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Performance evaluation of SUPERPAVE and Marshall asphalt mix designs to suite Jordan climatic and traffic conditions
Construction and Building
MATERIALS
Construction and Building Materials 21 (2007) 1732–1740
www.elsevier.com/locate/conbuildmat
Performance evaluation of SUPERPAVE and Marshall asphalt mix designs to suite Jordan climatic and traffic conditions Ibrahim M. Asi
*
Department of Civil Engineering, Hashemite University, Zarqa 13115, Jordan Received 28 March 2005; received in revised form 1 February 2006; accepted 31 May 2006 Available online 22 September 2006
Abstract Due to the empirical nature and the drawbacks of the Marshall mix design procedure, the Strategic Highway Research Program (SHRP) has developed a Superior Performance asphalt Pavements (SUPERPAVE) mix design procedure. In this research a comprehensive evaluation of the locally available aggregate usually used in the asphalt concrete mixtures was carried out to ensure that these materials conform to the new mix design procedures developed by SUPERPAVE. A performance grading map was generated to the Hashemite Kingdom of Jordan. In this map the country was divided into different zones according to the highest and lowest temperature ranges that the asphalt might be subjected to. Using local materials, loading and environmental conditions, a comparative study of the performance of two mixes designed using SUPERPAVE and Marshall mix design procedures was carried out in this research. Samples from both mixes were prepared at the design asphalt contents and aggregate gradations and were subjected to a comprehensive mechanical evaluation testing. These tests included Marshall Stability, Loss of Marshall Stability, Indirect Tensile Strength, Loss of Indirect Tensile Strength, Resilient Modulus, Fatigue Life, Rutting, and Creep. In all the performed tests SUPERPAVE mixes proved their superiority over Marshall mixes. Therefore, serious plans should be set up in Jordan to shift from the presently used Marshall mix design procedure to SUPERPAVE mixture specifications. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: SUPERPAVE; Marshall; Asphalt mix design; Temperature zoning; Performance grading; Fatigue; Rutting; Creep
1. Introduction The major properties to be incorporated in bituminous paving mixtures are stability, durability, flexibility and skid resistance (in the case of wearing surface). Traditional mix design methods are established to determine the optimum asphalt content that would perform satisfactorily, particularly with respect to stability and durability. There are many mix design methods used throughout the world e.g. Marshall mix design method, Hubbard-field mix design method, Hveem mix design method, Asphalt Institute Triaxial method of mix design, etc. Out of these only two are widely accepted, namely Marshall Mix design method and Hveem mix design method [1]. In Jordan, Marshall mix *
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design procedure (ASTM D 1559) [2] is used for designing the asphalt concrete mixes. In Jordan, roads were built to the best international standards. After a short period of service, some of these roads have shown signs of major distresses due to the harsh environmental conditions and traffic loading [3]. Another reason which is contributing to these early distresses is the continuation of the use of Marshall mix design procedure for asphalt mixtures. The Marshall mix procedure is empirical and suffers the limitation of accuracy in determining the full effects of variations in environmental and loading conditions, and material properties and types on the pavement performance. It cannot identify the mixes with high degree of shear susceptibility. In addition, the impact method of compaction in the Marshall mix method does not simulate densification that occurs under traffic in a real pavement [4]. Therefore, due to its drawbacks, it was
I.M. Asi / Construction and Building Materials 21 (2007) 1732–1740
dropped from the American Standard Testing Procedures in 1998 [5]. This situation calls upon the country, a leading country in the region, to adopt up-to-date mix design and evaluation procedures to alleviate these problems. Recent research and development efforts in the Strategic Highway Research Program (SHRP) have focused on the establishment of performance-based asphalt binder and asphalt mix specifications [4,6]. The main objective of SHRP Asphalt Program was to develop a mixture design method that incorporates a performance-based asphalt binder specification and an accelerated performance-based tests. The product that was designed by the new mixture design system was known as SUPERPAVE (SUperior PERformance PAVEments). 1.1. Current asphalt binder testing philosophy The current philosophy that deals with asphalt binder evaluation in Jordan uses the traditional old fashion testing that deals mainly with the physical properties of the asphalt cement. It uses testing such as penetration, viscosity and ductility. These tests are performed at standard test temperatures. The results of these tests are used to determine if the material meets specification criteria. Several limitations exist to the use of physical evaluation only. Limitations can be summarized as follows: Many of the current tests are empirical, i.e., the pavement performance experience is required to relate the test parameters with pavement performance. The tests do not give information about the entire range of typical pavement temperatures, for example, viscosity is an important property of asphalt binders, however, the viscosity gives an indication about the behavior of the material at high temperatures, viscosity does not provide any information about low and medium temperature behavior of asphalt binders. The current asphalt specifications can classify different asphalts with the same grading, when in fact these asphalts may have very different temperature and performance characteristics.
1.2. Development of the SUPERPAVE mix design procedure Due to the drawbacks in both binder and mix specification, the US congress, in 1987, supported a five year research program to improve the performance and durability of the US roads and to make those roads safer to both motorists and highway workers. Part of this research funds were used for the development of performance-based asphalt specifications to directly relate laboratory analysis with field performance [7]. A bimodal grading system, which is based on rational performance indices, was established for both low temperature and high temperature pavement service. Thus, precise
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grade may be selected to accommodate the need to control low-temperature cracking, rutting or both in a particular construction project. In addition, it will address certain aspects of fatigue cracking [8]. For a given type of asphalt cement to satisfy performance criteria for a given temperature zone, it must satisfy SHRP performance tests which must be conducted at designated temperatures. The suitability of a given asphalt binder to a certain area is determined by the extreme temperatures (average sevenday maximum pavement design temperature and the minimum pavement design temperature), required reliability, traffic level and speed anticipated to use the facility under consideration. The asphalt binder rheological properties related to both high temperature distresses such as rutting or shoving, and low-temperature cracking distress were specified and are required to satisfy a certain threshold value at the temperature regime in which the binder is expected to serve. The SUPERPAVE system consists of three interrelated areas: (1) a performance graded (PG) asphalt binder specification and tests that are based on the range of temperatures experienced by the pavement; (2) aggregate criteria and tests; and (3) a mixture design system utilizing both a volumetric mixture design with a Superpave gyratory compactor (SGC) and an analysis/performance prediction element [4]. SGC (1.25°, 30 gyration/min and 0.6 MPa ram pressure for 150 mm mold) is used for the evaluation of volumetric properties and strength of compacted mixes [9]. Sousa et al. [10] found that the SGC is capable of producing laboratory specimens whose volumetric and engineering properties adequately simulate those of field specimens from a wide variety of pavements. In this research, a performance grading map showing the required asphalt binder grades for the different parts of Jordan was generated. Representative aggregate and asphalt samples were collected. A comprehensive evaluation of the collected materials was carried out to ensure that these materials conform to the SUPERPAVE mix design procedures considering country specific conditions of traffic and environment. Marshall and SUPERPAVE mix design procedures were performed using the collected asphalt and aggregate samples. Comparison between the two mix design procedures included optimal asphalt content, aggregate gradation, and mixes mechanical performance. Mechanical performance evaluation consisted of Marshall Stability, Loss of Marshall Stability, Indirect Tensile Strength, Loss of Indirect Tensile Strength, Resilient Modulus, Fatigue Life, Rutting Behavior, and Creep Performance. 2. Experimental procedure Fig. 1 shows a flow chart of the experimental procedure followed in this investigation. The work started with a literature review of available literature related to the investigation. Required amounts of aggregate and asphalt were collected and characterized according to the locally
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Literature Review Collection of Test Samples Physical and Mechanical Characterization of the Aggregate Samples
Physical Characterization of the Asphalt Samples
Collection of Weather Data Generation of Temperature Zoning Map
Selection of MPW’s&H Aggregate Gradation
Selection of Optimal Aggregate Gradation Using SUPERPAVE Procedure
Asphalt Content Optimization According to Marshall Mix Design Procedure
Asphalt Content Optimization According to SUPERPAVE Mix Design Procedure
Preparation of Test Samples @ Optimum Marshall Asphalt Content
Preparation of Test Samples @ Optimum SUPERPAVE Asphalt Content
Mechanical Evaluation of Prepared Samples - Marshal Stability - Loss of Marshall Stability - Indirect Tensile Strength (ITS) - Loss of ITS - Modulus of Resilience - Fatigue Life - Permanent Deformation - Creep Fig. 1. Flow chart of the followed work.
followed testing procedures and according to SUPERPAVE recommended evaluation tests. The asphalt samples were collected from the asphalt cement-producing refinery in Jordan. Physical evaluation of the collected asphalt samples was conducted. The evaluation included Flash Point, Rotational Viscosity at 135 °C, Rotational Viscosity at 165 °C, Penetration at 25 °C, Specific Gravity at 25 °C, Ductility at 25 °C, Softening Point, Penetration of Residue, Weight Loss on Heating, Dynamic Shear Rheometer testing of fresh and aged samples at different test temperatures, and Bending Beam Rheometer testing of Pressure Aging Vessel aged samples at 6 °C. The aggregate selected for the laboratory work was crushed limestone which was obtained from Amman vicinity, Jordan. Physical evaluation of the collected aggregate samples was conducted. These tests included Coarse and Fine Aggregate Angularity, Flat/Elongated Particles, Sand
Equivalent, Coarse and Fine Aggregate Specific Gravity and Absorption, and Los Angeles Abrasion test. The selected aggregate gradation was in accordance with the Jordanian Ministry of Public Works and Housing (MPWs&H) 1991 recommended gradation for heavy traffic wearing course [11] (Fig. 2). Minimum and seven-day consecutive maximum air temperature data from the different weather stations located in the different parts of Jordan were collected from the Jordan Meteorological Department. Collected air temperature data were converted into pavement temperatures and were analyzed to generate the temperature zoning map for Jordan. Since it is required for selecting asphalt binder grades to use pavement temperature rather than air temperature, obtained air temperatures were converted into pavement temperatures. For surface layers, SUPERPAVE defines the location for high pavement design temperature at a depth 20 mm below the pavement surface, and the low pavement design temperature at the pavement surface. Long Term Pavement Performance Program [LTPP] Bind software [12] was used to convert the air temperatures into pavement temperatures. Marshall Mix design (ASTM D1559) [2] and SUPERPAVE mix design (AASHTO TP4) [13] procedures were used to design asphalt concrete mixes using the local materials. In these mixes MPWs&H 1991 recommended gradation for heavy traffic wearing course were followed. In addition, two extra gradations were suggested and evaluated according to SUPERPAVE gradation optimization procedure. Two sets of samples were prepared using the same compaction procedure, i.e., using the gyratory compactor at 4% air voids. The first set was compacted using MPWs&H 1991 recommended gradation (Fig. 2) and compacted at the obtained optimum asphalt content from Marshall mix design procedure. The other set was compacted using the optimal gradation and asphalt content obtained from SUPERPAVE design procedure. Performance of both mixes was evaluated by running the following tests, Marshall Stability, Loss of Marshall Stability, Indirect Tensile Strength, Loss of Indirect Tensile Strength, Modulus of Resilience, Fatigue Life, Permanent Deformation, and Creep. 3. Results and discussion 3.1. Characterization of the used materials Asphalt cement classification tests that included Flash Point, Rotational Viscosity at 135 °C, Rotational Viscosity at 165 °C, Penetration at 25 °C, Specific Gravity at 25 °C, Ductility at 25 °C, Softening Point, Penetration of Residue, and Weight Loss on Heating were performed on the asphalt cement that was used in the study. Results of the performed tests are shown in Table 1. Results of the tests indicate that the used asphalt can be graded as 60/70-penetration asphalt according to AASHTO M 20 specifica-
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NOMINAL SIZE =19 mm
100 90 80
% PASSING
70 60 MPW's&H Above RZ Below RZ
50 40 30
Restricted Zone
20 10 0 0.000
1.000
2.000
3.000
4.000
5.000
SIEVE SIZE (0.45PWOER) mm Fig. 2. Gradation of the different used aggregate blinds drawn on SUPERPAVE recommended gradation chart.
Table 1 Physical properties of the used asphalt cement Test
Test result
Criteria
Flash point Rotational viscosity at 135 °C Rotational viscosity at 165 °C Penetration Specific Gravity at 25 °C Ductility at 25 °C Softening point, C Penetration of residue, % of original Weight loss on heating, % G*/sin d @ 64 °C (Fresh) kPa G*/sin d @ 64 °C (RTFO) kPa G* sin d @ 28 °C (PAV) MPa Stiffness S @ 6 °C (PAV) MPa Slope m @ 6 °C (PAV)
320 0.488 Pa s 0.150 Pa s 66 1.019 134 53 66 0.22 1.765 4.010 1.344 66.67 0.304
230 C minimum 3 Pa s maximum n/a 60–70 1.01–1.06 100 minimum 48–56 54 minimum 0.8 maximum 1.0 minimum 2.2 minimum 5.0 maximum 300 maximum 0.3 minimum
tions. In order to find the performance grade of the used asphalt cement according to SHRP binder performance specification (AASHTO MP1) [4], the Dynamic Shear Rheometer testing of fresh and Rolling Thin Film Oven and Pressure Aging Vessel aged samples at different test temperatures, and Bending Beam Rheometer testing of Pressure Aging Vessel aged samples at 6 °C were performed on the asphalt cement. It was found that the performance grade of the asphalt is PG 64-16 (Table 1). Therefore, this asphalt has met both the high temperature property requirements at least up to a temperature of 64 °C and low-temperature physical property requirements of at least 16 °C [13]. SUPERPAVE requirements for aggregate properties are based on both consensus and source properties. Consensus properties include coarse aggregate angularity, fine aggregate angularity, flat and elongated particles and clay con-
tent. Consensus properties levels of acceptance depend on traffic level and depth of the layer below the surface. Source properties include toughness, soundness, and deleterious materials, and they depend on the source specification limits. Table 2 shows the used aggregate properties. The results indicate that the used aggregate meets both the consensus properties and source (Jordan MPWs&H, 1991) properties requirements for high traffic volumes regardless of depth. 3.2. Temperature zoning for hashemite kingdom of Jordan In this part of the study, weather data from eleven weather stations distributed across HKJ were collected. Collected data covered a minimum of 20 years of continuous temperature recording. The data were analyzed to obtain the yearly minimum recorded air temperature, the yearly average consecutive seven-day maximum air temperature, in addition to standard deviations of both temperatures. Calculated average air temperatures and standard deviations at all stations in addition to stations locations are shown in Table 3. In addition, Table 3 shows the calculated pavement high and low temperatures using 98% reliability. Ninety-eight per cent reliability level was used in this conversion (Table 3). Reliability is the percent probability in a single year that the actual temperature (oneday low or seven-day high) will not exceed the design temperature. A higher reliability means lower risk. Selection of degree of reliability depends on road class, traffic level, and binder cost and availability [13]. Fig. 3 was drawn to divide the HKJ into the different temperature zones. It was found that four asphalt grades are required for the HKJ. PG 64-10 is suitable for most
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the required grade is PG 76-10. To reach to this grade, local asphalt has to be modified using polymers.
Table 2 Physical properties of the used aggregate Property
Criteria
Test results
Coarse aggregate angularity Fine aggregate angularity Flat/elongated particles Sand equivalent
100/100% min 45% min 10% max 45 min
100/100% 53% 0% 59
Coarse aggregate specific gravity Coarse aggregate absorption Fine aggregate specific gravity Fine aggregate absorption Combined aggregate specific gravity Combined aggregate apparent specific gravity
n/a n/a n/a n/a n/a n/a
2.539 2.7% 2.502 5.0% 2.522 2.784
Abrasion loss (500 Rev), % Abrasion ratio (100/500), %
35% max 25% max
25.6 13.8
areas of Jordan; Shoubak requires the asphalt to be of PG 64-16 grade. In Aqaba, Ruwaishied, and Ghorsafi, PG 7010 grade of asphalt is required. Selected high temperature asphalt grades have to be shifted one or two grades up for slow or standing loads. In addition, high temperature grades have to be shifted up in case of extraordinarily high numbers (higher than 30 million) of heavy traffic loads [13]. Since high reliability value was used in calculating the high and low pavement temperatures, and since limited number of highways in Jordan has equivalent single axle loads (ESAL) higher than 30 million, no shift in the high temperature grade will be applied. Since local asphalt grade is PG 64-16 (Table 1), it can be used in all parts of Jordan except Aqaba, Ruwaishied, and Ghorsafi (Fig. 3). In these areas, local asphalt should be modified to shift its grade to PG 70-10. This modification might just require air blowing of the local asphalt. In steep climbing lanes in these areas, where there will be a reduction in the speed of the heavy trucks, it is required to shift the required asphalt grade by one extra grade. Therefore,
3.3. Marshall mix design (ASTM D1559) Marshall asphalt concrete mix design procedure (ASTM D1559) [2] using 4 in. samples is the currently followed procedure in Jordan. Using MPWs&H 1991 recommended gradation for heavy traffic wearing course (Fig. 2), Marshall Mix design procedure was used to determine the optimum asphalt content. The selected optimum asphalt content (OAC) was the one that produced 4% air voids. The obtained OAC was 5.20% AC of total mix weight. At the obtained OAC, Marshall Stability, flow, voids filled with asphalt, and voids in mineral aggregate values were checked. They were within the specification limits of MPWs&H for heavy traffic loads wearing course. 3.4. SUPERPAVE mix design (AASHTO TP4) SUPERPAVE uses volumetric analysis for the mix design and follows three major steps in the testing and analysis process. They are selection of a design aggregate structure, then optimizing the asphalt content for the selected structure. The last step is the evaluation of moisture sensitivity of the design mixture. For the sake of comparison, two extra aggregate structures (blends) were selected in addition to the MPWs&H recommended gradation for heavy traffic loads for wearing course. Fig. 2 shows the selected aggregate blends. The first blend was selected to be above the restricted zone, named ‘‘above RZ’’. While the second blend was selected to be below the restricted zone, named ‘‘below RZ’’. Fig. 2 shows that MPWs&H recommended gradation passes through the restricted zone. SUPERPAVE recommends that special precautions should be taken when compacting such mixes in the field [14].
Table 3 Minimum and seven-day maximum air and pavement temperatures at the different weather stations Station
Amman Baqura Irbed Deir Ala Ghorsafi Dhulail Mafraq Ruwaishied (H4) Ma’an Shoubak Aqaba a b c
Seven-day maximum temperature (°C)
Minimum temperature (°C)
Mean aira
Stdb
98% Rel.c
Mean aira
Stdb
98%c
36.1 41.0 34.5 41.4 42.6 39.0 37.0 40.6 37.4 32.4 42.1
1.7 1.3 1.2 1.1 1.2 1.6 1.5 1.7 1.4 2.7 0.9
61.4 65.3 58.7 65.3 66.8 64.0 61.8 65.6 62.3 60.1 65.9
0.9 2.0 1.0 5.9 5.8 3.4 3.8 4.1 4.3 8.5 4.7
1.6 1.6 1.5 1.7 1.3 1.6 1.5 1.9 1.7 2.5 1.2
4.1 1.3 4.1 2.3 3.1 6.6 7.0 8.0 7.8 13.7 2.3
Mean air temperature. Standard deviation of temperature. Calculated pavement temperature at 98% reliability.
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Therefore, the locally used MPWs&H gradation for heavy traffic loads wearing courses failed SUPERPAVE mix design criteria in more than one property, VMA and dust proportion. In addition, SUPERPAVE recommended asphalt content is 4.6%, which is much lower than Marshall design recommended optimum asphalt content for the same gradation. This might explain the reason that most of HKJ roads are having bleeding problems. In addition, obtained dust proportion is higher than the maximum specified limit. High dust proportion will usually lead to brittleness of the mixes [9]. The design optimization curves for the selected blend (‘‘Below RZ’’) revealed a design asphalt binder content of 4.8%. Evaluation of the moisture sensitivity of the design mixture was performed according to AASHTO T283 test procedure. Obtained ratio of the indirect tensile strength for the obtained mix structure at the optimum asphalt content was 83.2%, which exceeded the minimum criteria limit [8].
34
33 Ruwaishied (H4)
Baqura Deir Ala
Irbed
Mafraq
PG70-10
Dhulail
32 Amman
PG70-10 Ghorsafi
31
PG64-10 Shoubak
PG64-16 Ma'an
30 Aqaba
PG70-10
29
34
35
36
37
38
1737
39
40
Fig. 3. Temperature zoning for asphalt binder specifications for Jordan.
Since the gyratory compactor is used in SUPERPAVE mix design, the number of gyratory compactor gyrations should be specified. Number of gyrations depends on both average design high air temperature and design ESAL. A traffic level between 30 and 100 million ESALs was selected. This traffic level was selected because it is the common traffic level operating on most Jordan highways. At this traffic level, and at the average design high air temperature of Jordan (39 °C), the recommended numbers of gyrations are, Ninitial = 9 gyrations, N-design = 126 gyrations, and Nmaximum = 204 gyrations. These levels of gyrations were kept constant for the rest of the design phase. The initial trial asphalt binder content for the three blends was estimated to be 5.2%. Two specimens from each trial blend were compacted using SUPERPAVE Gyratory Compactor (SGC). Table 4 shows the results of the tested samples in addition to the required estimated properties (VMA, VFA, %GMM at Ni, and Dust Proportion) at the estimated asphalt content to achieve 4% air voids at N-design. Table 4 indicates that MPWs&H gradation failed to meet the VMA and dust proportion criteria. ‘‘Above RZ’’ blend failed to meet the dust proportion criteria. Just ‘‘Below RZ’’ blend satisfied all the specification limits; therefore, it will be carried to the second design stage, i.e., optimization of the asphalt content.
3.5. Performance evaluation of Marshall and SUPERPAVE mixes To compare the performance of both Marshall and SUPERPAVE mix design procedures, samples were prepared at the obtained optimum mix design asphalt contents of both procedures, using the locally used MPWs&H recommended gradation for the Marshall samples and the aggregate gradation ‘‘Below RZ’’ for SUPERPAVE samples. The gyratory compactor was used to compact both sets of samples. The test samples were 101.6 * 63.5 mm (4 in. * 2.5 in.) and were compacted to achieve 4% air voids. These samples were subjected to a comprehensive mechanical evaluation testing. These tests included Marshall Stability, Loss of Marshall Stability, Indirect Tensile Strength, Loss of Indirect Tensile Strength, Resilient Modulus, Fatigue Life, Rutting Behavior, and Creep Performance. 3.5.1. Marshall stability and loss of Marshall stability test results (ASTM D1559) Six samples from each mix were placed in the water bath at 60 °C. After 30 min immersion in the water bath, three samples from each mix were tested for Marshall Stability. The other three samples were tested for Marshall Stability after 24 h immersion in the water bath. Table 5 shows results of the tested samples. The results show that the SUPERPAVE samples have 32% higher Marshall Stability after 30 min immersion in water bath and 66% higher
Table 4 Estimated properties of the trial blends to achieve 4% air voids at Nd Blend
Trial AC%
Estimated properties to achieve 4% air voids at Nd AC %
VMA %
Criteria
VFA %
Criteria
% Gmm @ Ni
Criteria
Dust prop.
Criteria
MPWs&H Below RZ Above RZ
5.2 5.2 5.2
4.6 5.0 5.1
12.5 13.4 13.3
13 min 13 min 13 min
67.97 70.18 69.95
65–75 65–75 65–75
84.7 84.4 86.0
89 max 89 max 89 max
1.4 0.8 1.6
0.6–1.2 0.6–1.2 0.6–1.2
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Table 5 Marshall Stability test results for both mixes Sample #
1 2 3 Average a
Marshall samples
SUPERPAVE samples a
Initial stability (N)
Conditioned stability (N)
13,324 14,075 13,578
8211 7954 7201
13,659
7789
% Loss
43.0
Initial stability (N)
Conditioneda stability (N)
18,275 17,951 18,019
13,410 12,498 12,799
18,082
12,902
% Loss
28.6
Sample tested after 24 h immersion in water bath @ 60 °C.
the next pulse was 900 ms. The deviator stress during each loading pulse was 207 kPa, and the contact stress that was applied so that the vertical loading shaft does not lift off the test specimen during the rest period was 9 kPa. The test was performed at 40 °C. The specimen’s skin and core temperatures during the test were monitored by two thermocouples which were inserted in a dummy specimen and located near the specimen under test. The testing was continued until the maximum axial strain limit reached 10,000 micro-strains, or until 10,000 cycles, whichever occurred first. Three samples (100 * 63.5 mm at 4% air void) from each mix were tested. Fig. 4 shows the relationship between the number of cycles and the axial accumulated permanent deformation for both mixes. SUPERPAVE samples showed better creep performance than Marshall samples. This behavior difference is attributed to the lower asphalt content and coarser structure of SUPERPAVE mixes.
stability after 24 h immersions in water bath than Marshall samples. In addition, the SUPERPAVE samples have 14.4% lower loss of Marshall Stability than the Marshall samples. The superiority of SUPERPAVE samples over Marshall samples is attributed to the improved aggregate structure and the lower asphalt content and lower dust proportion of the SUPERPAVE samples. 3.5.2. Water sensitivity test (Lottman test AASHTO T-28389) The stripping resistance (water susceptibility) of both asphalt concrete mixes was evaluated by the decrease in the loss of the indirect tensile strength (ITS) after immersion in water for 24 h at 60 °C, according to AASHTO T-283 test procedure. The obtained results (Table 6) indicate that the average loss in strength due to water damage is lower in the SUPERPAVE samples than Marshall samples. This is attributed to the lower quantity of the fine aggregate in the SUPERPAVE samples. In addition, ITS loss value for SUPERPAVE samples is 18% which is within the 20% allowable loss limit specified in SUPERPAVE specifications [8]. In addition, Table 6 indicates that both SUPERPAVE conditioned and non conditioned samples have higher ITS values than corresponding Marshall samples. This is attributed to the improved aggregate structure of the SUPERPAVE samples.
Permanent Deformation, mm
3.5.4. Resilient modulus test, MR (ASTM D 4123) Resilient modulus is the most important variable that is used in the mechanistic design of pavement structures. It is
3.5.3. Dynamic creep test The Dynamic Creep Test is a test that applies a repeated pulsed uniaxial stress on an asphalt specimen and measures the resulting deformations in the same direction using Linear Variable Differential Transducers (LVDTs). The test was performed in accordance with the protocol developed by NCHRP 9-19 SUPERPAVE Models, Draft Test Method W2 [15]. The applied stress on the specimen was a feed back haversine pulse. The pulse width duration was 100 ms, and the rest period before the application of
1
Marshall SUPERPAVE
0.1
0.01 1
10
100
1000
10000
Number of Repetitions Fig. 4. Comparison of creep behavior of the different mixes at 40 °C.
Table 6 Indirect tensile strength test results for both mixes Sample #
1 2 3 Average a
Marshall samples
SUPERPAVE samples a
Initial ITS (kPa)
Conditioned ITS (kPa)
761 738 783
545 514 505
761
521
Sample tested after 24 h immersion in water bath @ 60 °C.
% Loss
31.5
Initial ITS (kPa)
Conditioneda ITS (kPa)
1006 1103 1052
822 892 844
1053
853
% Loss
19.0
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Table 7 Resilient modulus test results for both mixes Sample #
1 2 3
Marshall samples
SUPERPAVE samples
MR @ 1st position (MPa)
MR @ 2nd position (MPa)
Average MR (MPa)
MR @ 1st position (MPa)
MR @ 2nd position (MPa)
Average MR (MPa)
486 384 449
445 506 307
465.5 445.0 378.0
964 955 1080
897 1050 869
930.5 1002.5 974.5
Average
429.5
the measure of pavement response in terms of dynamic stresses and corresponding strains. Three samples from each fly ash content were tested at two position under the diametral resilient modulus (MR) test at 40 °C. Table 7 shows the obtained MR values for all the tested mixes. It indicates that SUPERPAVE mixes have higher diametral resilient modulus than Marshall mixes. This can be attributed to the lower asphalt content and coarser structure of SUPERPAVE mixes. 3.5.5. Fatigue performance Samples from both mixes were tested diametraly under repeated pulsed uniaxial loading to determine the number of loading cycles required to fail the samples. To have a wide range of failure cycles, test samples were tested at different initial tensile strain levels. At least nine samples from each mix (three at each initial tensile strain level) were tested at 40 °C. Fig. 5 shows the results of these tests. In this figure, regression lines were drawn through the mean values of the tested samples at each strain level. The results show a normal linear relationship between the logarithm of applied initial tensile strain and the logarithm of fatigue life (number of applied load repetitions until failure). The fatigue data were analyzed by running a regression analysis to
Marshall SUPERPAVE 100 100
determine the fatigue relationship parameters in the following form: et ¼ I ðN f Þ
10000
100000
No. of Repetitions
Fig. 5. Comparison of fatigue behavior of the different mixes at 40 °C.
ð1Þ
et = initial tensile strain, Nf = number of load repetitions to failure, I = anti-log of the intercept of the logarithmic relationship, and S = slope of the logarithmic relationship. Regression parameters for the Marshall samples regression line are I = 4374.7, S = 0.3497, and R2 = 0.9986. While the regression parameters for the SUPERPAVE samples regression line are I = 16471, S = 0.4449, and R2 = 0.9908. Analysis of the obtained fatigue results shows significant improvement in fatigue life of SUPERPAVE mixes over Marshall mixes This can be attributed to the higher dust proportion of Marshall samples over SUPERPAVE samples, which leads to brittleness of the Marshall mixes. 3.5.6. Permanent deformation Using two vertical LVDTs, the vertical permanent deformation was simultaneously recorded while running the fatigue tests. All tested samples showed lower permanent deformation values for SUPERPAVE samples than Marshall samples when tested at the same stress level. Fig. 6 presents the tests results which were performed at a repeated stress of 200 kPa. The three stages that the asphalt concrete passes through in rutting testing (densification, 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0
Marshall Samples
SUPERPAVE Samples
0
1000
S
where
Permanent Deformation, mm
Initial Tensile Strain, microstrain
1000
969.2
500
1000
1500
2000
2500
3000
3500
Number of Repetitions Fig. 6. Comparison of permanent deformation behavior of the different mixes at 40 °C and at 200 kPa dynamic loading.
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steady state and failure) clearly appear in this figure. In comparing the performance of the both mixes (Fig. 6), the trend is similar to that of fatigue testing, i.e., SUPERPAVE mixes performance is far better than Marshall mixes performance. This can be attributed to the higher dust proportion of Marshall samples over SUPERPAVE samples, which leads to brittleness of the Marshall mixes.
Acknowledgements
4. Conclusions
References
This research was conducted to find the adoptability of Superior Performance asphalt Pavements (SUPERPAVE) mixture specifications to the Hashemite Kingdom of Jordan specific materials, traffic and environmental conditions. A comparison study was carried out to use local materials to design the asphalt mixes using both Marshall and SUPERPAVE mix design procedures. In addition, performance of both mixes was evaluated. Based on the findings of the experimental results, the following main conclusions can be drawn:
[1] Bahia HU. Bibliographies for physical properties of asphalt cement. SHRP-A-626, National Research Council, Washington, DC. [2] American Society for Testing and Materials (ASTM). Standard test methods, vol. 4.03. West Conshohocken, PA: ASTM; 1997. [3] Asi IM. Role of roads in traffic safety. Traffic safety. . .everybody’s responsibility symposium. Jordan: Hashemite University; 2004. [4] Roberts F, Mohammad M, Wang L. History of hot mix asphalt mixture design in the USA. J Mater Civil Eng 2002;14(4):279–93. [5] American Society for Testing And Materials (ASTM). Standard test methods, vol. 4.03. West Conshohocken, PA: ASTM; 2000. [6] Brown R, Kandhal P, Zhang J. Performance testing for hot mix asphalt. National Center for Asphalt Technology, Report No. 200105A, Auburn University, Alabama; 2001. [7] Federal Highway Administration (FHWA). Background of SUPERPAVE asphalt mixture design and analysis. Publication No. FHWASA-95-003, US Department of Transportation, Washington, DC; 1995. [8] Cominsky RJ, Huber GA, Kennedy TW, Anderson M. The Superpave mix design manual for new construction and overlay. SHRP-A407, National Research Council, Washington, DC; 1994. [9] Anderson RM. SUPERPAVE level 1 mixture design example. A first look at volumetric mix design in the SUPERPAVE system. Lexington, KY: Asphalt Institute Research Center; 1993. [10] Sousa J, Harvey J, Painter L, Deacon J, Monismith C. Evaluation of laboratory procedures for compacting asphalt–aggregate mixtures. Report SHRP-A/UWP-91-523, University of California – Berkeley, September, 1991. [11] Ministry of Public Works and Housing. Specifications for Highway and Bridge Construction. vol. II, Hashemite Kingdom of Jordan; 1991. [12] Federal Highway Administration (FHWA).LTPPbind software [Computer program]. US Department of Transportation, Washington, DC; 1999. [13] Asphalt Institute. Superpave Mix Design Series No. 2 (SP-2), Asphalt Institute Research Center, Lexington, KY; 2001. [14] Anderson R, Bahia H. Evaluation and selection of aggregate gradations for asphalt mixtures using SUPERPAVE. Transportation Research Record 1583. TRB, National Research Council, Washington, DC; 1997. pp. 91–97. [15] Witczak M, Schwartz C, Von Quintus H. NCHRP Project 9-19: Superpave support and performance models management. Interim Report, Federal Highway Administration and the National Cooperative Highway Research Program; 2001.
1. In general, the performance grade of the locally produced asphalt is PG 64-16. 2. A temperature zoning map was developed for the Hashemite Kingdom of Jordan. It consisted of three grade zones, PG 64-10, PG 64-16, and PG 70-10. 3. Locally produced asphalt can be used without the need of modification in all parts of Jordan except Aqaba, Ruwaishied, and Ghorsafi. In these areas, it should be modified to shift its grade to PG 70-10. This modification might just require air blowing of the local asphalt. 4. Local aggregate meet both SUPERPAVE consensus properties and source properties. 5. Locally used aggregate gradations are not suitable according to SUPERPAVE mix design procedure. 6. SUPERPAVE mix design procedure recommended, for the local environmental and loading conditions, lower asphalt content than that predicted by Marshall mix design procedure. This might explain the causes behind the bleeding asphalt concrete surfaces and some of the distresses common in the local asphalt structures. 7. SUPERPAVE mixes showed superior performance over Marshall mixes. 8. In Jordan, serious plans should be set up to shift from the presently used Marshall mix design procedure to SUPERPAVE mixture specifications.
The authors would like to acknowledge the support of the College of Graduate Studies and Scientific Research at Hashemite University for funding this research study. Thanks are extended to Jordan Meteorological Department for helping in providing and analyzing weather data for Hashemite Kingdom of Jordan.
MATERIALS
Construction and Building Materials 21 (2007) 1732–1740
www.elsevier.com/locate/conbuildmat
Performance evaluation of SUPERPAVE and Marshall asphalt mix designs to suite Jordan climatic and traffic conditions Ibrahim M. Asi
*
Department of Civil Engineering, Hashemite University, Zarqa 13115, Jordan Received 28 March 2005; received in revised form 1 February 2006; accepted 31 May 2006 Available online 22 September 2006
Abstract Due to the empirical nature and the drawbacks of the Marshall mix design procedure, the Strategic Highway Research Program (SHRP) has developed a Superior Performance asphalt Pavements (SUPERPAVE) mix design procedure. In this research a comprehensive evaluation of the locally available aggregate usually used in the asphalt concrete mixtures was carried out to ensure that these materials conform to the new mix design procedures developed by SUPERPAVE. A performance grading map was generated to the Hashemite Kingdom of Jordan. In this map the country was divided into different zones according to the highest and lowest temperature ranges that the asphalt might be subjected to. Using local materials, loading and environmental conditions, a comparative study of the performance of two mixes designed using SUPERPAVE and Marshall mix design procedures was carried out in this research. Samples from both mixes were prepared at the design asphalt contents and aggregate gradations and were subjected to a comprehensive mechanical evaluation testing. These tests included Marshall Stability, Loss of Marshall Stability, Indirect Tensile Strength, Loss of Indirect Tensile Strength, Resilient Modulus, Fatigue Life, Rutting, and Creep. In all the performed tests SUPERPAVE mixes proved their superiority over Marshall mixes. Therefore, serious plans should be set up in Jordan to shift from the presently used Marshall mix design procedure to SUPERPAVE mixture specifications. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: SUPERPAVE; Marshall; Asphalt mix design; Temperature zoning; Performance grading; Fatigue; Rutting; Creep
1. Introduction The major properties to be incorporated in bituminous paving mixtures are stability, durability, flexibility and skid resistance (in the case of wearing surface). Traditional mix design methods are established to determine the optimum asphalt content that would perform satisfactorily, particularly with respect to stability and durability. There are many mix design methods used throughout the world e.g. Marshall mix design method, Hubbard-field mix design method, Hveem mix design method, Asphalt Institute Triaxial method of mix design, etc. Out of these only two are widely accepted, namely Marshall Mix design method and Hveem mix design method [1]. In Jordan, Marshall mix *
Fax: +962 6 551 8867. E-mail address: [email protected].
0950-0618/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2006.05.036
design procedure (ASTM D 1559) [2] is used for designing the asphalt concrete mixes. In Jordan, roads were built to the best international standards. After a short period of service, some of these roads have shown signs of major distresses due to the harsh environmental conditions and traffic loading [3]. Another reason which is contributing to these early distresses is the continuation of the use of Marshall mix design procedure for asphalt mixtures. The Marshall mix procedure is empirical and suffers the limitation of accuracy in determining the full effects of variations in environmental and loading conditions, and material properties and types on the pavement performance. It cannot identify the mixes with high degree of shear susceptibility. In addition, the impact method of compaction in the Marshall mix method does not simulate densification that occurs under traffic in a real pavement [4]. Therefore, due to its drawbacks, it was
I.M. Asi / Construction and Building Materials 21 (2007) 1732–1740
dropped from the American Standard Testing Procedures in 1998 [5]. This situation calls upon the country, a leading country in the region, to adopt up-to-date mix design and evaluation procedures to alleviate these problems. Recent research and development efforts in the Strategic Highway Research Program (SHRP) have focused on the establishment of performance-based asphalt binder and asphalt mix specifications [4,6]. The main objective of SHRP Asphalt Program was to develop a mixture design method that incorporates a performance-based asphalt binder specification and an accelerated performance-based tests. The product that was designed by the new mixture design system was known as SUPERPAVE (SUperior PERformance PAVEments). 1.1. Current asphalt binder testing philosophy The current philosophy that deals with asphalt binder evaluation in Jordan uses the traditional old fashion testing that deals mainly with the physical properties of the asphalt cement. It uses testing such as penetration, viscosity and ductility. These tests are performed at standard test temperatures. The results of these tests are used to determine if the material meets specification criteria. Several limitations exist to the use of physical evaluation only. Limitations can be summarized as follows: Many of the current tests are empirical, i.e., the pavement performance experience is required to relate the test parameters with pavement performance. The tests do not give information about the entire range of typical pavement temperatures, for example, viscosity is an important property of asphalt binders, however, the viscosity gives an indication about the behavior of the material at high temperatures, viscosity does not provide any information about low and medium temperature behavior of asphalt binders. The current asphalt specifications can classify different asphalts with the same grading, when in fact these asphalts may have very different temperature and performance characteristics.
1.2. Development of the SUPERPAVE mix design procedure Due to the drawbacks in both binder and mix specification, the US congress, in 1987, supported a five year research program to improve the performance and durability of the US roads and to make those roads safer to both motorists and highway workers. Part of this research funds were used for the development of performance-based asphalt specifications to directly relate laboratory analysis with field performance [7]. A bimodal grading system, which is based on rational performance indices, was established for both low temperature and high temperature pavement service. Thus, precise
1733
grade may be selected to accommodate the need to control low-temperature cracking, rutting or both in a particular construction project. In addition, it will address certain aspects of fatigue cracking [8]. For a given type of asphalt cement to satisfy performance criteria for a given temperature zone, it must satisfy SHRP performance tests which must be conducted at designated temperatures. The suitability of a given asphalt binder to a certain area is determined by the extreme temperatures (average sevenday maximum pavement design temperature and the minimum pavement design temperature), required reliability, traffic level and speed anticipated to use the facility under consideration. The asphalt binder rheological properties related to both high temperature distresses such as rutting or shoving, and low-temperature cracking distress were specified and are required to satisfy a certain threshold value at the temperature regime in which the binder is expected to serve. The SUPERPAVE system consists of three interrelated areas: (1) a performance graded (PG) asphalt binder specification and tests that are based on the range of temperatures experienced by the pavement; (2) aggregate criteria and tests; and (3) a mixture design system utilizing both a volumetric mixture design with a Superpave gyratory compactor (SGC) and an analysis/performance prediction element [4]. SGC (1.25°, 30 gyration/min and 0.6 MPa ram pressure for 150 mm mold) is used for the evaluation of volumetric properties and strength of compacted mixes [9]. Sousa et al. [10] found that the SGC is capable of producing laboratory specimens whose volumetric and engineering properties adequately simulate those of field specimens from a wide variety of pavements. In this research, a performance grading map showing the required asphalt binder grades for the different parts of Jordan was generated. Representative aggregate and asphalt samples were collected. A comprehensive evaluation of the collected materials was carried out to ensure that these materials conform to the SUPERPAVE mix design procedures considering country specific conditions of traffic and environment. Marshall and SUPERPAVE mix design procedures were performed using the collected asphalt and aggregate samples. Comparison between the two mix design procedures included optimal asphalt content, aggregate gradation, and mixes mechanical performance. Mechanical performance evaluation consisted of Marshall Stability, Loss of Marshall Stability, Indirect Tensile Strength, Loss of Indirect Tensile Strength, Resilient Modulus, Fatigue Life, Rutting Behavior, and Creep Performance. 2. Experimental procedure Fig. 1 shows a flow chart of the experimental procedure followed in this investigation. The work started with a literature review of available literature related to the investigation. Required amounts of aggregate and asphalt were collected and characterized according to the locally
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Literature Review Collection of Test Samples Physical and Mechanical Characterization of the Aggregate Samples
Physical Characterization of the Asphalt Samples
Collection of Weather Data Generation of Temperature Zoning Map
Selection of MPW’s&H Aggregate Gradation
Selection of Optimal Aggregate Gradation Using SUPERPAVE Procedure
Asphalt Content Optimization According to Marshall Mix Design Procedure
Asphalt Content Optimization According to SUPERPAVE Mix Design Procedure
Preparation of Test Samples @ Optimum Marshall Asphalt Content
Preparation of Test Samples @ Optimum SUPERPAVE Asphalt Content
Mechanical Evaluation of Prepared Samples - Marshal Stability - Loss of Marshall Stability - Indirect Tensile Strength (ITS) - Loss of ITS - Modulus of Resilience - Fatigue Life - Permanent Deformation - Creep Fig. 1. Flow chart of the followed work.
followed testing procedures and according to SUPERPAVE recommended evaluation tests. The asphalt samples were collected from the asphalt cement-producing refinery in Jordan. Physical evaluation of the collected asphalt samples was conducted. The evaluation included Flash Point, Rotational Viscosity at 135 °C, Rotational Viscosity at 165 °C, Penetration at 25 °C, Specific Gravity at 25 °C, Ductility at 25 °C, Softening Point, Penetration of Residue, Weight Loss on Heating, Dynamic Shear Rheometer testing of fresh and aged samples at different test temperatures, and Bending Beam Rheometer testing of Pressure Aging Vessel aged samples at 6 °C. The aggregate selected for the laboratory work was crushed limestone which was obtained from Amman vicinity, Jordan. Physical evaluation of the collected aggregate samples was conducted. These tests included Coarse and Fine Aggregate Angularity, Flat/Elongated Particles, Sand
Equivalent, Coarse and Fine Aggregate Specific Gravity and Absorption, and Los Angeles Abrasion test. The selected aggregate gradation was in accordance with the Jordanian Ministry of Public Works and Housing (MPWs&H) 1991 recommended gradation for heavy traffic wearing course [11] (Fig. 2). Minimum and seven-day consecutive maximum air temperature data from the different weather stations located in the different parts of Jordan were collected from the Jordan Meteorological Department. Collected air temperature data were converted into pavement temperatures and were analyzed to generate the temperature zoning map for Jordan. Since it is required for selecting asphalt binder grades to use pavement temperature rather than air temperature, obtained air temperatures were converted into pavement temperatures. For surface layers, SUPERPAVE defines the location for high pavement design temperature at a depth 20 mm below the pavement surface, and the low pavement design temperature at the pavement surface. Long Term Pavement Performance Program [LTPP] Bind software [12] was used to convert the air temperatures into pavement temperatures. Marshall Mix design (ASTM D1559) [2] and SUPERPAVE mix design (AASHTO TP4) [13] procedures were used to design asphalt concrete mixes using the local materials. In these mixes MPWs&H 1991 recommended gradation for heavy traffic wearing course were followed. In addition, two extra gradations were suggested and evaluated according to SUPERPAVE gradation optimization procedure. Two sets of samples were prepared using the same compaction procedure, i.e., using the gyratory compactor at 4% air voids. The first set was compacted using MPWs&H 1991 recommended gradation (Fig. 2) and compacted at the obtained optimum asphalt content from Marshall mix design procedure. The other set was compacted using the optimal gradation and asphalt content obtained from SUPERPAVE design procedure. Performance of both mixes was evaluated by running the following tests, Marshall Stability, Loss of Marshall Stability, Indirect Tensile Strength, Loss of Indirect Tensile Strength, Modulus of Resilience, Fatigue Life, Permanent Deformation, and Creep. 3. Results and discussion 3.1. Characterization of the used materials Asphalt cement classification tests that included Flash Point, Rotational Viscosity at 135 °C, Rotational Viscosity at 165 °C, Penetration at 25 °C, Specific Gravity at 25 °C, Ductility at 25 °C, Softening Point, Penetration of Residue, and Weight Loss on Heating were performed on the asphalt cement that was used in the study. Results of the performed tests are shown in Table 1. Results of the tests indicate that the used asphalt can be graded as 60/70-penetration asphalt according to AASHTO M 20 specifica-
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NOMINAL SIZE =19 mm
100 90 80
% PASSING
70 60 MPW's&H Above RZ Below RZ
50 40 30
Restricted Zone
20 10 0 0.000
1.000
2.000
3.000
4.000
5.000
SIEVE SIZE (0.45PWOER) mm Fig. 2. Gradation of the different used aggregate blinds drawn on SUPERPAVE recommended gradation chart.
Table 1 Physical properties of the used asphalt cement Test
Test result
Criteria
Flash point Rotational viscosity at 135 °C Rotational viscosity at 165 °C Penetration Specific Gravity at 25 °C Ductility at 25 °C Softening point, C Penetration of residue, % of original Weight loss on heating, % G*/sin d @ 64 °C (Fresh) kPa G*/sin d @ 64 °C (RTFO) kPa G* sin d @ 28 °C (PAV) MPa Stiffness S @ 6 °C (PAV) MPa Slope m @ 6 °C (PAV)
320 0.488 Pa s 0.150 Pa s 66 1.019 134 53 66 0.22 1.765 4.010 1.344 66.67 0.304
230 C minimum 3 Pa s maximum n/a 60–70 1.01–1.06 100 minimum 48–56 54 minimum 0.8 maximum 1.0 minimum 2.2 minimum 5.0 maximum 300 maximum 0.3 minimum
tions. In order to find the performance grade of the used asphalt cement according to SHRP binder performance specification (AASHTO MP1) [4], the Dynamic Shear Rheometer testing of fresh and Rolling Thin Film Oven and Pressure Aging Vessel aged samples at different test temperatures, and Bending Beam Rheometer testing of Pressure Aging Vessel aged samples at 6 °C were performed on the asphalt cement. It was found that the performance grade of the asphalt is PG 64-16 (Table 1). Therefore, this asphalt has met both the high temperature property requirements at least up to a temperature of 64 °C and low-temperature physical property requirements of at least 16 °C [13]. SUPERPAVE requirements for aggregate properties are based on both consensus and source properties. Consensus properties include coarse aggregate angularity, fine aggregate angularity, flat and elongated particles and clay con-
tent. Consensus properties levels of acceptance depend on traffic level and depth of the layer below the surface. Source properties include toughness, soundness, and deleterious materials, and they depend on the source specification limits. Table 2 shows the used aggregate properties. The results indicate that the used aggregate meets both the consensus properties and source (Jordan MPWs&H, 1991) properties requirements for high traffic volumes regardless of depth. 3.2. Temperature zoning for hashemite kingdom of Jordan In this part of the study, weather data from eleven weather stations distributed across HKJ were collected. Collected data covered a minimum of 20 years of continuous temperature recording. The data were analyzed to obtain the yearly minimum recorded air temperature, the yearly average consecutive seven-day maximum air temperature, in addition to standard deviations of both temperatures. Calculated average air temperatures and standard deviations at all stations in addition to stations locations are shown in Table 3. In addition, Table 3 shows the calculated pavement high and low temperatures using 98% reliability. Ninety-eight per cent reliability level was used in this conversion (Table 3). Reliability is the percent probability in a single year that the actual temperature (oneday low or seven-day high) will not exceed the design temperature. A higher reliability means lower risk. Selection of degree of reliability depends on road class, traffic level, and binder cost and availability [13]. Fig. 3 was drawn to divide the HKJ into the different temperature zones. It was found that four asphalt grades are required for the HKJ. PG 64-10 is suitable for most
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the required grade is PG 76-10. To reach to this grade, local asphalt has to be modified using polymers.
Table 2 Physical properties of the used aggregate Property
Criteria
Test results
Coarse aggregate angularity Fine aggregate angularity Flat/elongated particles Sand equivalent
100/100% min 45% min 10% max 45 min
100/100% 53% 0% 59
Coarse aggregate specific gravity Coarse aggregate absorption Fine aggregate specific gravity Fine aggregate absorption Combined aggregate specific gravity Combined aggregate apparent specific gravity
n/a n/a n/a n/a n/a n/a
2.539 2.7% 2.502 5.0% 2.522 2.784
Abrasion loss (500 Rev), % Abrasion ratio (100/500), %
35% max 25% max
25.6 13.8
areas of Jordan; Shoubak requires the asphalt to be of PG 64-16 grade. In Aqaba, Ruwaishied, and Ghorsafi, PG 7010 grade of asphalt is required. Selected high temperature asphalt grades have to be shifted one or two grades up for slow or standing loads. In addition, high temperature grades have to be shifted up in case of extraordinarily high numbers (higher than 30 million) of heavy traffic loads [13]. Since high reliability value was used in calculating the high and low pavement temperatures, and since limited number of highways in Jordan has equivalent single axle loads (ESAL) higher than 30 million, no shift in the high temperature grade will be applied. Since local asphalt grade is PG 64-16 (Table 1), it can be used in all parts of Jordan except Aqaba, Ruwaishied, and Ghorsafi (Fig. 3). In these areas, local asphalt should be modified to shift its grade to PG 70-10. This modification might just require air blowing of the local asphalt. In steep climbing lanes in these areas, where there will be a reduction in the speed of the heavy trucks, it is required to shift the required asphalt grade by one extra grade. Therefore,
3.3. Marshall mix design (ASTM D1559) Marshall asphalt concrete mix design procedure (ASTM D1559) [2] using 4 in. samples is the currently followed procedure in Jordan. Using MPWs&H 1991 recommended gradation for heavy traffic wearing course (Fig. 2), Marshall Mix design procedure was used to determine the optimum asphalt content. The selected optimum asphalt content (OAC) was the one that produced 4% air voids. The obtained OAC was 5.20% AC of total mix weight. At the obtained OAC, Marshall Stability, flow, voids filled with asphalt, and voids in mineral aggregate values were checked. They were within the specification limits of MPWs&H for heavy traffic loads wearing course. 3.4. SUPERPAVE mix design (AASHTO TP4) SUPERPAVE uses volumetric analysis for the mix design and follows three major steps in the testing and analysis process. They are selection of a design aggregate structure, then optimizing the asphalt content for the selected structure. The last step is the evaluation of moisture sensitivity of the design mixture. For the sake of comparison, two extra aggregate structures (blends) were selected in addition to the MPWs&H recommended gradation for heavy traffic loads for wearing course. Fig. 2 shows the selected aggregate blends. The first blend was selected to be above the restricted zone, named ‘‘above RZ’’. While the second blend was selected to be below the restricted zone, named ‘‘below RZ’’. Fig. 2 shows that MPWs&H recommended gradation passes through the restricted zone. SUPERPAVE recommends that special precautions should be taken when compacting such mixes in the field [14].
Table 3 Minimum and seven-day maximum air and pavement temperatures at the different weather stations Station
Amman Baqura Irbed Deir Ala Ghorsafi Dhulail Mafraq Ruwaishied (H4) Ma’an Shoubak Aqaba a b c
Seven-day maximum temperature (°C)
Minimum temperature (°C)
Mean aira
Stdb
98% Rel.c
Mean aira
Stdb
98%c
36.1 41.0 34.5 41.4 42.6 39.0 37.0 40.6 37.4 32.4 42.1
1.7 1.3 1.2 1.1 1.2 1.6 1.5 1.7 1.4 2.7 0.9
61.4 65.3 58.7 65.3 66.8 64.0 61.8 65.6 62.3 60.1 65.9
0.9 2.0 1.0 5.9 5.8 3.4 3.8 4.1 4.3 8.5 4.7
1.6 1.6 1.5 1.7 1.3 1.6 1.5 1.9 1.7 2.5 1.2
4.1 1.3 4.1 2.3 3.1 6.6 7.0 8.0 7.8 13.7 2.3
Mean air temperature. Standard deviation of temperature. Calculated pavement temperature at 98% reliability.
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Therefore, the locally used MPWs&H gradation for heavy traffic loads wearing courses failed SUPERPAVE mix design criteria in more than one property, VMA and dust proportion. In addition, SUPERPAVE recommended asphalt content is 4.6%, which is much lower than Marshall design recommended optimum asphalt content for the same gradation. This might explain the reason that most of HKJ roads are having bleeding problems. In addition, obtained dust proportion is higher than the maximum specified limit. High dust proportion will usually lead to brittleness of the mixes [9]. The design optimization curves for the selected blend (‘‘Below RZ’’) revealed a design asphalt binder content of 4.8%. Evaluation of the moisture sensitivity of the design mixture was performed according to AASHTO T283 test procedure. Obtained ratio of the indirect tensile strength for the obtained mix structure at the optimum asphalt content was 83.2%, which exceeded the minimum criteria limit [8].
34
33 Ruwaishied (H4)
Baqura Deir Ala
Irbed
Mafraq
PG70-10
Dhulail
32 Amman
PG70-10 Ghorsafi
31
PG64-10 Shoubak
PG64-16 Ma'an
30 Aqaba
PG70-10
29
34
35
36
37
38
1737
39
40
Fig. 3. Temperature zoning for asphalt binder specifications for Jordan.
Since the gyratory compactor is used in SUPERPAVE mix design, the number of gyratory compactor gyrations should be specified. Number of gyrations depends on both average design high air temperature and design ESAL. A traffic level between 30 and 100 million ESALs was selected. This traffic level was selected because it is the common traffic level operating on most Jordan highways. At this traffic level, and at the average design high air temperature of Jordan (39 °C), the recommended numbers of gyrations are, Ninitial = 9 gyrations, N-design = 126 gyrations, and Nmaximum = 204 gyrations. These levels of gyrations were kept constant for the rest of the design phase. The initial trial asphalt binder content for the three blends was estimated to be 5.2%. Two specimens from each trial blend were compacted using SUPERPAVE Gyratory Compactor (SGC). Table 4 shows the results of the tested samples in addition to the required estimated properties (VMA, VFA, %GMM at Ni, and Dust Proportion) at the estimated asphalt content to achieve 4% air voids at N-design. Table 4 indicates that MPWs&H gradation failed to meet the VMA and dust proportion criteria. ‘‘Above RZ’’ blend failed to meet the dust proportion criteria. Just ‘‘Below RZ’’ blend satisfied all the specification limits; therefore, it will be carried to the second design stage, i.e., optimization of the asphalt content.
3.5. Performance evaluation of Marshall and SUPERPAVE mixes To compare the performance of both Marshall and SUPERPAVE mix design procedures, samples were prepared at the obtained optimum mix design asphalt contents of both procedures, using the locally used MPWs&H recommended gradation for the Marshall samples and the aggregate gradation ‘‘Below RZ’’ for SUPERPAVE samples. The gyratory compactor was used to compact both sets of samples. The test samples were 101.6 * 63.5 mm (4 in. * 2.5 in.) and were compacted to achieve 4% air voids. These samples were subjected to a comprehensive mechanical evaluation testing. These tests included Marshall Stability, Loss of Marshall Stability, Indirect Tensile Strength, Loss of Indirect Tensile Strength, Resilient Modulus, Fatigue Life, Rutting Behavior, and Creep Performance. 3.5.1. Marshall stability and loss of Marshall stability test results (ASTM D1559) Six samples from each mix were placed in the water bath at 60 °C. After 30 min immersion in the water bath, three samples from each mix were tested for Marshall Stability. The other three samples were tested for Marshall Stability after 24 h immersion in the water bath. Table 5 shows results of the tested samples. The results show that the SUPERPAVE samples have 32% higher Marshall Stability after 30 min immersion in water bath and 66% higher
Table 4 Estimated properties of the trial blends to achieve 4% air voids at Nd Blend
Trial AC%
Estimated properties to achieve 4% air voids at Nd AC %
VMA %
Criteria
VFA %
Criteria
% Gmm @ Ni
Criteria
Dust prop.
Criteria
MPWs&H Below RZ Above RZ
5.2 5.2 5.2
4.6 5.0 5.1
12.5 13.4 13.3
13 min 13 min 13 min
67.97 70.18 69.95
65–75 65–75 65–75
84.7 84.4 86.0
89 max 89 max 89 max
1.4 0.8 1.6
0.6–1.2 0.6–1.2 0.6–1.2
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Table 5 Marshall Stability test results for both mixes Sample #
1 2 3 Average a
Marshall samples
SUPERPAVE samples a
Initial stability (N)
Conditioned stability (N)
13,324 14,075 13,578
8211 7954 7201
13,659
7789
% Loss
43.0
Initial stability (N)
Conditioneda stability (N)
18,275 17,951 18,019
13,410 12,498 12,799
18,082
12,902
% Loss
28.6
Sample tested after 24 h immersion in water bath @ 60 °C.
the next pulse was 900 ms. The deviator stress during each loading pulse was 207 kPa, and the contact stress that was applied so that the vertical loading shaft does not lift off the test specimen during the rest period was 9 kPa. The test was performed at 40 °C. The specimen’s skin and core temperatures during the test were monitored by two thermocouples which were inserted in a dummy specimen and located near the specimen under test. The testing was continued until the maximum axial strain limit reached 10,000 micro-strains, or until 10,000 cycles, whichever occurred first. Three samples (100 * 63.5 mm at 4% air void) from each mix were tested. Fig. 4 shows the relationship between the number of cycles and the axial accumulated permanent deformation for both mixes. SUPERPAVE samples showed better creep performance than Marshall samples. This behavior difference is attributed to the lower asphalt content and coarser structure of SUPERPAVE mixes.
stability after 24 h immersions in water bath than Marshall samples. In addition, the SUPERPAVE samples have 14.4% lower loss of Marshall Stability than the Marshall samples. The superiority of SUPERPAVE samples over Marshall samples is attributed to the improved aggregate structure and the lower asphalt content and lower dust proportion of the SUPERPAVE samples. 3.5.2. Water sensitivity test (Lottman test AASHTO T-28389) The stripping resistance (water susceptibility) of both asphalt concrete mixes was evaluated by the decrease in the loss of the indirect tensile strength (ITS) after immersion in water for 24 h at 60 °C, according to AASHTO T-283 test procedure. The obtained results (Table 6) indicate that the average loss in strength due to water damage is lower in the SUPERPAVE samples than Marshall samples. This is attributed to the lower quantity of the fine aggregate in the SUPERPAVE samples. In addition, ITS loss value for SUPERPAVE samples is 18% which is within the 20% allowable loss limit specified in SUPERPAVE specifications [8]. In addition, Table 6 indicates that both SUPERPAVE conditioned and non conditioned samples have higher ITS values than corresponding Marshall samples. This is attributed to the improved aggregate structure of the SUPERPAVE samples.
Permanent Deformation, mm
3.5.4. Resilient modulus test, MR (ASTM D 4123) Resilient modulus is the most important variable that is used in the mechanistic design of pavement structures. It is
3.5.3. Dynamic creep test The Dynamic Creep Test is a test that applies a repeated pulsed uniaxial stress on an asphalt specimen and measures the resulting deformations in the same direction using Linear Variable Differential Transducers (LVDTs). The test was performed in accordance with the protocol developed by NCHRP 9-19 SUPERPAVE Models, Draft Test Method W2 [15]. The applied stress on the specimen was a feed back haversine pulse. The pulse width duration was 100 ms, and the rest period before the application of
1
Marshall SUPERPAVE
0.1
0.01 1
10
100
1000
10000
Number of Repetitions Fig. 4. Comparison of creep behavior of the different mixes at 40 °C.
Table 6 Indirect tensile strength test results for both mixes Sample #
1 2 3 Average a
Marshall samples
SUPERPAVE samples a
Initial ITS (kPa)
Conditioned ITS (kPa)
761 738 783
545 514 505
761
521
Sample tested after 24 h immersion in water bath @ 60 °C.
% Loss
31.5
Initial ITS (kPa)
Conditioneda ITS (kPa)
1006 1103 1052
822 892 844
1053
853
% Loss
19.0
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Table 7 Resilient modulus test results for both mixes Sample #
1 2 3
Marshall samples
SUPERPAVE samples
MR @ 1st position (MPa)
MR @ 2nd position (MPa)
Average MR (MPa)
MR @ 1st position (MPa)
MR @ 2nd position (MPa)
Average MR (MPa)
486 384 449
445 506 307
465.5 445.0 378.0
964 955 1080
897 1050 869
930.5 1002.5 974.5
Average
429.5
the measure of pavement response in terms of dynamic stresses and corresponding strains. Three samples from each fly ash content were tested at two position under the diametral resilient modulus (MR) test at 40 °C. Table 7 shows the obtained MR values for all the tested mixes. It indicates that SUPERPAVE mixes have higher diametral resilient modulus than Marshall mixes. This can be attributed to the lower asphalt content and coarser structure of SUPERPAVE mixes. 3.5.5. Fatigue performance Samples from both mixes were tested diametraly under repeated pulsed uniaxial loading to determine the number of loading cycles required to fail the samples. To have a wide range of failure cycles, test samples were tested at different initial tensile strain levels. At least nine samples from each mix (three at each initial tensile strain level) were tested at 40 °C. Fig. 5 shows the results of these tests. In this figure, regression lines were drawn through the mean values of the tested samples at each strain level. The results show a normal linear relationship between the logarithm of applied initial tensile strain and the logarithm of fatigue life (number of applied load repetitions until failure). The fatigue data were analyzed by running a regression analysis to
Marshall SUPERPAVE 100 100
determine the fatigue relationship parameters in the following form: et ¼ I ðN f Þ
10000
100000
No. of Repetitions
Fig. 5. Comparison of fatigue behavior of the different mixes at 40 °C.
ð1Þ
et = initial tensile strain, Nf = number of load repetitions to failure, I = anti-log of the intercept of the logarithmic relationship, and S = slope of the logarithmic relationship. Regression parameters for the Marshall samples regression line are I = 4374.7, S = 0.3497, and R2 = 0.9986. While the regression parameters for the SUPERPAVE samples regression line are I = 16471, S = 0.4449, and R2 = 0.9908. Analysis of the obtained fatigue results shows significant improvement in fatigue life of SUPERPAVE mixes over Marshall mixes This can be attributed to the higher dust proportion of Marshall samples over SUPERPAVE samples, which leads to brittleness of the Marshall mixes. 3.5.6. Permanent deformation Using two vertical LVDTs, the vertical permanent deformation was simultaneously recorded while running the fatigue tests. All tested samples showed lower permanent deformation values for SUPERPAVE samples than Marshall samples when tested at the same stress level. Fig. 6 presents the tests results which were performed at a repeated stress of 200 kPa. The three stages that the asphalt concrete passes through in rutting testing (densification, 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0
Marshall Samples
SUPERPAVE Samples
0
1000
S
where
Permanent Deformation, mm
Initial Tensile Strain, microstrain
1000
969.2
500
1000
1500
2000
2500
3000
3500
Number of Repetitions Fig. 6. Comparison of permanent deformation behavior of the different mixes at 40 °C and at 200 kPa dynamic loading.
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steady state and failure) clearly appear in this figure. In comparing the performance of the both mixes (Fig. 6), the trend is similar to that of fatigue testing, i.e., SUPERPAVE mixes performance is far better than Marshall mixes performance. This can be attributed to the higher dust proportion of Marshall samples over SUPERPAVE samples, which leads to brittleness of the Marshall mixes.
Acknowledgements
4. Conclusions
References
This research was conducted to find the adoptability of Superior Performance asphalt Pavements (SUPERPAVE) mixture specifications to the Hashemite Kingdom of Jordan specific materials, traffic and environmental conditions. A comparison study was carried out to use local materials to design the asphalt mixes using both Marshall and SUPERPAVE mix design procedures. In addition, performance of both mixes was evaluated. Based on the findings of the experimental results, the following main conclusions can be drawn:
[1] Bahia HU. Bibliographies for physical properties of asphalt cement. SHRP-A-626, National Research Council, Washington, DC. [2] American Society for Testing and Materials (ASTM). Standard test methods, vol. 4.03. West Conshohocken, PA: ASTM; 1997. [3] Asi IM. Role of roads in traffic safety. Traffic safety. . .everybody’s responsibility symposium. Jordan: Hashemite University; 2004. [4] Roberts F, Mohammad M, Wang L. History of hot mix asphalt mixture design in the USA. J Mater Civil Eng 2002;14(4):279–93. [5] American Society for Testing And Materials (ASTM). Standard test methods, vol. 4.03. West Conshohocken, PA: ASTM; 2000. [6] Brown R, Kandhal P, Zhang J. Performance testing for hot mix asphalt. National Center for Asphalt Technology, Report No. 200105A, Auburn University, Alabama; 2001. [7] Federal Highway Administration (FHWA). Background of SUPERPAVE asphalt mixture design and analysis. Publication No. FHWASA-95-003, US Department of Transportation, Washington, DC; 1995. [8] Cominsky RJ, Huber GA, Kennedy TW, Anderson M. The Superpave mix design manual for new construction and overlay. SHRP-A407, National Research Council, Washington, DC; 1994. [9] Anderson RM. SUPERPAVE level 1 mixture design example. A first look at volumetric mix design in the SUPERPAVE system. Lexington, KY: Asphalt Institute Research Center; 1993. [10] Sousa J, Harvey J, Painter L, Deacon J, Monismith C. Evaluation of laboratory procedures for compacting asphalt–aggregate mixtures. Report SHRP-A/UWP-91-523, University of California – Berkeley, September, 1991. [11] Ministry of Public Works and Housing. Specifications for Highway and Bridge Construction. vol. II, Hashemite Kingdom of Jordan; 1991. [12] Federal Highway Administration (FHWA).LTPPbind software [Computer program]. US Department of Transportation, Washington, DC; 1999. [13] Asphalt Institute. Superpave Mix Design Series No. 2 (SP-2), Asphalt Institute Research Center, Lexington, KY; 2001. [14] Anderson R, Bahia H. Evaluation and selection of aggregate gradations for asphalt mixtures using SUPERPAVE. Transportation Research Record 1583. TRB, National Research Council, Washington, DC; 1997. pp. 91–97. [15] Witczak M, Schwartz C, Von Quintus H. NCHRP Project 9-19: Superpave support and performance models management. Interim Report, Federal Highway Administration and the National Cooperative Highway Research Program; 2001.
1. In general, the performance grade of the locally produced asphalt is PG 64-16. 2. A temperature zoning map was developed for the Hashemite Kingdom of Jordan. It consisted of three grade zones, PG 64-10, PG 64-16, and PG 70-10. 3. Locally produced asphalt can be used without the need of modification in all parts of Jordan except Aqaba, Ruwaishied, and Ghorsafi. In these areas, it should be modified to shift its grade to PG 70-10. This modification might just require air blowing of the local asphalt. 4. Local aggregate meet both SUPERPAVE consensus properties and source properties. 5. Locally used aggregate gradations are not suitable according to SUPERPAVE mix design procedure. 6. SUPERPAVE mix design procedure recommended, for the local environmental and loading conditions, lower asphalt content than that predicted by Marshall mix design procedure. This might explain the causes behind the bleeding asphalt concrete surfaces and some of the distresses common in the local asphalt structures. 7. SUPERPAVE mixes showed superior performance over Marshall mixes. 8. In Jordan, serious plans should be set up to shift from the presently used Marshall mix design procedure to SUPERPAVE mixture specifications.
The authors would like to acknowledge the support of the College of Graduate Studies and Scientific Research at Hashemite University for funding this research study. Thanks are extended to Jordan Meteorological Department for helping in providing and analyzing weather data for Hashemite Kingdom of Jordan.