Introduction
With the construction aggregate industry placing a larger focus on sustainability and responsible material processing, C&D recycling is becoming more than just a buzzword – it’s becoming part of the future.
C&D recycling, which stands for construction and demolition recycling, is the process of recovering valuable aggregate from inert waste streams. Aggregate that had previously been used in construction projects can be reprocessed and given new life for reuse in new construction projects.
Sustainability with C&D recycling
C&D recycling contributes to sustainable construction practices in several ways. First, it reduces reliance on natural resources. Because virgin aggregate is a finite resource, there’s a limited supply available. Like a going-out-of-business sale, once it’s gone, it’s gone.
Demand for construction aggregate is increasing, as more infrastructure is required to support growing populations, accommodate increases in travel and tourism, etc. To help meet these demands, recycled aggregate from C&D waste streams offer a cost-effective solution to help alleviate strain on natural resources.
Minimizing waste
By recycling the aggregate material from C&D waste streams, the amount of waste destined for landfill is minimized. This is the second way that C&D recycling can help contribute to sustainable construction practices. In many areas, landfills are reaching capacity and it can take a while to find suitable locations and obtain the required permits to open others once existing landfills are closed.
Reducing the amount of waste sent to landfills is responsible, not just from an environmental and social aspect, but for financial reasons as well. Hauling construction debris to landfill is costly, but recycling that debris either in situ or at a local recycling facility and returning it to the construction industry can add another area of revenue or add to an already existing revenue stream.
Creating profit from waste
This leads to a third benefit of C&D recycling: transforming waste into a valuable resource. Rather than paying to haul debris away and/or paying to bring in new aggregate material for jobs, the debris in C&D waste can be reprocessed into an as-new material.
Supporting a circular economy
The final way that C&D recycling can help contribute to sustainable construction practices is it supports a circular economy. A circular economy in the construction industry is one where previously used aggregate materials are returned to the industry as like-new materials in a closed-loop system, creating a continuous cycle of reuse and recycle rather than one-time use products.
Natural aggregate producers can also contribute to the circular economy by adding a C&D recycling circuit to their existing process. The recycled aggregate from the C&D waste stream can be combined with the natural aggregate and sold as product, increasing yield and improving the bottom line.
C&D recycling processes
C&D debris is processed using many of the same types of equipment used in processing natural aggregates:
Dry processing
The dry processing stage consists of a system of feeding, scalping, crushing, screening and ferrous material removal equipment. Large aggregate debris, such as concrete slabs or asphalt, are fed to a primary crusher for initial size reduction. The crushed material may then need to be further refined in a secondary or even tertiary crusher to achieve the required product size.
Types of crushers typically used for processing C&D materials include Jaw Crushers and Impact Crushers.
After crushing and screening, the recycled aggregates are suitable for use as road base and drainage materials as well as in landscaping projects.
Wet processing
Recycled aggregates can also be used in many non-load bearing applications if they undergo an additional washing process to remove deleterious material that can affect the structural integrity and cosmetic appearance of the end-use product. This is where the wet processing stage of recycled aggregate processing comes into play.
A wet processing system can be configured a variety of ways, depending on the product requirements and the contaminant to be removed. Wet processing plants can consist of one or more of the following stages:
- Washing
- Scrubbing
- Classifying
- Dewatering
The washing stage involves the use of water to remove contaminants. For certain applications, washing along may not be enough to remove tough contaminants, so in these cases, a scrubbing stage is added. Scrubbing equipment facilitates material-on-material attrition to remove tough contaminants.
Classifying and dewatering are typically reserved for fine aggregate products. Dewatering removes excess moisture from the final product. In addition to providing a drip-free product for immediate sales, dewatering improves site housekeeping by reducing the amount of water that is discharged with the sand product.
Like any wet processing system, washing recycled aggregate will produce a waste stream that consists of the water used in the washing process as well the fine particles and contaminants that have been removed.
Water recycling and tailings management systems complete a closed-circuit C&D recycle process that continuously provides immediately reusable process water. It also converts the tailings into dewatered, manageable filter cakes that can be moved with mechanical handling equipment. Depending on the composition of the solids, filter cakes can potentially be sold as backfill or pond lining, or they can be reused to rehabilitate mine sites.
Recycling aggregates from C&D waste offers a sustainable way to create necessary construction materials as well as minimize waste destined for landfill. The right C&D recycling solution will further offer a sustainable way to process these materials for reuse in the industry.
