A vision for spent foundry sand.

A Wisconsin crusader discusses beneficial reuse applications.

Tarun Naik points to a poster on the wall of his office at the Center for By-Products Utilization (CBU), Univ. of Wisconsin-Milwaukee. It says "Recycling works . . . in Wisconsin." Naik smiles and says, "That's true, but I think it's true for the rest of the country, as well."

Recycling is his job. CBU is dedicated to finding uses for industrial by-products, and Naik is dedicated to finding uses for spent foundry sand. His laboratories at CBU are filled with concrete samples made with foundry sand undergoing all the rigors of testing: freeze/thaw cycles, tensile and compression strength tests, and other trials of strength and durability.

Naik has long experience at reuse, having been in the forefront of the charge to make coal fly ash from Wisconsin utility plants an ingredient in portland cement. Today, 27% of all the fly ash in the U.S. is recycled, while in Wisconsin, the figure is 65%.

In an interview with modern casting, Naik discussed his vision for beneficial foundry sand reuse.

Q What can be done with spent foundry sand?

There is a lot you can do with it. You can make good quality ready-mix concrete, bricks and paving stones, as well as road base applications and flowable fill. Different ratios and added enhancers can make a superior product. All the major concrete industry test parameters prove that foundry sand in the mix makes a stronger concrete.

Q What has to happen for a foundry to do it?

It's a process that takes three people: the foundry manager has to decide not to throw away $500,000 a year anymore. Then he consults an engineer, who identifies the potential applications for use, and then the marketer comes in and sells the sand, the same way you sell castings. But there's a lag time between the decision and the sale, and it takes patience and commitment.

Q So you believe foundries will be able to make money from their spent sand?

Why not? The utility industry was in the same position 20-30 years ago. They had to convince people to use their fly ash, and now it's an integral ingredient in many high-quality concretes - it's become necessary. But even if you only get one cent, compared to the $25 per ton average disposal costs foundries are paying, it's worth it.

Q What stands in the way of widespread reuse?

Time. We are convinced ourselves, but we are one project away from having the data to convince everyone else. That project will cover durability, economics and long-term environmental impact. if I look at a brick made with 100% new sand, I can be sure it will still be solid decades from now. I can't say that about one made from foundry sands. When we began this project five years ago we did a worldwide literature search on foundry sand reuse and came up with almost nothing. Five years ago, we didn't know anything about concrete applications.

Foundries need to take an active role in this research, because nobody's going to do it for them. We have a grant from the Wisconsin Dept. of Natural Resources (WDNR) for this project, but we need matching funds from the industry, as well as interest and cooperation. Again, it takes a conscious decision to stop throwing money away, and to invest in the future.

Q So what is the time frame?

Five to ten years - as long as it takes to determine durability and marketability. After that, I believe there won't be one wasted ton of foundry sand in Wisconsin. Wisconsin produces 8 million cu yd of concrete per year. If that were all a mix of 40% foundry sand it would require 2 million tons of foundry sand, and all the foundries in the state of Wisconsin collectively produce only 800,000 tons a year. Therefore, replacing just 10% of the concrete producers' new sand use would eliminate all the landfilled foundry sand in the state.

Q How do you convince end-users to take the sand?

All we have to do is convince 40% of the producers in the state. We do that by proving to them that foundry sand will make their product better and that it will pose no environmental liability. Another thing is that our nation's resources are not unlimited, and end-users may run out of sources of cost-efficient, quality sand. They may eventually have to say "this new sand is a luxury we can no longer afford."

Q What will be the fastest market to open?

Flowable fill is a perfect application. All it requires is cement and water. And it is meant to be fairly weak so it can be dug up - a manufactured dirt. The leachate properties for various sands need to be tested case by case, but most problem substances in the foundry sand are completely encapsulated in impervious materials and therefore harmless. I know flowable fill made with foundry sand has been used at various places around the country, and it definitely works.

Q Are any sands more useful than others?

While we haven't tested all that many sands, and there are differences between sands, those we have responded well. I imagine those from copper and brass foundries would require special applications due to any lead content, but other than that I see few restriction on sand types. We never met a foundry sand we didn't like.