Effects of waste PVC addition on the properties of (40-50) grade asphalt

. Disposal of plastic waste poses a serious threat nowadays. Effective solutions are required to reduce or eliminate this problem. One of these solutions is to use these materials in asphalt mixtures. PVC (Poly Vinyl Chloride) during melting has adhesive properties which can be used with asphalt to reduce the bitumen mixture costs. Investigation of physical characteristics of asphalt cement (40-50) mixed with PVC is presented in this paper. The main objective is to study the change in bitumen properties after mixing with PVC of percent (2.5, 5, 7.5, 10, 12 and 15) % by weight of bitumen. Penetration, ductility, loss on heating, softening point, flash and fire tests were conducted for each percent. It is concluded that penetration decreases by 62.8% on addition of 15% PVC. Ductility also drops when PVC dosage increases. Softening point increases when PVC dosage increases by 6 % for 15% PVC.


Introduction
There is an urgent requirement to improve the road performance in view of the increase in traffic volume on roads and overloading of transport vehicles along with an absence of effective legislation to protect the highways, and also due to the significant difference in temperatures during day and night and across seasons. Hence the need to improve the properties of asphalt material. Population increase and industrial growth throughout the world result in creation and production of new types of non-biodegradable plastic waste. Recent studies have shown that plastic waste can stay on earth for 4500 years unchanged and without degradation. [1] In order to reduce pollution due to plastic waste an effective solution for recycling must be found. One such solution is the use of plastic waste materials in flexible pavement mixture. This process can reduce the cost of construction. The use of plastic wastes with asphalt mixture in pavement construction is not a new work. The idea began to spread across the world in the last two decades, where researchers have put together various ideas and researches to find alternatives to the use of plastic waste with asphalt. Rajasekaran et al. [2] investigated possibility of Polyethylene polypropylene polystyrene in coating aggregate, which is showing better aggregate properties that can be used in flexible pavement construction. Marshall Mix sample prepared using the coated aggregate. Marshall Stability improve in range of (18-20) kN. This process is environment friendly and helps reduce costs. Rahman et al. [3] used two types of plastic waste, polyethylene and PVC to improve asphalt mixture properties using Marshall Mix design. The tests includes measurement of unit weight, stability, flow, and V.T.M, the study concluded that polyethylene modifier up to 10 % and PVC up to 7.5 %, can be used for flexible pavement construction". Chavan [4] utilized waste plastic bags in coating the aggregate then used in the asphalt mixture to enhance properties of asphalt mix besides solving the plastic waste problems" Gawandea etal. [5] Reviewed developed techniques to use plastic wastes for construction of flexible pavement. Bitumen material can be modified by using plastic waste, so the modified mixture can be used on the wearing surface of the pavement. The modified mixtures show good stability, flow and moisture resistance. Jassim et al. [6], investigated stability of Marshall and retained strength index to evaluate plastic waste particles properties such as thickness, size and content percent. Basis results of the tests, it was found that the plastic waste reduced to a thin size of fine particles, thin thickness resulted in developing stability of Marshall and water resistance to damage, and could also solve environmental problems.

Asphalt material
The asphalt material used for this study is (40-50) penetration graded bitumen, which is supplied by Al-Dura refinery in Baghdad city. Al-Dura refinery produces asphalt cement graded from refined crude oil petroleum, which is used for pavement construction. Usually the penetration graded asphalt classified to (40- Standard ASTM tests were performed on the original bitumen getting the following properties shown in Table  1.

Poly Vinyl Chloride (PVC)
Plastic waste may be grouped depending on their physical properties to thermoplastic and thermosetting materials. Thermoplastic materials can be formed into any desired shape under the effect of pressure and heat. Thermoplastic materials become solid when cooled. Some examples of thermoplastic and thermosetting materials are tabulated below in Table 2.
[1]. Plastics can also be classified according to their chemical sources. According to sources of plastic, there are six types: Cellulose Plastics, Synthetic Resin Plastics, Protein Plastics, Natural Resins, Elastomers and Fibres. Table 3 gives the source of waste plastic generation.
[1]. The essential raw materials for PVC are derived from salt and oil. PVC is manufactured from two starting materials; • 57% of the molecular weight derived from common salt • 43% derived from hyrdocarbon feedstocks (increasingly ethylene from sugar crops is also being used for PVC production as an alternative to ethylene from oil or natural gas).
[7]  3 Plastic PVC preparation PVC collected from factories which produce PVC doors and windows to house construction. The plastic waste is cleaned well to ensure no unwanted material.

PVC Shredding
Shredding is cutting the PVC into small particle sizes between 2.5 to 3.0 mm by shredding machine from the seller where the waste PVC supplied.

Preparation of blend
First step to mix PVC with asphalt was heating the PVC particles until they soften then added to hot asphalt. It was found that PVC particles soften at (180-200) ᵒC. This process would fail if the PVC particles are gathered and clustered. Particles were added gradually to hot asphalt of (180-200) Cᵒ. PVC mixed with percent of (2.5, 5, 7.5, 10, 12, and 15) % by weight of bitumen until plastic waste mixture with bitumen became homogeneous. Figure (1) shows the shredded PVC. Figure (2) shows mixing process with bitumen. (1) Where: P.I = penetration index Trb= softening point temperature Tpenteration= penetration temperature = 25ᵒ C P.I range from (-2, 2) which indicate normal temperature susceptibility. P.I greater than 2 indicates low temperature susceptibility, while P.I less than -2 indicates high temperature susceptibility. [9]

Results and Discussion
The Penetration values decrease significantly when (40-50) bitumen is mixed with the modifier (PVC). The original grade decreases by 62.8 % on adding 15 % of PVC by weight of bitumen. Figure (3) shows the relationship between penetration and PVC content. It may be seen that the ductility values for bitumen modified with 12 and 15 percent are very low compared to original binders. It drops from 105 cm to 16 cm at 15 % PVC. The ductility values decrease with the increase in percentage of modifier (PVC) because asphalt becomes harder. Table 5 Properties of Asphalt with PVC  Table (5) which shows that penetration index decreases with increase in PVC %. The penetration index from 2.5% to 12% indicate normal susceptibility to temperature, while at 15% PVC asphalt material become high susceptibility. Figure (6) shows the relation between P.I and PVC%. Flash and fire points decrease with PVC increase, this can be shown in Figure (7

Conclusions
This study investigates the use of PVC with bitumen as additives to study the change in physical properties of (40-50) graded asphalt. From the experimental work, the following can be concluded: