The Ohio Department of Transportation (ODOT) pretreats the roadways of Ohio two times a week with 23% NaCl at 40 gallon/lane*mile application rate when weather conditions warrant. To be able to come up with the most effective anti-icing program for ODOT, field and laboratory investigation of pretreatment was studied on pavements.
Brine decay was studied on highways ATH-50 PCC and PICK-23 AC versus time, traffic and humidity. The field tests for brine were conducted with modified versions of the SOBO 20 by Boschung Megatronic AG (YSI and Wally BO). Humidity values were obtained from RWIS data.
The laboratory part included the detailed investigation of issues encountered in the field due to the grooved texture of concrete and porous texture of asphalt pavements. Correction factors for the salt readings on porous asphalt and grooved concrete surfaces were developed. Based on lab data grooved and porous surfaces appeared to decrease the efficacy of pretreatment. Correction equations due to pavement-fluid temperature difference were developed. A roadway field study (Della Drive) was conducted on a non-trafficked road to study application of salt at two different truck speeds. An in situ test was conducted using CaCl2 and NaCl (brine) on street adjacent to Stocker Engineering building in order to compare the effectiveness of two anti-icing chemicals. CaCl2 survived on the pavement for about the same time compared to NaCl; however, it is seven times more expensive according to pretreatment needs of Ohio.
The modeling of the salt decay on state roads (versus time and traffic) provided statistically good results with high R2 values. The laboratory data were integrated with the field study results by the construction of a decision tree which is the product of this dissertation study. Remaining salt density after certain time or traffic can be found from the decay equations for porous and grooved pavements and the freezing point temperatures can be obtained before an ice/snow event. By this way, the ODOT personnel can decide when to pretreat and can know to what temperature extent the salt on the pavement is effective.