Precisely placed explosives have traditionally been used in the demolition of old buildings. Over the years, the process has been refined, and buildings are now demolished with minimal disturbances to adjacent structures. An example of this is the Landmark Tower in Fort Worth, USA, which was demolished in 2006. The below video captures the elegance of the buildings demolition:
Despite advances in the industry, there are many issues associated with this type of demolition. For one, the explosions cause dust and debris, and the clean up process can be quite gruelling. In addition, buildings demolished in dense urban areas run the risk of causing damage to nearby structures. In 1997, the implosion of the Royal Canberra Hospital in Australia killed a spectator after debris was thrown over 400m (Canberra Times Report).
As a result, researchers in Japan have developed a safer process for demolishing buildings in dense areas. Instead of imploding the building, it is disassembled from the top down. A multi-storey scaffolding system is used to hide the demolition of individual floors. Columns and beams are removed, and temporary jacks are used to lower each floor, leading to minimal disturbances to nearby infrastructure. The process can be seen in this CNN report:
This process, although slow and costly, does circumvent much of the risk traditionally associated with building demolitions.
Recycling Demolition Waste
One of the biggest concerns with demolishing older structures is disposing of the old material. To deal with this, the crushed concrete by-product of demolition is now being collected, cleaned and reused as aggregate in new concrete structures (Concrete Recycling). This process provides a number of benefits, including: a reduction in disposal and transportation costs, minimal project carbon footprint, and an increase in the projects efficiency as the aggregate can be re-used directly on site.
However this process is impractical and cannot be used in the majority of construction projects. In addition, a tremendous amount of water is used to prevent dust from the demolition. As a result, researchers have been looking to refine the process.
Omer Haciomeroglu, a recent graduate of Umea Institue of design in Sweden, has developed a revolutionary design for recycling concrete on site (International Design Excellence Awards). The idea is simple: by pumping high pressurized water, the concrete is crushed into smaller pieces, and the the water-concrete mixture is collected. This slurry is then filtered, and all the aggregate retained from the process is sorted and bagged on site. The water from the slurry is later used as grey water to clean the site after demolition. By not using highly destructive methods, the reinforcing bars can be recycled for future use.
This product, despite only being in the concept stage, is the catalyst that the industry needs. As new ideas for safer, more environmentally friendly processes emerge, the risk associated with building demolition can be mitigated, and future disasters can be avoided.