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Yes, pervious concrete is very suitable in areas of heavy rainfall. Pervious concrete, when properly installed, should last and wear similar to ordinary concrete for most pedestrian and low-vehicular traffic areas. The wearing of the very top layer of cement will not affect the aggregate below.

I would say yes. You would want to pour it thicker tho. The voids in the slab will hold a lot of water. You'll be surprised. Now when it comes to driving on it, it can be done but you'll have to add more cement and I would use larger rock and probably have less void area and remember the 6 inches is a standard driveway thickness and with previous concrete I would pour it thicker. I would probably go up to 10 inches. I'm not a soil or cement guy just a diy guy that has played with this idea so take it for what it's worth. I would demo it in 12x12 forms until you got it the way you like it. I had a mix set up but didn't write it down so I have to start all over the same way. Walkway use pea pebble unless you never plan on walking on it with bare feet.

@@roshawnsims8390 We typically pour residential driveways and low volume parking lots at 5 1/2" to 6" thick (150 to 152.5 mm). However, this is usually done over an equally thick layer of crushed 3/4" (57) rock, with a heavy duty geotextile fabric spread on the subsoil. If the subsoil is particularly sandy or well-draining, then the rock layer can be much less. Good idea, to practice first!

Adding fibers and/ or mesh to pervious concrete can be beneficial. Just about any type of fiber or synthetic mesh is compatible, except notably, do not use metal in pervious concrete. Metal, whether it is rebar, wire mesh or steel fibers (except stainless) will get exposed to water in pervious concrete and rust, corrode and expand damaging the concrete and becoming ineffective. Basalt rebar, fiberglass and other composite or coated rebar can be used in pervious concrete. We have also used anodized aluminum for doweling with success so far. In regards to the effect that adding fibers or mesh will have on pervious concrete it is difficult to quantify. In general one would want to measure for a higher tensile ductility, but since there aren't even any ASTM or other approved compression strength tests for pervious concrete, any tests will need to be set up and documented very carefully. Anecdotally, I will say pervious concrete samples that we crush for physical strength tests that have fibers notably stay together much better past failure and do not tend to 'explode' as much as samples without fibers. So the right type, combination and dosage of fibers should translate into a pavement that does not crack as much or as noticeably.

Yes, pervious concrete and other permeable pavements are great at capturing water and returning it to our continuously diminishing groundwater storage. By keeping our groundwater levels up, we not only get to continue to rely on them for our water usage, but it also keeps the ground from sinking (subsidence) and further contributing to flooding potential. Unfortunately lately there has been more reports of devastating urban flooding in the U.S. and other parts of the world. According to this article from June of 2022, www.theguardian.com/environment/2022/jun/07/slow-water-urban-floods-drought-china-sponge-cities? : "Globally, urban flooding has become particularly acute as the land area covered by cities worldwide has doubled since 1992. Researchers from Johns Hopkins University calculated how impervious surfaces increase flooding: every time a city increases coverage of absorbent soil with roads, pavements or car parks by 1%, runoff boosts the annual flood magnitude in nearby waterways by 3.3%." And according to this article from way back in July 2005, www.ncbi.nlm.nih.gov/pmc/articles/PMC1257665/ : "Paving Paradise: The Peril of Impervious Surfaces In the United States alone, pavements and other impervious surfaces cover more than 43,000 square miles-an area nearly the size of Ohio-according to research published in the 15 June 2004 issue of Eos, the newsletter of the American Geophysical Union. According to the nonprofit Center for Watershed Protection, as much as 65% of the total impervious cover over America’s landscape consists of streets, parking lots, and driveways. Another big problem for urban areas is the flash flooding that can occur when heavy rains fall over a city, according to hydrometeorologist Matt Kelsch, an authority on urban flash flooding with The University Corporation for Atmospheric Research in Boulder. Since runoff from an acre of pavement is about 10-20 times greater than the runoff from an acre of grass, Kelsch says impervious surfaces can quickly trigger devastating floods that can produce a host of their own environmental health hazards."

Though there are no standardized ASTM or other compressive strength tests for Pervious Concrete, typically when it is installed properly in the field one would expect it to achieve around 2500 to 3000 psi (17 to 21 MPa) compressive strength. This is on the lower end of more traditional concrete, but more than adequate for most vehicular and other applications. However, if the pervious concrete mix was designed very optimally, 4000 psi (27.5 MPa) compressive strengths can be attained. Even higher strengths, 5000+ psi (34+ MPa) are attainable with Pervious Concrete utilizing very fine aggregates, but this tends to significantly reduce its permeability at much thickness. Determining a particular Pervious Concrete's proper water cement ratio (w/c) is tricky and is therefore we feel best finalized by visual confirmation using the descriptions in the video. The main reason for this is the amount of moisture in/ on the aggregate that is used. Inevitably this amount will vary within a pile of aggregate, throughout the course of a day, and from one day to the next. Just a small change in this water in the aggregate pile will make a significant difference in the water needed for the mix. For instance, the amount of water in an aggregate pile following a rain event can sometimes provide practically all the water that is needed for that mix. The types and amounts of admix used in the Pervious Concrete mix design will also have a huge impact on the water cement ratio. Because of this, we have designed mixes with below a .2 and above a .5 w/c, however most often we end up being around a .35 w/c. But please take the time to really dial in your own particular mix's optimal water cement ratio and keep an eye on your aggregate's water content!

Though there are no standardized ASTM or other compressive strength tests for Pervious Concrete, typically when it is installed properly in the field one would expect it to achieve around 2500 to 3000 psi (17 to 21 MPa) compressive strength. This is on the lower end of more traditional concrete, but more than adequate for most vehicular and other applications. However, if the pervious concrete mix was designed very optimally, 4000 psi (27.5 MPa) compressive strengths can be attained. Even higher strengths are attainable with Pervious Concrete utilizing very fine aggregates, but this tends to significantly reduce its permeability at much thickness.

For really strong pervious concrete, technically higher compressive strengths are attainable with very fine aggregates/ coarse sand. However, the permeability is significantly reduced using very fine aggregates at driveway thicknesses. So, unless you are going to utilize a two step process like with our PerkTop (perviousproducts.com/perktop/), about the finest aggregate you could use would be about 1/4" (6 mm) and possibly a little finer if the design is carefully implemented. Often asphalt plants stock this gradation of aggregate as a manufactured/ crushed rock, which would be fine. Pervious concrete mixes using 1/4" or 3/8" aggregates will provide more than adequate strength for 7000+ kg (15,500+ lbs) trucks. They should be poured at least 5 1/2" to 6" thick over several inches of crushed, coarse aggregate and if there is a lot of this type of traffic, then thicker pavements could be necessary. When engineers, architects and other specifiers reach out to us to see if our PerkTop is suitable for heavy vehicles like yours and fire trucks in particular, we like to reference this work put out by Timothy Lawrence and Monique Myers of the 'California Sea Grant College Program', titled 'Emergency Services and Stormwater Management': "California allows fire engines to have a single axle weight of 23,000 pounds on the steering axle (2 tires/steering axle) and 24,000 on the drive axle. Tandem axles can be up to 48,000 pounds and tridem axles up to 54,000 pounds. All fire engine drive axles have dual tires (4 total/axle), so each steering tire can support up to 13,500 pounds (54,000 ÷ 4). Determining the support capability of any surface is based on the displacement of the weight over the surface area in direct contact with the vehicle tires. The contact surface area can vary by tire size, brand and inflation pressure. An example of the weight distribution of a fire engine in psi for a tire commonly found on fire engines is the Goodyear G286 12R22.5. Inflated to 90 psi, the average surface area of tire contact is 95 in 2(613 cm2). The weight displacement for each tire, if the maximum allowable load on a steering axle is 12,500 pounds or 357.14 psi, gives a 7-fold safety factor for a typical pervious concrete pavement rated at 2,500 psi."

Please see our video, "How To Make Pervious Concrete" for mix design ratio and other info.

It very much depends on the type of gravel. However, in general with this high of a ratio one would have extremely high permeability and much lower strengths.

Hi, I admire your expertise and experience in this field. With the suggestions you've given, I can say you are very knowledgeable and respectable. I encounter numerous issues with this type of concrete, and I was hoping for your assistance with my research on it. Your kind and considerate response is highly appreciated. I look forward to your positive feedback.

Hey Steve, thanks for checking out our latest PerkTop pervious concrete installation! A couple of years ago we also installed a driveway around the corner at: 670 Stetson St. Moss Beach, CA 94038. And just down the road a bit a couple of months ago we installed a PerkTop driveway in tan color at: 608 Ruisseau Francais Ave. Half Moon Bay, CA 94019. A little further afield, we installed pervious concrete for significant portions of the large parking lot at the new Cadillac dealership in Colma, CA. Upcoming, at the start of the new year we will begin installing 57,000 square feet of pervious concrete for large portions of the new 'Veterans Memorial Parking Lot' in San Rafael, CA. We have installed countless other PerkTop projects in the San Francisco/ San Jose Bay Area. If you would like to check out any of those, let me know and I can provide a list accordingly. Thank you, Ryan

Pervious concrete has been installed successfully all over the U.S. and Canada for over 40 years. So it does survive some pretty heavy freeze/ thaw cycles. Pervious concrete needs to have the proper air entrainment and/ or other freeze/ thaw resistant attributes just like ordinary concrete. However in regards to the visible water flowing through the pavement getting trapped in it and freezing, this is not typically a problem because it still has room to expand, up and out of the pavement. This is perhaps similar as to why rain gutters with water in them don't typically get damaged during the winter months. That all being said, pervious concrete should be placed over a well-draining, typically crushed rock base. This will minimize the occurrence of water getting trapped in the pavement during a freeze/ thaw cycle as well as provide protection from frost heave as long as the crushed rock base is designed with the proper depth.

Sealing or adding adhesive to raveling, loose rock on the surface of pervious concrete will not do much to slowing this from occurring. However, raveling will typically stop about 6 months after the installation. If around this time the surface is aggressively brushed and vacuumed and/ or blown off, then applying a film-forming, high solids sealer, like an acrylic or polyurethane can help to minimize the typically small amount of further raveling that can still occur over the years. If the raveling is significant and the pavement is not considered acceptable and it needs to be replaced, then applying a 1/2" thick layer of PerkTop over it instead will permanently lock and solidify the surface. PerkTop will also provide a whole new aesthetic and cost much less than having to replace the entire pavement.

Yes, pervious concrete can have less strength than traditional concrete. However, with the use of admixes, careful mix design and proper installation in the field the strengths of pervious concrete can be close to and similar to traditional concrete pavement, which usually achieves from 2500 psi (17.2 MPa) to 4000 psi (27.5 MPa) compressive. Even without special admixes and a deep understanding of mix designs, pervious concrete as demonstrated in this video, typically will have way more than adequate strengths for most pedestrian and light vehicular applications. Concrete pavement most commonly fails because it cracks and becomes unsightly, which usually has little to do with its strength. One major contributor to concrete cracking is that concrete shrinks, but because pervious concrete tends to shrink considerably less than traditional concrete, it can crack less. Perhaps the most telling example of pervious concrete's more than adequate strength, is that its most common application in the U.S. has been for parking lots. Moving forward we are demonstrating it is even possible for pervious concrete to be stronger than typical concrete pavement. We are achieving compressive strengths sometimes well over 4000 psi with our very fine pervious concrete PerkTop & PerkGrout.

Yes, decorative stones, tile, glass, etc. can be embedded in PerkGrout as it is being placed. PerkGrout is similar to concrete, so the vast majority of weeds cannot grow through joints filled with it. Some very aggressive weeds like bermuda grass that spread by underground runners could make it through. In cases like this, it is recommended to treat the joints prior to installing PerkGrout or spreading a double layer of weed fabric in the bottom of the joints.

Yes, the cement for pervious concrete can be tinted a wide range of colors. With the use of white portland cement or other lighter colored cements, it can even be made to be white and in very light colors. However, because pervious concrete traditionally needs to be cured with plastic, this will discolor it and produce efflorescence, whitish appearance. Therefore we typically use a stain to produce the final color, which offsets the discoloration.

Unfortunately our geographic range for pervious concrete installations for now is limited to the west coast. Thank you for asking!

Taking the sand, fine aggregate, out of ordinary concrete is generally what produces pervious concrete. However, it is possible to add very small, controlled amounts of sand back to the pervious concrete mix. This may be advantageous to reduce the permeability somewhat and gain strength and durability in mixes containing particularly large coarse aggregate or possessing 'too much' voids.

A video detailing our results, with closeups and permeability shots, from a few different projects is one we have been wanting to produce for some time now. Hopefully we can get to it soon...

We have not tried making hollow blocks out of pervious concrete yet. I assume with vibration it could be done.

Yes, typically the cement used in pervious concrete is 'portland cement'. It can be any of the types of portland cement used in the U.S., Types I, II, III & V. However, other types of cement can also be used successfully in in pervious concrete. For instance, our PerkGrout product utilizes CSA (calcium sulfoaluminate) cement or 'rapid set'. The primary reason for its usage in this application is due to CSA cement's low shrinkage and therefore reduced cracking potential.

There is generally not an advantage to slowing down the curing process for pervious concrete. It appears the main key to successfully curing pervious concrete is maintaining the proper water content throughout the hydration process. So not allowing water to evaporate during its placement and locking the water in right away as soon as finishing is completed for each little section of the pavement. As a side note, one has to be extremely careful adding sugar to concrete as it doesn't take much to completely kill/ stop the concrete from curing and setting at all. So sugar in concrete has to be dosed extremely carefully to avoid problems.

Typically when pervious concrete is placed without other pavement draining onto it or dirt eroding on to it, it will not clog. If a lot of debris and dirt is allowed on to the pavement, it is possible that it can clog up. However, because pervious concrete often allows over 600"/ hour (4.2 mm/ second) of water to flow through it, even if it were to become over 95% clogged any rain event will still be readily absorbed by it. It if were to become more clogged than this because of erosion or the pervious concrete is being used as a drain collecting runoff from surrounding pavement, then much of the original permeability can be restored with pressure washing - blasting the pavement with concentrated water to flush out trapped dirt and debris.

PerkGrout can be purchased online perviousproducts.com/shop or for orders of 30 bags or more it can be shipped freight.

Though pervious concrete allows air and water through it does not allow light. It is not translucent in any way.

@@perviousproducts6648 Thank you so much

Yes, pervious concrete can be used as a base for many products, including resin bound.