Assignment 1

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Assignment 1

  1. 1. COURSE NAME: PAVEMENT Management System Assignment 1 Master of Highway and Transportation Engineering Faculty of Engineering Department of Civil Engineering Universiti Putra Malaysia November 2012 SAEED BADELI GS 32514
  2. 2. 1.0 Bitumen hardening is one of the possible causes for several pavement distresses. State the pavement distresses that can be linked to hardening of bitumen. Explain how you would curtail bitumen hardening at the production, construction and in-service stages. Pavement Distresses : A. Cracking B. Patching and Potholes C. Surface Deformation D. Surface Defects E. Miscellaneous Distresses A) CRACKING 1. Fatigue Cracking 2. Block Cracking 3. Edge Cracking 4. Longitudinal Cracking 5. Reflection Cracking at Joints 6. Transverse Cracking Pavement Distress In This Category That Can Relate To Hardening : 1)Fatigue Cracking : Fatigue cracking is a interconnected cracks and can be created by reapeated traffic.This crack can begin at the top of the surface. Aligator cracking is a load-associated distress. Hardening issue can affect to this type of distress with the traffic issue.
  3. 3. 2)Block Cracking : Block cracking is an interconnected crack that can divide the pavement in the rectangular blocks.Block cracking is not a load-associated cracks and that can be caused primarily by shrinkage of asphalt and daily temprature cycling. Block Cracking can show that asphalt has hardening highly. 3)Longitudinal Cracking These type of cracks are parralell to the center line . They may be caused by: 1. A poorly constructed paving lane joint. 2. Shrinkage of the AC surface due to low temperatures or hardening of the asphalt and/or daily temperature cycling. 3. A reflective crack caused by cracking beneath the surface course
  4. 4. 4)Transverse Cracking This crack extend across the center line and They can be caused by a shrinkage of asphalt surface due to low temperatures or to asphalt hardening or can result from reflective cracks caused by cracks beneath the asphalt surface. 5) Ravelling Raveling is deterioration due to water entering the asphalt mat through interconnected air voids. Wearing away of the pavement surface caused by the dislodging of aggregate particles and loss of asphalt binder. Raveling ranges from loss of fines to loss of some coarse aggregate and ultimately to a very rough and pitted surface with obvious loss of aggregate. Raveling can indicate that asphalt is hardening .
  5. 5. Effective Factors That Can Cause Hardening Introduction Bitumen is common binder and has gradually replaced road tar for construction purposes mainly because of the cancer risk. It is a mixture of organic liquids that are highly viscous, black, sticky and entirely soluble in carbon disulfide. Hot mix asphalt normally known as asphalt, is a composite material commonly used for construction of pavement, highways and parking lots. It is a proportionately mixture of mineral aggregates (filler, sand, gravel or crushed stone) that are glued together by a bituminous binder. It is produced in asphalt plant, then lay down in layers and compacted. Although the binder is the component having the lowest percentage in asphalt mixture, its characteristics are those which predominantly influence the properties and the performance of the mix as a whole. Varieties of asphalt mixture exist. Asphalt concrete, stone mastic asphalt, hot rolled asphalt; porous asphalt and gussaspalt are produced according to the layer type and local conditions. All these mixtures display different rheological properties depending on binder and aggregate characteristics. Bitumen, like any organic matter, is affected by factors like presence of oxygen, changes in temperature. These factors are responsible for hardening of bitumen. Hardening results in decline in penetration increase in softening point and grow in penetration index (PI). For increased life of bituminous pavement it is essential that excessive hardness does not take place. Hardening of bitumen takes under the influence of external factors in the following ways: 1)Oxidative Hardening : When bitumen is exposed to atmosphere for a prolonged period the oxygen starts reacting with the bitumen components and higher molecular weight molecules are formed. Larger molecules results in lesser flexibility and hence increased hardness. The degree of hardness is dependent on factors like ambient temperature, exposure time & thickness of bitumen film. It is observed that for 10 0C increase in temperature above 100 0C the oxidation rate doubles. 2) Hardening Dou To Loss Of Volatile: Over a period of time the volatile components in bitumen evaporate. The rate of evaporation is dependent on temperature only. The volatiles in bitumen are relatively very low and hence hardening due to loss of volatiles is relatively small. 3) Physical Hardening:
  6. 6. At ambient temperatures bitumen molecules slowly reorient themselves .This result in physical hardening. This process is an extremely slow process and hence actual hardening due to the above factor is very low. 4) Exudative Hardening: Educative hardening takes place due to the movement of oily components out of bitumen over a period of time. The rate of hardening due to this process is dependent on the type of bitumen and also on the porosity of the aggregate. 5) HardeningOf Bitumen During Storage: Hardening of bitumen during storage can be easily minimized by taking a few simple precautions. Bitumen is stored in above ground tanks at high temperatures and high temperature and presence of oxygen are the two primary factors responsible for hardening of bitumen. Hence it is very important that bitumen be handled at the lowest possible temperature, consistent with efficient use. Also the storage tanks should have low surface to volume ratio so as to minimize the exposed surface area. Lower exposed surface area would mean lower oxidation rate. While designing the tanks it should be ensured that the recirculation pipelines always enter the tank below the bitumen surface. This will reduce splashing during recirculation. When the recirculation line enters the tank above the product surface all the three factors which promote oxidation viz. high temperature, access to oxygen and high exposed surface to volume ratio, are present. Therefore bitumen quality deteriorates very fast. If handled properly the hardening in tanks can be insignificant as the product is stored for shorter durations. If bitumen is to be stored for long durations(4 to 5 days) then the temperature should be reduced to 20 0C to 25 0C above softening point. In case where bitumen is to be reheated to increase the temperature adequate precautions have to be exercised. Bitumen should not be heated continuously in the beginning. Continuous heating can result in very high localized temperatures in area close to the heating source. 6) Hardening Of Bitumen During Mixing: During with a thin film of bitumen the size of which may vary from 5 microns to bituminous macadam is approximately 10, 000 sqm. Therefore again the conditions are very favorable for oxidation and hardening. It is generally observed that bitumen hardens by one grade
  7. 7. during mixing and laying. The above factor is taken into consideration while selecting the right grade of bitumen. 7) Hardening Of Bitumen On Road: Some hardening of bitumen can take place on the road also due to oxidation. The level of oxidation is purely dependent on the access to oxygen. If the pavement is well graded and well compacted the hardening is nominal as the void content will be low. 2.0 Production of a consistent and good quality bituminous mixtures by the quarry/asphalt plant is one of the quality requirement in a road project. Explain how do you approve the bituminous mixture to be used in your road project. Introduction:
  8. 8. Good QC/QA practices are important to gain a satisfactory product.QC refers to those tests necessary in order to control the product and to establish the quality of the product being produced. Those tests are usually done by the contractor.QA mentions to those tests to make a decision on acceptance of a project and hence to ensure that the product being assessed is intended what the owner specified. These QA tests are normally performed by the owner. Testing of the asphalt mixture during the production is essential to ensure that a satisfactory product is obtained. The tests that should be performed during manufacture and placement of the asphalt mixture ,including : aggregate gradation , asphalt content , temperature , mixture properties of laboratory samples, theoretical maximum density , in-place density , smoothness elevations , and visual inspections. The contractor is responsible for quality throughout hot mix asphalt production and laying down. Therefore, the contractor must ensure that the materials and work provided by subcontractors, suppliers, and producers are adequate and meet the specifications of the project. Process monitoring has action limits and specified steps to be taken if the action limits are broken. The specified steps are taken for the following reasons: • To keep the process in control. • To quickly determine when the process has gone out of control. • To respond adequately to correct the situation and bring the process back into control. QC/QA program consist of following major components: A.Quality control B.Quality assurance
  9. 9. C.Independent assurance D.Dispute resolution E.Acceptance and payment A. Laboratory The contractor is responsible for providing adequate laboratory facilities to fulfill the specified testing requirements and quality control needs for production and placement of hot mix asphalt. The Engineer will be notified by the contractor prior to the first day of production of mix that the lab is ready for inspection by the Resident Engineer for this project, which must also be done prior to any mix production. In the event of laboratory equipment breakdown, the equipment will be repaired or replaced immediately or the mix production will be shut down until the equipment is in working order. B. Materials and Inspection
  10. 10. Materials which use for the HMA should be coming from appropriate sources.materials must be examined by the manufacturer for compliance with the requirements of the code material specifications. Inspectors must verify that only code-acceptable materials are used in the fabrication of pressure vessels. The properties of materials are various, and materials have differs. C. Mix Designs The contractor should provide appropriate mix design with complete understand about type of road and minimum requirements and standards for that. Design also demands close attention to the details of testing procedures to ensure an economical blend and gradation of aggregates. Durable asphalt mixes must provide for stability, sufficient voids and workability to permit efficient construction. 1. Marshall Mixture Designs
  11. 11. The basic concepts of the Marshall mix design method were originally developed by Bruce Marshall of the Mississippi Highway Department around 1939 and then refined by the U.S. Army. Currently, the Marshall method is used in some capacity by about 38 states. The Marshall method seeks to select the asphalt binder content at a desired density that satisfies minimum stability and range of flow values (White, 1985). Today the Marshall method, despite its shortcomings, is probably the most widely used mix design method in the world. It has probably become so widely used because (1) it was adopted and used by the U.S. military all over the world during and after WWII and (2) it is simple, compact and inexpensive. Marshall Mix Design Procedure The Marshall mix design method consists of 6 basic steps: 1.Aggregate selection. 2.Asphalt binder selection. 3.Sample preparation (including compaction). 4.Stability determination using the HveemStabilometer. 5.Density and voids calculations. 6.Optimum asphalt binder content selection. 2. Superpave Mixture Design The Superpave mix design method was designed to replace the Hveem and Marshall methods. The volumetric analysis common to the Hveem and Marshall methods provides the basis for the Superpave mix design method. The Superpave system ties asphalt binder and aggregate selection into the mix design process, and considers traffic and climate as well. The compaction devices from the Hveem and Marshall procedures have been replaced by a gyratory compactor and the compaction effort in mix design is tied to expected traffic. Superpave Criteria for the Mixture Design
  12. 12. a. Superpave Mix Design General Guidelines For all projects containing the Special Provision for Superpave Bituminous Mixtures, the Contractor will supply the Superpave Mix Design to the PWD .The Superpave Mix Design must be prepared by a private testing laboratory, either the Contractoror consultant. Superpave Mix Designs must be prepared in accordance with the SUPERPAVE. 3. Superpave Procedure
  13. 13. The Superpave mix design method consists of 7 basic steps: 1. Aggregate selection. 2. Asphalt binder selection. 3. Sample preparation (including compaction). 4. Performance Tests. 5. Density and voids calculations. 6. Optimum asphalt binder content selection. 7. Moisture susceptibility evaluation. The PWD will only accept one passing design per course, per project. The maximum number ofdesigns per course, per project, that any one Contractor or Consultant laboratory may submit istwo. D. HMA Plant Hot mix asphalt is used primarily as paving material and consists of a mixture of aggregate and liquid asphalt cement, which are heated and mixed in measured quantities. Hot mix asphalt facilities can be broadly classified as either drum mix plants or batch mix plants, according to the process by which the raw materials are mixed. In a batch mix plant, the aggregate is dried first, then transferred to a mixer where it is mixed with the liquid asphalt. In a drum mix plant, a rotary dryer serves to dry the aggregate and mix it with the liquid asphalt cement. After mixing, the HMA generally is transferred to a storage bin or silo, where it is stored temporarily. From the silo, the HMA is emptied into haul trucks, which transport the material to the job site. Figure 1 presents a diagram of a typical batch mix HMA plant; a typical drum mix HMA plant is depicted in Figure 2.
  14. 14. Material Sampling Frequency and Testing Refer to appendix for frequency and testing of material samples E. Testing Aggregate Tests: 1. Gradation Test 2. Sieve 3. Coarse Aggregate Specific Gravity 4. Coarse Aggregate Angularity 5. Sand Equivalent 6. Flat and Elongated Particles 7. Los Angeles Abrasion 8. Fine Aggregate Angularity 9. Fine Aggregate Specific Gravity 10. Triaxial Test 1. Aggregate Gradation: There are several aggregate properties that are important but routine testing during construction is usually limited to gradation only. Visual inspections must be made to ensure
  15. 15. the aggregate being produced is similar to the aggregate tested during development of the mix design. For QC/QA testing, aggregate samples are typically taken from the stockpile , cold feeder belt , hot bins , and extracted asphalt mixture. The gradation of the aggregate from the asphalt mixture is most important since this is the end product ; however, the aggregate gradation must be controlled at the other points to ensure that the gradation of the final product is satisfactory. The stockpile should be sampled and tested during the mix design process and approve for use. Once production begins, it is only necessary to sample new material that is added to stockpile since the overall stockpile gradation has already been determined. The new material added to the stockpile must have the same gradation as the original stockpile, within reasonable tolerance , otherwise the gradation of the final mixture is affected. Causes in gradation variations at the stockpile include changes at sources , segregation during or stockpiling , and sampling and testing errors. 2. Asphalt Content: Another mixture property that must be evaluated is asphalt content. The asphalt content of a mixture is a very important to ensure satisfactory performance. A mixture with low asphalt content is not durable, and one with high asphalt content is not stable and can lead to rutting. The actual asphalt content directly affects mixture properties such as asphalt film thickness, voids, stability, and marshal flow. Therefore, it is important to monitor asphalt cement, but it is really these mixture properties that need to be controlled. ASTM D 70 Test Method for Specific Gravity and Density of Semi-Solid Materials ASTM C 117 Test Method for Materials Finer than 75 μm
  16. 16. (No. 200) Sieve in Mineral Aggregates by Washing ASTM C 136 Sieve or Screen Analysis of Fine and Coarse Aggregate ASTM C 566 Total Moisture Content of Aggregate by Drying ASTM D 75 Sampling Aggregates ASTM D 1559 Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus ASTM D 2041 Theoretical Maximum Specific Gravity and Density of Bituminous Paving Mixtures ASTM D 2172 Quantitative Extraction of Bitumen from Bituminous Paving Mixtures ASTM D 2726 Bulk Specific Gravity of Compacted Bituminous Mixtures using Saturated Surface Dry Specimens ASTM D 3203 Percent Air Voids in Compacted Dense and Open Bituminous Paving Mixtures ASTM D 2950 Density of Bituminous Concrete in Place by Nuclear Method ASTM D 4125 Asphalt Content of Bituminous Mixtures by Nuclear Method ASTM C 127 Standard Test Method for Specific Gravity and Absorption of Coarse Aggregate ASTM C 128 Standard Test Method for Specific Gravity and Absorption of Fine Aggregate
  17. 17. IDOT Ignition Method for Determining Asphalt Content F. Mix Production The quality of hot mix asphalt (HMA) is directly related to the quality of the input aggregates and thecontrol of the production process. . Many factors such as aggregate gradation and moisture level affect thequality of hot mix asphalt. As state agencies dictate certain standards on quality of the product, somequality assurance techniques have been used in HMA plants. One of the important and basic luxuries to know the quality of HMA production is that an adequate supply of suitable materials be available in previously and during mixing operation.
  18. 18. These control policies work according to the moving average of the sieve gradations. As variability inthe inputs can cause natural spikes in the gradation, detection of a sudden and temporary shift may not bethe best option. By using moving average the persistent shifts in the process can be detected easily. G. Laydown The mix will be laid on the prepared base in accordance with the specifications using the following equipment: Should any adverse mix characteristics be observed, the laydown superintendent will notify the QC Officer to review the manufacture of the mix and make adjustments if necessary to correct the situation. No changes to the mix shall be made without concurrence by the Division of Aeronautics. Placement of hot mix asphalt is a two-part process. The first portion of placement is laydown, accomplished using an asphalt paver. An asphalt paver has two major components - the tractor and the screed. The tractor is the prime mover that is used for self-propulsion of the asphalt equipment. The screed is the working tool, the equipment that spreads the HMA into asphalt pavement.
  19. 19. The operator must judge three factors when determining paving speed: First, the operator must see how much hot mix asphalt is being delivered to the asphalt paver. Second, the operator must look down at the width and thickness of the asphalt pavement panel being laid. Third, the operator must check behind the asphalt paver to see if the compactor train is able to keep up with the paver. This balance between production and placement needs to be maintained throughout asphalt paving. If the delivery of asphalt mix to the paver is interrupted, the asphalt paver needs to stop. Current practice is to rapidly stop and start the paver so the screed level does not fluctuate because of asphalt paving speed or head-of-material in front of the screed. If the paver outruns the compactor train, the entire asphalt paving operation is at risk of failing to achieve target density and/or asphalt pavement smoothness.
  20. 20. References: Roberts, F. L., P. S. Kandhal, et al. (1996). "Hot mix asphalt materials, mixture design and construction". Whitoeak, D. (1991). "The Shell Asphalt Hand Book." Shell Asphalt--Surrey, UK: 332. Miller, J. S. and W. Y. Bellinger (2003). Distress identification manual for the long-term .pavement performance program Mubaraki, M. (2010).Predicting deterioration for the Saudi Arabia Urban Road Network, University of Nottingham. Roberts, F. L., P. S. Kandhal, et al. (1996). "Hot mix asphalt materials, mixture design and construction." Brown, E. R., Kandhal, P. S., & Zhang, J. (2001).Performance testing for hot mix asphalt. National Center for Asphalt Technology Report, (01-05). Little, D. N., Epps, J. A., &Sebaaly, P. E. (2001). The benefits of hydrated lime in hot mix asphalt. National Lime Association. Mubaraki, M. (2010).Predicting deterioration for the Saudi Arabia Urban Road Network, University of Nottingham. Roberts, F. L., P. S. Kandhal, et al. (1996). "Hot mix asphalt materials, mixture design and construction."

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