Mix design is the main stage in the cold recycling procedure. Human plays an important role in all mix design procedures such as task 38 AASHTO method. This factor leads to imposing the high cost and the low quality in the mixture production. In this study, a mathematical model was developed to determine the percentage of optimum bitumen emulsion in the Cold In-Place Recycling Mix Design. The mix design results of task 38 AASHTO were considered as model inputs. Firstly, the equations of effective parameters with respect to the recycled material’s mix design were determined by the least square method and then percentage of optimum bitumen emulsion was determined by the SIMPLEX method. To validate the model, six cold recycling mix designs from the QoochanChenaran road in the province of Khorasan Razavi, Iran, were studied and results were examined by considering bitumen emulsion as an additive material. It was found that an excessive percentage of bitumen emulsion consumption, not only leads to the increasing expenses but also affects the recycled materials’ quality.
