Laboratory evaluation of properties of modified asphalt binder with different types of additives

This research aims to assess the properties of Polymer Modified Bitumen (PMB) binder prepared with different types of additives such as (Waste low density polyethylene (W-LDPE) and crumb rubbers (CR)and Styrene Butadiene Styrene (SBS)). Most of these additives are sustainable materials since it is derived from old scrap materials. All the above-mentioned materials (W-LDPE, CR and SBS) were added with percentages of (2, 4, and 6 percentage) of the weight of pure asphalt binder. Several tests were conducted to evaluated the properties of improved asphalt binder such as penetration test, Ductility test, Softening point test, Rotational viscosity test as well as thin-film oven test. The results of investigation revealed that, the using of different types of PMB significantly improved the physical properties and performance of asphalt. The using of sustainable waste materials such as W-LDPE and CR significantly improve the properties of PMB and contribute in recycling great amount of waste materials. Also, the results showed that the using of high percentage of SBS (6%) significantly increase the viscosity of asphalt binder and that can affect workability of Hot Mix Asphalt (HMA) compared with same percentages of W-LDPE and CR).


Introduction
Asphalt is the most often used pavement materials because it provides excellent driving comfort, durability, stability, and water resistance.In general, the viscoelastic characteristics of asphalt are time-as well as temperature-dependent [1].Many researches on bitumen modification have been done to produce bitumen of higher quality over the last four decades.One of the most prevalent ways for modification is to use a polymer to modify the asphalt binder.Polymers may help bitumen have superior qualities such low-temperature fracture resistance, high-temperature stiffness, longer fatigue life, and improved moisture resistance.The ultimate qualities of polymer modified of bitumen are determined by the properties of the asphalt with polymer, as well as the production techniques and amount of polymer utilized [2].Plastomers (e.g., ethylene-butyl acrylate (EBA), polyethylene (PE), polypropylene (PP)) as well as thermoplastic elastomers, ethylene-1232 (2023) 012043 IOP Publishing doi:10.1088/1755-1315/1232/1/012043 2 vinyl acetate (EVA), (e.g., styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), as well as styrene.These polymers can be introduced in two ways: by mixing polymer into the asphalt (wet process) or by mixing polymer with the aggregate and asphalt cement directly (dry process) [3].The environmental problems caused by improper the waste disposal, including the improper disposal of rubber and plastic scraps, as well as the expansion the environmental of regulations to protect and promote green infrastructure in the pavement construction materials have prompted an effort to investigate the possibility of the recycling of this waste in a variety of ways, including using it as asphalt cement modifiers.[4,5].Therefore, one of the many solutions to the problem of excessive solid waste material in rural and urban areas is successful waste material re-use.Reusing waste materials may have a positive impact on the environment and economy in a variety of ways, including: x It contributes to the reduction of overuse of natural resources and their protection from exhaustion.
x It contributes to the reduction of environmental pollution caused by waste produced in urban and industrial areas.
x It leads to energy and financial savings.In recent years, it has become common practice to construct HMA using the waste materials which have the potential to improve the mechanical properties of asphalt pavement.This increases the pavement's resilience and resistance to damaging elements like fatigue cracks and long-term deformation of the pavement [6].The widespread use of asphalt materials offers a viable strategy for recycling household wastes and recycle industrial wastes.Waste plastic is a typical example of a waste material that has been used into asphalt mixes, reclaimed asphalt pavement (RAP), crushed brick, waste glass and rubber obtained from waste tires [7][8][9].When it comes to employing by-products in asphalt, its linked businesses have vast expertise using recyclable resources in road building [10].However, a careful investigation of these by-products' sources and properties is necessary for their effective application.On the one hand, consuming the waste mentioned above is a practical strategy to control waste.
Waste materials' constituents improve the functionality of asphalt materials in certain ways.In particular, laboratory studies have shown that it is feasible to use crumb rubber modification (CR) made from scrap tires for vehicles as a modifier for asphalt binder, HMA and concrete pavement [11][12][13].
Using waste materials-modified asphalt to achieve preferable asphalt pavement performance has been noted for a long time.Consequently, waste tire rubber and waste plastics are considered the most outstanding modifiers broadly used worldwide.
The SBS polymer has a high degree of compatibility as well as the tensile strength under tension.It has the ability to improve the flexibility of asphalt and its efficiency at low of temperatures [14].Yan, et al. [15] found that combining waste tire rubber (WTR) and recovered low density polyethylene (WLDPE) with binder reduced penetration while increasing softening point and viscosity, indicating an enhancement in deformation resistance in the intermediate and high temperature range.The most widely utilized plastic in the world is polyethylene (PE), which is a semi-crystalline material with good chemical, wear resistance and fatigue, wear resistance as well as reduced moisture absorption rates.It increases adhesive between both the asphalt cement and the aggregate, increases fatigue resistance, and lessens pavement deformation when used to enhance asphalt pavement.The basic building block of polyethylene is a lengthy chain of carbon atoms connected by two hydrogen atoms.According to density, polyethylene is divided into two categories: high-density polyethylene (HDPE) as well as low-density polyethylene (W-LDPE).In summary, virgin bitumen will not satisfy in all conditions without any modification, as soft, medium viscosity binders are appropriate for cold weather.Whereas, harder and high viscosity binders are needed in hot weather [16].Many investigations and experiments have been performed to increase the bitumen quality.Polymer modification is one of the most common ways to modify bitumen [17].Therefore, the purpose of the following study was to investigate the impact of various PMB types on the physical characteristics of asphalt cement.A complete experimental program was performed, including tests for penetration, ductility, softening point, rotational viscosity, as well as thin-film oven test.

Materials 2.1 Asphalt cement
The asphalt bitumen is (40/50) grade utilized in this study obtained from the Al-Nasiriyah refinery, which is located southeast of Baghdad and is more suited to hot climates like those prevalent in Iraq.

Additives
Three types of additives were used in the current research, which are W-LDPE, CR, and SBS with asphalt cement as shown their details below.

Waste Low-Density Polyethylene (W-LDPE):
W-LDPE was provided by a recycled materials firm in AL-Diwaniyah .The qualities of this material, which was given by a recycled materials firm, are listed in Table (2).Plate (1) shown the particles of W-LDPE.

Preparation the asphalt modified with types of additives
The asphalt cement is typically heated to about 160 ° C before being combined with three amounts (2,4,6%) by the weight of asphalt (RC, W-LDPE, SBS).This mixture was performed with a proper the shear mixer at a mixing speed of (3500) r.p.m and at mixing temperature (180 ± 10) °C for a duration of (45) min for RC and (150 ± 10) °C for a duration of (45) min for LDPE and mixture temperature of (180) °C for 2 hours as well as 30 minutes for SBS.A skilled mechanical engineer created the shear mixer to finish this task and replicate the typical conditions of the mixture by regulating the mixture temperature, the necessary mixing speed, and avoiding asphalt binder exposure to the air.This process is shown in plate (4).

Testing of Physical Properties of PMB 4.1 Penetration test:
The determination of bituminous materials' ability to penetrate solid and semi-solid surfaces is covered by this test technique.Bituminous materials' consistency/hardness are assessed using the penetration test.
The asphalt binder is heated at (110) °C above its predicted softening point during the testing procedure and is placed into the piercing contained then set to cold at the room of temperature.The asphalt sample is kept for (60-90) minutes in a water bath at (25±0.1) °C.Finally, a penetrator would be used to test the specimen, where the asphalt is penetrated for a time of (5) seconds with a needle (100) g by weight.The depth of penetration is finally measured in (0.1) mm unit.Higher penetration numbers correspond to softer consistency.Lower penetration values, on the other hand, denote harder consistency.
The ASTM D36-compliant softening point measurement has been used.The test's objectives include determining the asphalt materials' surface temps as well as demonstrating the material's propensity for movement at high temperatures.
During the test, two steel balls are put on the vertical of support with the horizontal of asphalt binding disks that contain metal rings of mounted on it.A water bath is used to gradually warm the component (5°C/min).The measurement for bitumen softening point is displayed in Plate (5).The end calculation for the softening-point is the average temperature at which each ball, enclosed in the binder, can fall a vertical displacement of (25) mm between the two asphalt disks. .

Ductility:
The tensile properties of examples of asphaltic materials are assessed using the ductility test, as according (ASTM D113-2017).The ductility test for asphalt adhesive is shown in Plate 3.10.To prevent the bitumen from sticking to the mold, the platform and inner surfaces of a mold are put on a plate and oiled, with the exception of the two ends.The hot bitumen is then placed in the mold and left to settle at room temperature for 90 minutes at (25±0.1) °C before being tested.Finally, the sample is placed in the ductility machine and the ductility is measured under standard test conditions (5-cm/min stretching-speed at 25±0.5°C) by the extension length (in centimeters) of typical bitumen specimen.Asphalt binder with a high ductility value is normally considered to be highly effective at low temperatures in service.As shown in Plate (6).

Rotational viscosity Test
According to ASTM D4402, the Brookfield (DV-III) rotational viscometer was used to measure the viscosity of asphalt binder.A spindle which is dipped in a binder specimen is subjected to torque.A beaker with a thermostat controls the temperature at which the binder specimen is kept.With a specific

Softening point:
rotational speed, the relative resistance to rotation is calculated.The viscosity is then determined using the relative resistance, spindle size, and rotational speed as illustrated in Plate (7).

Rolling Thin Film Oven Test
During the aging process, oxidation and dehydrogenation actually occur in the asphalt binder.Asphalt binders go through a number of physical and chemical modifications during the mixing, storing, shipping, and paving operations.The substance eventually loses its initial qualities, becoming brittle and tougher.
Aging is the term used to describe these changes.One of the most popular test techniques to simulate the aging of asphalt plant mixing is the Rolling Thin Film Oven Test (RTFOT), as shown in Plate (8).
Plate 8. RTFO Device with Glass Bottle

Characteristics of PMB 5.1.1 Effect of additives type on the penetration values of asphalt binder:
This test is employed to evaluate the consistency of the asphalt binder and determine the impact additive types have on its penetration levels.the penetration testing results for both the modified and the unmodified asphalt binder before and after the thin film oven testing (aging) are present as shown in Figure (9).Generally, the results showed that the values obtained decreased as the additive concentration increased.By addition, (2, 4, and 6) % of (W-LDPE, SBS , CR) respectively, the penetration was decreased before the thin film oven test by (27, 38 , 59)% , (15, 23, and 30)%, and (10, 20, and 27)% as comparison to the un-modified asphalt binder.These interactions between the polar asphaltene molecules and the polymer, which improve asphalt's polarity qualities and build a network of polymeric molecules, as well as the migration of maltenes (the oil part of bitumen), which occurs in the polymeric phase, are what produce swelling.

Effect of additives type on the softening values of asphalt binder:
The softening point is an alternative test to determine the asphalt binder's consistency.Figure (10) shows, before as well as after aging, the softness points of modulated and original binder with different modifier percentages.The value of the soften points increase as the modifiers content increased, as can be observed.,indicating an increase in deformation resistance.Before aging, softening point increased by (10%, 19%, 40 %), (23%, 31%, 36%) and (14%, 19%, 23%) as compared to the unmodified asphalt binder by adding, respectively, 2%, 4%, and 6% of (W-LDPE, SBS, CR) respectively.This increasing may associate an improvement of adhesive properties of the asphalt binder.It can be observed that the amount of increase due to the addition of (W-LDPE, SBS, CR).After thermo-oxidative aging, the softening point values are increased with increasing in all modifiers content.Softening point values increased by (10%, 7 % and 5 %), (7%, 8%, 8%), and (4%, 5%, 5 %) as a result of modification with (W-LDPE, SBS, CR) respectively.The same explanation mentioned in section above (5.1.1)can be adopted.
The viscosity of the bitumen binder modified with 2%, 4%, and 6% is high than that of B0, indicate a reduce susceptibility to temperature than B0.

Summary and conclusions
In the light of the results obtained in this paper; which deals with using the (W-LDPE, SBS, CR) to produce sustainable polymer modified binder the following: 1.The usage of different waste types while constructing asphalt paving benefits the both systems for road building as well as protection of environmental.2. Laboratory experiments prove that CR and plastic waste has a high of ability to advance the characteristics of asphalt.This was reflected positively on the results of lab tests shown in the current research.3. The use of low-density polyethylene waste that passed through the No. 50 sieve also demonstrated greater efficacy and homogeneity with the bitumen during the wet mixing process, similarly to use of extremely fine CR that passing through the sieve No. (100).This is because both the rubber and polyethylene crumb particles have larger surface areas.4. Addition of SBS to the bitumen results in a decreased in penetration, temperatures sensitivity, ductility as well as an increased in viscosity, softening point, as well as aging resistance. 5.The findings indicated that utilizing 6% percent rubber crumbs produced positive outcomes in each of the laboratory tests carried out for this investigation.
6. Through the outcomes of the lab tests carried out in this research, all percentages of W-LDPE and SBS shown good results and significant improvement in performance.7. Through all laboratory findings from this research as the results of the characteristics of asphalt modified with these additives, the optimal percentages of additives of CR, LDPE, and SBS were 6%. 8.As a result, using waste products in paving of construction would reduce their environmental impact and the costs of transferring, storing, as well as recycling these waste products, which are brought on by the accumulation of solid wastes in landfills as well as cities, in addition to a pollution and environment problems they cause.

Figure 9 .
Figure 9. Penetration at 25°C for Un-modified and Modified Bitumen Before and After Aging

Figure 10 .
Figure 10.Softening Point at (R&B °C) for Un-modified and Modified Bitumen Before and After Aging.

Figure 11 .
Figure 11.Ductility for Un-modified and Modified Bitumen5.1.4Effect of additives type on Rotational Viscosity value of bitumen:This test was done to find out how viscous bitumen was under application conditions according to ASTMD6926.Figure shows the link between viscosity and temperature for both un-modified as well as modified bitumen.Although the viscosity values fell as the test temperature rose, asphalt modified with various modifier ratios had viscosities that were higher than those of B0.It may be shown that the modified bitumen exhibits less

Table 1 .
Table (1) shown the physical characteristics of asphalt pure.The physical of characteristics the Asphalt

Table 2 .
(3)racteristics of W-LDPE Crumbs rubber were brought from tire plants in the governorate of AL-Diwaniyah and utilized as an ingredient in this project.CR are little black particles made from discarded tires that have been recycled.There are numerous sorts of compounds in tires, and the hydro-carbon content of the rubber has the highest impact on the physical qualities of modified asphalt with rubber; nevertheless, natural rubber content can have additional effects.The CR were sieved to the necessary size through (No.100) of sieve.The physical characteristics of waste rubber tire and Plate of the (CR) utilized in this investigation are shown in Table(3)and Plate (2) respectively.

Table 3 .
Physical characteristics of Crumb rubbers Passing through (No.100) sieve 96 % Plate 2. Particles of Cumber Rubber waste [19] 2.2.3 Styrene Butadiene Styrene (SBS): SBS polymer was provided by the Ministry of Industry and Minerals/State Company for Mining Industries.SBS is an elastomer with white particles of various shapes and sizes created from two monomers, styrene and butadiene, that exhibits both plastic and rubber qualities.It is commonly utilized due to these qualities.It is one of the most significant polymers used to increase asphalt binder performance.The characteristics of SBS Polymer and the particles of SBS as shown in Table (4) and Plate (3) respectively.