Researchers at the Institute of Industrial Science, part of The University of Tokyo, have developed a new procedure for recycling concrete with the addition of discarded wood. They found that the procedure can yield a new building material with a bending strength superior to that of original concrete.
Finding the right proportion of concrete and recycled wood was critical to obtaining concrete with the most strength. The researchers adjusted the mixture proportion, pressure, temperature, pressing duration, and water content. Wood gets its rigidity from lignin, which are highly crosslinked organic polymers. In this case, lignin fills the gaps in the concrete and functions as an adhesive when mixed with waste concrete powder and heated. The strength was also improved by higher temperatures and pressures during pressing.
Recycling concrete is even likely to be biodegradable because the concrete waste is attached to the wood component. The method could also be extended to recycle other types of discarded plant matter, instead of wood, or even brand-new concrete made from plants, sand, and gravel.
“Most of the recycled products we made exhibited better bending strength than that of ordinary concrete,” said senior author Lecturer Yuya Sakai.
“These findings can promote a move toward a greener, more economical construction industry that not only reduces the stores of waste concrete and wood, but also helps address the issue of climate change.”