Improving Demolition and Waste handling practices in India: The Equipment prespective

 -         Nikita P. Kumar, Architect, Mumbai

As construction methods and materials have grown increasingly complex over the years, the process of creating accurate demolition plans to safely and successfully bring down structures has also become more complex.  Without a way to accurately and efficiently analyze demolition plans, most of the learning curve has taken place during live building demolitions.  Unfortunately, this learning can come at a ghastly cost to adjacent structures, infrastructure, and even human life. However, such lessons combined with technological breakthroughs in past decades, have gifted the global demolition industry with some amazing tools, equipment and methodologies, to enable them wreck effectively and efficiently. 

                      

                      

Another massive challenge during the demolition process is the handling, disposal and recycling of debris that is generated. According to the report of JNNURM (Jawaharlal Nehru National Urban Renewal Mission), it is estimated that the C&D industry in India generates about 10-12 million tons of waste annually. While some of the items like bricks, tiles, wood, metal are re-used and recycled to an extent, concrete and masonry – which constitute about 50 per cent of the this waste are not currently recycled in India. The presence of C&D waste and other inert matters is significant (almost one third of total MSW on an average), but so far, no notable development has taken place for utilizing this in an organized manner. At present, private contractors remove this waste to privately owned low-lying land for a price, or more commonly, dump it in an unauthorized manner along roads or other public land.

It is clear that while demolishing a building, effective equipment need to be utilized; not only to bring down the structure safely, but to also ensure proper and profitable handling of debris. This brings us to the mammoth and sometimes even diminutive, but highly efficient tools and equipment that have changed the way demolition industry functions, from tearing down structures and handling scrap, to recycling it for good!

Pulling the Gear: Grasping the Current Situation

With growing urban density, contractors in India are now distancing themselves from dangerous demolition tools like the Wrecking Ball, and are increasingly adopting long-reach excavators, with which one has better ability to control the demolition process, which is especially critical in urban areas. As this technique of controlled demolition, i.e., using high-reach hydraulic handlers or skid-steer loaders, fitted with variety of attachments to carefully deconstruct a building, gains popularity, so does the importance of having the appropriate battery of attachments to perform a variety of tasks common to many demolition sites.

Also, in addition to demolishing structures, contractors face a variety of recycling-related tasks, including the primary sizing and separation of materials, but the prevailing lack of awareness among many medium and small scale Indian contractors and agencies about the global technological advancements in demolition and recycling methods, and equipment, continues to hamper the growth of scrap recycling in India.

When coupled with hydraulic excavators, loader backhoes, compact excavators and skid steers, the right attachments can increase a demolition contractor's productivity on site and make the recycling of those materials that much easier. Some attachments gradually gaining popularity in the Indian market include hydraulic breakers, demolition processors, shears and demolition grapples. Hydraulics are especially popular when working with concrete, because they enable a contractor to process more in a given time frame, while reducing carrier wear. However, it is imperative that all contractors and agencies (especially small scale) are educated about these equipment and their usage, which can yield major benefits for them and the environment.

The Inside Job: Mini Excavators and Steer Skids

In controlled demolition the contractor will normally remove any material with salvage value, such as wires, conduits, pipes and electrical equipment, using small shears and grapples on skid-steer loaders or mini/ standard-size excavators. A mini-excavator is really the best carrier for a hydraulic attachment. It is better suited than a skid steer because it allows positioning the tool in many different angles and can complete jobs on walls and structures, but due to the compact size, low weight and speed, and great selection of work tools available for the skid-steer loader, they are also widely used in selective demolition jobs, like refurbishment of residential and office buildings. A skid steer equipped with a bucket is also ideal for picking up material and loading it out.

Apart from the above, there is a whole new range of remote controlled robots for interior demolition. These automatic, unmanned machines are posing a tough challenge to the modified steer skids and mini excavators in the first world nations, but are still struggling to find their way in ‘cheap-labor’ nations like India due to the associated capital requirement. 

Wrecking for Progress: Demolition Machines and Work Tools

There are few jobs more demanding, on human or machine, than demolition and scrap recycling. Demolition today has become a dynamic and increasingly complex business. Contract periods are becoming shorter, legislation is stricter, environmental pressure is increasing and skilled labor is harder to find. As a consequence, demolition contractors are looking for the most efficient, cost effective and safe equipment for deconstructing buildings and structures.

1. Hydraulic concrete splitters:  This equipment is mainly applied to partial or integral demolition of concrete facilities (walls, cement road, machinery base, bridge building parts etc). About the size of a jackhammer, the tool utilizes a shaft known as a plug-and-feather assembly which, when inserted into a drilled hole and forced downward by the tool’s piston, creates the lateral forces that break the concrete. No heavy impact is utilized to form the crack, which spreads quickly and without any noise between the pre-drilled holes until the concrete is split into manageable pieces.

Hydraulic splitting eliminates both shocks and vibrations associated with large impact tools. It can split the rock or concrete in seconds, and the direction of breaks can be controlled as required. It is suited for a place where there are strict limitations on noise, dust, flying debris, vibrations and exhaust gas. It is thus widely use in conditions where the demolition has to be non-explosive and blasts are forbidden.

2. Hydraulic Concrete Crushers: These are excavator mounted mechanical tools for demolition works. The action of HCC is by the opening and closing of its jaws to crush concrete, powered by the hydraulic fluid supplied by the excavator. The main noise source from HCC is from the excavator itself.

Interchangeable jaws in some crushers, including cracking jaws, shear jaws and pulverizing jaws are often used to work along with various types and configurations of jaw teeth in order to better fit the crusher to a particular job.

Secondary concrete crushers usually have some type of pulverizing jaws and are used on jobs where primary demolition is accomplished by hammers, crushers, blasting, ball and crane, or sawing. In this instance, the primary demolition work creates large quantities of concrete rubble which the secondary crusher further reduces, separating concrete from reinforcement.

3. Diamond Wire Saw: A loop of diamond wire mounted on a flywheel is driven by a hydraulic or electric motor. Using diamond beads strung on special aircraft cable separated by springs or plastic, the wire can be wrapped around any length, depth, or configuration of reinforced concrete.

These lightweight, portable saws have changed the character of building modification. Cutting openings in concrete walls with diamond tools causes no structural damage and requires little patching. Diamond wire saws are more efficient than circular saws, able to cut concrete of almost any thickness.

This makes them very useful for the kind of heavy demolition found in bridges, damns and thick concrete structures. In addition, they create little dust, noise and vibration, making them ideal for demolition work within inhabited structures. If time is money, this tool is superior to all.

4. Mounted Hydraulic breakers:  The demolition industry forever changed in 1968 when the first hydraulic breaker was mounted on a backhoe. These demolition hammers vary greatly in size to accommodate almost any carrier application available, from the smallest skid-steer loader to the largest class of excavators.

But the tool that is right for you is dependent on the size of your job and your budget. Attaching a hammer to a lightweight carrier not only decreases the boom’s reach, it also can potentially be the cause of an overturning accident. Breakers that weigh 60 pounds or more can handle heavy reinforced concrete jobs such as demolishing roads, pavements and thick concrete.

Due to their unmatched versatility when compared to other demolition equipment, their speed of processing without the footprint and safety zone requirements of explosion and wrecking ball demolition, these breakers turn out to be an excellent option.

5. Expansive Demolition Agents: The expansive demolition agent is a cementitious powder. Using a drill with a mixing attachment, the powder is mixed in a bucket and poured or tamped into drilled holes. As the mix hardens and expands, the concrete cracks between the drilled holes. As the hairline cracks develop over the slab, they run outward into each other and grow wider, until the slab literally falls apart under an expansive force that can exceed 83,000 kpa.

Used correctly, expansive demolition agents produce little dust or debris. The only labor involved is in drilling the holes, mixing and applying the agent, and then hauling the broken up pieces of concrete away.

6. Pneumatic Hammer: They only account for a small portion of total hammers in use today. There are still a number of advantages in using pneumatic hammers, however. They can be mounted on lighter carriers, since their external air compressor negates the extra hydraulic demands of a hydraulic hammer. Moreover, pneumatic hammers work better in confined spaces than hydraulic hammers due to their high weight-to-power ratio and are more conducive to underwater use.

7. Demolition Robots: Demolition robots add a new dimension to interior demolition. These robots have a more narrow application focus and can cost significantly more than a mini-excavator, but there are advantages that make them the most effective choice in certain applications. Unlike mini-excavators, demolition robots are unmanned and allow the operator freedom to move around the job site because they are operated by a remote control feature with Bluetooth technology.

These robots are able to climb stairs, and the outriggers, on various models, allow them to fit in tight spaces while still ensuring stability. The ability to mount a camera on the unit opens up even more possibilities.

Rethinking Debris: Scrap Handling & Recycling Equipment

Apart from those valuable metals such as steel rebars and aluminum window frames, which have high scrape value, rubble and demolished concrete can be processed into recycled rock fill or aggregates for use in construction.

As landfill costs for construction, demolition, and land-clearing debris continue to rise and the landfills become more heavily regulated, it makes economic sense to seek alternative means of disposal of concrete from construction and demolition operations. Many equipment like track loaders, wheel loaders & steer skids can be used to collect & deposit scrap at the recycle plant, which can be on or off the site depending on its portability.

1. Grapples and Bucket attachments: The versatility of grapples on a demolition site is often understated. Many grapples are built to do a lot of actual demolition in terms of ripping and tearing a structure apart. It can act almost as a shear to an extent if the steel is in the realm of the excavator's break-out force. The grapple then can be used to pick and sort through the resulting rubble.

Their dexterity and ability to handle large volumes of bulky, inconsistently sized material gives grapples an advantage over standard buckets on the demolition site. There is normally quite a bit of material sorting done of C&D, and the sorting requirement is almost certainly increasing in importance. The mechanical grapple is much better suited for the sorting task than a bucket.

2. Portable Concrete crushers: This impressive piece of demolition equipment crushes concrete into reusable coarse/ fine aggregate, which can then be recycled onsite. With the help of such concrete crusher, you can recycle thousands of tons of concrete every year.

After tearing down a building, the concrete slab is pulled up and cut into 2-foot squares to run through the crusher. The machine then grinds it into gravel-sized chunks, which can be used for road compaction, structural fill, pipe bedding and other applications.

3. Materials Sorting Screens & Steel Separation Magnets: Typically, mixed C&D debris is tipped at a central facility, and the materials with a high market value, such as large pieces of sawn lumber, are removed. The remaining mixed C&D materials are then processed using one of two primary methods. The mechanized size reduction method uses a crusher, a dozer, or a compactor.

The materials are then passed through a series of screens, magnets, and other separation equipment. The manual labor method relies on human sorters to pick out materials and place them in specific containers. Screens and magnets may also be employed with the human labor method, but the materials are left in their original form rather than crushed so that they can be easily distinguished and sorted. The most common approach is a blend of the mechanized size reduction and the human sorter methods.

Conclusion

A primary success for a debris recycling operation hinges on the degree of contamination of the valued materials by other types of waste such as nails, paint, foil, oil or plastic. Some processing facilities that aggressively handle a mixed waste stream may cause contamination of the C&D materials, thereby limiting their potential to be recycled. Educating contractors and owner-agencies about latest demolition/ scrap recycling methods, tools and equipment through a cost benefit approach will help improve the existing scenario in the industry. 

So far in India there has been very little effort to manage and utilize construction and demolition waste. Each city needs to have its own mechanism for collection and disposal of waste from bulk waste producers and major/ minor construction & demolition sites. It is necessary to evolve a system in which the generator of such waste, whether small or large, pays for appropriate disposal. Not much effort has been made in this sector and data on generation and characteristics is scarcely available.

The awareness level and availability of technology for Demolition waste re-use and recycling needs to be improved to make a sustainable change in India. Quality standards for the recycled or re-used products need to be developed and monitored by Bureau of Indian Standards. Separation of C&D waste at source through Public-Private-Partnership schemes should be promoted to be a possible mechanism of implementation of waste management in India. 

References:

1. Diven, R., & Taylor, M.R. (2006). Demolition Planning. Supplemental Architectural Services, The American Institute of Architects
2. Hemalatha, B.R, Prasad, N., & Subramanya, B.V. (2008). Construction and demolition waste recycling for sustainable growth and development. Journal of Environmental Research and Development, Vol. 2 No. 4
3. Atlas Copco Construction Tools. (2010). Selective and powerful demolition: Sink your teeth into this. Stockholm, Sweden
4. DeAnne Toto. (2004). Demolition Tools. Construction & Demolition Recycling 
5. Bhavani Balakrishna. (2013). Concrete Recycling: Need of the Hour. The Masterbuilder Construction Magazine
6. Ghosh, S., & Ghosh, S. (2011). Rebuilding C&D waste recycling efforts in India. Waste management World Press
7. Volvo Construction Equipment. (2009). Volvo Excavators: Demolition. Sweden