فهرست مطالب hasan mohammadi anaie

Overburdens are stones that lack the required properties of minerals to be extracted and are piled adjacent to mine, while they may be used as aggregates in the asphalt mixture. Set-tlement is a cheap mineral composed of iron oxide, silicone and aluminum oxide, application of iron, silica and aluminum as aggregates in pavement industry has great effect on per-formance of asphalt mixtures. In this study, we investigated the effect of using Sillimanite aggregate material as an alter-native for Limestone aggregates on resilient modulus, Mar-shall Strength and skid resistance parameters at various tem-peratures. The modeling was carried out by using finite ele-ment software based on the elastic behavior of the layers to determine the effect of elasticity modulus variations due to the change in aggregate type on the pavement response. The re-sults indicated that the use of Sillimanite aggregates in the asphalt mixture led to a lower optimum bitumen percent than Limestone material; and also, in the asphalt mixture made of Sillimanite aggregates with optimum bitumen percent, Mar-shall Strength was increased by 15% and the resilient modulus by 25% compared to the mixture with Limestone material. Application of Sillimanite material in the asphalt mixture could enhance the friction resistance of the mixture against the abrasion resulting from traffic loading due to its higher hardness compared to Limestone material. The results of nu-merical analysis showed that the aggregate’s type had the lowest effect on the critical tensile strain at the bottom of the asphalt layer, then came the percentage of bitumen in the mix-ture and, finally, the bonding of the layers had the highest ef-fect.

Construction of roads and development projects on sandy soils is usually done due to lack of adequate strength to the displacement of subgrade soil or redirecting. Therefore, stabilization and investigation of the factors affecting its strengthening with different materials have always been of interest to the researchers. Studies have shown that the use of polypropylene fibers generally increases the ductility and mechanical strength, such as compressive strength and shear strength, of soils. On the other hand, the initial moisture content plays an important role in stabilizing with emulsion bitumen. Therefore, in this study, the stabilization and improvement of dune sand, using different initial moisture contents, emulsion asphalt binder, and fiber in optimum cement percent were considered. Uniaxial compressive test results showed that addition of fiber increases the bearing capacity by an average of 10%. Increasing the initial moisture content increased the strength performance of the sand subgrade and then decreased in high moisture contents. Also, increasing the percentage of emulsion asphalt binder and fiber had a significant impact on the enhancement of stabilized subgrade ductility.