Civl19603_II.qxd 1. Introduction Aggregate chemistry plays a key role in asphalt-aggre- gate adhesion. It was found (Curtis et al., 1993) that when cohesive asphalt failures do not occur, aggregate chem- istry is much more influential than asphalt composition. Active sites on the aggregate surface promote adsorption of polar asphaltic compounds. When these active sites are covered by non-polar compounds or dust that exist natu- rally on the aggregate surface, the bonding force that ______________________________________________ *Corresponding author E-mail: hawahab@kfupm.edu.sa maintains the pavement is weakened. Curtis et al. (1991) developed a limestone reactivity test that can determine the number of active sites present on the aggregate sur- face. After laying the pavement, asphalt-aggregate bonding forces can be weakened by the effects of water. Water mol- ecules intrude or diffuse to the aggregate surface and com- pete with the polar asphaltic compounds for interactions with the active sites. The affinity or compatibility of an asphalt-aggregate pair is very important for minimization of water induced damage. If the affinity is large, only a small percentage of the asphalt-aggregate interaction sites will be lost to water molecules. ring Research 1 (2004) 29-38rnal of EngineeThe Jou Pavement Stripping in Saudi Arabia: Prediction and Prevention H.I. Al-Abdul Wahhab*1, I.M. Asi1, S.A. Ali2, S. Al-Swailmi3 and A. Al-Nour4 1 Department of Civil Engineering, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia. 2 Department of Chemistry, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia. 3 Operations & Maintenance, Riyadh Municipality, Riyadh, Saudi Arabia. 4 M&R Department, Ministry of Communications, Riyadh, Saudi Arabia. Received 19 June 2002, accepted 11 October, 2003 Abstract: Pavement weathering or stripping is a major distress in highway networks in arid regions. Using the Saudi Arabian road network as a case study area, seventeen road test sections were selected, out of which eight were stripped and nine were non-stripped. Aggregates from quarries used to build these sections were also collected and subjected to detailed physical and chemical tests to evaluate the ability of these tests to distinguish between stripped and non-stripped sections. The modified Lottman test was used to distinguish between compacted mixes. In addition, the Swedish Rolling Bottle test, was also found to be effective in being able to distinguish between different asphalt-aggregates for stripping potential. Eleven anti-stripping liquid additives, lime and cement, in addition to two polymers, were evaluated for their ability to reduce/eliminate stripping potential of stripping-prone aggregates. It was found that EE-2 Polymer, Portland cement, and their combination were effective with all aggregate sources. Keywords: Pavement stripping, Roads, Polymer, Anti-stripping agents, Lottman test :¢ü∏îà°ùŸŸG¥ô£dG äɵѰT É¡d ¢Vô©àJ »àdG á«°ù«FôdG ôgGƒ¶dG øe á«NÉæŸG ájô©àdG πeGƒY ÖÑ°ùH ∞°UôdG äÉ≤ÑW øe ᪰ü◊G ∫É°üØfG á«∏ªY Èà©J á©°ùJ ɪæ«H ᪰ü◊G ∫É°üØfG IôgÉX øe ÊÉ©J ¥ôW á«fɪK É¡æe áµ∏ªŸÉH ≥jôW ô°ûYá©Ñ°S QÉ«àNG ” IôgɶdG √òg á°SGQ~d .á∏MÉ≤dG ≥WÉæŸG ‘ ¢üFÉ°üÿG ~j~ëàd É«FÉ«ª«ch É«FÉjõ«a É¡∏«∏–h É¡à°SGQO â“h ¥ô£dG √òg É¡æe â«æH »àdG QOÉ°üŸG ™«ªL øe ΩÉcôdG ™«ªŒ ” .᪫∏°S Èà©J É¡æe ‘ á«à∏Ø°S’G áfÉ°SôÿG ≈∏Y √É«ŸG á«°SÉ°ùM QÉÑàNG AGôLG ” É° jG .¥ô£dG øe ᪰ü◊G ôjÉ£Jh ájô©àdG á«∏HÉb IOÉjR ‘ QhO É¡d ¿ƒµj ~b »àdG ÚH õ««ªàdG ‘ ¬«∏Y OɪàY’G øµÁ ¬fG ~Lh ~bh IQGh~dG áj~jƒ°ùdG áLÉLõdG QÉÑàNG AGôLG ” ɪc .É¡æ«H õ««ªàdG á«fɵeG ~j~ëàd ácƒe~ŸG äÉæ«©dG äÉ£∏î∏d äÉaÉ° ŸG øe áYƒª› ΩG~îà°SÉH ájô©à∏d ᪰ü◊G áehÉ≤e Ú°ù– á«fɵeG á°SGQO â“ .ájô©à∏d πHÉb Ò¨dGh ájô©à∏d πHÉ≤dG ΩÉcôdG äÉæ«Y ¿Éªà°ùjG øFG~d ¿G ~Lh .øFG~∏dG øe ÚYƒæd áaÉ°V’ÉH ,…OÉY â檰SGh ,»Ø£ŸG Ò÷G ,»FÉ«ª«c Öcôe 11 πª°ûJ á«à∏Ø°S’G(EE-2)â檰S’Gh .ájô©àdGh ôjÉ£àdG ~°V ᪰ü◊G ´GƒfG πµd á«à∏Ø°ùdG äÉ£∏ÿG áeƒ≤e IOÉjR ‘ á«dÉ©a OGƒŸG ÌcG âfÉc …OÉ©dG :á«MÉàØŸG äɪ∏µdG √É«ŸG ÒKÉJ QÉÑàNG ,á«FÉ«ª«c äÉaÉ° e ,øFG~∏dG ,∞°UôdG ,᪰ü◊G ôjÉ£J Pairs of low affinity will lose a large percentage of the asphalt-aggregate interaction sites to the more polar and hydrogen bonding water molecules. This leads to strip- ping. Tests were devised (Curtis et al., 1993) to determine this important affinity or compatibility for different pairs of asphalt-aggregates. If water is the cause of an asphalt- aggregate problem, these tests will allow one to evaluate the possibility of future pavement stripping based on this affinity. When an aggregate absorbs water, the asphalt is “stripped” away. This ultimately leads to pavement failure. Moisture degrades the integrity of an asphalt concrete matrix in three areas: loss of cohesive strength in the asphalt film, failure of the adhesive bond between the aggregate and asphalt (stripping), and loss of the chemi- cal bond (integrity) between the asphalt film and the aggregate. Other modes of pavement failure due to the presence of water are also possible. Water can remove the soluble compounds from the asphalt causing it to fail. Failure within the aggregate can also occur. Water can promote phase separation within the asphalt, where the more polar molecules form a separate phase with water. A reduction in water induced damage can be achieved by selecting asphalt-aggregate pairs of high affinity, mod- ifying the aggregate surface through silylation, or adding antistripping agents. Building roads with low air voids and good drainage reduces water-induced damage by limiting the exposure to water. The pH of the medium can also affect the asphalt-aggre- gate bond. It was found (Curtis et al., 1993) that a high pH (basic or alkaline environment) is detrimental to most asphalt-aggregate bonds. Additives such as lime or some liquid anti-stripping agents can improve the performance of some asphalt-aggregate pairs in highly basic environ- ments. Among the many factors that contribute to the degrada- tion of asphalt concrete pavements, moisture is a key ele- ment in the deterioration of the asphalt mix. Since the 1930s, pavement engineers have been working to deter- mine the moisture sensitivity of asphalt concrete mixtures. Since that time, numerous tests have been developed to identify moisture-susceptible asphalt concrete mixtures. In general, there are two categories into which the water sen- sitivity tests can be divided. The first category includes tests which coat “standard” aggregates with asphalt cement. In these tests, the loose mixture is immersed in water, either at room temperature or at boiling tempera- ture, and a visual evaluation is made of the separation of asphalt from the aggregate. The second category includes those tests that use compacted specimens, either laborato- ry compacted or cores from existing pavement structures (Terrel and Shute, 1989). These specimens are then water conditioned to simulate the in-service conditions of the pavement structure. The results of these tests are general- ly evaluated by the ratios of conditioned to unconditioned results using a stiffness or strength test, such as the diame- tral resilient modulus test. Several methods have been developed to determine if an asphalt concrete mix is sensitive to water. The main methods can be summarized as follows (Terrel and Shute, 1989; Curtis et al., 1991; Terrel and Al-Swailmi, 1992; AASHTO, 1995): 1. NCHRP 246 – Indirect Tensile Test and/or Modulus Test with Lottman Conditioning. 2. NCHRP 247 – Indirect Tensile Test with Tunnicliff and Root Conditioning. 3. AASHTO T-283 – Combines feature of NCHRP 246 and 247. 4. Boiling Water Tests. 5. Immersion-Compression Tests (AASHTO T-165, ASTM D 1075). 6. Freeze-Thaw Pedestal Test. 7. Static Immersion Test (AASHTO T-182, ASTM D 1664). 8. Conditioning with Stability Test (AASHTO T-245). 9. Net Absorption/Desorption Test (developed by SHRP). 10. Environmental Conditioning System (ECS) (developed by SHRP). Pavement weathering or stripping is one of the major distresses in the highway network in the case study area, the Kingdom of Saudi Arabia. Pavement stripping severi- ty varies from region to region in the Kingdom. The high- way network in Al-Qassim and Hail regions is the most affected by pavement stripping. In certain roads where maintenance programs are not efficient, stripping develops potholes that severely affect road performance. The water sensitivity test used in local road departments is the typi- cal water conditioning and evaluation by the Marshall sta- bility test. The conditioning phase includes partial satura- tion of specimens with asphalt and then soaking in a water bath. The specimens are then tested for Marshall stability and compared with the results of unconditioned speci- mens. If the ratio (condition divided by unconditioned) is less than 75%, the mixture is considered sensitive to water. Those roads experiencing stripping and weathering have all passed the water sensitivity test. This has indicated that the water sensitivity test using Marshall stability is not reliable in determining the sensitivity of asphalt mixtures to water. With the recent developments in the design and evaluation as a result of strategic highway research pro- gram (SHRP), the Ministry of Transport (MOT) in the case study area has adopted a Superpave mix design that utilizes a gyratory compactor. The northern part of the study area is mostly affected by this phenomenon due to the existence of water sensitive aggregates. The overall objective of this paper was to assess strip- ping problems in arid regions using the highway network of Saudi Arabia as a case study. Secifically, current prac- tices by road agencies were reviewed and the tests used by these agencies were included in the test program. Binder aggregate adhesion and susceptibility of that adhe- sion to water damage were analyzed. Comprehensive tests that predict the resistivity of asphalt-aggregate materials 30 ring Research 1 (2004) 29-38rnal of EngineeThe JouAbdul Wahhab et al. / (individually or as a mix) were adapted or modified. Practical treatment methods were suggested to improve stripping resistance of local mixes. 2. Methodology The work was carried out in three tasks and extended for 30 months. Task 1: Literature review: Available literature from main research institutions locally and abroad related to the sub- ject of the research were collected, summarized, and uti- lized to support the knowledge of the researchers in this field. Task 2: Stripping test selection and evaluation: Different tests (physical and chemical) that might be used to detect susceptibility of pavement mixes and/or materials to strip- ping were evaluated (Table 1). Construction materials (fresh aggregates, slabs, and cores) from known perform- ance road sections were collected, in consultation with government personnel. These materials were subjected to different tests to evaluate their ability in predicting strip- ping potential. A total of seventeen test sections were selected: eight stripped and nine unstripped. In selecting the study sections several criteria had to be met Adequate drainage had to be present for the pavement surface. Construction had to be according to specifications, (i.e. percent air voids (AV%) had to be 31 ring Research 1 (2004) 29-38rnal of EngineeThe JouAbdul Wahhab et al. / Serial # Crusher Road name Pavement condition Age Symbol Al-Qassim 1 Al-Swailem Ring road (North + East) Excellent 5–6 years QN-1 2 Burma Ring road mid -east flange V. good 5–6 years QN-2 3 Debiah 414 west road Stat. 45+600 V. good 10 years QN-3 4 Artic Al-Jamal Avenue junction road Medium stripping 3 years QS-4 5 Al-Fahd Ring road -West flange Stat. 14+550 High stripping 5–6 years QS-5 Hail 6 Al-Swailem Bagaà road Low stripping 3 years HS-1 7 Al-Hudaires At Humairah road (Madinah junction) (RD -7771) Medium to high stripping 5 years HS-2 8 Al-Namlah Ring road Stat. 17+000 V. good 14 years HN-3 Eastern Province 9 Road Construction Establishment Salasel -Abqaiq, KP7 Low stripping 7–8 years ES-1 10 Al-Hazaà Nuaireah -Qaysoma road, after Nuaireah intersection bridge Excellent 6–7 years EN-2 Riyadh Region 11 Shibh Al-Jazira Riyadh-Dammam Expressway Stat. 980+000 V. good 8 years RN-1 12 Al-Awaidah Riyadh-Taif Expressway Stat. 511+00 Medium stripping 5 years RS-2 Taif 13 Al-Harameen Taif-Baha road, KP 1220 V. good 5-6 years TN-1 Abha 14 Ben-Jarrallah Prince Salman Sport City road V. good 7-8 years AN-1 Al-Jouf 15 Al-Swailem Sakaka Domat Al -Jandal road V. good 5-6 years JN-1 16 Al-Harbi Tabargel Al -Quriyat road High stripping 15 years JS-2 Northern Region 17 Al-Sagaf Arar-Taif Highway, km sign 1523 Low stripping 7 years NS-1 Table 1. Selected test sections from case study area within design limits, compaction temperature within allowable limits, no overheating of asphalt, aggregate gra- dation within limits). Aggregate quarry used for supplying aggregate in the asphaltic concrete layers had to be known and active so that fresh aggregate could be obtained sim- ilar to that used in the section. The collected materials were subjected to a number of chemical and physical evaluation tests to evaluate the abil- ity of those tests to predict stripping. These tests included compacted mix evaluation methods such as environmental conditioning system (ECS), modified Lottman test and Marshall durability test.; Asphalt/aggregate blend evalua- tion methods such as net adsorption in the presence of moisture and the Swedish Rolling Bottle test and aggre- gate tests such as methylene blue value (MBV), soundness and physical properties. Experimental design for the first phase of the project is shown in Table 2. The response variables measured on individual materials, mixtures, compacted specimens, pavement cores were used for selection of applicable physical and/or chemical tests that are able to predict strip- ping and used for evaluation of the different mixes in the second phase of the study. Task 3: Material collection, mix designs and evaluation: In the second phase, different additives that are known from literature of being useful in preventing stripping were collected and used with the collected aggregate from stripped sections to prepare asphalt mixes using different percentages of additives and combinations. The Marshall mix design procedure was used to determine the optimum asphalt content for each aggregate source as shown in Table 1. Different percentages of anti-stripping agents (as recommended by the manufacturer) were added to each mix. Mixes were evaluated using the stripping tests. 3. Results and Discussion As an initial step in the statistical analysis, the normal- ity assumption of the distribution of the test results was checked by drawing normal probability plots of the data. The statistical data analysis was then carried out in three stages. In stage I, the preliminary analysis, was to confirm that 32 ring Research 1 (2004) 29-38rnal of EngineeThe JouAbdul Wahhab et al. / NUMBER OF REPLICATES Stripped Sections Non-Stripped Sections Field Samples Laboratory Samples Field Samples Laboratory Samples Laboratory Test/Road Section Number 1 2 3 . 8 1 2 3 . 8 1 2 3 . 9 1 2 3 . 9 Swedish Ro lling Bottle X X X . X 2 2 2 . 2 X X X . X 2 2 2 . 2 Aggregate- Asphalt Blend Absorption -Desorption X X X . X 2 2 2 . 2 X X X . X 2 2 2 . 2 Volumetric Properties 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 Marshall Compaction, Vacuum Saturation Conditioning a nd Resilient Modulus Testing 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 Marshall Compaction, Vacuum Saturation Conditioning and Split Tensile Testing 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 Marshall Compaction, Marshall Conditioning and Split Tensile Testing 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 Gyratory Compaction, Vacuum Saturation Conditioning and Split Tensile Testing (7% Air Voids) 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 Marshall Stability Loss 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 3 3 3 . 3 Asphalt Concrete Mix Environmental Conditioning System (ECS) 2 2 2 . 2 2 2 2 . 2 2 2 2 . 2 2 2 2 . 2 Table 2. Experimental design X = Test is not applicable there was a difference in behavior between stripped and non-stripped sections and that the grouping of the sections was correct. Therefore, the statistical evaluation tests for this stage were performed on the test results of the extract- ed field cores. Single factor analysis of variance (ANOVA), using STATISTICA statistical program, was carried out for the test results of the field cores to find if there was a significant difference between the means of the different performed tests of stripped and non-stripped sections. The null hypothesis for the ANOVA test is (Lapin, 1997): Ho : m-stripped = m- non-stripped vs. where, Ho = null hypothesis Ha = alternate hypothesis µ = mean value of the test results for the specific test. 33 ring Research 1 (2004) 29-38rnal of EngineeThe JouAbdul Wahhab et al. / Non-Stripped Sections Stripped Sections Test P-value Avg. S.D. Avg. S.D. Discriminant test limit Probability of not being stripped if observation is less than set limit* % Loss of resilient modulus 4.3E-05 38.13 10.01 60.84 23.57 45 75% % Loss of split tensile strength + (vacuum saturation) 8.6E-07 41.49 7.65 63.63 18.34 48 80% % Loss of split tensile strength (no vacuum saturation) 0.00017 32.25 10.03 53.31 24.29 38 73% Marshall stability loss, % 9.4E-08 20.05 4.77 52.13 25.87 25 80% % Loss of split tensile strength ++ (gyratory compaction) 4.6E-09 38.20 9.26 66.40 17.48 48 86% Environmental Conditioning System (ECS), after first loading cycle (%) 0.00082 16.67 6.99 32.48 15.80 22 78% Environmental Conditioning System (ECS), after sec ond loading cycle (%) 0.00455 30.63 10.77 45.94 16.49 37 72% Environmental Conditioning System (ECS), after third loading cycle (%) 0.01452 42.99 7.40 54.78 17.04 47 71% Swedish Rolling Bottle value after 12 hrs. 0.02715 36.33 17.52 56.92 12.21 48 75% Aggregate soundness test 0.0023 7.64 1.65 13.36 4.35 9 83% Table 3. Summary of analysis of variance results for significant tests * Similarly, the probability of being stripped if observation is greater than set limit + Conventional Lottman test ++ Modified Lottman test (AASHTO T-283) ANOVA analysis was performed for the test results of the extracted field cores as shown in Table 2. Results indi- cated that at α = 0.05 (the higher the α value, the lower the significance of the difference), for all the performed tests, except the ECS, the means of the stripped and non- stripped sections were significantly different. This implied that the tests were capable of differentiating between stripped and non-stripped sections and therefore indicated a good matching between the classification of the different sections into stripped and non-stripped sec- tions and the test results. Stage II was to find which of the laboratory tests was capable of predicting the stripping potential of the asphalt concrete mixes. Therefore, the single factor ANOVA sta- tistical evaluation was performed on the test results of the fresh aggregate and the laboratory prepared mixes, Table 2. Table 3 shows only tests that were significant and that had a P-value (Probability to reject Ho when Ho is true) less than 0.05 in differentiating between mixes that were prone to stripping from sound mixes (Lapin, 1997). The most significant test in predicting stripping (having the smallest P-value) was the loss in split tensile strength when performed on gyratory compacted samples that had 7 ± 1% air voids followed by vacuum saturation then soak- ing at 60°C for 24 hours (i.e. modified Lottman test). The other tests in a decreasing order of significance were: Marshall stability test; split tensile strength of Marshall compacted specimens soaked @ 60°C for 24 hours after 34 ring Research 1 (2004) 29-38rnal of EngineeThe JouAbdul Wahhab et al. / S.N. Product name Physical state Recommended dosage (wt%)* Stability Chemical name Flash point 1 Lilamin VP 75E Liquid 0.2–0.4 heat stable mixture of alkyl and alkylene amines 120°C 2 WETFIX AD-4F m.p. 63ºC fatty amine salt >150ºC 3 WETFIX® BE viscous liquid; b.p. >200ºC 0.2–0.5 heat stable (upto 170ºC) fatty acid + polyamine >100ºC 4 ITERLENE IN/400-S liquid 0.2–0.4 heat stable (170ºC) alkylamido - imidazo- polyamine >180ºC 5 CECABASE® 260 liquid 0.2–0.4 heat stable alkylamido - imidazo- polyamine >100ºC 6 POLYRAM® L200 liquid heat stable N-alkyl’tallow’ dipropylene triamine >100ºC 7 EC9194A (EXXON Energy chemicals) liquid 0.2–0.4 heat stable (<250ºC) alkyl imidazoline in aromatic hydrocarbons 8 ITERLENE IN/400 liquid 0.3–0.6 heat stable (upto 170°C) alkylamido - imidazo- polyamine >180°C 9 ITERLENE IN/400-R liquid 0.2–0.4 heat stable (upto 170°C) fatty alkylamido - imidazo- polyamine >180°C 10 ITERLENE IN/400-R-1 liquid 0.2–0.4 heat stable (upto 170°C) fatty alkylamido- imidazo- polyamine >180°C 11 MORELIFE 3300 viscous liquid 0.2–0.5 heat stable (upto 150°C) polycyclo - aliphatic polyamines 170°C 12 POLYBILT granules 2.0–5.0 heat stable >200°C >200°C 13 EE-2 Polymer granules 2.0–5.0 heat stable >200°C modified olefin >200°C 14 Cement powder 2.0–4.0 − Portland cement − 15 Lime powder 2.0–4.0 − hydrated lime (calcium hydroxide) − Table 4. Collected liquid antistripping agents *weight (5) of the antistripping agent added to the bitumen vacuum saturation; resilient modulus of Marshall com- pacted specimens soaked @ 60°C for 24 hours after vacu- um saturation; split tensile strength of Marshall compact- ed specimens soaked @ 60°C for 24 hours without vacu- um saturation; resilient modulus of gyratory prepared samples having a target air void between 6 and 8% after one cycle in ECS; aggregate soundness test; resilient mod- ulus of gyratory prepared samples having a target air void between 6 and 8% after two cycles in ECS; Loss of resilient modulus of gyratory prepared samples having a target air void between 6 and 8% after three cycles in ECS; and Swedish Rolling Bottle value after 12 hrs. rolling. Although all tests were statistically significant, it can be seen that they can be divided into three groups: com- 35 ring Research 1 (2004) 29-38rnal of EngineeThe JouAbdul Wahhab et al. / Antistripping Agent Code Hail Al-Jouf Eastern Province Riyadh Hail (HS1) (JS2) (ES1) (RS2) (HS2) % Loss % Loss % Loss % Loss % Loss Lilamin VP 75E 36.45% 61.47% 100.0%* 100.0% 48.00% WETFIX AD -4F 71.15% 100.00% 38.4% 100.0% 40.30% WETFIX® BE 32.98% 69.10% 100.0% 100.0% 44.90% ITERLENE IN/400-S 58.40% 79.20% 100.0% 100.0% 51.20% CECABASE® 260 40.54% 55.80% 100.0% 47.6% 48.00% POLYRAM® L200 44.30% 72.90% 100.0% 100.0% 53.00% EC9194A 29.24% 64.60% 100.0% 100.0% 41.20% ITERLENE IN/400 45.80% 76.80% 100.0% 100.0% 53.70% ITERLENE IN/400-R 32.59% 57.40% 100.0% 100.0% 44.50% ITERLENE IN/400-R-1 52.80% 86.40% 100.0% 69.0% 32.40% MORELIFE 3300 21.54% 67.80% 100.0% 31.7% 36.60% POLYBILT 70.46% 80.80% 100.0% 100.0% 39.21% EE-2 Polymer 28.75% 32.30% 35.8% 41.9% 42.40% Cement 35.85% 40.80% 38.5% 46.9% 46.00% Lime 41.80% 49.20% 75.5% 74.9% 48.30% Control 49.40% 77.40% 100.0% 100.0% 58.30% Table 5. Effect of different antistripping agents using modified Lottman test % loss of 100 means that conditioned samples have collapsed, resulting in ITS of zero and 100% ITS pacted mix, asphalt/aggregate blend and aggregate. From the first group, it can be seen from Table 3 that both the modified Lottman test (AASHTO T-283) and the Marshall stability loss test (MOT-MRDTM 410) had the lowest dis- criminant probability P-value of 4.6E-09 as compared to a P-value of 9.4E-08 for Marshall stability loss. Moreover, the government in the case study area is in the process of adopting the Superpave mix design. This will eliminate the use of the Marshall mix design. Lottman, on the other hand, is a simple test that has proven effectiveness and is currently used widely in the United States. The Lottman test was therefore selected as the best mix evaluation test to discriminate between compacted mixes. The Swedish Rolling Bottle test was the only one in the second group 36 ring Research 1 (2004) 29-38rnal of EngineeThe JouAbdul Wahhab et al. / Antistripping Ave. Initial ITS. Ave. Final ITS. Average Agent Code Sample* ID Initial ITS Kg/cm2 Final ITS Kg/cm2 Kg/cm2 Kg/cm2 % Loss 12.1 8 11.9 7.9 CECABASE® 260 + Cement RS2 12.3 8.3 12.1 8.1 33.33% 12.9 9.2 11.2 8.3 MORELIFE 3300 + Cement RS2 11.6 9 11.9 8.8 25.77% 11.9 7.6 12.1 7.7 EE-2 Polymer + Cement RS2 12.4 8.1 12.1 7.8 35.71% 13.7 9.6 12.9 9.3 WETFIX AD- 4F + Cement ES1 13.5 9.3 13.4 9.4 29.68% 13.9 9.9 13.5 10 EE-2 Polymer + Cement ES1 13.2 9.7 13.5 9.9 27.09% 12.7 7.7 13.4 8 CECABASE® 260 + Cement JS2 13.1 7.6 13.1 7.8 40.56% 12.2 8.8 13.1 9.4 EE-2 Polymer + Cement JS2 12.6 9.1 12.6 9.1 27.97% 12.1 7.6 13 8.2 MORELIFE 3300 + Cement HS1 11.6 8.1 12.2 8.0 34.88% 15.5 11.4 15.8 11.1 EE-2 Polymer + Cement HS1 15.1 10.8 15.5 11.1 28.23% 11.4 7.3 10.9 7.1 MORELIFE 3300 + Cement HS2 11.8 8.1 11.4 7.5 34.02% 14.7 9.6 14.2 9.4 EE-2 Polymer + Cement HS2 15.1 8.9 14.7 9.3 36.59% Table 6. Effect of combined antistripping agents using modified Lottman test * RS: Riyadh aggregate JS: Al-Jouf aggregate ES: Eastern Provience aggregate HS: Hail aggregate that was significant (P=.02715) in evaluating loose aggre- gate-asphalt blends stripping tendencies. In the third group, aggregate soundness, which was a significant test (P=0.0023), had the ability to distinguish between aggre- gates prone to stripping. This test, however, did not have the capability to evaluate additives to asphalt mixes and therefore was eliminated. Stage III was to find the test limits that could be set to screen mixes that were prone to stripping. This was based on the test results of the fresh aggregate and the laborato- ry prepared mixes. Specification limits were calculated for each of the significant tests. These limits could then be used to test if the mix was prone to stripping (i.e. if the result of the evaluation test was higher than the set limit, then the mix would be prone to stripping). Assuming a normal distribution of the results, the average and standard deviation values for the samples Table 3, were used to find the test limits. The aim was to find the limit that would produce an equal probability of classifying the mix as not being prone to stripping if the test value was lower than the limit, to the probability of classifying the mix as being prone to stripping if the test value was higher than the limit. For example, Table 3 shows that for the modified Lottman test (AASHTO T-283) and the Marshall stability loss test (MOT-MRDTM 410), the discriminating limits were 48% and 25%, respectively. In addition to lime and cement dust, several liquid anti- stripping agents were purchased and specifications of the products as provided by the companies were also obtained, Table 4. The Marshall mix design was used to arrive at the opti- mum asphalt content for the four selected stripped loca- tions. Eleven liquid antistripping agents were collected from the original manufacturers and administered at the maximum recommended percentage. Moreover, cement, lime and two polymers (Polybilt 101 and Eastman EE-2) were used at a dosage of 4% as recommended by govern- ment guidelines and polymer manufacturers. Work was carried out in two stages. The maximum recommended dosages of the antistripping additives were used to quanti- fy the effect of the additive on stripping phenomena and to screen the additives, Table 5. In the second stage , addi- tive combinations of promising mixes were evaluated. Combinations included dry additives (Portland cement and/or lime) and liquid additives or polymers. Liquid addi- tives were not mixed with polymers. This was done to avoid adverse chemical reactions, Table 6. The modified Lottman test and the Swedish Rolling Bottle test were used to evaluate the effectiveness of the different treat- ments. Table 5 shows the typical stage I test results for the Hail, Al-Jouf, Eastern Province and Riyadh region. The results show the loss in the indirect tensile strength values (ITS), according to the modified Lottman test procedure, for all treatment combinations. The effectiveness of the treatments was evaluated based on the level of ITS improvement for each aggregate as compared to the con- trol mix (no additive). It should be noted that 100% ITS loss indicated that samples failed during the conditioning phase ,indicating severe stripping. This resulted in a final ITS of zero and therefore a 100 % ITS loss. Table 6 shows the results of the combined additives. In general, it can be seen that the ITS of each mix was dependent on the aggregate type. The results of the second phase indicated that for Hail aggregate, treatments EC9194A, Iterlene IN/400, Iterlene IN/400-R, Polyram L200, CECABASE 260, WETFIX BE, Lilamin VP 75E, Morelife 3300, EE-2 Polymer, cement, and lime were effective in eliminating the stripping potential of the aggregate. For Al-Jouf aggregate, only EE-2 Polymer and cement were effective in eliminating the stripping poten- tial of the aggregate. For Eastern Province aggregate, only WETFIX AD-4F, EE-2 Polymer, and cement were the effective additives. With the Riyadh aggregate, only Morelife 3300 and EE-2 Polymer were effective addi- tives. The EE-2 Polymer was effective in eliminating the stripping potential of all aggregates from all sources. Eastman EE-2 Polymer and Portland cement and their combination proved to be effective with all studied aggre- gate sources. Morelife 3300 antistripping additive com- bined with cement was the most effective with Riyadh and Hail aggregates. WETFIX AD-4F combined with cement was the most effective with the Eastern Province aggre- gate. Finally CECABASE 260 combined with cement was effective with the Al-Jouf aggregate. For each type of aggregate, there were specific addi- tives that were effective in eliminating the stripping poten- tial. However, cement and EE-2 Polymer combinations were effective in eliminating or effectively reducing the stripping potential of all the tested aggregates. 4. Conclusions Based on the Analysis of Variance (ANOVA) results, the modified Lottman test, the Marshall stability loss test, Environmental Conditioning System (ECS), and the resilient modulus loss were effective in distinguishing between stripped and non-stripped mixes. ECS had the lowest significance (P = .00082) among these tests while the modified Lottman had the highest significance (P = 4.6E–09). The Swedish Rolling Bottle was found to be effective in screening asphalt-aggregate materials for stripping potential. Eastman EE-2 Polymer and Portland cement and their combination proved to be effective with all studied aggregate sources. Morelife 3300 anti-stripping additive combined with cement was the most effective with Riyadh and Hail aggregates. WETFIX AD-4F com- bined with cement was the most effective with the Eastern Province aggregate. CECABASE 260 combined with cement was effective with Al-Jouf aggregate. Acknowledgements The authors would like to acknowledge the support 37 ring Research 1 (2004) 29-38rnal of EngineeThe JouAbdul Wahhab et al. / of KACST for funded this project, KFUPM for provided the research facility, and MOT for provided the logistical support in selecting and sampling test sections. References American Association of State Highway and Transportation Officials (AASHTO), 2000, “Resistance of Computed Bituminous Mixtures to Moisture Induced Damage,” AASHTO T-283-89, Washington, D.C., USA, pp. 983-991. Curtis, C.W., Terrel, R.L., Perry, L.M., Al-Swailmi, S., and Brannan, C.J., 1991, “Importance of Asphalt- Aggregate Interactions in Adhesion,” Proceedings, Association of Asphalt Paving Technologists (AAPT), Vol. 60, p. 476. Curtis, C.W., Ensley, K., and Epps, J., 1993, “Fundamental Properties of Asphalt-Aggregate Interactions Including Adhesion and Absorption,” Strategic Highway Research Program Publication, SHRP-A-341, Washington, D.C., USA. Lapin, L.L., 1997, Modern Engineering Statistics, Wadswoth Publishing Company, Belmont, CA. Terrel, R.L., and Shute, J.W., 1989, “Summary Report on Water Sensitivity,” Strategic Highway Research Program, SHRP-A/IR-89-003, Washington, D.C., USA. Terrel, R.L., and Al-Swailmi, S., 1992, “Final Report on Water Sensitivity of Asphalt-Aggregate Mixtures Test Development,” Strategic Highway Research Program, National Research Council, Washington, D.C., USA. 38 ring Research 1 (2004) 29-38rnal of EngineeThe JouAbdul Wahhab et al. /