Hot Mix Asphalt Concrete (HMAC) Rehabilitation Design on Flexible Pavement PEIMAN AZARSA 1, DR.P.SRAVANA 2

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1 ISSN Vol.03,Issue.31 October-2014, Pages: Hot Mix Asphalt Concrete (HMAC) Rehabilitation Design on Flexible Pavement PEIMAN AZARSA 1, DR.P.SRAVANA 2 1 Dept of Civil Engineering, JNTUH, Hyderabad, India, peyman.azarsa@gmail.com. 2 Professor, Dept of Civil Engineering, JNTUH, Hyderabad, India. Abstract: This paper presents the hot mix asphalt concrete (HMAC) rehabilitation design on flexible pavement. The HMAC pavement is the high type asphalt pavement. The major advantages of HMAC are recyclable and staged construction. The overlay thickness is designed by modified AASHTO method. This method includes the determination of traffic factor, immediate bearing value, required structural number, and existing structural number. Soil test data and traffic data are obtained from the study area. The study area is located on Sagaing- Monywa highway road. The portion of this road is from (mile 82/0) to (mile 84/1). Required data for this road are obtained from the Road Research Laboratory, Thuwana, Yangon and Shwe Taung Development Co, Ltd. Keywords: HMAC, Modified AASHTO Method, Traffic Factor (TF), Structural Number (SN). I. INTRODUCTION Roads are constructed to move people and goods efficiently and economically. The nature of asphalt pavements and their construction is such that they can be built quickly and opened to traffic immediately. Rapid construction is particularly critical when overlaying an existing pavement. Asphalt pavements, with their lack of a required curing period, mean minimum delays to the travelling public. Asphalt overlays can be scheduled for off peak hours and re-opened in time for the rush hour. After placement, traffic can use the pavement almost immediately. The proper design thickness of an overlay depends upon the condition of the existing pavement. Major advantage of HMA is its ability to be completely recycled. Not only can the aggregates be reused, but the asphalt binder also retains its adhesive properties and can be re-used in a new HMA mix. The objectives of the hot mix asphalt concrete (HMAC) overlay design are to protect a deteriorated pavement, to reduce roughness of the pavement, to improve ride quality, to restore skid resistance and to save and comfort to the road user. II. HOT MIX ASPHALT CONCRETE (HMAC) Hot mix asphalt is known by many different names: HMA, asphaltic concrete, plant mix, bituminous mix, bituminous concrete and many others. The aggregates total approximately 5 percent asphalt binder to produce HMA. It is a combination of two primary ingredients- aggregates and asphalt binder. The aggregates and asphalt are combined in a manufacturing plant capable of producing specified materials. HMA mixture salvaged from rehabilitation of existing pavement can and should be recycled into the new HMA mixture. HMA pavement mix types include Open graded Friction Courses (OGFC), Stone Matrix Asphalt (SMA), and fine and coarse graded dense mixes. HMA pavement mixtures are expected to perform over extended periods of time under a variety of traffic and environmental conditions. A. HMA Overlays HMA overlays are used to restore an aged pavement to like-new condition. HMA overlays can be placed with minor traffic disruptions during off-peak times and, when properly designed and constructed, will provide a smooth, durable surface for many years. The overlay thickness, which is related to its intended function, may be determined based on a number of analysis techniques. B. Thin HMA Overlays Thin HMA overlays are used to protect a deteriorated pavement, reduce roughness, improve ride quality, and restore skid resistance. When thin HMA overlays are used, it is important to ensure that 1) the maximum size of the aggregate is appropriate for the overlay thickness, 2) a proper tack coat is applied, 3) work is carried out in warm weather to obtain the desired level of compaction, and 4) good construction quality control is maintained. C. Structural HMA Overlays Structural overlays are used to increase or restore the structural integrity of a pavement. Structural overlays may be required when a dramatic increase in heavy truck traffic is experienced or when existing pavements are approaching the end of their designed service life. Overlays will increase pavement life, reduce routine maintenance costs, provide a smoother riding surface, and improve skid resistance. The design of an HMA overlay requires that the existing structure, including the sub-grade, be evaluated. The strength of the existing pavement structure gives an 2014 IJSETR. All rights reserved.

2 indication of both the thickness and condition of the pavement layers. Strength variability along the road can be determined by periodic measurements (every 100 ft or so) along the length of the roadway. III. RECOMMENDED DATA ELEMENTS A. Introduction Based on the review of published overlay design procedures and the survey of surrounding State DOTs, it is recommended that the WisDOT flexible pavement overlay design procedures include measures of both pavement condition and surface deflections and allow for independent as well as integrated usage. The WisDOT flexible pavement overlay design procedures must be compatible with current WisDOT design procedures for new pavements and must be flexible enough to be integrated into revised pavement design procedures which may include items such as the sub grade resilient modulus and design reliability. The overlay design procedures should be applicable to deteriorated pavements in need of repair as well as newer pavements which require structural improvements to handle increased traffic demands, such as detour routes. The following sections describe the framework for key data elements recommended for inclusion into the WisDOT flexible pavement overlay design procedures. B. Effective Structural Number of Existing Pavement The current WisDOT flexible pavement design procedures are based on the structural number (SN) concept developed as a result of the original AASHTO Road Test. At this time, the procedures are based on 1972 AASHO design equation. Discussions with WisDOT design engineers have indicated that the current design procedures may be updated within the next 3-5 years, depending on the applicability of the Mechanistic-Empirical AASHTO design procedures currently under review. In the interim, it is recommended that the overlay design procedures developed through this research be based on the existing SN concept, which requires the determination of the effective structural number, SNeff, of an existing pavement. Table I: Example Decision Matrix for Establishing SNEFF It is highly recommended that deflection testing be required for establishing SNeff for all but lightly trafficked routes. Recommended procedures for this analysis are provided. For those cases where deflection data is unavailable, procedures PEIMAN AZARSA, DR.P.SRAVANA are provided for establishing SNeff based on pavement condition measures (ride quality, distress) and the original pavement structural number. Recommended procedures for this analysis are provided. It is further recommended that multi-level procedures that allow for the determination SNeff using distress, ride quality, and/or deflection data based on design ESALs be considered. An example of a decision matrix for this purpose is provided in Table 1. C. Pavement Condition Measures WisDOT routinely collects flexible pavement distress data and ride quality measures on a system-wide basis. The Marquette University research staff has obtained historical flexible pavement distress and ride quality data from WisDOT. Historical distress data is available dating back to 1985 and ride quality data is available back to Distress data is currently utilized by WisDOT to compute the overall Pavement Distress Index (PDI), a value which has been used to indicate the need for pavement rehabilitation. Fig.1 illustrates PDI data trends for a subset of the available WisDOT data. This subset was selected for illustrative purposes and represents the first 500 non-zero entries within the PDIFLEX database. It is also recommended that a new distress index, such as a Structural Distress Index, (SDI) be considered for development which uses using only key structural distress data such as alligator cracking and rutting. Fig.1. PDI versus Age for Wis DOT Performance Data. The SDI could be computed in a manner similar to the existing PDI equation, with possible modifications to the distress factors currently used for PDI calculations. This concept could also be integrated with other condition measures such as the Pavement Condition Index (PCI). A numerical and graphical procedure, similar to the 1993 AASHTO procedure (1), could be developed to use the SDI to estimate of the remaining service life of the pavement and to select a condition factor for modifying the in situ pavement=s effective structural number, SNeff. This procedure should be developed based on historical distress data already available from WisDOT. Fig.2. illustrates example SDI trends for the data subset illustrated in Fig.3. For this illustration, SDI was calculated only from rutting,

3 Hot Mix Asphalt Concrete (HMAC) Rehabilitation Design on Flexible Pavement alligator cracking, and transverse cracking distress data using standard WisDOT distress factors. D. Pavement Deflection Measures Pavement deflections obtained with heavy-load deflection devices provide a valuable assessment tool for estimating the structural capacity of in situ pavements. It is highly recommended that pavement deflection data be required for estimating both SNeff and the sub grade resilient modulus, MR, for all but lightly traffic roadways. WisDOT currently owns and operates a KUAB falling weight deflect meter (FWD) for collecting pavement deflection data FWD testing data can also be provided by a number of independent contractors. Various techniques for utilizing deflection data for analysis of in-place flexible pavements are provided in the following sections. Research factorial of pavement response data was generated to provide response data to test the validity of available analysis procedures as well as to develop new equations, where appropriate. Fig.2. SDI versus Age for Wis DOT Performance Data Fig.3 illustrates a comparison of SDI versus PDI for this data. The poor correlations exhibited in Fig.2 and 3 indicate more analysis is required before these concepts could be utilized within the overlay design procedures. Ride quality is currently calculated from profile data and reported in terms of the International Roughness Index (IRI). Fig.4 illustrates IRI trends for a similar data subset (i.e., first 500 non-zero entries) extracted from the PSIFLEX database. It is recommended that a procedure be developed to utilize IRI data for estimating the remaining life of a given pavement and to select a condition factor for modifying the in situ pavement=s effective structural number, SNeff. A numerical and graphical procedure, similar to the Asphalt Institute=s procedure (3), should be developed based on historical IRI trends of flexible pavements in Wisconsin. Fig.3. SDI versus PDI Values. Fig.4. IRI versus Age for WisDOT Performance Data. The KENLAYER (5) computer program, which allows for stress-dependent base and sub grade layer analyses, was utilized for this effort. Table 2 provides the range of pavement structures investigated. A circular surface loading of 9,000 lb at psi (radius = in) was applied in all cases to represent a standard FWD loading. Surface deflections were calculated at offset locations similar to those used during FWD testing. The complete factorial of KENLAYER runs included 7,680 separate pavement structures (8x8x8x3x4) with base to HMA thickness ratios varying from 0.67 to 7.5. The output results were parsed to include only those pavement structures where the ratio of base to HMA layer thickness was in the range of 1.8 to 3.25, which is more in line with pavement design practices in Wisconsin, resulting in a total of 2,592 separate pavement structures as shown in Fig.5. The input SN of each pavement structure was computed based on the input thickness and modulus values for each layer. The computed SN values for the parsed factorial ranged from 2.09 to These values, along with the surface deflections generated by the program were used to test the validity of available models and to

4 PEIMAN AZARSA, DR.P.SRAVANA developed improved equations, where warranted, to estimate For 20 years, key structural pavement parameters. Table II: KENLAYER Pavement Factorial Step 3: From field data, soil classification is A-6, Therefore, IBV = 3 Using Fig.6; TF 15 = 0.36, SN F = 3.52 TF 20 = 0.48, SN F = 3.8 Step 4: Existing cross section is composed of: 4 in of Class I HMA surface, 6 in of Lime Stabilized Soil base, and 16 in of Granular Material, Type A, Crushed. From Equation 2: Existing structural number, SN F, e = 3.02 (3) IV. DESIGN CALCULATION In calculation of required overlay thickness for Sagaing- Monywa road portion from (mile 37/0-39/1) is as follows. The required data are obtained from Road Research Laboratory, Thuwanna, Yangon and Shwe Taung Development Co.Ltd. The following calculation is represented for mile 37/0-84/1. Step 1: From the traffic data of case study area, the no. of vehicles per month is 5505 vehicles and no. of days is 31. The result value is So the average daily traffic (ADT) on this pavement is between 400 and The study area of Sagaing Monywa highway. Step 2: According to the lane pavements; DP= Design period (the number of years that a pavement is to carry a specific traffic volume and retain a minimum level of service) PV= Passenger Vehicles (automobiles, pickup trucks, vans, and other similar two-axle, four-tire vehicles) SU = Single units (Trucks and buses having either 2 axles with 6 tires or 3 axles) (1) Step 5: The design of hot mix is used with the 19.0 mm HMA binder course and a 9.5 mm or 12.5 mm HMA surface course. From Equation 3, the overlay thickness is For 15 years design period, For 20 years design period, These thicknesses should be rounded to the nearest 0.25 in: D O, 15 = 2 in; and D O, 20 = 2.5 in. The minimum overlay thickness (D O ) for SNF 3.0 to 3.49 is 3.0 in (Table 6). Therefore, either the 15-year or 20-year DP will provide the minimum thickness. Use the 20-year DP since this will only increase the pavement thickness by 0.5 in. The overlay thickness of other portions is calculated with the above procedures. The designs of thickness are mentioned in Table 5. TABLE III: Overlay Thickness (4) (5) MU = Multiple Units (truck tractor semi-trailers, full trailer combination vehicles, and other combinations of a similar nature) From 1784 ADT: PV=88% ( ), SU=7% (124.88), MU= 5% (89.2) For 15 years, (2)

5 Hot Mix Asphalt Concrete (HMAC) Rehabilitation Design on Flexible Pavement TABLE IV: Coefficients for HMA Overlay on Flexible Pavement or Recycled Base (Modified AASTHO Design) Fig.5. HMA Overlay on Flexible Pavement/Base Design NOMOGRAPH (Modified AASHTO Design: Class II, III, and IV Facilities). TABLE V: Minimum Thickness and Material Requirements for HMA Overlays on Flexible Pavement/ Base (Modified AASHTO Design) V. CONCLUSION The board objective of highway maintenance is to keep the highways in the original condition as much as possible. The 47 mile-portion of Sagaing-Monywa highway is selected for the study area. The traffic volume depends on one month. The design period is considered as 15 years and 20 years. Sagaing-Monywa highway is becoming structurally inadequate because of the rapid growth in traffic volume and axle load. In addition, the sub-grade of the existing road has not achieved the compaction and not stable. Therefore, the various failure patterns such as cracking, rutting, shoving, deep depressions, etc, are formed. The sub-grade of the existing pavement is important factor for the design of overlay thickness. According to the soil test, from mile 37/0 to 39/0, mile 57/0 to 59/0, and 77/0 to 84/1 are water bound macadam road. So these portions are not needed overlay layer before the paving of HMAC. The other portions need this layer. As a standard rule, the lift thickness should be at least twice the maximum aggregate size in the mixture. In table 6 the required overlay thickness are varied with the value of existing structural number. VI. REFERENCES [1] Tin Wint Wint War, Tin Tin Htwe, Hot Mix Asphalt Concrete (HMAC) Rehabilitation Design on Flexible Pavement, Vol.02, Issue.02, July [2] Kinchen, R.W. and W.H. Temple. Asphalt Concrete Overlays of Rigid and Flexible Pavements. Report No.

6 PEIMAN AZARSA, DR.P.SRAVANA FHWA/LA-80/147, Louisiana Department of Transportation and Development, [3] Abaza, K. A. Performance-Based Models for Flexible Pavement Structural Overlay Design. J.Transp. Eng., 131(2), 2005, pp [4] American Association of State Highway and Transportation Officials (AASHTO). AASHTO Guide for Design of Pavement Structures, Washington, D.C., [5] Asphalt Institute (AI). Asphalt Overlays for Highway and Street Rehabilitation. Manual Series MS-17, Lexington, Ky, [6]Hall, K. D. and N. H. Tran. Improvements to the ROADHOG Overlay Design Program. Final Report TRC- 0209, University of Arkansas, Fayetteville, Arkansas, [7] Darter, M.I., Elliott, R.P., and Hall, K.T., "Revision of AASHTO Pavement Overlay Design Procedure," Project 20-7/39, National Cooperative Highway Research Program, Transportation Research Board, Washington, D.C., September Newcomb, D. E., Development and Evaluation of Regression Method to Interpret Dynamic TRB.