World of Concrete 2011 - Pervious Concrete Student Competition

The pervious concrete student competition will take place this year at WOC in an effort to provide quality pervious concrete for the Pave ll Save Habitat for Humanity Service Learning Program while maintaining continuity with pervious concrete placements. Teams are challenged to create a pervious concrete mix design and submit a specimen for judging which is aesthetically pleasing while maximizing durability and maintaining good permeability. The mixes will incorporate products manufactured by Sponsors of the Pave ll Save program and the winning mix will be used for pervious concrete driveways and sidewalks to upwards of 600 homes throughout the service year.

Prizes: Three prize categories are offered, Aesthetic, Durability, and Permeability. The prizes for each category are independent of each other and teams may win in one or more categories. First, second, and third place entries in all categories will be awarded a certificate of recognition, will be recognized in Concrete Construction magazine if space allows, and will be recognized on NPCPA's website. For each category, the first place team will receive a $250 award, and the second place team will receive $100 award.

In addition, a Grand Prize will be awarded to the team with the best overall balance of all three categories. The winning mix design will be used on the Pave ll Save service learning program for one (1) year. The Grand Prize team will receive a $250 award, a one year NPCPA membership and be credited for the Habitat for Humanity mix design in all NPCPA media relations. Each school shall be eligible for only one prize per category.

Each entry consists of one specimen sized to fit in a medium USPS flat rate shipping box. Attendance at WOC is not required.

For more information contact:
NPCPA
125 TownPark Drive, Suite 300
Kennesaw, GA 30144
404.835.7190
404.835.7199 Fax
info@npcpa.org

***ADDED 11/18/2010***
Forta has grabbed the Fiber Sponsorship spot. Forta did a test on tuesday with their macro-fiber using 2.5 lbs/cu yd of the 1 ½” length. They reported that it mixed extremely well and uniformly, and would love to see several of the student groups play with even higher dosages and/or longer lengths.

What's your Watershed?

Can you name your watershed? 

We all live in one; an area that drains to a common waterway, such as a stream, lake, or even the ocean.  Perhaps you're like me and never really thought about it, but why is it we all know our state, our city, and our street, and yet, we have no idea what the name of our watershed is.  

What would you think of someone that didn't know the name of the town they lived in?  You would probably question their mental state.   A better question is, what would it say as to their citizenship?  I've been thinking a lot about this lately and, because we promote low impact development (pervious concrete), I think our watershed should be known.  So here it is, my new address:

Dale Fisher, NPCPA, 125 TownPark Drive, Suite 300, Kennesaw, GA 30144, Etowah Watershed 03150104

Click here to find your watershed.

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DNR Loves Pervious Concrete!

Carroll County will be required to pay more than $100,000 to the Environmental Protection Division of the Georgia Department of Natural Resources.  The EPD is requiring  the County to install pervious concrete along new road. 


Read more: Times-Georgian - County to pay EPD more than $100,000 in fines.http://www.times-georgian.com/view/full_story/9775501/article-County-to-pay-EPD-more-than--100-000-in-fines-?instance=TG_home_story_offset

Mix Challenge

Good answers all!  First increase the stone to 27 CF (dry rodded unit weight x 27) to correct the yield, then, if needed, remove cement to increase voids. 

Mix Challenge 2

Here are the poll results of the Mix Design Challenge:

16% said Mix will perform as designed...
33% said Yield will increase...
33% said Yield will decrease...
16% said Mix will appear wet...
50% said Mix will appear dry...

As you can see, the majority thinks that the mix will not perform as designed and they are correct, but as for what will happen to the mix seems to be a guess.  50% of those polled think the mix will be dry and, as for the yield, half think it will increase and half think it will decrease. 

The correct answers are: The mix will appear wet and the yield will decrease.

I'll explain why.....

In our example, the gradation changed without the producer's knowledge.  So what started as yard of pervious concrete with 2,700 lbs of aggregate became .95 yards of pervious concrete with 2,565 lbs of #89 limestone aggregate and 135 lbs of sand (this explains why the yield will decrease).  The mix is batched with 600 pounds of cement which translates to 600 lbs per .95CY or 632 lbs per CY.  It has 21 gallons of water (175 lbs) per .95CY or 22 gallons per CY.  The water/cement ratio stays the same but the sand will increase the paste volume from .22% to .26%.  The voids will decrease to 15% and, seeming to seal easily, "jelled" spots will appear and make the the mix look as if it is to wet, and indeed, if any water is added to the truck, it may seal completely (these "jelled" spots are a good indicator that there are unplanned fines in the mix).

Now here's the next challenge.  How do you fix it?

Look at this week's Poll and try to pick the right answer or answers.

Mix Challenge

Consider an example of a pervious concrete project using a #89 crushed limestone aggregate with a specific gravity of 2.70 and a dry rodded unit weight of 100 lbs/CF. The mix is designed and produced with 2,700 lbs of stone, 600 pounds of cement and 21 gallons of water (175 lbs). This mix has a cement/aggregate ratio of .22 with 22% paste by volume (water/cement ratio of .29). Admixtures are used to control hydration and improve workability and so the mix is easily discharged from the truck and easily compacted due to its "fluid" nature.

Now here comes the challenge....what would happen if we threw in 5 lbs/CF of sand (into the stone at the quary) without the producer's knowledge? In other words, what if the gradation changed in this way during the course of the project?

Look at this week's Poll and try to pick the right answer or answers.
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An Old Dog Learns a New Trick

For years I have been asked about fibers for pervious concrete and I have always answered the same. “No comment”. It’s not that I didn’t think fibers were of any benefit, it’s just that I really didn’t have a strong opinion either way. I’ve placed projects with fiber and I’ve placed projects without fiber, and both have performed well. I’ve read literature that says fibers help in this or that way, but I’ve never been in a situation that I could tell hands down that fibers made pervious concrete better. Not until now.

Last year we placed a pervious concrete pavement for Thomas Concrete in Atlanta, Ga. and I was asked by Forta to try fibers in the mix. At the time, I was just comparing the difference in the ease of placement, with or without fibers. The placement went as easily with fibers and that was the end of the story.

Later, after the curing plastic was removed, it was decided by Thomas not to saw any joints and “let’s see what it’ll do”. The slab is 60’x30’ with a nasty dog-leg around a utility pole. I was pretty sure that we would get one crack down the middle with a couple of cracks across, but I was positive that we would get one off the dog-leg.  And then.......none....., not one crack. A year and a half later and still not one crack.

I think these fibers work after all!

If you have had any similar experiences, please let me know.

Symposium on Pervious Concrete

 Papers are invited for a Symposium on Pervious Concrete to be held Sunday, December 4, 2011. Sponsored by ASTM Committee C09 on Concrete and Concrete Aggregates, the symposium will be held at the Tampa Marriott Waterside in Tampa, Florida, in conjunction with the December 4-7 standards development meetings of Committee C09.

For more info go to:
http://www.astm.org/SYMPOSIA/filtrexx40.cgi?+-P+EVENT_ID+1822+/usr6/htdocs/astm.org/SYMPOSIA/callforpapers.frm

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NPCPA - Why Now?

The question of how NPCPA will function without duplicating the efforts of existing organizations has been asked by many in our industry. It is a great question and it really focuses on not only the "how?", but also the "why?" as well as the "why now?".

I agree that our industry organizations have been instrumental in the development and promotion of pervious concrete for the better part of this last decade. Nine years ago, ACI formed committee 522, which has produced both a Report and Specifications for pervious concrete. Five years ago, NRMCA adopted the role of trainer with the development of the craftsman certification program and the Association's National Resource Directors have taken the lead in national promotion through the National Accounts Program. Three years ago, ASTM formed the pervious concrete sub-committee for writing pervious concrete standards. In addition, PCA and ASCC, as well as many regional, state and local associations, groups, and individuals have supported and contributed their resources to promotion of pervious concrete.

It is undeniable that the cement/concrete industry is proud and supportive of its child, the "green sheep of the family". And coming from someone who has been involved with pervious concrete for more than 25 years, we have done an incredible job taking pervious concrete to its current level. We in the cement/concrete industry have always been aware of the financial benefits to our industry (e.g. cement companies sell more cement, concrete producers sell more concrete, concrete contractors install more concrete) so we have a vested interest in pervious concrete as a result. And, perhaps because of this interest, coupled with pervious concrete being non-proprietary, we as an industry feel that we "own" pervious concrete. However, I propose that we change this thinking.

Now, before there is a call to burn me at the stake as a heretic, please let me explain.

Through the efforts of those previously mentioned, we have long touted the environmental and financial benefits of pervious concrete to regulators, specifiers, designers, and owners. In fact, we have marketed pervious concrete as the pavement of choice for true sustainability and the market has responded, not only by accepting pervious concrete, but by producing “champions” that actively promote and campaign for “our product”. This begs the following questions:

1. Do the purchasers (or owners) of pervious concrete pavements have a vested interest in pervious concrete, as they are concerned with product quality as well as life cycle and maintenance?
2. Do the designers and specifiers of pervious concrete projects have a vested interest in pervious concrete, considering their reputation may be affected by the product’s success, or lack thereof?
3. Do the regulators who pass ordnances requiring use of pervious concrete have a vested interest in pervious concrete?

If, like me, you answer yes to these questions, you realize that pervious concrete really “belongs” to everyone that has this vested interest. And when we as an industry come to that realization and capitalize on it, just imagine what we can accomplish in promoting pervious concrete.

The designers and specifiers that have a voice in NPCPA will “champion” pervious concrete to their clients and among their industry leaders through groups like ASCE, AIA, ASLA and USGBC. The owners that have a voice in NPCPA will “champion” pervious concrete to their industry leaders through groups like RILA and NEWH. The regulators who have a voice in NPCPA will “champion” pervious concrete among their communities and to their peers through groups like APWA and AWSPS.

Any clear thinking business person would agree that this is a worthy aspiration. However, previously, we did not have an adequate vehicle to accomplish this goal. PCA, as a cement association, has no allowance for these “voices”. NRMCA, as the voice of ready mix producers, is also not fitted for these groups. Likewise, ASCC (contractors) and ACPA do not provide a place for association. In fact, we as an industry, primarily, only associate with our market “across the table”. As you may see, we have a missing piece in the pervious concrete puzzle.

NPCPA is uniquely shaped to fit in this puzzle, allowing us to develop and support champions outside our industry. Working alongside and in support of ACI, ACPA, ASCC, PCA, and NRMCA, NPCPA fills the gaps in our collective efforts in advancing pervious concrete. NPCPA provides a venue for interchange to all those vested in pervious concrete. As founding members of NPCPA, our existing industry associations will sit on the same side of the table with outside industry groups that are turning to pervious concrete to meet their sustainable goals.

Many today feel that the economy is on the upswing and will continue to improve. Now is the time to build these relationships, before the market gears up and is too busy to change its status quo. It is my hope that all those in the concrete industry will join NPCPA and will help build lasting relationships with the users of pervious concrete.

Pervious Concrete Champions

Shoreview Public Works Director Mark Maloney named CEAM Municipal Engineer of the Year

Posted by Release in Public Works

At the City Engineers Association of Minnesota (CEAM) Annual Conference, Mark Maloney, Shoreview Public Works Director, was named Municipal Engineer of the Year, which honors the special achievements of municipal engineers.

Mark has more than 25 years of engineering experience, including the past 15 years as Shoreview Public Works Director/City Engineer. During Mark’s tenure at Shoreview he has been involved in many significant projects that have greatly improved the quality of life in the community. Projects include road and infrastructure improvements for the Rice Creek Corporate Park, expansion of Shoreview’s trail and sidewalk system and most recently the innovative use of pervious concrete surface to infiltrate stormwater in a smaller lakeshore neighborhood, which received national recognition.

Recognized by his peers, MnDOT Commissioner, Tom Sorel, was one of many to recommend Mark for the award. Sorel wrote, "Mark is a strong visionary in his field. He understands the value of creating a sustainable transportation system that will be responsive to the needs of future generations of Minnesotans."

Mayor Sandy Martin presented Mark his award and said, "Mark is unique in his combination of expertise, pride and personal and professional ethics. It truly is a pleasure working with him."

Pervious Concrete Association

Although the past few years have been tough on many in the concrete industry, we see the light at the end of the tunnel. We have seen a marked increase in the National interest and demand for pervious concrete over the first half of this year. This demand is equivalent to the growth period of pervious concrete in the southeast in the mid/late 90s.

Historically, the marketplace has dictated the growth of pervious concrete through its demands. Pervious concrete has grown from localized grassroots efforts to a macro-environment with interest at both the Federal and State level. Recently several DOTs have advanced from lab testing pervious concrete and have progressed to not only writing specifications, but actually letting and constructing pervious concrete pavements, replacing their traditional asphalt pavement. We are on the threshold of explosive growth of the pervious concrete marketplace.    

Therefore, I'm excited about the timely formation of the National Pervious Concrete Pavement Association. The Association has not been organized to work against or separate from groups that have developed pervious concrete to its current state. It has been organized to stimulate and advance the common interests and general welfare of the pervious concrete industry. It is organized to work closely with associations like ACI, ACPA, ASCC, NRMCA, and PCA to meet this collective goal.

Membership is open to any individual, entity, firm or corporation engaged in the concrete construction industry as a contractor, architect, engineer, consultant, developer, owner, technician, student, manufacturer or supplier of materials, products, tools, equipment or services, and any affiliated trade or professional association.

For more information, go to npcpa.org

Airports - Unpaved Runways

Although not the focus of this Blog, from time to time I'm going to voice my opinion on subjects that I feel strong about.  The subject of pervious concrete & airports is one of them.

It seems that when this subject comes up, inevitably comments turn to loose stone and jet intakes.  Yes, large jet aircraft land on unpaved airstrips in third world countries, and yes they do have to put stone guards on the engines, and no we don't want the liability, and yes there's the jet fuel, and yes, and yes, and no, and no......

These concerns of some are valid as they apply to commercial aviation, but let me be very clear...what we are talking about is general aviation.  General aviation covers a large range of activities, both commercial and non-commercial, including private flying, flight training, air ambulance, police aircraft, aerial firefighting, air charter, bush flying, gliding, and many others.  Experimental aircraft, light-sport aircraft and very light jets have emerged in recent years as new trends in general aviation.

I still remember my first experience flying.  I was five years old and I sat in the back seat of a J-Cub behind my dad while we did touch-n-goes on a grass airstrip/cow pasture with the side windows folded down.  I was traumatized for years.  Years later, after I flew the coup, he bought a 200+ MPH Mooney and we were able to fly all over in style.  I grew up in Lakeland, FL, home of "Sun-N-Fun" the southeast's premier fly-in, so flying was a large part of my early years.  My dad no longer flies due to medical reasons and long ago my wife clipped my wings.  Perhaps one day......

Anyway, my point is, there are many general aviators out there, taking off and landing on, not only concrete and asphalt, but also on grass, dirt, sand, and gravel.

In fact here are some statistics on general aviation in the US:

Number of:
Student Pilots........................84,339 (2007)
Private Pilots.......................228,475 (2007)
Piston Engine Aircraft.............163,743 (2007)
Airports w/Paved Runways..........5,174 (2009)
Airports w/Unpaved Runways.......9,921 (2009)

Don't be quick to close your mind to this market.  As you can see, most runways in the US are unpaved.  They are grass, dirt or gravel, with the majority being gravel.  Averaging 2000' in length, these unpaved runways represent approximately 600 million square feet!  So if you come across anyone in general aviation asking about pervious concrete, please don't shut the door on the opportunity, it could be huge.

Here is an example of a project that is an ideal fit for pervious concrete:
http://www.workingwaterfront.com/articles/Improvements-planned-for-island-airstrips/13728

By the way, concerning last week's poll, the majority (75%) likes tooled joints.

Cleaning Pervious Concrete

Kentucky Ready Mix Concrete Association just uploaded this video of the cleaning of their parking lot.

Minimum Cement Content

Question of the Week (5/31/2010): What should be the minimum cement content for pervious concrete?

Poll Results:
700 lbs. ld/yd3 …………… 0%
600 lbs. ld/yd3 …………… 38%
500 lbs. ld/yd3 …………… 12%
None of the Above………. 50%

The NRMCA Pervious Concrete Certification program correctly states that “500 to 600 ld/yd3 would be a good starting point…..and further fine tuning can be accomplished by the concrete producer”. 

In the early days of pervious concrete promotion, statements were made about proportioning mixes, specifically 600 lbs/CY as a good starting point. This idea seems to have carried itself along and wound up in many documents about pervious concrete and ultimately in the minds of specifiers.  And what started as a "starting point" became a "minimum" in the conservative mind.  Not surprisingly, the poll result reflects this mindset.....38% chose 600 ld/yd3.

You need cement to make pervious concrete, however, caution should be taken when specifying minimum cement content. The producer needs the freedom to develop his mix design based on locally available materials and its' available gradations. Although I typically work with mix designs containing 500-600 ld/yd3, some aggregate gradations I’ve worked with required less than 500 ld/yd3. In fact there are some mixes (high sand) that require less than 400 ld/yd3!

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Be sure and take part in the new Poll: What is Your Preferred Joint for Pervious Concrete?

Yield....the dirty little secret

It's somewhat of a balancing act to develop a pervious concrete mix that places easily, performs well, and has good durability.  Finding this balance requires the producer to develop mix designs for each of his aggregates and also have the ability to adjust the mixes on-the-fly based on field density tests.  Unfortunately, a concrete producer or contractor that doesn't have the experience or ability to make these adjustments, will have problems on the job site as the aggregate gradations will typically change during the project.  There may be yield issues, mixes that wont drain, mixes that ravel, and the list goes on.

As for yield issues in pervious concrete, understand that changes in aggregate gradation always affect the yield.  I'll say it again for emphasis....changes in gradation  always affect the yield.  If the gradation becomes more uniform in the mix, the yield increases...if more fines are introduced, the yield decreases (it could be as much as 5% and still meet common specs).  I should note that pervious concrete mixes rarely become more uniform during the course of the job, but typically mixes increase in density as the gradation changes.  

This is really a lose/lose scenario from the producer and contractor's perspective.  Not only will the producer waste material like cement and admixtures (I'll explain later in another post), but the contractor will work harder to place a mix that will under-yield (I'll explain this later too).  This is why I encourage good communication between the producer and the contractor, good quality control, and do your density tests.

Remember pervious concrete's dirty little secret......keep the gradation under control or your yield will be out of control!

 

Earth Day 2010

This Earth Day (April 22nd) I had the privilege of training Auburn University Students, AU Facilities and the City of Auburn as they were certified as NRMCA Pervious Concrete Technicians. Professer Michael Hein of AU's BSCI (Building Science) has done an impressive job educating and promoting pervious concrete in the Auburn community. So far AU-BSCI has trained and certified over 75 future users/specifiers of pervious concrete!

Here are some photos of Auburn's contribution to Earth Day 2010...










Michael Hein (AU-BSCI) and Bobby Maddox (AU Facilities)

The Crew!

For More Photos Go To: http://picasaweb.google.com/aubscipervious/DuckSamfordPerviousPavingSpring2010#

Integral Color: Liquid vs. Powder

I’m often asked what method of coloring pervious concrete works best; liquid color or dry powders?  There seems to be a trend in the industry to suggest that one is superior over the other, mainly liquid being the better choice.  I’ve heard explained that this is due to liquid being better distributed in the mix, especially in drier mixes.  This makes sense to me, but I have to question why anyone would want to place a dry mix.

I’ve found that both systems work equally well, but if given the choice, I’ll use dry color and I’ll explain why….

Dosage rates for regular concrete and pervious vary greatly as the color in pervious is not competing with sand. For example, an 8 CY load of regular concrete (4 sack mix) requires five (5) 25lb bags of color (4% rate) but an 8 CY load of pervious concrete (600 lbs/yd) could be colored with just one (1) 25lb bag, for the whole load.

I’ve used heaver doses with pervious but I’ve found that the extra color is a waste of money because of the process of curing pervious concrete. It seems that no matter how much color you put in the mix, the pavement will be bleached when you remove the plastic sheeting. But here's the trick...spray on a matching color-cure after the curing sheet is removed and you'll have the best looking pervious you've ever seen. This method makes beautiful pervious concrete.............. and you’ll save money!