as fabric slings) to avoid structural damage. Other materials, such as fiberglass, can suffer structural damage during compaction. In contrast, precast concrete is less susceptible to vibratory damage while the surrounding soil is backfilled. Consequently, backfilling operations can usually proceed much faster around precast concrete structures.
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Resists Buoyancy
Precast concrete increases efficiency because weather will not delay production. In addition, weather conditions at the job site do not significantly affect the schedule. Conversely, forming and placing of concrete in cast–in–place applications can cause significant delays due to poor weather.
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Corrosion Resistant
Precast concrete is resistant to most corrosive substances. While no material is completely immune to chemical attack, the mix designs used to produce precast concrete can be adjusted to help withstand anticipated corrosive agents. Materials such as steel and other metals quickly deteriorate in the presence of corrosive agents, some in the presence of water alone. To better protect reinforcement from corrosion, the precast concrete strength should be designed to 4,000 psi or more.
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Enviromentally Friendly
Besides water, concrete is most used material on earth. It is nontoxic and environmentally safe. As environmental laws heighten, especially those that prohibit pollutant discharge into rivers and lakes, precast concrete is additionally beneficial because it is made of natural materials. Precast concrete products are buried throughout the world as part of the stormwater treatment systems of nearly every modern city but do not themselves contribute to poor water quality.
Precast concrete is the choice material for products used in stormwater treatment systems. Precast structures are modular, can fit any design situation, are produced in a quality–controlled environment and are ready to install immediately upon arrival at the job site. Precast stormwater treatment components are easily produced to be watertight, durable during storage and transportation, easy to install, less vulnerable than competing products to damage during backfill, and are environmentally safe during operation.
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