Evaluation of Engineering Properties of Plastic Modified Bitumen

Objectives: To make an efficient utilization of waste plastics for pavement construction stronger, economical and ecofriendly. Methods/Statistical Analysis: Comparative experimentations are carried out on three sets of samples: pure bitumen & modified bitumen, conventional mix& modified bituminous mix and uncoated aggregates & plastic coated aggregates. Modified bitumen is prepared by mixing powder ground plastic (10% by weight of bitumen) in pure bitumen. Dry mix process is employed to prepare plastic coated aggregates and modified bituminous mix. Findings: The experimentations result showed that the modification of conventional bitumen with waste plastic shows positive margin in all the tests carried out except ductility test. The conventional roads are constructed using bitumen, which is not only expensive but also have some pre and post constructional problems like rutting, potholes, stripping out of aggregates, etc. This work justified the utilisation of waste plastic as a partial substitute of bitumen in which the extent of replacement of bitumen with waste plastic is 10% by weight of bitumen. Waste plastic not only reduces the cost but also improves constructional features such as reduced rutting as it increases the softening point and reduces cracking and pothole as loss on heating of modified bitumen is less. Application/Improvements: In binding and surface courses of pavement bitumen can be successfully replaced with 10% of waste plastic to impart greater strength and durability to the pavement.e. *Author for correspondence


Introduction
For development of every nation connectivity is the basic necessity. Connectivity is ensured by road construction. With increasing traffic, the high strength pavements are becoming the need of the hour. But the conventional bituminous roads are unable to perform well and bear such a huge traffic. The problems such as rutting, pothole formation, cracking, etc. are common with conventional bituminous roads. On the other side, plastic is now becoming an integral part of our life. In India as per reported by Mr. Dave, our environment minister, "Central Pollution Control Board has estimated the generation of 15,342 tonnes of plastic waste in the country, out of which, 9,205 tonnes were reported to be recycled and leaving 6,137 tonnes uncollected and littered. The lack of awareness and absence of effective tools to collect back the discarded plastic products including the wrapping material has led to the indiscriminate littering and disposal of plastic waste. 1 Thus plastic imposes giant disposal problem. So, if we see these two problems simultaneously they can serve as solution to one-another i.e. we can use waste plastic as a partial substitute of bitumen which improves the level Keywords: Bitumen, Conventional Mix, Modified Mix, Pavement, Waste Plastic of serviceability provided by the road, imparts better binding, increases strength and service life of pavement, makes road construction economical and avoids disposal problem of plastic waste.
In the reported article concluded from their investigation that the pavement constructed after modification in bitumen binder with waste plastic showed better moisture resistance which is justified from reduction in stripping of plastic coated aggregate as compared to uncoated aggregates. 2 He also stated that the concept of utilization of waste plastic in the construction of pavement has made see off to the disposal problem of waste plastic, as it is a finest way to reuse the plastic waste ecologically.
In the article studied the effect of addition of plastic in bitumen, on its stability, life and strength. All of them showed positive results, that plastic addition improves stability, enhances strength and increases life when added in bitumen. 3 In the article performed thin film oven test and reported less ageing of plastic bitumen blends in comparison with the neat bitumen. 4 This justified better performance of the blend and build resistance to cracking. This is the reason due to which less premature failures are observed on the pavements made with modified bitumen with plastic bend. Other characteristics are also improved such as: the plastic blend in bitumen has improved indirect tensile strength and better rutting resistance as compared to conventional bituminous mix. For checking moisture resistance Stripping test was conducted after proper mixing. The test inferred that the adhesion of the stone-plastic waste-bitumen aggregate was good. Tar road is performing efficaciously great when laid, when diversified with stone and bitumen at high speed asphalt plant.
In the article studied chemically modified polyethylene and find characteristics of partial asphalt substitute in them, so that it can be used as paving materials. 5 Chemically grafted polymers are readily miscible with asphalt. The blend thus prepared have increased softening point, decreased degree of penetration, improved performance at higher temperatures, better rutting resistance and high flow activation energy.

Present Investigations
The conventional bitumen roads can be economically and structurally improved by using waste Plastic, which can serve two purposes which are safe disposal of waste plastic and economized roads with enhanced characteristics. Method of construction of plastic blended pavement is similar to the flexible pavement construction the only processes vary are pre-construction processes which are as follows:-

Segregation
Waste plastic in the form of plastic carry bags, disposal cups, PET bottles, etc. are collected from roads, garbage trucks, municipal offices and compost plants, rag pickers and segregated from other wastes.
Segregation of waste plastic includes following steps: • The waste plastic is separated out from other wastes.
• Then from different forms of plastic wastes i.e.
PET, HDPE, LDPE, etc. PVC and Other plastic wastes are discarded as they release lethal products on burning.
• Now the collected Plastic forms are sorted as per the required thickness. Generally, polyethylene of 60 micron or below is used for the further process due to the fact that less micron plastic is easily mixable in the bitumen at higher temperature (160°C-170°C).

Cleaning
The segregated plastic is then cleaned by de-dusting or washing if required. Generally water washing is used for cleaning them. Washing is done by blowing streams and then the washed plastic is allowed to dry for further processing. Sometimes de-coloring is also adopted to remove harmful colors and improve characteristics of the blend.

Shredding and Collection
Cleaned Plastic is shredded into fine pieces by shredding machine. The shredded plastic pieces are sieved. The shredded plastic passing through 4.75 mm sieve and retaining at 2.36 mm sieve are collected.

Field Trials
In field it can be processed by two processes viz. Dry Process and Wet Process. In this document dry process is evaluated, as it is easy to go through dry process where as the wet process needs central mixing plant with heavy mixing equipments.

Field Trial for Dry Process 6
• The aggregates of different grading are mixed thoroughly. • Then the aggregates are heated to a temperature of 165-170˚C. • That temperature is maintained for 2-3 minutes.
• Then the shredded plastic of required size is added in equal proportions and mixed to obtain a homogeneous mix. • Then hot bitumen is added to the plastic coated aggregates. The mix is then laid for constructing pavement similar to the mix used in conventional pavements.

Performance Evaluations
For

Conclusion
In construction of pavement, bitumen is used in binding course and surface course. It can be successfully replaced from waste plastic by 10% by weight of bitumen. As it enhances the characteristics of bitumen by improving its engineering properties. By doing so we can save huge sum of the nation in construction (per kilometre of pavement stretch). This is an innovative approach to dispose highly pollutant material, waste plastic, in most beneficial and ecological way which not only results in improved pavement material in surface courses but also, make it economical and durable and helps in keeping environment healthy and clean. Plastic coated aggregate Nil Table 3. Result of tests on Aggregates