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Huge amount of sulfur production as a side product in petrochemical industries and its low application in country has been a challenging issue. In this paper, application of sulfur as a partial substitute for bitumen in process of asphalt mixture production is investigated. According to the results, the characteristics of the sulfur extended asphalt in comparison with the conventional asphalt made from pure bitumen, and the impact of sulfur addition on asphalt performance are expressed and the optimized formula for making the asphalt mixture is obtained. In this content, the modified asphalt was produced in mass production scale and its performance was studied. In this paper, the method of sulfur addition to pure bitumen and then its mixture with aggregate and finally optimized condition of sulfur modified asphalt production regarding pollution and environmental issues are also proposed.

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The standardized FAO-56 Penman-Monteith (PM) equation requires a great number of input parameters that are difficult to record. The Hargreaves method is another approach. It has high accuracy, while it requires fewer input parameters. In the present study, the Hargreaves-Samani method was calibrated by the PM equation under different climate conditions, in the western Iran. Different correction coefficients were used for each station under study instead of the constant coefficient 0.0023 in the Hargreaves equation based on monthly and annual scales. The corrected coefficients obtained for different regions can be used to estimate ETo for the PM method under the same climates where reliable data are available. The results also showed that as a larger study area with more weather stations is used and a larger amount of data is obtained, the coefficient of 0.0023 in the Hargreaves equation does not need further corrections for local calibration purposes.