Reference Library

Asphalt modification usually involves the dispersion of different polymers within the neat asphalt (bitumen). ECOPATH Holdings engineering places a high importance on the identification of compatible asphalt-polymer blends to ensure that the optimum properties are achieved at the most competitive price.

Examples of this innovation have included: the addition of saturated polymers to paraffin deficient asphalts to produce a gelling asphalt. Similarly, for asphalts deficient due to the viscosity of the maltenes, ECOPATH Holdings has improved these binders by dispersing unsaturated polymers throught out the binder.

If asphalt properties are deficient due to the molecular weight of the asphaltenes, ECOPATH Holdings has derived solutions involving insoluble polymers for paving materials.

As is often the case, these issues tend to arise simultaneously; therefore, ECOPATH engineers have developed specific formulations to combat these issues by incorporating various polymers at the required doses and using the appropriate production processes.

State agencies have recognized the benefits of using modified asphalts, specifically because pavements made with these modifiers result in pavements which require significantly less maintenance and upkeep. From a performance standpoint, the benefits of using modified asphalt are summarized below:

Asphalt pavement.

• Obtain more elastic blends at low service temperatures and reduce cracking
• Reduce rutting
• Reduce viscosity at laydown temperatures
• Increase the stability and the strength of mixtures
• Improve the abrasion resistance of blends
• Improve fatigue resistance of blends
• Increase oxidation and aging resistance
• Reduce structural thickness of pavements
• Reduce lifecycle costs of pavements.

Asphalt rubber (AR) (usually called ground tire rubber (GTR) modified asphalt or crumb rubber modified (CRM) asphalt ) originally was designed to fall under the specifications of ASTM D6114 - 97(2002). This type of modified asphalt is consistent with traditional asphalt rubber where a crumb rubber concentration by total weight is necessary. This type of modified asphalt binder has been shown to exhibit excellent properties with regards to safety, noise reduction, and field performance.

ASTM D8-88 defines AR as “a blend of asphalt cement, reclaimed tire rubber, and certain additives in which the rubber component is at least 15% by weight of the total blend and has reacted in hot asphalt cement sufficiently to cause swelling of the rubber particles." Research has shown that the addition of crumb rubber to virgin asphalt produces binders with improved resistance to rutting , fatigue cracking, and thermal cracking, and also reduces reflective cracking at reduced thickness of asphalt overlay.

Research has shown that crumb rubber modification of asphalt binder has many similar effects to polymer modification. The major changes noted by these researchers are seen with the increase in the high temperature stiffness, and these are often seen to exceed levels normally achieved by polymer modification. Similarly it has been shown that crumb rubber modifier also results in a reduction of dependency on temperature and loading frequency. However, it also has been suggested that the main function of crumb rubber is that of interactive filler as crumb rubber remains as particulates even after mixing. As the crumb rubber particles do not dissolve in the asphalt, they have been shown to swell in the asphalt, resulting in effective volumes that are larger than their initial volume.

Asphalt rubber blending equipment.These improvements in pavement performance are due to the significant quantities of elastic rubber used in the asphalt blend. By incorporating and reacting large quantities of rubber into the blend, a number of the elastic properties of the crumb rubber are proven to be transferred to the asphalt binder as well. These properties equate to reduced cracking (due to the increased elasticity), reduced rutting (due to the increased rheological properties of asphalt at high temperatures) and also greater safety and noise reduction (due to the ability of the binder to perform in quiet and safe mix designs).

As environmental concerns continue to increase, AR is becoming a more attractive solution as it incorporates a waste material (scrap tires) into the blend, thereby also producing an environmentally sustainable asphalt binder.

The modification of asphalt using crumb rubber has been performed in a number of states, depending on the state. Many states have had success using traditional wet method procedures; these procedures are similar to the ones initially developed by Charles McDonald and typical specifications are similar to the ones shown below.

Table 1: Typical wet method binder evaluation

Test performed	60 minute specification
Rotation Viscosity @ 350 oF ( Pascal Seconds)	1.5-4.0
ASTM D5 Penetration @39.2 (oF, 200g, 60 sec.)	11 (min)
ASTM D36 Softening Point(oF)	135 (min)
ASTM D5329 Resilience @ 77 oF (% Rebound)	25 (min)

Table 2: Typical wet method rubber gradation

Sieve size	Type B Specified Requirements
# 10	100
# 16	65-100
# 30	20-100
# 50	0-45
# 200	0-5

With the development of conventional polymer modified asphalt, new testing procedures were developed by the FHWA. These binder tests were conceived with the purpose of evaluating the binder using “real world” testing and loading conditions. With regards to asphalt rubber, many of these tests are applicable and provide insights into the actual mechanism by which asphalt rubber resists permanent deformation and its increased elasticity. Using the latest testing methods developed by the FHWA, Ecopath engineers have evaluated the properties of asphalt rubber using the multiple stress creep recovery test. This test was designed specially to evaluate the effect of the polymer modifier, rather than simply testing for the presence of a modifier. Furthermore, using this test it is possible to see how the binder behavior changes as the binder undergoes numerous loading cycles. Figure 1 provides data obtained from the Ecopath offsite laboratory which provides information on how different PMAs respond to multiple stresses.

MSCR test results of various modified asphalt binders.

Research conducted by Ecopath suggests that asphalt rubber exhibits greater resistance to deformation as it requires more applied stress than conventional PMAs to strain. As seen in Figure 1, while other PMAs strain more under the same stress, AR tends to strain less. Furthermore, it can also be seen that the elastic recovery of the AR specimen is much greater than the other modified asphalts. It is thought that this considerable elastic recovery is due to the large quantity of rubber (> 20 wt%) in the asphalt. Incorporating such large amounts of rubber into the binder typically results in greater viscosities, but it also tends to transfer some of the elastic properties of the rubber to the asphalt binder.

ECOPATH has extensive experience in binder design where emphasis is placed on achieving specified binder in the most cost effective manner. ECOPATH provides unique solutions for every asphalt concern, moreover ECOPATH is dedicated to developing solutions with economic efficiency as a priority. Please contact us for further information on binder design services.

Asphalt rubber pavement.The correct answer is definitely NO!

At ECOPATH Holdings we know the importance of both raw ingredients and the processes behind the development of a successful asphalt rubber binder. Due to our experience in the field we have come across a number of state specifications requiring various additives, crumb rubber types, reaction times, crumb rubber gradations and reaction procedures.

This experience allows us to better design the appropriate modified binder for our clients as we are aware of the specific requirements of each individual market, as well as the state binder specifications, and the need to balance these with the appropriate engineering properties.

For this reason, we do not advocate a "one solution fits all" model. Instead, we perform an analysis of the pavement site to determine what properties that pavement will require for the best performance. Simlilarly, we balance the economic considerations to develop the best binder design for that particular location.

By following different state requirements, our research team investigated and showed the differences behind the different practices.

While all of the following asphalt rubber binders showed in this study performed better than conventional binder, it is apparent that performance properties differ depending on the modification method.

The material performs better when the elasticity indicator shows minimum changes with respect to temperature. From this point of view the Arizona and California method produced asphalt rubbers performed the best followed by the Texas method manufactured asphalt rubber (Fig.1.a).

Investigation of rutting potential from temperature sensitivity showed again the advantageous effect of 20 % rubber used by the Arizona and California blends, which was followed by the Texas method produced sample (Fig.1.b). Elasticity and rutting sensitivity of various crumb rubber modified asphalts.

The following information presnted here provides an indication of the peformance of various asphalt rubber binders as speed is varied. The testing was done using a Dynamic Shear Rheoemeter, during testing the frequencies were varied to simulate the effects of various speeds.

Low frequencies represent high speeds, while high frequencies represent low vehicle speeds. The less steep the curve is, the less sensitive the binder is with respect to rutting. Also the higher the value of the rutting potential indicator the higher the resistance of the binder.

Based on these findings, the Arizona method was found to be the most resistant against rutting, followed by the California and Texas (Fig.2.). The principal reason for these differences lies in the various rubber concentrations used.

When comparing all the rubber modified binders to the neat, virgin asphalt at high vehicle speed around one decade differences were observed. Specifically, significant differences were found at low vehicle speeds. These findgs indicate that even at low speeds the type of binder used in the asphalt pavement plays an important role in the pavement properties.

Rutting sensitivity of various blended crumb rubber modified asphalts as a function of vehicle speed.

The benefits of asphalt rubber are comparable to the benefits witnessed earlier by the concrete industry with the advent of chemical and mineral admixtures. Modifiers allow the designer to customize the final product (the asphalt) with specific performance parameters in mind. Following years of research at both university and federal labs, the properties by which safer, quieter, smoother, and longer lasting pavements are created have been identified.

AR is defined by the American Society for Testing Materials (ASTM) D8-88 as:

"A blend of asphalt cement, reclaimed tires and certain additives in which the rubber component is at least 15% by weight of the total blend and has reacted in the hot asphalt cement to cause the swelling of rubber particles."

Crumb rubber modified asphalt is generally produced by three methods:

• Dry method,
• Terminal blend
• Wet method

The dry method is the introduction of un-reacted crumb rubber during the mixing of the asphalt cement and rock aggregate at the Hot Mix Asphalt (HMA) plant. The terminal blend is produced at the asphalt cement terminal, where a low weight percentage (typically 2%-5%) of crumb rubber is blended with the oil for delivery by conventional tank trucks to the hot mix asphalt plants. Both of these processes are referred to as rubberized asphalt.

By far the greatest performance benefits are realized with the wet method wherein crumb rubber is mixed with asphalt cement in a specialized blending system and allowed to react with the asphalt cement, then mixing the modified asphalt cement binder with the aggregate. The weight percentage is generally in the 18%-22% range and results in a much higher viscosity, allowing the binder to form a superior film around the rock aggregate, and added resilience, among other benefits. When produced with the wet method with rubber content in excess of 15%, the product is referred to as AR.

AR Technology Benefits

AR can be applied as a sprayed-on “chipseal”, as a stress absorbing membrane between paving layers, or as a surface friction course pavement. There are numerous documented cases of roads using AR technology lasting 10-18 years. Benefits of this technology include:

• Safety
• Significant reduction of traffic noise in urban areas
• Improved surface water drainage, reducing safety hazards of hydroplaning and visual impairing water spray
• Potentially major cost savings through elimination of sound barriers
• Reduction of maintenance costs through improved crack resistance
• Conserves natural resources (friction course can be reduced in thickness, conserving aggregate and asphalt cement)
• Can save initial capital construction costs through cost-effective alternative to road construction
• Improved road structural stability by preventing moisture penetration into road foundation
• Elimination of waste tires through productive recycling

Safe Pavements

Research has shown that safe pavements are dependent on the friction present between tire and pavement, and also on driver visibility. One solution that the asphalt industry has developed to improve these properties are permeable or open graded friction courses. These pavements enhance safety by allowing the water to drain through the wearing course; this promotes a more rapid removal of the storm water from the pavement surface and thus reduces the risk of hydroplaning.

The design of such pavements requires an open graded aggregate blend and a modified binder with a high viscosity to reduce the effect of draindown. Draindown is the phenomenon by which heated asphalt drips off the aggregate due to the absence of fine aggregate in open graded mixes. This problem is overcome through the addition of fibers in the mix to absorb some of the binder, but also through the use of modified asphalts which exhibit much greater viscosities at elevated temperatures.

Asphalt rubber has a long history of use in open graded mixes. Due to the high viscosities associated with AR it is a natural choice for these pavements. The motives for using asphalt rubber are not confined to high viscosities though; the elastic tendencies of asphalt rubber and decreased temperature susceptibility mean that this type of binder is ideally suited for open graded mixes in both warm and cool climates. Warm climates present the challenge of increased rutting susceptibility due to the softening of the asphalt binder, while cool climates cause the asphalt to become brittle and fracture. For these reasons it is necessary to incorporate an appropriate “glue” to the open graded mix to ensure that it is held together.

The benefits of AR permeable friction courses have been documented in Texas where pioneering work into the field evaluation of pavement safety was undertaken. In one study conducted by TXDOT, an existing CRCP was overlaid with a 1.5 inch AR permeable friction course overlay. The resulting benefits of this work included:

• Improved ride quality over the existing CRCP of 61%
• Increase in excess of 200% for skid resistance
• Significant reduction in major accidents

Pavement safety studies have shown that proper design and implementation of AR permeable friction courses lead to large decreases in wet weather accidents. As seen in another study performed by TXDOT, the addition of an AR permeable friction course led to large decreases in the number of wet weather accidents.

These findings provide evidence suggesting that rapid removal of storm water from the roadway surface provides a safer pavement. In addition to this phenomenon, the removal of storm water from the surface also provides the additional benefit of reduced splash and spray, and therefore increased visibility. As seen in the previously mentioned TXDOT study.

Quiet Pavements

Focusing on the pavement for noise reduction purposes tends to be more effective as studies have shown that the majority of noise produced from a highway is due to the tire/pavement interaction rather than the noise generated by aerodynamic and power train noise.

These findings suggest that if tangible noise reductions are to be achieved, then significant advances are necessary in the field of pavement design. Arizona has witnessed significant improvements in the field of noise reductions. Following years of success in implementing AR pavements, ADOT has also had favorable results in noise emissions using rubberized asphalt. Studies have shown that the use of rubberized asphalt, in certain applications, produces higher quality pavements with reduced noise emissions.

REDUCING NOISE AT THE SOURCE

As mentioned previously, one of the principal methods by which significant noise reduction may be achieved is by reducing the amount of noise from the source. Amundsen and Klaeboe (2005) report that possible methods of reducing noise include:

• Noise reduction due to speed reductions
• Low noise road surfaces
• Reducing noise from vehicles
• Reducing noise from tires

REDUCED NOISE PAVEMENT PRINCIPLES

The mechanisms by which noise is generated in the tire/pavement interaction vary, and will also be dependent on the match between tire characteristics and pavement properties. However, in general the pavement-noise generation relationships presented in Table 3 have been proven valid.

Table 3: Effect of pavement properties on noise emissions.

Pavement Property	Effect on Noise Emissions
Smoothness	Smooth surfaces are quieter than rough surfaces
Porosity	Porous surfaces are quieter than non-porous surfaces
Elasticity	Elastic surfaces are quieter than non-elastic surfaces

ASPHALT RUBBER AND NOISE REDUCTION

The process of blending ground recycled tires into asphalt binder has been growing in popularity in the US since its initial development in the 1960s. Today, interest is particularly high as it presents an environmentally friendly approach to road construction. Studies have confirmed its applicability for conventional polymer modified asphalt purposes; however, more and more studies are also indicating that this material can successfully be used for the construction of quiet pavements as well.

The use of AR for noise mitigation purposes becomes apparent when examining Table 3. The research has shown that elasticity, porosity, and smoothness all play a role in determining the quietness of a pavement. AR has an excellent track record with regard to these properties, and is therefore considered an excellent material for noise reduction purposes.

Elasticity

A common issue with many pavements is loss of elasticity or resilience of the asphalt through oxidation due to exposure to the elements. This phenomenon tends to adversely affect the asphalt pavement; as temperatures fluctuate, repeated stresses occur in the asphalt due to expansions and contractions of the material, thus causing cracks to appear. As seen in Figure 4, even after 16 years of field life, the asphalt pavement which had previously been prone to cracking exhibited much better properties following the rubberized asphalt overlay.

Before rubberized asphalt inter (SAMI) and overlay.After rubberized asphalt inter (SAMI) and overlay - 16 years performance.

Porosity

One of the main uses of rubberized asphalt to date has been its application in rubber modified open graded friction courses (R-M OGFC). This type of pavement is typically used as an overlay and will exhibit a higher amount of air voids than conventional dense graded mixes. AR is a popular choice for such applications as it prevents draindown of the binder and permits the necessary levels of adhesions and mix stability to be achieved (ARTS, 2003).

States such as Arizona, California, Florida, Rhode Island, South Carolina, and Texas have all successfully used rubberized asphalt in OGFC applications. One of the main areas in which rubberized asphalt has been used the most has been for porous paving designs.

Smoothness

Smoothness of asphalt pavements is often a function of the number of distresses present on the riding surface. Distresses may include:

• Reflective cracking,
• Longitudinal cracking,
• Thermal cracking, and
• Permanent deformation.

As the occurrence of these pavement failures increases, so too does the amount of noise generated. The addition of crumb rubber to asphalt binder has been documented to improve the pavement’s resistance to the surface distresses mentioned above. Therefore, as rubberized asphalt is generally less susceptible to pavement failures, it provides a smoother ride and, consequently, also a quieter pavement.

Durable Pavements

Testing conducted at the FHWA accelerated loading facility (ALF) concluded that AR compares favorably compared with other modified asphalt pavements. The study was conducted in an effort to refine the Superpave binder system for modified binders as well and specifically for developing field performance data on hot mix asphalt mixtures with modified asphalt binder.

Cost Effective Pavements

AR pavements have proven cost effective in light of their ability to allow engineers to used thinner asphalt lifts. Following years of research Caltrans developed guidelines for thinner asphalt pavements lifts using AR pavements; these pavements permitted up to 50% reductions in thickness when compared to conventional pavements. Such experiences have led many to believe that with regards to fatigue, thin asphalt rubber overlays perform better than conventional dense graded overlays with unmodified binders. The cost savings associated with such reductions are numerous, specifically in times when asphalt prices are high and inconsistent.

Life cycle analysis has also been used to measure the cost effectiveness of AR. Studies at both Oregon State University and University of Nevada Reno have found that AR is more cost effective than conventional asphalt. The advantages of AR lie in the significant reductions in maintenance rehabilitation necessary when dealing with AR.

What makes it last longer?

The high carbon black content of the vulcanized rubber that retard aging and provides antioxidation effect; this prevents the pavement from becoming brittle and cracking. When rubber is blended with asphalt, it creates a flexible AR pavement that resists and reduces rutting, reflective and thermal cracking, thus not allowing water into the sub-surfaces, which create pot-holes and deteriorate the road surface.

Will AR wear more quickly than regular asphalt and add to the pollution problem?

AR has twice the life span of conventional asphalt. Experts have learned that when the AR begins to deteriorate, it breaks up into pieces that are too large to become airborne and add to the air pollution problem. There is no evidence to indicate that AR will add to air pollution.

How many used tires will be recycled in AR?

Waste tires are environmental problems. If buried whole in a landfill, they can float to the surface, break through the cap of the landfill, and expose once buried waste to the environment. In whole tire stockpiles, water can sit in the tires making them ideal breeding grounds for mosquitoes. The EPA estimates that over $5,000,000 USD is spent each year to combat mosquito borne diseases, such as encephalitis and yellow fever. As with whole tire stockpiles, shredded tire stockpiles are high risk fire hazards that create environmental disasters in the air and water tables. It is estimated that between 1500 and 2000 old tires are used for every lane-mile that is resurfaced at a depth of 1-inch with AR. About 300-million used tires are generated annually in the United States alone.

How much quieter can freeways be with an AR overlay?

Approximately 75% of freeway noise is generated from the tire-to-road contact, and AR reduces that noise at its source. The decibel range from vehicle tires rolling across AR pavement is considerably lower than with concrete surfaces, reducing the noise levels that tend to be irritating to homeowners and freeway drivers. International studies have shown that AR pavements can reduce traffic noise up to 85% in some cases. Generally, AR will provide a 50% reduction in noise. Elimination of the construction of abatement walls can save between $200.00 to $400.00 USD per linear foot (or $1 to $2 million per mile.) www.rubberpavements.org

Do AR pavements cool faster than conventional pavements?

AR pavements are more porous. Because of this and the insulating effects of the rubber crumbs, the pavement doesn't retain heat as much as conventional asphalt. AR pavements are cooler at night, but not during the day.

The cool pavement mechanism is based on the idea that by increasing the reflectance of the pavement surface, less sunlight will be absorbed, lowering the daytime temperature of the pavement.

In case of hot climate places, where icing is not an issue light-colored aggregate (e.g.,limestone) is suggested to be applied, which appear very light in color. New asphalt pavements, with a black binder, are generally much less reflective. So not really the AR, but the aggregates are behind this phenomena.

Can AR be used in cold climates?

AR has been successfully used in some of the coldest regions of the U.S., such as Alaska and Nebraska. In the Flagstaff, Arizona area (>7,000 ft. / 2,134 m. elevation), the winters have extreme freeze/thaw conditions. AR has better temperature sustainability than conventional asphalt. The State of California has also successfully used AR in the high Sierra Mountains, where its performance has been remarkable as well. Internationally, AR is being used to pave highways in Siberia Russia, China, northern Spain, Germany, Canada, Sweden and Portugal.

In many asphaltic compositions it is particularly desirable to have a high degree of flexibility combined with toughness and durability. High ductility is especially desirable for meeting the specifications demanded in industrial asphalts used in materials such as roofing shingles, built-up roofs, canal linings, pipe coatings, etc. Additionally, because of the temperature stress to which these asphalts may be subjected, it is desirable to have an asphalt which can withstand low temperatures over time without developing significant brittleness and not flow at high temperatures. The parameters of these conditions may also be expressed as the well known physical properties of asphalt: viscosity, penetration and softening point.

It has been discovered that paving asphalts (especially of the hot mix, hot laid type) may be modified so as to have improved stability and rheological properties by the addition of certain copolymers of ethylene with vinyl acetate or lower alkyl esters of acrylic acid and methacrylic acid to an asphalt, provided said asphalt has an asphaltene content below a critical level. More specifically, an asphalt cement or binder having both enhanced storage stability and creep reisistance relative to conventional binders (i.e., straight-run asphalts obtained from residua from vacuum distillation of crude oil) is formed when the asphalt used in said binder has an asphaltene content of about 7 wt% or less, based on wt% of the asphalt.

These blends comprise a homogeneous dispersion of polymeric additive in asphaltic material. The blends can be used hot, cut back with lighter hydrocarbons (as cub-back asphalts are used) or as aqueous emulsions. The compositions of our invention can be used in a conventional manner such as by spraying, brushing, precoating, e.g., dipping, or the like.

Ethyl vinyl acetate is an asphalt modifier which is typically added at concentrations between 2-5% by weight of asphalt binder. It is typically dispersed to the hot asphalt binder at temperatures between 149-171oC. Benefits of this polymer modifier include the fact that only moderate agitation is necessary. Furthermore, the blends can be stored for weeks without succumbing to separation. Consistent with many other polymer modified asphalts, the compatibility of the EVA and asphalt binder is vital for achieving the desired properties.

Studies have shown that at lower polymer contents (3% by weight), EVA modified binders exhibit dispersed polymer particles in a continuous bitumen matrix. EVA modified binder properties, such as morphology and storage stability, are influenced by the characteristics of the base bitumen and binders. Generally, increases in EVA concentration yield greater improvements in the binder; however, these increases also lead to reductions in storage stability. Other studies have shown that, when EVA and SBS modified binders are compared to neat binders, SBS binder exhibit a significantly higher elastic recovery than neat binders. Also, EVA binders tend to exhibit fewer improvements in elastic recovery while losing ductility and elastic recovery at a greater rate.

ECOPATH has extensive experience in binder design where emphasis is placed on achieving specified binder in the most cost effective manner. ECOPATH provides unique solutions for every asphalt concern, moreover ECOPATH is dedicated to developing solutions with economic efficiency as a priority. Please contact us for further information on binder design services.

Ethylene polymers are characterized by a low polarity and low reactivity plastomers. They are like waxes in this respect, having a low dielectric constant and being soluble in hot oils, hot wax and hot hydrocarbons. They also are well known to be inert. For some uses it is desirable to modify the ethylene polymers to make them flexible, to impart more polarity to the polymers, and to be able to use them in reaction with other resins. To obtain high degree of polarity (to improve the dispersion of these materials in asphalt) high level of ester are required, which turn adversely affects the inherit advantage of the long ethylene chain (low cost, good temperature behavior, etc.) while retaining the hydrocarbon chain as the major feature of the polymer.

Commercially available thermosetting resins such as phenolics, epoxys etc. have been found to be useful because of retention of their performance at elevated temperatures. This retention of performance is associated with the crosslinking or curing action inherent in the structure of the thermosetting resins utilized. However, this retention of high temperature performance is accompanied by high stiffness of such material or if some stiffness is desired by providing a higher degree of toughness. For these reasons ECOPATH has developed the technology to blend flexible polymers into the thermosetting resin.

Glycidyl acrylate group.Studies have shown that Elvaloy modified binders show increased high temperature viscosities, however they demonstrate limited viscosity changes at colder temperatures. As such, Elvaloy modified binder enhances the high temperature properties of the asphalt mix. Furthermore, it tends to exhibit significant improvements in the moisture susceptibility properties of the asphalt mix.

Hybrid binders (e.g. SBS-crumb rubber systems) have become more popular in the past couple of years as scientists have established the benefits of blending these two modifiers. Using this technology it is possible to bring together many of the advantages of the various polymers used. Specifically, by using CRM-SBS binders excellent results have been achieved in enhanced performance with improved storage stability.

Also with regards to paving properties, terminal blends have been very popular in chip seal applications and have proven to be an economic alternative to completely replacing the pavement. The introduction of CRM-SBS modified binders represents an evolution in the modified asphalt industry and is widely thought to be the future of the PMAs.

The addition of PPA has long been known to increase the performance grade (PG) of the asphalt binder. Many studies have shown that appropriate introduction and dosing of PPA into asphalt binder can yield cost effective solutions which translate to improved performance properties.

Studies have shown that PG grade of the asphalt binder tends to increase with the addition of PPA. This increase has been attributed to the stiffening of one of the two main phases in the asphalt. This study indicated that the stiffening effects were base binder dependent. However, the following mechanisms were proposed to explain the stiffening of the PPA modified asphalt: formation of PPA aducts, alkylation of aromatics, cross linking of neighboring asphalt segments, formation of ionic clusters and the cyclization of alkyl aromatics.

PPA modified asphalt pavement.Furthermore, it has been suggested that the addition of PPA to asphalt contributes to more interactions within the asphaltenes network, thus increasing the elastic behaviour. This occurs through the increases in the complex modulus values (G*) and decreases in the phase angle (d). Typically the amount of PPA added to asphalt binder is between 0.5 -1.5%, resulting in a PG grade increase of the asphalt binder.

Additional benefits of PPA modification include its suitability for use with other polymers. Studies have shown that PPA can successfully substitute for partial quantities of SBS. Thus, it provides economical solutions for reaching desired performance grades.

ECOPATH has extensive experience in binder design where emphasis is placed on achieving specified binder in the most cost effective manner. ECOPATH provides unique solutions for every asphalt concern, moreover ECOPATH is dedicated to developing solutions with economic efficiency as a priority. Please contact us for further information on binder design services.

SBS modified asphalt pavement.The basic process used to modify asphalt cement with polymers (primarily SBS polymer) is to introduce both liquid asphalt cement and polymer pellets into a heated mixing (or wetting) tank, where they are mixed and the polymer is softened. The mixture is then pumped out through a mill (or grinder) into a storage tank. This mixture is usually made at a higher concentration (about 8% to 12% by weight) than the finished product to minimize the energy required. At this stage, a chemical additive (cross-linker) is added to chemically finish the chemical bonding. The mixture is then transferred to a finished product tank, where it is diluted to the final concentration (about 2% to 2.5%).

Our blending technology utilizes the Modified Asphalt Contactor™ reactor for the mixing tank. The higher effective blending and heating capabilities will allow milling to be accomplished in a single pass, eliminating the need for multiple passes. This will result in significant energy savings due to the large motor of the mill (typically 200-300 HP), which would otherwise be operated for three to six times longer. This also would result in reduced processing time.

ECOPATH Holdings has extensive experience in binder design where emphasis is placed on achieving specified binder in the most cost effective manner. ECOPATH Holdings provides unique solutions for every asphalt concern. Moreover, ECOPATH is dedicated to developing solutions with economic efficiency as a priority. Please contact us for further information on binder design services.

STRATCO® semi-continuous grease process has been documented in various trade and research publications. Below you can find how STRATCO® has contributed to the lubricating grease field.