What is Pervious Concrete | Pervious Concrete Problems | Pervious Concrete Advantages & Disadvantages
What is Pervious Concrete?
Pervious concrete, also known as porous concrete or permeable concrete, is a unique type of concrete with a high porosity that allows water from precipitation and other sources to pass directly through, decreasing runoff and permitting groundwater recharging.
It is a type of porous concrete composed of cement, water, coarse aggregate, and a trace of fine aggregate (sand). Pervious concrete generates a porous medium that allows for the passage of water from precipitation and other sources to the underlying soil.
Pervious concrete is composed primarily of coarse particles and contains little to no fine aggregates. After that, the concrete paste coats the aggregates and allows water to permeate the concrete slab.
Historically, pervious concrete has been utilized in parking lots, low-traffic areas, residential streets, pedestrian pathways, and greenhouses. It is a critical application for sustainable construction and one of the low-impact development approaches builders utilize to maintain water quality.
How Is Pervious Concrete Made?
Pervious concrete is a mixture of precisely measured amounts of water and cementitious ingredients that combine to make a paste that forms a thick covering around aggregate particle.
In comparison to traditional concrete, the mixture contains little or no sand, resulting in a high void percentage – between 15% and 25%.
How Is Pervious Concrete Installed?
Typically, pervious concrete is delivered to job sites by ready-mix trucks. To level the concrete, a vibratory screed is used, and the concrete is subsequently compacted with a large steel roller to strengthen its strength.
Due to the low water content of pervious concrete, the curing process is complicated: after placement, it is misted with water, covered with a plastic sheet, and maintained moist for at least 7 days to allow appropriate hydration. This enables pervious concrete to achieve the desired strength.
How Strong Is Pervious Concrete?
Pervious concrete typically has a strength of 600–2500 pounds per square inch (4.1–10.3 MPa), but can reach 4,000 psi (28 MPa).
It is possible to reach compressive strengths of 3000–4000 psi and flexural strengths of 500–600 psi with pervious concrete, which are comparable to conventional concrete.
Today’s pervious concrete mixes can be manufactured with less water, increasing strength and durability. Compressive strength is not standardized.
Additionally, improved placement techniques have resulted in more compact pavements that preserve point-to-point contact between all aggregates while maintaining the required void content.
How is the Maintenance of Pervious Concrete Handled?
Generally, the only maintenance required is to sweep, pressure wash, or vacuum the pavement on an as-needed basis to remove material that could clog the voids and prevent water penetration.
What Are the Benefits of Using Pervious Concrete?
Pervious Concrete Environmental Benefits
Stormwater runoff is a significant cause of water pollution: approximately 90% of surface pollutants are transported into bodies of water during the first 1.5 inches of rainfall.
Sediment, heavy metals, and hydrocarbons are the three primary contaminants found in urban runoff.
Vehicle oil spilling onto the pavement is one source of hydrocarbons in urban drainage. Another source of hydrocarbons, accounting for 90-95 percent of them, is the binder and sealer used in asphalt pavement.
When it comes to stormwater management, the EPA and municipalities have tight rules, and pervious concrete has emerged as a viable solution with numerous benefits.
Other key benefits include:
- Recharges groundwater directly
- Prevents “first flush” pollution
- Protects streams, watersheds, and ecosystems
- Reduces surface temperatures and heat island effects
- Provides a higher albedo surface reflectivity index (0.35 or greater)
- Eliminates the need for costly collection and detention systems
- Eliminates untreated storm water runoff!
Pervious Concrete Cost
Installing pervious concrete costs between $8 and $16 per square foot, whereas plain concrete costs between $4 and $8 per square foot. A pervious concrete driveway or parking lot may cost two to three times as much as a conventional concrete driveway.
This is partly because pervious concrete is typically built thicker — around 6 inches or more, compared to 4 inches for ordinary concrete — and further preparation of the concrete base for water infiltration is required. The materials themselves are comparable in price, but the preparation is what makes the difference.
Pervious Concrete Uses & Applications
Pervious concrete generates a porous medium that allows for the passage of water from precipitation and other sources to the underlying soil. This minimizes runoff from a site while also replenishing groundwater levels.
Pervious concrete is frequently used in sustainable building for sidewalks, parking lots, and greenhouses.
The US Environmental Protection Agency (EPA) recognizes the use of pervious concrete as a Best Management Practice for Stormwater because it provides pollutant management.
Drainage systems used to manage stormwater runoff are becoming increasingly challenging to construct, owing to their size and the associated costs of complying with stormwater rules.
By using pervious concrete for paved areas, runoff is reduced, which minimizes the requirement for stormwater retention ponds and the capacity necessary for storm sewers.
Enhance the sustainability and environmental friendliness of your construction projects.
Natural stormwater filtering by pervious concrete reduces the quantity of pollutants that enter streams and other bodies of water. This concrete acts as a rainwater retention basin, which helps regulate the area’s groundwater levels.
Another advantage of pervious concrete is that it mitigates the impact of construction on neighboring trees by allowing both water and air to reach the root systems.
Pervious Concrete Advantages and Disadvantages
Pervious Concrete Advantages
- Pervious concrete is more eco-friendly because it is devoid of any harmful chemicals which may otherwise impact the environment, at least to a lesser extent than traditional concrete.
- Pervious concrete is a paving material that encourages the passage of water through the surface of the pavement. The water is then absorbed into the ground naturally, preventing water from becoming stagnant and pooling on the surface of the street. Can be used for roads, walkways, parking lots, basement floors, and more
- Pervious concrete also has the potential to save money and energy by reducing the heating and cooling costs in homes and buildings. Has the potential to save money and energy Is more environmentally friendly
- According to the Center for Watershed Protection, typical curbs, gutters, storm drain inlets, piping, and retention basins can cost between two and three times as much as low-impact water runoff management options such as pervious concrete. Pervious concrete projects often have lower installation costs since they do not require storm sewer connections, which eliminates the cost of underground piping and storm drain installation. Grading standards for the pavement are also decreased, as the parking space is not required to slope toward storm drains.
- It has the potential to improve drinking water quality
- Because a pervious concrete pavement serves as a stormwater management system, no extra land is required for the installation of big retention ponds and other water-retention and filtering systems. This enables developers and property owners to make better use of available land and maximize their investment’s return.
Pervious Concrete Disadvantages
- The disadvantages of pervious concrete are the additional time it takes to cure before it can be used and the increased time it takes to construct pervious concrete structures.
- Abrasion and raveling of aggregate particles can be a concern with pervious concrete due to the rougher surface texture and open structure, particularly if snowplows are used to clean sidewalks. Raveling on the surface of new pervious concrete can occur when loosely bonded rocks pop out under traffic stresses.
- Another disadvantage of pervious concrete is cost. A pervious concrete driveway or parking lot may cost two to three times as much as a conventional concrete driveway.
Pervious Concrete Problems
Generally, problems with pervious concrete mixtures are connected to the water content, the proportions of the mixture, or the dosing of admixtures. C
Certain material-related difficulties can be resolved by altering building procedures, but this article will focus only on suggested improvements from the standpoint of the concrete supplier.
Clogging problems are mainly an issue of design. If a natural area with grass or exposed soil is allowed to drain stormwater across a pervious concrete pavement, fine material can be introduced into the system causing localized clogging.
Vegetative matter can collect on the surface of the pervious concrete causing some clogging, but routine sweeping or vacuuming will restore porosity. Studies have been conducted that indicate pressure washing will restore the porosity of clogged pervious concrete to nearly new conditions.
While pervious concrete offers numerous beneficial features, a failure installation is feasible without an expert contractor and ready-mix supplier. Pervious concrete is complex to correctly install and finish, and the right mix, compaction, and curing are key to success.
Another problem is that pervious concrete pavement systems should be used only where the underlying soil percolates readily or where a subbase drainage system is present.
Contractors must be knowledgeable with pervious concrete, as it is not the same as conventional concrete.
Abrasion and raveling of aggregate particles can be a problem with pervious concrete due to the rougher surface texture and open structure, particularly if snowplows are used to clean sidewalks.
Raveling on the surface of new pervious concrete can occur when loosely bonded rocks pop out under traffic stresses.