5. SBS polymer modified bitumen and properties

Styrene-butadiene styrene (SBS) polymer additives used as additives in bitumen are one of the most preferred additive materials since they give positive results in physical and mechanical properties of HMA blends.

SBS additive and its three-dimensional structure is indicated in Figure 4.

SBS polymers are randomly formed as bond shapes in different forms such as block, styrene, butadiene, and linear.

Figure 4. General view of SBS-additive and three-dimensional SBS structure [30].

Figure 5. SBS molecular structure [31].

• Increase of adhesion, • Reduction of noise,

26 Modified Asphalt

Plastomers +

Sulfur + Chemical modifier +

properties of HMA blends.

butadiene, and linear.

• Reduction of groove marks on wheel load can be summarized [37, 38].

provided according to their shape of deterioration are shown in Table 3.

5. SBS polymer modified bitumen and properties

Figure 4. General view of SBS-additive and three-dimensional SBS structure [30].

Table 3. Benefits of different types of modifications [27].

Processed rubber + +

SBS additive and its three-dimensional structure is indicated in Figure 4.

Additives used in the modification of bituminous and bituminous mixtures and the benefits

Modifier Permanent deformation Thermal cracking Fatigue crack Moisture damage Aging Elastomers + ++ +

Black carbon + + Lime +

Antioxidants + Hydrated lime + +

Styrene-butadiene styrene (SBS) polymer additives used as additives in bitumen are one of the most preferred additive materials since they give positive results in physical and mechanical

SBS polymers are randomly formed as bond shapes in different forms such as block, styrene,

Figure 6 is indicated a three-dimensional view of asphalt-coated SBS molecules and the SBS modified bitumen structure consisting of asphaltic cell form and styrene butadiene bonds.

Figure 6. Three-dimensional appearance of asphalt-coated SBS molecules bond structure of SBS coated asphalt film [30, 32].

When the structure of SBS is examined, the following conclusions can be drawn:


### 6. Materials and methodology

In this study, initially, some conventional tests were applied. The properties of bitumen and aggregates to be used in bituminous hot blends have been examined. In the performance tests; core samples were taken different time in 1 year period (1st, 4th, 8th and 12th months) and tested in Figure 7. Core samples achieved from the implementation of asphalt pavement which are prepared with SBS modified and neat bitumen of the asphalt pavement. When taking the

Molecular structure of SBS additives is illustrated in Figure 5.

A solid model consisting of superstructure layers was created with namely Ansys using the finite element program. The solid model is designed by using the field parameters obtained by considering the environmental conditions such as traffic and climate. HMA design has been applied in the solid model, and only by doing so could real conditions were simulated with the

S SBS modified samples on vehicle wheel passing line

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N Neat samples on vehicle wheel passing line

Identification of the samples State and location of samples SK SBS modified samples on road side

NK Neat samples on road side

Table 4. Classification of drilling core samples of the HMA mixtures [33–35].

Numerical analyses assure significant advantages in using parameters derived from empirical studies to determine the stress and deformation characteristics of the superstructure of roads, corrosion, binder, base and sublayers, and to make future estimates. The Finite Element Method is often favored among other numerical approaches since it allows to make various changes and provides precise measurements in creating numerical models of physical problems. The Finite Elements Program used in numerical analysis is a numerical solution method developed for the analysis of problems expressed by differential equations. In the program, a continuous medium is branched by finite elements, and the equations are enrolled for one element, and integrated to derived system equations. As a result, complex differential equations considered for continuous media transformed into matrix format and it is reduced to a

The Finite Elements Method is a numerical solution method used frequently in engineering practices for the purpose of examining the continuous medium problems by examining them after dividing into a certain number of elements. In the scope of this method, the solution is obtained by dividing a medium or an object by finite elements and writing the rigidity matrix for each element, and then integrating the solutions for all elements. The numerical solutions of the differential equations that express the mechanical behavior of the system in question are written in matrix format. Generally, bigger matrices appear for the geometrical applications that require multiple elements. In solving such problems, the necessary linear algebraic oper-

analyses.

6.1. Numeric analyses

set of linear equations [36].

6.2. The finite elements method

ations are performed via computers.

6.2.1. The advantages of the finite elements programs

• The Finite Elements Formulation may be applied to many problems.

Figure 7. Core samples of hot mix asphalt (HMA) [33].

core samples, the edge of the road and the wheel passage areas are taken into consideration in Figure 8. In a one-year time period, 7432 equivalent axle loads were evaluated on trial path. Small axle tracks are not considered and are not taken into consideration because of using a secondary road. The effects of temperature on stability, stiffness, indirect tensile strength and fatigue resistance were investigated. Furthermore, it was examined Von Mises stress and vertical deformation of asphalt pavement on different time period with numerical analysis.

The location of the samples in asphalt and identification of the sample types are given in Table 4.

As a neat binder, asphalt binder of B 50/70 type taken from TUPRAS refinery was used. In modification, KRATON D 1101 contains styrene-butadiene styrene (SBS) block copolymer produced by Shell Bitumen was used.

The materials used in the layers that constituted the super structure of the road are; crushed aggregate chosen in the lower base layer, granular crushed aggregate chosen in the base layer, and crushed limestone aggregate chosen in road coating layer.

Figure 8. Asphalt pavement type (a), the core holes (b) and core sample (c) [33, 34].


Table 4. Classification of drilling core samples of the HMA mixtures [33–35].

A solid model consisting of superstructure layers was created with namely Ansys using the finite element program. The solid model is designed by using the field parameters obtained by considering the environmental conditions such as traffic and climate. HMA design has been applied in the solid model, and only by doing so could real conditions were simulated with the analyses.

#### 6.1. Numeric analyses

core samples, the edge of the road and the wheel passage areas are taken into consideration in Figure 8. In a one-year time period, 7432 equivalent axle loads were evaluated on trial path. Small axle tracks are not considered and are not taken into consideration because of using a secondary road. The effects of temperature on stability, stiffness, indirect tensile strength and fatigue resistance were investigated. Furthermore, it was examined Von Mises stress and vertical deformation of asphalt pavement on different time period with numerical analysis.

The location of the samples in asphalt and identification of the sample types are given in

As a neat binder, asphalt binder of B 50/70 type taken from TUPRAS refinery was used. In modification, KRATON D 1101 contains styrene-butadiene styrene (SBS) block copolymer

The materials used in the layers that constituted the super structure of the road are; crushed aggregate chosen in the lower base layer, granular crushed aggregate chosen in the base layer,

Table 4.

28 Modified Asphalt

produced by Shell Bitumen was used.

Figure 7. Core samples of hot mix asphalt (HMA) [33].

and crushed limestone aggregate chosen in road coating layer.

Figure 8. Asphalt pavement type (a), the core holes (b) and core sample (c) [33, 34].

Numerical analyses assure significant advantages in using parameters derived from empirical studies to determine the stress and deformation characteristics of the superstructure of roads, corrosion, binder, base and sublayers, and to make future estimates. The Finite Element Method is often favored among other numerical approaches since it allows to make various changes and provides precise measurements in creating numerical models of physical problems. The Finite Elements Program used in numerical analysis is a numerical solution method developed for the analysis of problems expressed by differential equations. In the program, a continuous medium is branched by finite elements, and the equations are enrolled for one element, and integrated to derived system equations. As a result, complex differential equations considered for continuous media transformed into matrix format and it is reduced to a set of linear equations [36].

#### 6.2. The finite elements method

The Finite Elements Method is a numerical solution method used frequently in engineering practices for the purpose of examining the continuous medium problems by examining them after dividing into a certain number of elements. In the scope of this method, the solution is obtained by dividing a medium or an object by finite elements and writing the rigidity matrix for each element, and then integrating the solutions for all elements. The numerical solutions of the differential equations that express the mechanical behavior of the system in question are written in matrix format. Generally, bigger matrices appear for the geometrical applications that require multiple elements. In solving such problems, the necessary linear algebraic operations are performed via computers.

#### 6.2.1. The advantages of the finite elements programs

• The Finite Elements Formulation may be applied to many problems.

• It ensures the opportunity of speed and optimization that can be analyzed via computer.

second stage, various tests performed HMA samples. The mechanical properties of the samples collected from the different asphalt pavement were examined in the 1st, 4th, 8th and 12th

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The binder was used in B50/70 class and constituted the building block of the HMA, which was used in the road platform. The characteristics of the pure (neat) and HMA-modified bitumen are given in Table 5 that the neat and SBS modified bitumen are a little susceptible to temperature in relation to the penetration index and they have a value above the limits of

The gradation characteristics of the mixture are given in Table 6. The physical properties of the aggregate are shown in Table 7. It is understood that the aggregates used in the coating layer of HMA are within the limits of the related specifications in terms of their physical properties.

Property Test method Neat bitumen SBS modified bitumen

Penetration (25C, 0.1 mm) EN 1426 B-61 B-68 Softening point (C) EN 1427 51.7 54.0 Ductility (25C, cm) EN 13589 >100 >100 Fraas breaking point (C) EN 12593 17 17.5

) EN 15326 1.022 1.017

Sieve Size (mm) 12.5 9.5 4.75 2.00 0.425 0.18 0.075 Passed (%) 100 90.4 56.6 36.6 18.2 13.0 10.3

Tested property Standard Coarse Fine Filler Specification limit

) ASTM C127 2.733 — —

) ASTM C128 — 2.678 —

) ASTM D854 — — 2.764

Abrasion Loss % (Los Angeles) ASTM C 131 20.5 — — Max 35 Frost action % (with Na2So4) ASTM C 88 1.20 — — Max 10 Peel strength (%) ASTM D903 60–70 Min 50 Flatness index (%) BS 812 16.1 Max 30

Water absorption (%) ASTM C127 0.38 0.88 —

months for a one-year period.

the specification as softening.

Table 5. The properties of the neat bitumen [34].

Specific gravity (gr/cm3

Table 6. Aggregate gradation.

Specific bulk density (gr/cm<sup>3</sup>

Specific bulk density (gr/cm<sup>3</sup>

Specific bulk density (gr/cm<sup>3</sup>

Table 7. Aggregate characteristics [35].

7.1.1. Properties of bituminous binders and aggregates


In this chapter, a finite elements model was developed by using the ANSYS Finite Elements Program for the super-structure of the road. The models, which consist of asphalt coating, the base and sub-base include 79,045 elements and 558,224 nodal point in average.

Different models were prepared for various time periods, which were 1st, 4th, 8th and 12th Months, by considering the multi-layer structure of asphalt, the traffic and the environmental conditions [35].

The Finite element model (FEM) of road is given in Figure 9.

Figure 9. Finite element model (FEM) of road [34].
