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Go to Editorial ManagerField compaction equipment used for fine grained soil usually applies a kneading action or vibration that produces shear forces which also reshape soil particles arrangement. A state that might not be completely simulated by laboratory Proctor tests. This study aims at investigating the significance of using the newer modified Texas superpave gyratory compactor (SGC) to simulate field compaction of fine grained soil due to itsability to apply loads in different anglesgenerating shear forces on the compacted soilspecimens. Two types of soil (A-4) and (A-7-6)were compacted using standard Proctor,modified Proctor and (SGC). The results werecompared to dry field densities of the same soilin order to evaluate the most representative test.It was found that maximum dry densities of soiltype (A-4) obtained using (SGC) under (200kPa) and (600 kPa) were lower by (2.07%) andhigher by (1.35%) than the maximum drydensities obtained using standard and modifiedProctor tests respectively. It was also found thatmaximum dry densities of soil type (A-7-6)obtained using (SGC) under (300 kPa) and (600kPa) were lower by (1.02%) and higher by(1.23%) than the maximum dry densitiesobtained using standard and modified Proctortests respectively. The aforementionedconfinement pressure values were applied inorder to achieve dry densities similar to thatobtained by Proctor tests. When comparinglaboratory results to dry filed densities, it wasfound that (SGC) test results were slightly closerto them than Proctor tests results. Nevertheless,the difference between (SGC) and Proctor testsresults seems to be insignificant for these typesof soil compared to the higher effort needed toperform (SGC) tests.
In Iraq some pavements of the newly constructed highway appear precocious distresses with unfavorable implications especially on the safety and the frugality. Cracking and permanent deformation are main types of these failures. The filler is doubtful to be a master contributor to these failures where its content has a significance effect on the mixture stiffness, and thereby affect the HMA pavement performance. The main objective of this research is to appreciate the influence of different contents of filler on the volumetric properties of asphaltic mixtures thus performance of asphalt mixtures through Comparative Evaluation between conventional Marshall Method and Super pave system. The implementation of a detailed experimental work is carried out to achieve the study objectives through the preparation of asphalt concrete samples using aggregate from Al-Nebaie quarry, (40-50) asphalt cement from Dourah refinery and limestone dust filler with four different contents of (0%, 4%, 8%, and 12%) by weight of the total aggregate. The volumetric properties for each mix design method are evaluated using Marshall Test and the Super pave Gyratory Compacter. The influence of filler contents on the rendering of these mixtures was evaluated.
This paper focused on evaluating the effect of aggregate gradation and polymer modification on indirect tensile strength (ITS) and the static stiffness for hot asphalt mixtures. In particular, data from ITS tests have been processed to obtain stiffness measurements through the application of Hondros theory. The results showed that fine mixtures had a better tensile strength by 26.3% than the coarse mixtures. The effect of compaction also was examined, the results showed that samples compacted with the Superpave gyratory compactor (SGC) had an enhancement in ITS by 36.58 and 23.1% in comparison with Marshall and roller compactor respectively. Polymer modifiers were used to estimate their effect on tensile strength, adding 4, 6, and 8% of Styrene-Butadiene-Styrene (SBS), which can rise the ITS by 3.2,6.14 and 13.3% of the non-modified asphalt mixture. Furthermore, using 4, 6, and 8 percent of SBS could increase static stiffness by 53.9, 209.6, and 302.4% respectively for roller compacted fine mixes and 58, 220, and 379.3% for SGC compacted mixes. Furthermore, SBS raised the stiffness modulus by 52.3, 188, and 295% for Marshall compacted mixes. Using hybrid modifier can improve the stiffness of the asphalt mixture. However, The results indicate that using 1, 2 and 3% polyvinyl chloride (PVC) can magnify the stiffness of mixtures by 41.2, 199.8% and 262.6 for roller compacted mixtures and 133.4, 212.1 and 354% for SGC compacted mixtures, whereas there is a stringent increasing by 133.4, 189.2 and 354% for Marshall compacted mixes. Otherwise, polymer-modification can decrease the fracturing index for coarse and fine mixtures.