Recycled Concrete Update

"We are committed to witness through the good quality of our work and careful stewardship of our resources."

-From the Statement of Values of the Appalachia Service Project

The first week of work on the recycled concrete project is over, and I have an update. First of all, I need to re-issue the formula. Finally, here's the formula for making one cubic foot of concrete from recycled concrete aggregate.

To Make One Cubic Foot of Concrete From Recycled Concrete Aggregate
(combine these ingredients)

Ingredient	Volume	Weight	"Density"
	(Cubic Feet)	(Pounds)	(Pounds per Cubic Foot)
Cement:	0.14	13.16	94
Water:	0.12	7.44	62
Coarse Aggregate: (gravel)	0.39	46.8	120
Fine Aggregate: (sand)	0.35	35	100

Now, it seems obvious that this is a great idea which will help to preserve our natural environment while cutting costs, but we mustn't be hasty and presumptuous environmentalists. For this purpose, a cost-benefit analysis is necessary.

To make one cubic foot of concrete using Quickrete ready-mix bags costs $7.42.
To make one cubic foot of concrete using the recycled concrete method costs $1.32.

This is based on using 80-pound bags of Quickrete at $4.45 per bag, and using 94-pound bags of Portland cement at $9.45 per pound. These are the prices at the ACE Citizens Building Supply store here in Bluefield, WV.

And if you consider that using recycled aggregate keeps 82 pounds of aggregate from going to the dump (per cubic foot of concrete needed), $1.91 is saved in dump fees. This assumes a dump fee rate of $46.75 per ton, which is the Mercer County Landfill fee.

If you include the cost of dumping the old concrete, making one cubic foot of concrete from Quickrete Ready-mix bags costs $9.33.

That makes for a savings factor of 705%, and a savings of $8.01 per cubic foot of concrete needed. On our project, where 16.5 cubic feet were needed, we saved a total of $132.12 by going with recycled concrete.

What's missing? Labor. Here at ASP, labor is free. This would obviously be a major contributing factor to the cost of recycled concrete for a non-volunteer organization. I have no way of telling how much extra labor we put into breaking up the concrete blocks as opposed to the labor of loading it into a truck and hauling it to a landfill. We used sledge hammers and digging poles (a.k.a. "God Rods") to smash the blocks, and a clothes hamper with 1/2" hardware cloth over it to separate the fine from the coarse aggregate. Another thing to consider is that on a larger site, pneumatic or hydraulic tools would typically be used to break up the concrete into aggregate. That might speed up the process.

Another major variation from the conventional recycled concrete process is that we used aggregate from broken-up concrete blocks (a.k.a. "cinder blocks") instead of breaking up reinforced concrete, which would have been too difficult without the help of pneumatic or hydraulic tools.

If you're curious as to the performance of the final product, I'm sorry to say that we don't have the facilities to do stress tests here at ASP. I'm not concerned, though, because our recycled concrete will be going into post-holes. I wouldn't recommend making a structural member from recycled concrete without testing it first.

Environmental Impact: Making concrete from recycled aggregate eliminates the need to mine gravel. Gravel quarries strip land of vegetation and habitat, allow sediment runoff into streams, and require lots of energy to extract the gravel. Loss of vegetation and use of carbon fuels is double-trouble for climate change (if you're into that kind of thing).

Finally, I would like to address the educational impact of our project. Using this simple, sustainable method of making concrete, we were able to teach volunteers and community members how to really "think green." I urge you to involve others when you do cool things. They may have helpful input. For example, I didn't come up with the specifics on how to break up blocks, but the volunteers came up with a great system for doing it, and for separating the coarse and fine aggregates. So take the time to grab the people around you and teach them.

And remember: "These things won't fix themselves, and most of them can't be fixed alone."

Environmental Challenge of the Week

Last Wednesday, I was honored to be a guest on Radioactive's morning talk show with host Craig Hammond. If you're in Bluefield, you can tune to 1440 AM in the mornings. A "tape" of Wednesday's show is below. I cut out the parts that don't involve me.

The host, Craig is a friend of mine these days. I go to his coffee house when I get a chance and we talk about whatever the local issue happens to be that morning. So I went on his show to represent ASP. I talked for a couple minutes about ASP--let people know who we are, what we're doing, and where they can go to fill out an application.

Then, for the next 10-15 minutes, the conversation turned to environmental issues. We talked and debated about "square foot gardening," wastewater treatment, stormwater treatment, and whatever else. It was a lot of fun to have a former mayor of Bluefield asking me questions like that on a radio show.

Anyway, while my laundry was drying at the laundromat this Saturday, I stopped in at Craig's coffee house "News and Brew." I proposed that I should call in every Monday with a new "Environmental Challenge of the Week." He loved the idea. So from now on, I'm going to call in at 9:15 AM and offer a new challenge each week. The challenge isn't just for the listeners, but for the guys in the studio as well. The first will be to use reusable coffee mugs instead of disposable. I will try to offer pertinent statistics and information. Here's how it will go:

• Americans consume more than 16 billion paper cups per year

• In 2006, paper cups accounted for 252 million pounds of garbage. This required 4 billion gallons of water, and 6.5 million trees, and enough energy to power over 50 thousand homes

What about coffee cups from recycled paper? FDA regulations are very strict when it comes to beverages coming in contact with recycled paper, and recycled paper is too flimsy of a material to retain the liquid. Starbucks tried to manufacture a recycled paper cup, but was unable to succeed.

Alternatives? One sustainability engineer concluded that after 24 uses, a stainless steel mug is as environmentally friendly as using paper cups.

Is environmentalism expensive? No...a study done in 2000 showed that Starbucks could save $1 million dollars per year by switching to reusable cups.

So my challenge to you this week is to bring your reusable mug or travel mug next time you go to the Hardee's, or to your favorite coffee shop.

References: Sustainability Is Sexy (.com)
All references are detailed on the site

These posts can be found on their own site: http://bfenvrionmentalchallenge.blogspot.com/

"Green" ASP?

I'm an environmental engineer, but that doesn't necessarily make me feel like an environmentalist. What I'm about to tell you does.

Here at ASP, we care about our environment. That's why we're replacing unsafe concrete and block steps with new steps, using the old block as aggregate for the new concrete, which will hold the new posts in place. The design for this concrete was based on Minnesota DOT's numbers, found here. The numbers have been rounded a lot, since the new concrete will serve less of a structural purpose, and more of a filling or stabilizing purpose. Also, the volunteers probably won't be very precise in their measurements anyway.

For 6x6 post-holes, 1.85 cubic feet (cf) of concrete will be needed. With 4 6x6 posts, we will need about 7.5 cf of concrete. The amounts of each ingredient needed to make 7.5 cf of concrete are shown below. Nevermind the fact that it adds up to more than 7.5. Call it a safety factor. The same ratios are used for the 4x4 post holes, but in different amounts.

	cf	lb	Spec Gravity (pcf)
Cement	1.4	130	94
Water	1.1	70	62
Coarse Agg.	3.8	450	120
Fine Agg.	3.3	330	100

The volunteers are being instructed to "disassemble" the existing steps, and break up the concrete blocks into coarse and fine aggregate piles. We'll give them the cement and the rest is history. We'll see how it goes, and I'll try to check in with the family as to the concrete's performance some time later down the line.

All photos in this post were taken by Robyn Rosner.