OPTIMIZATION OF SPREADS WITH AN INCREASED BRINE CONTENT

摘要

The determination of optimized de-icing agent application rates for typical winter scenariosand each corresponding winter maintenance strategy have been in the focus of researchat the Institute of Transportation Sciences of the Technical University of Vienna in the pastyears. Based on extensive field and lab research it was possible to determine thenecessary application rate and timing based on precipitation, road surface temperatureand traffic on the basis of a comprehensive holistic model. The model developed alsoallows estimating the development of skid resistance during maintenance intervals. Thisresearch was based on a spreading technique of pre-wetted salt called FS30. FS30 standsfor a weight based mixture of 70 % dry salt and 30 % brine (with a 20% concentration).The brine is normally produced with sodium chloride. Based on a large number ofmeasurements at different conditions, the amount of residual salt on the road surface overtime was determined. Furthermore, these residual salt measurements allowed furtherinsight into the impact of different traffic volumes and amounts of precipitation. Based onthe results of freezing and thawing experiments the strategy of preventive salting wasintroduced into practices, above all to prevent freezing and slippery roads.With the success of this preventive treatment strategy the question was raised howspreading losses of salt could be reduced so as to lead to even better results. Examiningthe effect of pre-wetted salting based on different proportions of dry salt and brine up to anamount of 100% brine proved to be the best way. Based on further extensive testing it waspossible to provide statistical evidence for an increased proportion of residual salt withhigher portions of brine. Furthermore, a means for adapting existing equipment for higherfractions of brine and the optimal brine content for different situations were investigated.With this cost efficient approach already being introduced into practice it is possible tosave about 20% of salt without the need of extensive reinvestments. Subsequently, thisalso leads to less environmental impacts while keeping the roads safe.Climate data over the period from 1896 onwards were evaluated by the Department ofHydrology of the Office of the Government of Lower Austria.. The mean change in airtemperature of the past 100 years has resulted in an increase of the mean value of +0.7℃.This long-term evaluation also shows that in Austria snowy winters have increased in thepast decade. In line with the climatic changes and the development of a new salt-savingand environmentally friendly salt spreading technique, analyses carried out show adecreasing tendency in the average salt consumption. In the past nine years, an averagereduction in salt consumption per square meter salt-spreading-area of 39 g/m~² to now 27g/m~² is demonstrated for a salt-spreading-day. This is a more than a 30% lower saltconsumption while maintaining the high quality of winter maintenance.