الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 164 |  |  |
| | | from | 164 | | |
Abstract
Based upon the analyses of laboratory results and the finite element modeling results, the following conclusions may be drawn as follows. 1. Six mixtures were blended, and laboratory experiments were conducted to figure out the maximum dry density and California bearing ratio CBR of each mixture. 2. The results of CBR indicates to super high-performance base course materials, the highest CBR value was 222 % for a mixture from steel slag aggregate, manufactured sand, and dolomite mineral filler material, the next value was 197 % for a mixture of steel slag aggregates, natural sand, and dolomite mineral filler, the third mixture was from steel slag aggregates and natural sand only reach a CBR value of 160 %, and finally mixture four with the steel slag aggregates and calcareous quarry waste material get 134% CBR. 3. According to the CBR testing program, the value for 5mm penetration is always taken, which could be due to the high value of the interlocking actions between the steel slag aggregates and it may be the reason of the high value of CBR. 4. The high value of CBR indicates that when steel slag is used as a base course material, the behavior of the steel slag aggregate reveals a stable variation in performance as the temperature of the asphalt concrete varies between 0.0o c, 20°c, 60°c. 5. The performance of vertical stresses of the mixture which uses the steel slag aggregate compared to base65 ranges from 63.1% to 53.9 % at asphalt layer 0.0ºc reaches to 69.6 % to 58.3 % for asphalt layer 20ºc and 76 % to 61.9 % for at the case of asphalt layer 60ºc. 122 THE BEHAVIOR OF STEEL SLAG AS BASE COURSE MATERIAL 6. The performance of vertical displacement of the mixture which uses the steel slag aggregate compared to base65 ranges from 65.5% to 46.9% at asphalt layer 0.0ºc reaches to 59.5% to 48.7% for asphalt layer 20ºc and 67.1% to 52.5% for at the case of asphalt layer 60ºc. 7. The performance of horizontal stresses of the mixture of which uses the steel slag aggregate compared to base65 ranges from 26% to 21.8% at asphalt layer 0.0ºc, 36.9% to 28.5% for asphalt layer 20ºc, and 55.3% to 41.8% for at the case of asphalt layer 60ºc. 8. The performance of horizontal displacement of the mixtures which uses the steel slag aggregate shows a significant improvement compared to base65 range from 87.3 % up to 73.9 % at asphalt layer 0.0ºc, 85.4 % to 46.7 % for asphalt layer 20ºc, and 85.1 % to 69.5 % for at the case of asphalt layer 60ºc. 9. The changes in the behavior of steel slag aggregate base course material in response to changes in asphalt concrete temperature from 0.0o c to 20o c and 60o c were primarily on the vertical stress values appearing on the subgrade layer. The results show that the vertical stress values for the slag222 layer increased by 32% and 51% for 20o c and 60o c, respectively, while the base65 layer increased by 56 % and 127 %. 10. Additionally, the changes in the behavior of steel slag aggregate base course in response to changes in asphalt concrete temperature, the results show increasing changes in the vertical displacement ranges from 24% to 40.0% for 20o c, 60o c for the Slag222 layer, and 37% to 89.7% for 20o c, 60o c for the Base65 layer. 11. As well as the changes in the horizontal stress behavior due to the change of asphalt temperature range from 19%% to 32% for 20o c, 60o c for the Slag222 layer, and 39% to 118 % for 20o c, 60o c for the Base 65 layer, 12. On the other hand, the horizontal displacement behavior due to the change of asphalt temperature range from 60 % to 98 % and 38 % 68 % respectively for slag222 and base65 courses. 13. Based on the results, the performance may be coming out from the increasing stiffness of the base course layer using the steel slag aggregate. Also, the more gradation is the layer, the more stiffness the layer gets, which appears in the use of manufactured sand but using calcareous quarry dust also gives superior performance with its low-cost material. 14. Using steel slag as base course material could play a significant role in ending the environmental impacts of steel making industry. The steel-making factories bay much money in damping the slag in large areas. The expansion of using steel slag in pavement construction and repairs could also have a significant factor in lowering steel industry operation costs. 15. Utilizing steel slag aggregate as a base course material would not only end the negative environmental impacts associated with dumping slag in large fill areas but could also increase the efficient use of traditional local materials such as natural sand and calcareous quarry waste to get a high-performance base course material. 16. The expansion of enhancing the local materials such as natural sand and calcareous quarry waste could play a role in lowering the overall all pavement construction costs, especially in the region of steel making factories Gradation equals more stiffness, which appears in the use of manufactured sand but using calcareous quarry dust also gives superior performance with its low-cost material. 17. The coarser gradation for the bonding materials in base course material gives higher resilient modules Mr and CBR because of the increase in interlocking actions between aggregates particles that were obvious in the case of using manufactured sand than the natural sand. 18. Additionally, using steel slag aggregates material can increase the asphalt layer’s use when the stiffness of the asphalt layer changes due to the visco-elastic properties and when subjected to high traffic loads. 19. Using a high-quality asphalt layer with low-quality base course materials is not a practical solution because that asphalt layer absorbs the majority of comparison and tension stresses which leads to a higher fatigue cycle and, in final, decreasesthe pavement life cycle. It is essential to balance the overall stiffness of the materials used in a pavement structural system because a significant gap in stiffness could decrease the role of the other layer. 20. Steel slag aggregate as a base course material not only decreases the vertical stress and vertical deformation on the subgrade layer with a considerable limit, but the overall pavements section could be decreased and make an added lower cost by decreasing the number of materials used in pavement constructions. 21. Finite element analysis programs could play a big role in the development of pavements structural design, especially the analysis of the results because it shows the interaction and the integration between the layers of the pavement under the different cases of loading, especially the tension and compression distribution along the pavement cross section which could give a good view about the behavior of the pavement along with its life cycles and also play the big role in pavement structural design optimization.