One of the issues I’ve mentioned before amid the industry’s sustainability discussion is the danger of turning our pavements into landfills. It would be disastrous to think we can safely fling trash into asphalt mixes, label the practice recycling, and tout that as a fabulous green practice.
Luckily, we have engineers and researchers who test plastics, metal byproducts, glass, fishing nets and other random materials environmental warriors expend energy shredding or melting into an asphalt mix design. We have scientists who weigh the benefits of blending a cohesion agent to force garbage to work with bitumen to ensure the resultant mix will perform long term for a truly sustainable solution. One that won’t require repaving in 24 or 36 months.
The point I’m getting to is it makes me nervous when someone comes along and says, “Hey, we can shred this problematic thing and use it in asphalt roads!” When I, as the editor of an asphalt publication, ask which performance tests research teams conducted or what performance results are available, I don’t always hear back from the marketing agency. Sometimes, those entities fade away.
I offer kudos to the team at Alliant Energy for sharing copious testing data from third-party research with recycled wind turbine blades for asphalt and concrete fibers for use in pavement mix designs. You can read more about that in the December 2024 issue.
As it turns out, the asphalt industry isn’t alone in seeing oddities creeping into our mixes. On Oct. 1, the Environmental Engineering Materials Research Group at The University of Oulu, Finland, shared new research results—produced as part of the project KaiPa, co-funded by the European Union under the NextGeneration EU programme—about the use of industrial and mining brine wastewaters in concrete. The results were published in a journal titled Desalination under the headline, “Reverse Osmosis Reject Water Management by Immobilization into Alkali-activated Materials.”
Let’s turn to an Oct. 8 press release to learn what’s happened there. The release stated industrial and mining brine wastewaters could be mixed into an alternative cementitious binder with sufficient strength for a variety of applications, including mine backfilling. Several industrial sectors, such as battery production, mining or ash processing, generate high levels of saline wastewaters. “Sodium, sulphate and chloride are usually the main components of these effluents….In a new treatment method developed at the University of Oulu, concentrated brines can be stabilised [sic] using so-called alkali activation, which combines brines as a part of cementitious binder. The method, developed by researcher Sima Kamali in her doctoral thesis, mixes a calcium-, silicon- and aluminium-rich raw material with brine and a small amount of sodium hydroxide. The end result is a paste that can be used as a concrete binder, as it achieves sufficient strength for a variety of applications.”
The press release also listed slag as an ingredient in the process and offered more information at the university’s page.
What struck me was the lengths researchers will go to, to add elements that have not traditionally been a part of a mix, to make use of the elements. Are we being wise in pursuing these lengths?
As a conservationist, I applaud the concept of re-using and recycling materials. If we can prevent the waste of a product, that seems commendable. But are we doing more good than harm or more harm than good when we struggle to put the waste into a road that is performing properly without the waste? Should we be working so hard to add to something that isn’t broken? I’m interested in hearing your thoughts on how much energy we’re expending to remix what isn’t broken.
Stay Safe,
Sandy Lender