Proper Equipment for Pervious

What is proper equipment for placing pervious concrete? I you asked me that question 25 years ago I would have said a 2x4 screed. The first time I worked with pervious, in the spring of ’86, that’s what I used; a 2x4 magnesium screed. In fact, we would routinely hand rod pervious, using a hand float as a spacer to strike high and then follow with a static roller for compaction. We quickly learned that a truss screed was a much easier method for larger placements, but we still did our tie-ins by hand with a spreader, a large flat rake. Some jobs were so chopped up, especially when working around trees or on varying slopes, we would use a spreader on the whole job and follow with just a narrow cross-roller.


That is pretty much how it was done until about eight years ago. There were some other contractors trying plate compactors, but as it required placing a really dry mix, and I have always felt that more moisture was needed not less, I stayed away from that technique. Around eight years ago, I started working with a Bunyan roller screed and that became my new normal. David Mitchell w/ Bunyan had been trying to get me to try his screed for years but I had a pretty narrow mind as equipment was concerned. My hesitation to try the roller screed can be blamed on two things; 1) the type of mixes we working with; drier, pound into place mixes and 2) my idea that there was only one “best way” to do things.

As admixture companies began developing new products for pervious and making the mix more fluid; the options for equipment choices grew and I soon realized that there are many “best ways”. To explain what I mean, consider the debate of “prescriptive vs. performance”.

At its core, the idea behind “prescriptive” is that there is one “best way” to accomplish the goal. The problem with this idea is that this is not necessarily true. In fact, we spend a lot of time trying to get designers to go to performance based specifications because we know we can reach the goal more often without prescriptive requirements limiting our options. The same is true with equipment for pervious. When we “prescribe” the equipment, we lose focus on performance and we fall into the same trap that prescriptive designers find themselves. We say “they want their cake and eat it too”. Well now we know how they feel. It’s a tough choice, but we have to choose whether we want to control how to do it, or else set the standard for performance. And speaking from experience, the installers will figure out how to get it done with their equipment if we give them clear defined goals.

Today, there are even more equipment choices out there. Lura makes a lighter aluminum roller screed, Somero makes a pervious concrete head for the laser screed, and who knows what tomorrow will bring concerning pervious equipment, mixes, admixtures, uses, etc. By limiting options we can literally hold pervious concrete technology back, but by focusing on performance, we can allow pervious concrete technology to continue to advance and become an even better product.

So what is proper equipment for placing pervious concrete? Today, I say whatever gets the job done.

Auburn University Continuing Education

The first Auburn University Continuing Education class, “Design for Pervious Concrete”, has been scheduled for July 15, 2011 in Atlanta at the Georgia Association of Water Professionals. The program description is as follows:

This one-day program will provide participants a detailed understanding of pervious concrete stormwater systems and its use as a low impact paving alternative. It will discuss issues affecting successful design with pervious concrete, including mix design, sizing, hydrology, siting, site preparation and post placement landscaping, layout, certain aspects of placement execution, and long term care and maintenance. The course includes two workshops; in which the participants form teams and design and specify a pervious concrete stormwater system. This course should be of direct interest to those in the Civil Engineering and Landscape Architecture fields, including county engineers, city engineers, public works officials, transportation engineers, DOT personnel, consultants, and all those with responsibilities for stormwater design and control.

The course will soon be offered around the country.

For those of us who are promoters of pervious concrete, this course is a "must attend" as it is one of the required courses for “Pervious Concrete Professional” designation, a credential that identifies someone who has advanced knowledge of all aspects of pervious concrete. Design for Pervious Concrete was developed through a partnership with NPCPA and Auburn University and will be offered in various cities throughout the country. Each class will have instructors provided by both Auburn and NPCPA. Recently I sent out a request for instructors and received good response, but more are needed. If you have experience in teaching pervious concrete programs and would like to help, please contact me.