Plastic bottles could be used for construction, researcher says

In recent years, recycled plastic has been used to manufacture everything from shampoo bottles to toy cars. But can recycled plastic be used in construction? According to Andrew Graettinger, an assistant professor of civil and environmental engineering at the University of Alabama, it can.

Graettinger recently conducted research on using recycled plastic bottles as a lightweight fill for construction. While the space behind retaining walls has been traditionallyfilled with heavy soil, plastic blocks may someday be used as a lightweight alternative. Because the weight of the soil exerts pressure against the retaining wall, it sometimes causes the wall to lean or crack over time. The plastic blocks containing plastic bottles, on the other hand, are considerably lighter and can withstand 2 tons of weight.

“The plastic bottle blocks weigh considerably less than soil,” Graettinger told the Dialog. “For construction applications, the lighter-weight plastic bottle fill is easier to handle and will save money because the retaining wall does not have to be as strong.”

The plastic bottle blocks, which are approximately 4 square feet, weigh two pounds per cubic foot, compared to soil, which weighs approximately 110 pounds per cubic foot. The blocks contain 150 to 200 plastic bottles and are held together by Urethane foam.

“This means that five stories of plastic bottle fill weigh the same as one foot of soil,” Graettinger said.

According to Graettinger, it does not matter whether the bottles have been recycled or if they are new. For his research, the Coca-Cola Co. donated new plastic bottles so that a control group could be formed to distinguish if there would be a change in strength.

“We have started making blocks out of recycled bottles and have seen no difference in weight and strength testing,” Graettinger said. “It is exciting to work on a project that solves an engineering problem and provides a new environmental recycling initiative.”