2 th International Conference on Science and Technology Comparison between Rubber-Silicon and Polyethylene as an Additive to Hot Mix Asphalt Design Ms, Hamed Algassie,Member at Libyan Audit Bureau

PRESENTATION TOPICS PROPOSE OF PAPER BACKGROUND MATERIALS AND METHODS RESULTS AND DISCUSSION BENEFITS AND LIMITATIONS CONCLUSION AND RECOMMENDATION

BACKGROUND Distress in flexible pavements are among the most important problems met on highway construction and operation Various additives might be used for the modification process. Either the aggregate or the bitumen in the mixture can be modified according to the distortion problem faced

Asphalt Modifiers  Asphalt Modifiers May be added to: Lower viscosity & increase workability Increase viscosity & decrease rutting Increase adhesion between aggregate and binder (especially in presence of moisture) & decrease stripping Reduces landfill problems Recycling of wastes Noise abatement, etc  The primary aim of this study was to investigate the effect of adding rubber- silicon and Polyethylene Terephthalate (PET) waste bottles as an additive to dense- graded mixture performance properties.

Asphalt Modifiers Generic ExamplesGeneral Purpose or UseType Mineral filler,crusher fines Lime,portland cement,fly ash,Carbon black Fill voids and therefore reduce optimum asphalt content Meet aggregate gradation specifications Increase stability Improve the asphalt cement-aggregate bond Filler Sulfur Lignin Substituted for a portion of asphalt cement (typically between 20 – 35 % by weight of total asphalt binder) to decrease the amount of asphalt cement required Extender Natural latex Synthetic latex (e.g., Polychloroprene latex) Block copolymer (e.g., Styrene-butadiene-styrene (SBS)) Reclaimed rubber (e.g., crumb rubber from old tires) Increase HMA stiffness at high service temperatures Increase HMA elasticity at medium service temperatures to resist fatigue cracking Decrease HMA stiffness at low temperatures to resist thermal cracking Rubber Manganese saltsIncrease HMA stiffness after the HMA is placed.Oxidant Lead compounds Carbon Calcium salts Increase the durability of HMA mixtures by retarding their oxidationAntioxidant Recycling and rejuvenating oils Hard and natural asphalts Restore aged asphalt cements to current specifications Increase HMA stiffness in general Hydrocarbon Amines Lime Minimize stripping of asphalt cement from aggregatesAntistripping Agents Roofing shingles Recycled tires Glass Replace aggregate or asphalt volume with a cheaper waste productWaste Materials

Asphalt Modifiers Generic ExamplesGeneral Purpose or UseType Mineral filler,crusher fines Lime,portland cement,fly ash,Carbon black Fill voids and therefore reduce optimum asphalt content Meet aggregate gradation specifications Increase stability Improve the asphalt cement-aggregate bond Filler Sulfur Lignin Substituted for a portion of asphalt cement (typically between 20 – 35 % by weight of total asphalt binder) to decrease the amount of asphalt cement required Extender Natural latex Synthetic latex (e.g., Polychloroprene latex) Block copolymer (e.g., Styrene-butadiene-styrene (SBS)) Reclaimed rubber (e.g., crumb rubber from old tires) Increase HMA stiffness at high service temperatures Increase HMA elasticity at medium service temperatures to resist fatigue cracking Decrease HMA stiffness at low temperatures to resist thermal cracking (see Figure 2) Rubber Polyethylene/polypropylene Ethylene acrylate copolymer Ethyl-vinyl-acetate (EVA) Polyvinyl chloride (PVC) Ethylene propylene or EPDM Polyolefins Plastic Blends of rubber and plasticRubber- Plastic Combinations Natural: Asbestos Rock wool Manufactured: Polypropylene Polyester Fiberglass Mineral Cellulose Fiber Manganese saltsIncrease HMA stiffness after the HMA is placed.Oxidant Lead compounds Carbon Calcium salts Increase the durability of HMA mixtures by retarding their oxidationAntioxidant Recycling and rejuvenating oils Hard and natural asphalts Restore aged asphalt cements to current specifications Increase HMA stiffness in general Hydrocarbon Amines Lime Minimize stripping of asphalt cement from aggregatesAntistripping Agents Roofing shingles Recycled tires Glass Replace aggregate or asphalt volume with a cheaper waste productWaste Materials

OBJECTIVES OF BITUMINOUS MIX DESIGN To prevent asphalt pavement distresses various solutions such as adopting new mix designs or the use of asphalt additives Sufficient strength to resist shear deformation under traffic at higher temperature. Sufficient air voids in the compacted bitumen to allow for additional compaction by traffic. Sufficient workability to permit easy placement without segregation. Sufficient resistance to avoid premature cracking due to repeated bending by traffic. Sufficient resistance at low temperature to prevent shrinkage cracks.

Materials and Methods The main aim of the study is to deliver more insight into the contribution of the percentage of different modifiers of bituminous binder in Libyan conventional hot mix asphalt (HMA) towards enhancement of the mixture properties. Based on this aim, the objectives had been achieved by conducting laboratory investigations. Laboratory investigation has including  material characteristics,  mix design method  and experimental program. All data presented in this study had been conducted in the Road laboratory of the Civil Engineering Department at Sebha University.

Materials and Methods Aggregates Crushed limestone aggregates collected from the nearby quarry (Abushkaka Mountain) PropertiesStandardsTest Value Soundness (%)AASHTO T Crushing (%)AASHTO T Absorption (%) AASHTO T Bulk Specific Gravity (g/cm3)AASHTO T Apparent Specific Gravity (g/cm3)AASHTO T Flakiness index (%) BS – Elongation Index (%) BS – Filler  Limestone dust that passing 0.075mm sieve is used  The quantity of mineral filler used is 2%.

Materials and Methods Bitumen One binder of asphalt cement was tested, from Azzawiya Refinery with a grade of (60-70) penetration  The binder contents utilized in this study are 4%, 4.5%, 5%, 5.5%, 6%, and 6.5% by weight of the total mix. PropertyConditionsTest Asphalt Used Specific GravityPycnometer,25°CASTM D Penetration,0.1 mm25 °C, 100g, 5 SecAASHTO T-4967 Flash Point, °COpen CupAASHTO T Ductility, cm25 °C, 50 mm/minAASHTO T-51>100 Softening Point, °CRing and BallAASHTO T-5356

Materials and Methods Polyethylene-Terephthalate (PET) PET is a semi-crystalline polymer high tensile strength, high chemical resistance, a melting point of 260±10 °C. was collected from the local waste plastic. The specific gravity % PET by weight of the asphalt content

Materials and Methods Rubber-Silicone carry both inorganic and organic properties, unlike other organic rubbers. silicone rubber was superior to ordinary organic rubbers in terms of  heat resistance,  chemical stability,  electrical insulating,  abrasion resistance,  weatherability,  and ozone resistance. available in the local market for sealants or glue stick 4% Rubber-Silicon was added by weight to binder Rubber-Silicone was added to the binder at a temperature (150) °C with a stirrer for (20) minutes.

Results and Discussion Marshall Stability " a measurement of the susceptibility of a bituminous mixture to deformation ensuring from frequent and heavy traffic load." silicone rubber was superior to ordinary organic rubbers in terms of  heat resistance,  chemical stability,  electrical insulating,  abrasion resistance,  weatherability,  and ozone resistance. available in the local market for sealants or glue stick 4% Rubber-Silicon was added by weight to binder

Results and Discussion Marshall Flow " Flow can be understood to mean a measurement of the permanent strain which takes place in a Marshall test at failure." silicone rubber was superior to ordinary organic rubbers in terms of  heat resistance,  chemical stability,  electrical insulating,  abrasion resistance,  weatherability,  and ozone resistance.

Results and Discussion Bulk Density of mix (Gmb) " Flow can be understood to mean a measurement of the permanent strain which takes place in a Marshall test at failure." silicone rubber was superior to ordinary organic rubbers in terms of  heat resistance,  chemical stability,  electrical insulating,  abrasion resistance,  weatherability,  and ozone resistance.

Results and Discussion Voids in the Mix (VIM) Too many voids in the mix (high porosity) will provide passageways through the mix for the entrance of damaging air and water. Too low porosity could lead to flushing where the excess bitumen squeezes (bleeding) out of the mix to the surface.  heat resistance,  chemical stability,  electrical insulating,  abrasion resistance,  weatherability,  and ozone resistance.

Results and Discussion Optimum asphalt content (OAC) The optimum asphalt content (OAC) was calculated by taking the average of the three values given below:  The bitumen content corresponding to the maximum stability.  The bitumen content corresponding to the maximum unit weight.  The bitumen content corresponding to the median of the designed limits of percent air voids (VIM) in the total mix (4%).

BACKGROUND Hot mix asphalt (HMA) is produced by heating the asphalt binder to decrease its viscosity, and drying the aggregate to remove moisture from it prior to mixing The HMA design aims to determine the proportion of bitumen, filler, fine aggregates, and coarse aggregates to produce a mix which is workable, strong, durable and economical.

OBJECTIVES OF BITUMINOUS MIX DESIGN Sufficient bitumen to ensure a durable pavement. Sufficient strength to resist shear deformation under traffic at higher temperature. Sufficient air voids in the compacted bitumen to allow for additional compaction by traffic. Sufficient workability to permit easy placement without segregation. Sufficient resistance to avoid premature cracking due to repeated bending by traffic. Sufficient resistance at low temperature to prevent shrinkage cracks.

Requirements of Bituminous mixes Stability Durability Flexibility Skid resistance Workability Desirable properties

Requirements of Bituminous mixes  Asphalt Mix Design is a very delicate engineering activity.  It has to address many criteria : strength, stability, durability, impermeability, workability, surface skid resistance, resistance against fatigue cracking and rutting, appearance etc.  But the fundamental performance properties are not measured in the design mix, those are indirectly assessed by some empirical parameters.

Requirements of Bituminous mixes The parameters which have to be taken into account to achieve the desired criteria are :  Sufficient asphalt or bitumen in the mix to ensure durable pavement.  Sufficient voids in the compacted mix to allow a slight amount of expansion of asphalt due to increase in temperature and also by the action of additional compaction under the effect of traffic movement specially in summer season when viscosity of the binder comes down a bit, without flushing, bleeding and loss of stability.

Requirements of Bituminous mixes  Maximum void content in the mix to restrict the ingress of air and moisture causing early aging of the binder.  Sufficient mix stability to satisfy the demand of traffic without distortion or displacement.  Sufficient workability to permit efficient placement without segregation and without sacrificing stability and performance.  To provide sufficient skid resistance of the surface mix specially in unfavourable weather condition.  To provide a good appearance of the pavement surface as well as to provide a noise-less smooth interaction with the pneumatic tires of the vehicles.

Requirements of Bituminous mixes  The trick of the mix design for dense graded mixes is to find such a gradation which will yield not the densest packing but will have sufficient voids (Voids in Mineral Aggregate – VMA) to accommodate enough bitumen for ensuring durability against fatigue cracking ( Voids filled by Bitumen –VFB ) and most importantly some specified amount of voids ( air void or void in mix -VIM) to allow the expansion and expulsion of bitumen during summer and under the action of heavy traffic to ensure resistance against rutting, flushing, bleeding etc. This is different from densest gradation curve.  The amount of the bitumen which is added with the mineral aggregates are not totally utilized to act as the film to coat the aggregates, some amount of it is absorbed by the surface pores of the aggregates which is known as the absorbed bitumen and the rest is known as effective bitumen content. The aim of proper mix design is to determine the effective bitumen content because this bitumen is actually coming into play to create the coating film around the mineral aggregates.

Conventional Bituminous Mix Technologies Hot Mix Technologies-Shortfalls Heating of binder at C Heating of aggregates at C Production at C Laying at 140 C Compaction at 120 C Environmental pollution High energy consumption Limited work year Solution…!!! Cold mix technologies using bitumen emulsion as binder

The Hot Asphalt Mix modification process The modification process is usually established by mainly one of two common ways; WET PROCESS additive particles are mixed with asphalt at raised temperature before mixing with the hot aggregates DRY PROCESS additive particles replace a small portion of the mineral aggregate in the asphalt mix before the addition of the asphalt

WHAT IS ASPHALT RUBBER ? ASPHALT RUBBER ASTM D8 Distress in flexible pavements are among the most important problems met on highway construction and operation RELATED SPECIFICATION ASTM D 6114 Standard Specification for Asphalt Rubber Binder High viscosity material that typically requires agitation to keep CRM particles dispersed

Additives Used in conjunction with the CRM to enhance interaction and produce desirable properties  Extender oils  Anti-strip agents  High natural rubber (HNR)  Polymers – typically limited to no agitation 1 AR 101

Advantages of High Viscosity AR Binder  Allows higher binder content and increased film thickness-resulting in increased durability (moisture resistance and aging resistance)  Improves aggregate retention  Minimizes drain-down problems  Increases resistance to fatigue and reflection cracking  Increases resistance to bleeding, flushing and deformation 1 AR 101

Aggregate Gradation Comparison Open GradedGap Graded Dense Graded 3 RAC Applications

Dense-Graded HMA RAC-D  Limited performance improvements vs. cost  Inadequate void space to accommodate sufficient  AR binder to modify behavior  Discontinued use with high viscosity binder 3 RAC Applications EARLY USE

Gap Graded Mixes RAC-G  Currently the workhorse mix in CA  30 to 60 mm Thickness  Thickness reduction allowed when this mix is employed RAC Applications

HOT MIXES RAC-O  Widely used in California as surface course  Free draining with reduced splash and spray  Does not add any structural value 3 RAC Applications Open-Graded

HOT MIXES RAC-O-HB  Widely used in Arizona as surface course  Also used by Caltrans as surface course  Not as free draining, but improved durability 3 RAC Applications Open-Graded High Binder

AR USAGE GUIDELINES Section 4 RAC USAGE GUIDELINES A B C D DESIGN PRODUCTION & EQUIPMENT CONSTRUCTION SAMPLING & TESTING

Design Guide-Contents Design 1.Introduction 2.Asphalt Rubber 3.AR Design Considerations 4.AR Materials Issues 5.AR Construction Issues-HMA & Chip Seals 6.Pre-construction meeting 7.Environmental considerations 8.Current/Future Developments 9.References 1.Introduction 2.Asphalt Rubber 3.AR Design Considerations 4.AR Materials Issues 5.AR Construction Issues-HMA & Chip Seals 6.Pre-construction meeting 7.Environmental considerations 8.Current/Future Developments 9.References Rubberized Asphalt Concrete Technology Center (RACTC) 4 RAC USAGE GUIDELINES

AR Design Considerations Design 4 RAC USAGE GUIDELINES BINDER DESIGN STRUCTURAL DESIGN 1 2

Asphalt Rubber Blend Profile Design  Developed to evaluate compatibility between materials used  Checks for stability of the blend over time  Should be required for each project 4 RAC USAGE GUIDELINES

AR Benefits  Improved durability as surface layer  Resistance to fatigue cracking  Resistance to reflection cracking  Resistance to aging  Can be used in reduced thickness  Reduced noise  Lower life cycle costs  Environmental 4 RAC USAGE GUIDELINES

Improved Performance 4 RAC USAGE GUIDELINES Cracking resistance Durability-aging resistance

Increased Cracking Resistance 8” of Conventional Overlay After Twelve Years of Performance 5” of Asphalt Rubber Overlay After Twelve Years of Performance 4 RAC USAGE GUIDELINES

Frequently Asked Questions ? 1.Is the use of AR technically sound and cost effective? 2.AR be used in cold weather climates? 3.Can AR be rehabilitated and/or recycled? 4.Why isn’t AR more widely used by other agencies? YES Education 4 RAC USAGE GUIDELINES

Implementation  Educating users  Benefits of AR  Identifying best places to use AR  Understanding the Limitations 4 RAC USAGE GUIDELINES

Conclusions  In comparison to the control mix (mix with 0% additive), the values of Marshall Stability for HMA modified with rubber- silicone were generally higher as better adhesion is developed.  adding PET and Rubber-Silicone to the mixture increases the VIM of the mixture while decreasing its density.  The least OBC was found to be 4.91 % by weight of bitumen for hot mix asphalt modified by Rubber-Silicone.  PET and Rubber-Silicone mixture show acceptable trends and could satisfy the standard requirements and Libyan specification.

Recommendation for Future Studies  The use of different types of aggregate, aggregate gradation, different mixing methods, different compaction methods and various percentages of additive is recommended for further studies.

? ? Thank you for your time today. Any questions?