Published on 19 May 2022. Written by Sarvesh Saurav
When buildings are demolished as a result of disasters, their rubble contains fragmented building components, furnishings and organic matter that are difficult to separate. On the other hand, it is possible to selectively demolish a building if it is an intentional act; in which case, it is possible to reuse most of the building materials and components, and recycle much of the rubble.
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According to investigations on the composition of demolition waste in the Netherlands revealed that 20% of the wood, 90% of the steel and 100% of other metals like zinc, lead and copper are being removed from the structure, leaving behind building waste, which on the average is composed of:
Brickwork 62%
Concrete rubble 24%
Brick rubble 6.1%
Tiles 2.3%
Bituminous materials 0.2%
Wood 4.7%
Scrap steel 0.1%
Other 0.6%
Total 100%
Although the volume of demolition waste is huge, much of it is inert, allowing it to be crushed, processed, and reused as aggregate in building works. Nevertheless, large amounts still end up as landfill rather than being recycled. Waste containing half-used paint pots, discarded solutions, solvents and chemicals are potentially hazardous, and building waste likely to be contaminated with asbestos must also be treated as dangerous. It has been established that materials and components recovered from demolished buildings are being reused for new construction works as well as renovation projects, especially by low-income communities in developing countries. It has also been noted that material, which was not considered worthy of reuse a few years ago, has appeared in the market after the recent global economic crisis. For example, steel reinforcement from demolished buildings used to be recycled back into steel; however, it is now considered worthwhile to adopt measures to facilitate its reuse as a building material. Meanwhile, demolition contractors have also become increasingly aware of the feasibility of recovering as much material as possible, for new construction works. Consequently, they are giving considerable importance to the proper sorting, storing and display of their wares. Rapid industrial development causes serious problems all over the world such as depletion of natural aggregates and creates enormous amount of waste materials from construction and demolition activities. One of the ways to reduce these problems is to utilize recycled aggregate in the new construction concrete components.
Experimental Techniques for demolished concrete.
Concrete waste procured from the demolished site. The demolished waste is transported, crushed and segregated. Several tests on segregated concretes are conducted in the laboratory such as water absorption, sieve analysis, crushing value test, impact value test, and abrasion test, workability and crushing strength of natural & demolished waste by making cubes. The demolished waste is sieved through a set of IS sieves to obtain a fitness of fine aggregate which are also replaced.To study the partial replacement of demolished waste in fresh (new) concrete, effect of demolished waste are observed on the strength of concrete, by casting more than 180 cubes of size 150mm in the laboratory using two nominal mixes M15 & M20 (1:2:4 & 1:1.5:3). An effect of partial replacement of demolished waste are made to compare the strength of concrete. The same quality and required quantity of cement and fine aggregate is used for both the nominal mixes, replacing fresh coarse aggregate by 0%, 25%, 50%, 75% and 100% demolished waste aggregate concrete for both mixes are prepared and cubes are casted. Seven days and 28 days compressive strength of the cubes are obtained.
General conclusion
Very little demolished concrete is currently recycled in the country (India). Demolished concrete not even used as stabilized base or sub base in the highway construction. It is being dumped off as fill. It is right time to seriously think of reusing demolished concrete for the production of recycled concrete in our country. Recycling would not only conserve the resources but would also promote safe and economic use of such concrete which is the need of the hour for a country like Saudi Arabia and India.
Kit required to develop Utilization of demolished concrete :
