Post 405 – by Gautam Shah
Buildings are formed of huge volumes of materials. The materials of construction come to the site in small lots and over a long period of execution. Older buildings are likely to have greater volume of materials than any of the recent constructions. Recently constructed buildings are likely to have lighter but highly articulated forms. The composed materials and their integrated geometrical makeup make it difficult to demolish and separate the materials. For older buildings the recovery or recycling process involves large volumes and simpler mix of debris, whereas for recent buildings the recovery process is smaller but its complex mix of debris makes the recycling process difficult and costly.
Debris has been a problem of human settlements since prehistoric times. The problem was complicated because agricultural wastes of farms, excreta of humans and animals, ashes, broken pots, and kitchen garbage, all were dumped together with useless building materials. Some of the wastes like bones, skins, hairs, feathers, etc. were managed away from the settlements. Stems and husks of agro-products were managed at form locations. Organic wastes of animal urine and excreta were recycled for building finishing materials or as fuels.
Old historic sites show predominantly broken pots and rubble of building materials. Both of these forms are nearly indestructible, so last for a very long period. These materials were often used for land fill or leveling, but otherwise new buildings constructed over the dump. For example, Mohen-jo-daro and other Harappan sites, and ancient Vadnagar (Gujarat – India), are such hillock sites.
Disposal of debris is mainly of course a problem of transporting the waste to locations away from the settlements, but it was also due to the inability to use the older building materials like clay, broken bricks, pots or ceramics. Stone, however, is recyclable material to the smallest piece. Romans constructed many buildings with stones, and these were reused not only used in simpler dwellings, but also for mosaic and inlay work in public buildings. This activity of recycling the Roman old buildings continued for several centuries.
Time has not spared the Egyptian Labyrinth. The complex fell into ruin at an unknown date, but during Roman times it became the site of quarrying for its fine stone. It occupied such a number of masons that a small town sprung up on the site. When the British archaeologist Flinders Petrie excavated the site in 1888, he found nothing but a vast field of chipped stone, six feet deep.
Paris, once had a similar problem of managing the debris. Paris had no paved streets or with planned storm water drainage slopes. The town became muddy with little rain. The streets were covered by local residents with hard debris. This dumping was enhanced by dumping -spreading the waste whenever an old building was replaced with a new one. This raised the street levels to upper floors, burying the ground floor, and sometimes second floors as the cellar. “It occurred at varying rates and often accelerated following demolitions in times of conflict. Such dumping also occurred just outside the city walls as artificial hills. The hills remained, as these were difficult to transpose. In Paris such mounds have been integrated into the urban landscape (Jardin des Plantes is an example of a historical dump-site). Mumbai was a land of seven islands separated by creeks, but the land has been reclaimed by dumping debris, garbage and soil.
Building materials as debris result from demolition of nonviable structures, disasters and modifications. There are also mine head and on-site dressing wastage. The quality of construction materials and technology of assimilation determine the size and shape of elemental units, if any. Integrated buildings (like cement concrete) have little to offer in terms of elemental units. The process of debris formation, such step by step demolition, sudden collapse and historical neglect, determine the debris sorting, removal and reuse of materials. The reuse of material is of very high proportions for small buildings of self-help construction, historical neglect and for simpler and low cost recycling processes.
The problem of managing non-recyclable debris like clay, brick and ceramic pieces may not be very acute for one or two buildings in a settlement. But when there is a massive destruction due to earthquake, floods, invasion or forced evacuation due to disease, the mound of debris is immovable. The reconstruction must occur over the old heap or mound of debris, or a new site must be found. Both of these are evidenced in history.
Earth quakes in Kutchh and other parts of Gujarat created a huge problem of debris removal and disposal for reuse or safe dumping. Debris removal from narrow streets of age-old towns using automatic machines or dumper trucks was difficult. A greater problem was how and where to dump the material, when the entire village outskirt lands are for cattle grazing or farming. Local groups sorted good and whole bricks by temporarily employing jobless local people. Few structures were constructed with these recovered materials.