This article is reproduced with permission of the International Technology and Engineering Educators Association (ITEEA). Learn more about comprehensive STEM programs and teacher resources at www.ITEEA.org.

By
Harry T. Roman

Introduction
Our modern world is characterized by the extensive use of concrete and asphalt pavement. Periodically, these materials are replaced and the old materials disposed. In this challenge, students will be asked to develop ways to re-use the old materials.

The Problem
Both concrete and asphalt pavement are heavy, dense, and bulky in shape; and at first glance, not thought to be capable of easy reduction into something more manageable. Concrete especially has the feel and appearance of an incredibly durable substance.

A first order here is to determine what if any work has ever been done to address the recycling of these substances. Internet and literature searches through the school library/media center are a must to gather basic information about these substances and what work may have been addressed. Since roads have been constructed with both concrete and asphalt, and since cities and counties are always at work repairing the roads, might your local municipal and county governments be an early source to check; as well as road contractors who build and repair them? State and federal highway agencies likewise also would be a good primary source of information

Other places where useful information may reside might be:

• Engineering organizations that specialize in road building;
• Organizations that deal with recycling;
• Engineering colleges and universities that have civil engineering and road building courses … and conduct research; and,
• Companies that manufacture concrete and asphalt.

This is not an exhaustive list, but serves as a representative example to get the students engaged.

It is also important for the class to understand how concrete and asphalt are made and applied. Could there be suggestions in the manufacturing process that hold keys to how both products could be made into a recyclable material? How are both materials removed … and could this also hold a key to how the materials may be recycled? This indicates a field trip by the class could be insightful. Perhaps there is a concrete or asphalt facility nearby; or maybe there are local projects where concrete and asphalt are being removed that are worth visiting.

Recycling is taking on a whole new meaning compared to say 30 years ago. Companies are now talking about making whole computers and their peripherals recyclable … a cradle-to-grave philosophy of stewardship for managing waste streams. Can something like this apply to concrete and asphalt? Pay particular attention to how much energy is used to make these materials in the first place. Is there a way to recapture some of that invested energy?

Is it possible to develop technology that allows recycled concrete and asphalt to be re-used as patching materials for potholes in roads and damaged concrete? Might some of the recycled materials be mixed with fresh materials to make more durable repair surfaces?

For instance, when asphalt roads are prepared for a new coating of fresh materials, the road surface is scarified or scabbled to shred the old surface away, making a rough surface for the new material to adhere to. This ground-up old asphalt is then collected and hauled away. Can this powdered and ground asphalt material be reheated or chemically treated to somehow rejuvenate it for use as fresh material or as a patching compound? This is not without precedent. Many new asphalt roads have been compounded with a variety of materials like finely ground glass, old shredded tires, and recycled plastics to improve their durability and resiliency to temperature changes and cracking. Why not add a bit of the original materials too?

Concrete has also been compounded with different materials to improve its durability. Many concrete airport runways have been mixed with the captured fly ash from coal-burning electric power plants. This fine particulate material is filtered-out of the coal burning waste stream and not allowed to go up the power plant chimney stacks. It has also been used to make building materials. It gives the concrete a significant increase in shock-strength so that huge and heavy aircraft banging down on it during landings does not crack the runways. Could crushed concrete be added to fresh concrete, and would this increase its strength and durability after hardening?

Some Creative Fun
Why not enlist the class in some creative idea generation for how these materials may be recycled? Let student teams generate some novel approaches to re-using the materials. In addition to what has been discussed above, here are some starter ideas for how old concrete and asphalt might be used:

• Ground finely and used as road and construction fill?
• Ground finely and used to loosen up heavy clay soils and make them suitable for farming or ornamental growth?
• Used in bulk as ballast for ocean-going vessels?
• Mixed together and formed into ornamental yard displays for bricks, flower pots, planters and such?
• Used in bulk as a way to close-up old mines, shafts, and excavations to prevent later collapses?
• Used in bulk as ocean wave breakfronts and seawalls?
• Formed into a compound that can be applied to eroded hills and mountain areas to prevent slides?

Let student imaginations have a holiday and create all sorts of new ideas for using these venerable materials.