Natural resources are not unlimited in supply and conserving them should be one of our priorities. One of the ways to conserve them is through recycling the used material wherever possible. There are lot of opportunities (and also necessity) for recycling the used material in construction and building industry. In recent years, many countries have emphasised the use of C&D waste in construction as the industry is raw material intensive. Designing a concrete building for easy disassembly could enable the reuse of its component parts in other construction projects, reducing use of raw materials and lowering waste. This brings into fore the significance of Design for Disassembly.
The aim of design for dis-assembly (DfD) is to aid deconstruction (demolition) through planning and design. It allows components and materials to be removed more easily, facilitating their subsequent reuse. In fact, in buildings there is lot of scope for disassembly if it is properly designed at the time of construction. For example, elements such as columns, walls, beams, and slabs can be disassembled without material loss or pollution to be reused in extending existing buildings or in the production of new ones. DfD also enables flexibility and convertibility of whole buildings. DfD provides economic and environmental benefits to builders, occupants, and communities. It also helps to reduce the consumption of raw materials, as well as lowering waste during construction, renovation, and demolition.
It took many decades for the developed world to realise that letting the waste to waste is the biggest crime the present generation is committing on the future generation. In 2004, the European Union passed the landmark WEEE (Waste Electrical and Electronic Equipment) Directive, placing the responsibility of disposing electronic products with their manufacturers. This tectonic shift was recognized as a sign of things to come by global manufacturers, driving interest in the DfD strategy.
Concrete has several characteristics, such as durability, mechanical and fire resistance, global availability, variety of type and form, and flexibility in design and application, that give it significant potential for disassembly and reuse. Meanwhile, connections made from (among others) stainless steel and removable fasteners, allow for the efficient disassembly of concrete elements.
DfD requires new ways of designing
The cyclical model proposed by DfD requires new ways of designing structures and buildings, as well as developing new assemblies, components, materials, construction techniques, and information and management systems. For example, the new prefabrication and digital technologies that are being, and will be, implemented to deliver DfD, can be applied to the manufacture of concrete elements because of concrete’s fluidity, versatility in properties and range of reinforcement options.
The uncertainty and lack of information regarding the quality of the materials and elements for reuse must also be addressed; however, the long lifespan of concrete compared to other building materials makes a favourable case for the use of concrete elements in DfD systems.
“Designing elements in concrete for disassembly will maximise their reuse potential, as well as increase their reuse options, and therefore has the potential to reduce the environmental impact of construction through resource recycling, material reprocessing, component reuse and building relocation,” say the industry experts.
Waste generation is inherent to almost every process or service and leads to overall degradation of both raw material utility and monetary value. To design for disassembly or deconstruction is to create products with the intention of minimizing value loss at the end of life.
In the construction industry, many materials used on a large scale can be recovered, reused, and repurposed. Steel, wood, concrete, and asphalt can contribute to a more sustainable built environment by being reused. A material’s capability for reuse depends on its installation and formulation. Composite materials, or materials that are amalgamations of various natural resources and additives, are increasingly becoming incorporated into infrastructure, particularly for roofing and building exteriors. However, the material complexity of composites, such as fiber-reinforced polymer, makes disassembly difficult and highly energy intensive.
Benefits of DfD
DfD is environmentally beneficial as it helps in extending the life of raw material mines; lowers the cost of materials (if the supply chain is mature); and also reduces the embodied energy and carbon emissions of the construction industry. The waste diversion is by far one of the most impactful consequences of deconstruction as it reduces the disturbance of a site and contributes to a reduction of landfill areas. DfD helps to produce more flexible and adaptable buildings, with components that are more easily maintained and repaired.
Further, disassembly is a labour intensive work and can create lot of job opportunities, both for skilled and unskilled workers. Unlike demolition, there is no heavy equipment of specific skills required. The current practice of DfD is heavily dependent on labour force and best suited to countries like India which has abundant supply of labour.
Challenges for DfD
The uncertainty of the quantity and quality of used materials is quite a disincentive for buyers, due to varying quality and quantity from unreliable sources. There is also a lack of rules and standards to regulate the construction with such materials. However, in the long run, increased government and public involvement, revised building codes and regulations would begin to address issues pertaining to the application of such materials.
Further, lack of demand or low demand may discourage (at least initially) those who supply used materials. Also, developers’ interest will normally be limited to the life span of the structure and not beyond that. So, it would be difficult to convince them to build a structure keeping in mind the interests of those who demolish it at the end of the life of the building, unless there is statutory requirement.
Also, there is a challenge pertaining to consumer tastes: there is a common negative perception of such materials. They are perceived as being inferior in quality compared to virgin materials, both aesthetically and for safety reason. Presently, there is no system to certify their quality which makes the matter cumbersome.
Designing new buildings following the DfD principles can overcome most of the barriers to recycling. DfD requires standard size components, mechanical joint methods (instead of gluing or welding) and materials with simpler compositions that facilitate recycling and reusing processes. Incorporating DfD measures in building codes and proper system of subsidies for using the used materials can change the scenario altogether and help in popularising DfD.