At low temperatures, the polymer hardness modulus is less than bitumen, which results in a reduction in the brittleness of modified bitumen. Therefore, it can be concluded that the polymer dispersed in bitumen discontinuous phase improves the properties of bitumen at high and low temperatures. In this status, the properties of the base bitumen significantly affect the modified bitumen properties [ 4 ].
Controlling such a system is often difficult, and there is a problem of instability in it. In this method, the micromorphology and the properties of bitumen are usually dependent on the bitumen temperature history.
In this status, as the percentage of polymer increases, the softening point increases significantly [ 4 ]. In fact, this system is no longer bitumen, but it is a polymer plasticized with bitumen oil in which a heavy phase of bitumen is dispersed.
The properties of such a thermoplastic adhesive material are essentially different from those of bitumen, and in fact, it has the polymer properties. In this status, the softening point, which in the previous states increased with the increase of the polymer content, is fixed and may experience a minor change with the increase of polymer content [ 4 ].
The microstructure of the polymeric bitumen is very important, and as described above, there is a close relationship between polymer bitumen microstructure and its physical properties.
Studies have shown that in the same percentage of bitumen and base bitumen with the same grade but different sources, polymer bitumen can have a very different microstructure and properties, especially at low temperatures [ 4 ]. Sustainability is one of the most important issues in polymer-modified bitumen. In other words, the speed of dispersion of particles polymer particles in a bitumen matrix or bitumen in a polymer matrix increases with the increase of the particle size, with an increase of the difference between the density of the two phases, and with the decrease of the viscosity of the continuous phase [ 4 ].
In order to increase the stability of polymer-modified bitumen, it is necessary to control the particle size by controlling the production process. Furthermore, by controlling the chemical structure of the base bitumen and the polymer-modified bitumen, it is possible to move toward the equilibrium of the density of the two phases. For example, the stability of EVA-modified bitumen is highly dependent on the percentage of asphaltene in the base bitumen.
This process is shown in Figure 6. When this parameter is zero, it means no delamination occurred [ 4 ]. The effect of asphaltene content in the base bitumen on the stability of EVA polymer-modified bitumen [ 4 ]. A study in the LCPC laboratories in France showed that the formation of the continuous polymer phase in polymer-modified bitumen improves the properties of polymer bitumen, such as plasticity at low temperature. On the other hand, in polymer-modified bitumen, the plasticity of the continuous polymer phase is increased with the increase of the cooling rate in the laboratory.
In this status, the bitumen had the continuous phase, and the polymer had a discontinuous and dispersed phase. As shown in Tables 2 and 3 , the different types of polymers are used in bitumen modification, each of which is different in terms of modification mechanism and properties. In this section, some of the most common polymers that are used in the modification of bitumen properties have been reviewed.
SBR is a type of copolymer, in which styrene and butadiene monomers are irregularly bonded in a polymeric chain, based on their initial percentages. This copolymer has good strength due to the presence of thermoplastic styrene monomers between the layers of butadiene rubber monomers, which is why it is used extensively in the tire industry.
Unfortunately, this rubber inflated in bitumen to a limited extent is not compatible with bitumen, so it cannot significantly improve the properties of bitumen [ 13 , 14 , 15 ]. SBS is a block copolymer that increases the bitumen elasticity. This polymer is one of the most suitable bituminous modifying polymers in terms of improving the properties of bitumen, but it has some economic and technical limitations.
However, after the rubber powder, SBS is the most widely used modifier in pavement [ 3 ]. The morphology of the SBS and bitumen mix may vary depending on the source of the base bitumen and the polymer. In one of the bitumen statuses, the phase is continuous, and the SBS particles are dispersed in bitumen. In the other statuses, the bitumen cells exist in the polymer as a continuous phase. In the third status high polymer content , bitumen and polymer continuous phases interlock.
Performance tests at low temperatures by Bending Beam Rheometer BBR showed that this amount of SBS reduced the hardness range temperature, but due to a decrease in the creep rate m-value , resulting in an increase in the creep rate temperature, the low temperature performance grade in these types of bitumen got worse [ 16 ].
Other research have shown that using a higher percentage SBS, it is possible to improve the low- and intermediate-temperature performance grades [ 17 ]. According to the definition of the BBR test, the hardness range temperature is a temperature at which the stiffness bitumen hardness modulus reaches MPa and the temperature is the creep rate temperature range is a temperature at which the value of M-Value is less than 0.
It was also observed in high-SBS-containing bitumen that the oil content of the bitumen has a determining effect on the degree of penetration and plasticity point of polymer-modified bitumen [ 4 ].
Mohammad et al. The hardness of the samples at low and high temperatures was more than it was expected. By performing the test, they found that the effect of extraction and reduction of bitumen on the quality of bitumen containing SBS was very insignificant. The experiments showed that in asphalt recycling operation, increasing the percentage of reduced bitumen containing SBS increased rutting resistance, while it reduces fatigue-cracking resistance [ 18 ].
This behavior can be due to the increased hardness and brittleness of the aging bitumen containing SBS. Differential scanning calorimetry DSC analysis of bitumen showed that the aging process of bitumen tested with PAV reduces the number of paraffinic crystalline structures in bitumen, while natural aging in a sample extracted from the road increases the paraffinic crystalline structures of the bitumen, thereby in comparison with PAV tested bitumen, its hardness and brittleness increase [ 18 ].
Figure 7 shows that by increasing the percentage EVA, the degree of penetration decreases, and the softening point increases. In another study by Madela et al. At high percentages of EVA polymer matrix is dominant , it significantly reduces the effect of bitumen chemical structure [ 4 ]. The effect of percentage changes of EVA in bitumen and vinyl acetate, on the degree of penetration and softening point of polymer-modified bitumen [ 18 ].
The US Federal Highway Administration FHWA analyzed the life-cycle cost of the pavement, including rubber powder and other modifiers and showed that the use of rubber powder to modify bitumen is economical. Of course, this law was later changed. Typically, rubber is made from the recycled tires. This reduces the space needed to burrow worn tires [ 3 ].
Modifying bitumen with natural rubber increases the resistance of asphalt mixture to rutting and improves its flexibility. On the other hand, it tends to be delaminated. Due to the higher molecular weight of rubber powder, this material is less compatible than bitumen. Another common problem with the use of natural rubber is the need for a higher temperature and a longer time to mix and disperse rubber in bitumen [ 3 ].
Although much research has been done about the nature of the reaction of rubber and bitumen particles, the exact mechanism of this operation is still unknown.
Powdered rubber particles become soft and swollen that lead to an increase in the viscosity of the rubber-bitumen blend [ 19 ]. This swelling occurs because of the physical and chemical reaction of bitumen and particulates of rubber powder that the volume of powdered rubber particles rises two to three times the initial value. If the temperature or mixing time is high enough, the particles of the rubber are degraded and dispersed in the bitumen, and the polymeric chains are broken, which reduces the viscosity of the mixture.
The swelling of powdered rubber particles and the particle breakdown of powdered rubber are two factors affecting the properties of rubber-bitumen mixtures [ 20 ]. Adding rubber powder to bitumen can increase one to three performance grades PGs above the operating temperature and reduce one to two performance grades to lower temperatures which is the lower temperature for the operating temperature of bitumen.
Therefore, the operating temperature range of bitumen rises from both sides [ 21 ]. Other researchers also observed the same trend at high operating temperatures but did not see a change in the performance grade with the increase for rubber [ 22 , 23 , 24 ]. The lower limit in all cases was controlled by the value of the creep rate m-value which is obtained from the Bending Beam Rheometer BBR test. Overall, according to the results of various studies, it can be concluded that the rubber powder improves the performance grade but in the low performance, the amount of improvement is highly dependent on the bitumen, and the results are different depending on the bitumen used.
The effect of the rubber powder is more than other factors, while the particle size of the rubber does not affect it. Factors such as temperature, loading frequency in the test, type of bitumen, and the percentage of plastic powder are also effective [ 25 ]. Researchers have found that adding rubber powder reduces hardness at low temperatures. Gopal showed that this event happens for the different sizes and percentages of the rubber powder, and for each compound, the size and the optimal percentage should be determined [ 22 , 26 ].
The experiments, which were conducted by Bahia et al. One of the modifiers of bitumen is the polyphosphoric acid, which is added to it independently or as a substitute for other modifiers in bitumen like SBS. Polyphosphoric acid acts like deflocculant of the bitumen phases, the charge of polar groups, using neutralization of the load of polar groups. This can be done by neutralizing the bases with acid or esterification [ 27 ]. One of the important issues that should be considered in the use of acids as the modifier of bitumen is reversibility of bitumen modification.
The presence of lime, limestone, or anti-stripping agents can neutralize the acid added to bitumen. On the other hand, most of the acids, including PPA, are soluble in water and may be washed out by rain over time [ 28 ].
Researchers have paid more attention to this fiber because of the following reasons: Its good performance in strength. In recent decades, basalt fibers have been used in the asphalt concrete as a highly efficient additive. Compared to two other common additions, for the arming of asphalt, namely, polyester fibers and lignin fibers, basalt fibers have a higher tensile strength and elastic modulus and a lower elongation rate [ 29 ].
Its resistance to high temperature and good chemical stability of the basalt fiber makes it an excellent additive for asphalt concrete [ 30 ]. Different researchers have carried out various experiments to evaluate the applicability of basalt fiber as a reinforcing material for structural concrete, and they have compared the efficiency of basalt fiber and glass fibers.
Using the accelerated weathering test, they found that basalt fiber provides better resistance in comparison to glass fibers [ 31 ]. Basalt fibers especially those used with Scoria will not be dangerous to the environment, and basalt is not usable as a building material. This material is not new but can be used initially in construction with regard to mechanical and chemical properties.
The base cost of basalt fibers depends on the quality and chemical compounds, and this fiber has various types and different chemical properties [ 33 ]. However basalt fiber has properties like high Marshall stability, stability against water, and stability against rutting; fewer studies have been conducted to analyze the application of basalt fibers [ 34 , 35 , 36 ].
Bitumen modification using basalt fiber has the potential to perform better at low and high temperatures and to increase fatigue life and reduce permanent changes [ 36 , 37 ]. The use of fibers has a great influence on viscosity and mixed properties [ 38 ]. Zhao et al. The addition of basalt fiber to the asphalt mixture increases its dynamic modulus [ 40 ].
In order to increase the resistivity of the asphalt, Xiao et al. Synthetic basalt increases the shear modulus, and the viscosity of the bitumen, as a result, increases its stiffness and decreases the difference in the phase angle. These factors have been improved in the bitumen foam synthesized with the basalt, more than bitumen modification using synthetic basalt. In terms of molecular weight, the lower molecular weight of isocyanate used in the synthesis of basalt is the more effective synthetic basalt that is on increasing the shear modulus and reducing the phase difference angle.
Synthetic basalt is well adapted due to its chemical reaction with bitumen polar groups and the formation of new bonds in bitumen and stability in bitumen storage, which is achieved without any problem. Bitumen is one of the main components of the asphalt mixture, which plays a major role in creating adhesion between the aggregates in relation to environmental factors such as temperature and traffic loading in the asphalt mixture.
Because the vast majority of asphalt failures are due to the weakness of the rheological and chemical properties and the thermal sensitivities of the bitumen in asphalt, over time, with the development in the materials science of road building. Moreover, the use of polymer modifiers could potentially improve the bitumen in the asphalt, which has led to improve the durability of asphalt against breakdowns due to rutting, permanent deformations in the high temperature, and the increasing fatigue life.
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Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Abstract This chapter focuses on bitumen specifically. Keywords bitumen modify asphalt polymer. Introduction Traffic loading and environmental factors are one of the most important destructive causes in asphalt pavement.
History of bitumen and its reformation The Sumerians, the Assyrians, and many earlier civilizations have used bitumen widely.
Bitumen sources The bitumen used in the road construction industry is divided into two general categories: Bitumen mineral pitch Bitumen produced from distillation of crude oil petroleum pitch 1. Bitumen natural pitch When volatile crude oil components is vaporized in the depths of the earth, over time and under factors such as high temperature and pressure, the black substance remains in place, which is called natural bitumen. Petroleum pitch Oil pitch is obtained from the refinery of crude oil in distillation towers.
Chemical bitumen building Bitumen is a very complex chemical compound, composed of various hydrocarbons types, which are in colloidal form. Hydrocarbons Paraffinic crude oil Naftens crude oil Asphaltenes crude oil Paraffins 40 12 5 Naftens 48 75 15 Aromatics 10 10 20 Asphaltenes 2 3 Table 1. Chemical structure of different types of crude oil. Table 2. Bituminous ingredients.
Components of bitumen Bitumen consists of various hydrocarbon compounds, which according to the method of separation its compounds can be divided into different chemical groups. Asphaltenes Asphaltenes are a brittle solid substance in black to brown; in addition to carbon and hydrogen, they contain nitrogen, sulfur, and oxygen and usually have very polar compounds that contain highly aromatic complex components with high molecular weight.
Polar aromatics resins These compounds are usually composed of carbon and hydrogen, which also contain a small amount of oxygen, nitrogen, and sulfur. Oil aromatics The aromatic oils are the least molecular weight ring compounds that contain aromatic or petroleum lateral chains and are an excellent anticoagulant for asphaltenes.
Saturated materials paraffins Saturated compounds are composed of straight and branched chain aliphatic hydrocarbons with alkyl naphthenes and some aromatic alkyls. Mechanical and physical bitumen properties These two properties of bitumen are not only important during the fabrication, distribution, and density of asphalt mixtures, but these properties are also very important during servicing.
Bitumen behavior Bitumen from the behavior viewpoint is a viscoelastic substance that in the environment heat and under the specified load neither the behavior of an elastic material nor the behavior of a viscous material but is a combination of these two states, which is viscoelastic. Newtonian behavior of bitumen When there is a linear relationship between shear stress applied to fluids and velocity gradient or shearing strain rate, they are called Newtonian fluids.
Pseudo-plastic behavior and Bingham plastic A type of behavior which results in shear thinning of fluid decrease of viscosity with increase of stress or reduce of strength with increase of shear stress is called pseudo-plastic.
Bitumen temperature susceptibility Temperature susceptibility which may be defined as how changes made in consistency or stiffness of bitumen viscosity or degree of penetration at different temperatures is one of the effective parameters in the behavior of bitumen that for a variety of bitumen is classified in one group classification based on viscosity or classification based on degree of penetration may vary.
Bitumen hardening Bitumen hardening is a phenomenon that may occur under various conditions and factors in the short or long terms. Bitumen aging The gradual changes in the physical and chemical properties of oil bitumen have been accepted as a principle. Bitumen modification As mentioned before, there is a complex relation between bitumen chemical structure, bituminous colloid structure, and its physical and rheological properties.
Bitumen modification by polymer By adding polymers, the chain of small molecules is repeated, and as a result, the pavement performance improves. Table 3. Polymer bitumen stability Sustainability is one of the most important issues in polymer-modified bitumen.
Temperature history A study in the LCPC laboratories in France showed that the formation of the continuous polymer phase in polymer-modified bitumen improves the properties of polymer bitumen, such as plasticity at low temperature. Common polymers in bitumen modification As shown in Tables 2 and 3 , the different types of polymers are used in bitumen modification, each of which is different in terms of modification mechanism and properties. Styrene butadiene rubber SBR SBR is a type of copolymer, in which styrene and butadiene monomers are irregularly bonded in a polymeric chain, based on their initial percentages.
Ethylene vinyl acetate EVA Figure 7 shows that by increasing the percentage EVA, the degree of penetration decreases, and the softening point increases. Modification of bitumen with rubber powder CRM The US Federal Highway Administration FHWA analyzed the life-cycle cost of the pavement, including rubber powder and other modifiers and showed that the use of rubber powder to modify bitumen is economical.
Bitumen modification using polyphosphoric acid PPA One of the modifiers of bitumen is the polyphosphoric acid, which is added to it independently or as a substitute for other modifiers in bitumen like SBS. Researchers have paid more attention to this fiber because of the following reasons: Its good performance in strength Its suitability for a wide range of temperature variations Its durability In recent decades, basalt fibers have been used in the asphalt concrete as a highly efficient additive.
Notes Mode sol : in this case, the particles are dispersed uniformly and homogeneously in solution. The pitches obtained from the refinery are usually of this category. Mode gel : in this case, colloidal pitch particles create a regular sponge-like network that propagates throughout the system. In this case, the system is semisolid, and this is where the material constituting the maltene in terms of chemical compositions has the most properties of oil or paraffin hydrocarbons.
Wax: part of the paraffins is crystalline. The method for determining the amount of bitumen wax is given in DIN More Print chapter. How to cite and reference Link to this chapter Copy to clipboard. Available from:. Over 21, IntechOpen readers like this topic Help us write another book on this subject and reach those readers Suggest a book topic Books open for submissions. More statistics for editors and authors Login to your personal dashboard for more detailed statistics on your publications.
Access personal reporting. In addition to polymer additives, bitumen cracking resistance is improved by adding oil or oligomers, also called plasticizers, which enhance bitumen properties at low temperatures. Improving Bitumen Properties with Additives. This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Close Privacy Overview This website uses cookies to improve your experience while you navigate through the website.
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