19-07-2012, 10:51 AM
REVIEW NOTE ON USE OF WASTE PLASTIC LITTER IN ROADS
REVIEW NOTE ON USE OF WASTE PLASTIC LITTER IN ROADS.doc (Size: 47.5 KB / Downloads: 53)
The Problem
Waste plastic carrybags are a problem everywhere nowadays. They block drains and cause flooding in cities. Blowing across fields from open garbage dumps, they reduce germination and block rainwater percolation into the soil, affecting agriculture. Earlier these thin carrybags had a street price and were collected for recycling. In the last 3-4 years, national policies discouraging the use of black plastic pipe for underground use has caused the major recycling market for carrybags to evaporate. As a result, carrybags are found in garbage in increasing quantities, upto 12% by weight and over 50% by volume after sieving them out from compost windrows. This voluminous plastic content has totally destroyed the earlier culture of farmers taking city waste for on-farm composting, resulting in non-biodegradable waste piles that promote rampant mosquito breeding, apart from the flies, rodents and stray dogs that hunt village livestock in feral packs at night.
The Solutions
For sustainable living, what comes from the earth should go back to the earth. This has been done since millennia in rural India, by composting crop and food wastes. Now it is also possible for hydrocarbons and polymers. They can return to the earth as beneficial additives in bitumen roads and possibly soil roads too. Three such technologies are reviewed below, two for waste-polymer-modified bitumen roads and one for incorporation of plastic into aggregate-free soil-cement rural roads.
BANGALORE’S KK PROCESS FOR ASPHALTED HIGHWAYS
The Indian Roads Congress in 1999 issued Special Publication 53 titled : Tentative Guidelines on Use of Polymer and Rubber Modified Bitumen in Road Construction. It documented the excellent advantages of adding an optimum 6% by weight of virgin polymer into tar roads. The high cost of virgin polymer (about Rs 50/kg) for getting this added value has prevented its adoption in India until now.
Research began in 1997 by KK Polyflex for value-added disposal of shredded waste plastic litter into bitumen roads at an affordable cost to make the process viable. The approach was scientific, with exhaustive comparison of different proportions of different types of plastic done by a Ph D student. By now the technology and results are well-established. Marshall Stability values and even wet penetration values improve by addition of 8% shredded plastic by weight of bitumen used. Lab tests show 2-3 times superior performance. In practice, such a “plastic road” laid in Bangalore (at the busy Rajarajeshwari Junction) in March 2001 as a technology demonstration for the Chief Minister, showed superior smoothness and uniformity and less rutting as compared to a plastics-free road laid at the same time, which has begun to develop “crocodile cracks”. As a result, by now 25 km of “plastic roads” have been laid in Bangalore, unfortunately without another same-day plastics-free normal road. All these 25 km are performing well. The process was also approved in 2003 by the CRRI=Central Road Research Institute Delhi, and has thereafter been included in the Govt of Karnataka’s PWD Schedule of Rates. News reports say that Bangalore intends to lay a further 800 km of such plastic roads and the work order for this is expected shortly. Road life improves through improved tackiness and viscosity of the bituminous mix, thereby binding the stones more firmly together and improving the water-resistance of the mix to rain etc. For the same reason, the temperature of the mix both at the plant and at the point of laying, needs to be 20oC higher than normal.
The proprietary KK Process consists of procuring (by collection from roads, garbage trucks, dumpsites or compost plants, or from school collection programs, or by purchase from rag-pickers or waste-buyers at Rs 5-6 per kg) waste plastic litter in the form of thin-film carry-bags, use-and-throw cups, PET bottles, etc. These are sorted, de-dusted, washed if necessary, and finely shredded after treatment as required. Yield of useful material is poor, the rest being dust, rags and some unusables. This shredded material is added into the bitumen stream of Centralised Hot-Mix Plants in a proprietary manner, using KK’s own equipment (under patent) as an add-on to the plant and under their supervision. 1 km of single-lane road uses about 1 ton of plastic.
As there is so much scope for improper laying of India’s roads, bypassing the excellent specifications and procedures laid down, especially bitumen percentage and mixing temperatures, KK have decided to protect the reputation of their plastic-in-roads concept by taking total ownership of the process, right from waste-plastic collection/procurement to taking full responsibility for road quality and for operation, maintenance and transport of their proprietary equipment. The cost of all this has been built into the PWD-approved price for purchase of shredded plastic additive. Cost of roads go up by about 6% using the KK process, but the road life is likely to go up by 100% to 200%. Thus there are huge savings in road maintenance costs. The indirect savings through uninterrupted traffic in difficult terrain will be especially useful for Border Roads and the armed forces, because of cold cracking of roads in snowy mountainous areas.
In Uttaranchal, the added 6% cost of high-quality roads will also be more than offset by savings in the cost of plastic waste management. For example, the Nanda Devi Sanctuary authorities did a fantastic job of cleaning the Hemkund area of 52 tons of plastic, but at a cost of Rs 52 per kg to bring it down and transport it to Dehradun for eventual purchase by a Delhi buyer. If instead this plastic is used for asphalted roads as close to the collection point as possible, the cost savings will be huge. As there is a plan for similar plastic cleanup of the Char Dhams, waste-polymer-modified bitumen roads can be specified in and near these areas.
What is required from cities desiring this option are :
1, Use of sufficient land on the outskirts for processing of waste plastic litter into shredded additive, both of which are very bulky. For Bangalore’s 60 lac population, generating 200 tons a month of plastic waste, an area of 10 acres would be required.
2, Electricity connection of 100 HP at city’s cost, with power consumption paid for by KK.
3, orders for a minimum quantity of plastic-additive roads to be laid per quarter, with the additive to be procured from and added by KK. Escalation clause for increased cost of power, which should preferably be supplied at preferential rates for this pollution-abatement activity.
4, prompt payment of bills for shredded plastic supplied, preferably through bank against presentation of bills, and payment of 2% interest per month for delayed payment, as that is the cost of finance for industrialists.
5, an MoU for a 3-year period covering the above aspects.
Technical data and comments on road performance can be obtained from :
KK Plastic Waste Mgt P Ltd, kakbest[at]hotmail.com, 98450-78600 + 98443-06889.
R Jaiprasad, Engineer-in-Chief, Bangalore City Corporation, 98441-38952, 080-2297 5518 off
Dr CEG Justo, ex-Prof Civil Engg, cegjusto[at]hotmail.com, 080-2671 4171, 984482-74171
Dr A Veeraraghavan, Coordinator, Dept of Transportation Engg, Dept of Civil Engg, Bangalore Univ, Blr-560056. ccntrans[at]vsnl.com, off 080-2321 4001 ext 267 (now at IIT Madras)
Central Road research Inst New Delhi 110020. KK Project Leader Dr S Bose
sMADURAI PROCESS FOR RURAL MACADAM ROADS
In 2002, the Thiagarajar College of Engg at Madurai also began work on waste polymer modified bitumen roads in their Dept of Chemistry, along with many other very innovative and useful ways to utilize waste plastic road-litter. Their process for road-making was designed to suit the mini-hot-mix plants used in smaller cities and towns and rural areas. Here again the objective was eco-friendly disposal of plastic nuisance wastes, but the approach was more pragmatic, focusing less on the actual quality improvement of a road and more on its potential as a vehicle for waste management. The effort was given a big boost by CM Jayalalithaa’s announcement at a public function on Aug 16 2002, widely reported in the press, that “1000 km of such roads would be laid in rural areas within one year and the shredded plastic procured only from self-help groups at the rate of Rs 10 per kg”. Hence the Secy Rural Dev allowed the laying of such roads under the PMGSY= PM’s Gramin Sadak Yojana scheme and the Clean Village Campaign, both administered by her, more as a self-employment effort rather than for environmental or road-improvement reasons. In fact, the Self Help Groups in every District eagerly await the profitable orders for shredded waste plastic litter collected locally. The “1000 km” promise of CM was fulfilled by sanctioning 30-40 km of experimental roads in each district, the mean length of each stretch being 300 - 500m. This large-scale trial was conceived to rapidly evaluate their performance in as wide a range of eco-habitats and user conditions as possible within one 12-month range of seasons. The question of complying with PWD specifications or first getting it into their Schedule of Rates did not arise as these roads were laid to meet (and did meet) the finished specs laid down by the centre’s Rural Roads Institute (?) All data has been forwarded by the Secy Rural Dev TN to the Rural Roads Institute, which in turn has sent them on to the CRRI for evaluation and certification of the process.
The Madurai process is designed for Mini-Hot-Mix plants in which a bucket of about 1.5 cu m (amnually filled with aggregate at ground level) is mechanically lifted to unload this into a rotating steel drum heated by a naked diesel flame entering from one side. After stones attain their specified (160oC) temperature, the hot aggregate is unloaded, by means of a manual lever, into a stationary “puddling chamber” with heavy mixing paddles on a rotating shaft. Here buckets of hot liquid bitumen (which should be 170oC) are manually passed up, to be poured onto the stones in the puddling chamber. This is the stage at which the Madurai Process intervenes: shredded waste plastic in a basin (Ghamla) is passedup for manual sprinkling onto the hot stones before bitumen is added. At aggregate temperatures of at least 140oC or more, the shredded plastic gives the hot stones a uniform oily-looking coating of molten plastic, to which the molten bitumen adheres very well, with the plastic actually dissolving in the bitumen to an extent of only about 2% to increase the viscosity of the binder. However the plastic pre-coating has the effect of improving the stripping-resistance of the mix (i.e. water does not make the bitumen coating come off the stones easily). Madurai’s recommended additions of shredded plastic are for REPLACEMENT, not addition, of 10% waste plastic by weight of bitumen used.
SUPERVISION OF CONTRACTORS AND THEIR OPERATIONS is the key to a good quality road made by any process. The supervising site engineers are invariably absent for most of the day when roads are being laid, let alone to be found atop the Mini-Hot Mix PLANT which is the only location from where quality supervision is possible. Under-utilisation of specified bitumen and its theft occur to an extent of upto 50%. Neither the contractor nor supervisors have any means of ensuring that the good specifications for temperature of heated aggregate or bitumen are adhered to, although a hand-held battery-operated infrared laser thermometer is now available for as little as Rs 7000 (Korean make). Specified temperatures for road-making are 160oC for aggregate and 170oC for the liquid bitumen to be added to this in the puddling machine, to give a mix of 140oC while unloading wheelbarrows of hot mix onto the road for spreading and rolling. Spreading of a hot-mix with plastic added requires more effort than for normal bitumen mixes. Contractors also try to save heating fuel required for heating the aggregate by heating the stones only to 120oC and the bitumen (heated in a half-drum over fuelwood or old tyres) to 215oC. In such cases, the plastic does not melt and coat the stones at all. Reports have even been received of some contractors paying for false bills for shedded plastic at the rate of Re 1 per kg billed but not used at all. This is allegedly because they are unable to take shortcuts and lay twice the distance done by correct methods.
These mini-hot-mix Madurai-process roads are not as good as the KK-process roads in Bangalore for many reasons:
a), the specifications for rural roads are far less rigorous than for highways, which have a topping layer of fine aggregate to give a smooth non-porous finish.
b) it was obviously impossible for anyone from the University, which has no financial stake in the process or its implementation, to supervise so many widely-scattered stretches.
c) waste plastic is ADDED @ 10% by weight of bitumen used in the KK process, thus increasing binder proportions and hence road quality. In the Madurai process, 10% by weight REPLACEMENT of bitumen by waste plastic is recommended.
d) The KK process selects and cleans etc its shredded plastic. The Madurai process accepts any and all types of polymers and multi-films, which may often be dust-coated.
e) Addition of shredded plastic into computer-controlled central hot-mix plants in the KK process is mechanized and uniform, whereas the manual addition in the Madurai process could lead to inhomogeneous dispersion, especially if temperatures are not well maintained or monitored.
Citizen monitoring of road works is one solution. For this, a Citizens Guide called Monitoring the Quality of Road Works has been published by Public Affairs Centre Bangalore 560034, pacindia[at]vsnl.com , website http://pacindia.org .
NCB-FUJIBETON PROCESS FOR AGGREGATE-FREE SOIL ROADS
The National Centre for Cement & Bldg Materials (NCB) at 34 km stone, Delhi-Mathura Rd, Ballabgarh 121004 has laid in its campus a soil-cement road without any stone-metal aggregate for sub-base or surface, which sets in 8-10 hours to the strength of concrete. The secret is Fujibeton, a special rapid-hardening additive developed in Japan and supplied in India by Rahul Sharma of Tri International Ltd, B-3/10 Safdarjung Enclave, New Delhi 100029, 011-5165 7800