Effect of Sugar as an Additive on the Longevity of Salt on Pavements
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In winter maintenance of roads chemicals are applied to the road with the aim ofensuring that the friction is at an acceptable level so that the road is safe andaccessible. Sodium chloride is a common used chemical due to its effect and price.There is however negative impacts related to the use of salt, it is not good for theenvironment (like vegetation and groundwater). A reduction of the salt usage istherefore highly desirable. One way of reducing the salt applied on the roads, is toreplace parts of it with other more environmental friendly substances that gives thesame or better effect or/and an increased longevity. SafeCote is an additive that hasbeen more and more used in the recent years in some countries of the world.According to the manufacturer this product both makes the salt more effective onlower temperatures and gives an increased longevity.This thesis studies the effect of sugar (which is one of the components in SafeCote)as an additive has on the longevity of salt. To study this, it first had to be collectedinformation about what has been done in this area before. Therefore the thesispresents an overview of literature on residual salt, like mechanisms that remove saltfrom the road and the believed effect of dissolution of salt in these loss mechanisms.The laboratory experiment conducted in this thesis was new and unknown, so ascope of the thesis was also to develop the experiment and make a judgement overwhat could be changed in further work on the experiment. In the experiment asphaltsubstrates are applied with different salt/sugar solutions, and after it had dried thesubstrates were rinsed with water to simulate rain. Conductivity of the water that hadbeen on the substrates was measured, and in that way the residual salt on thesubstrate could be calculated.The results from the experiment showed that the more sugar was added, the moreresidual salt was left on the substrate. After first rinse in room temperature theNaCl/sugar mixes 90/10, 50/50 and 33/67 had respectively 27%, 46% and 81% moreresidual salt on the substrate than NaCl with no added sugar. After five rinses therewas almost no difference between them. When moving the experiment into the icelaboratory, where NaCl with no sugar and NaCl/sugar 50/50 were tested, the resultsshowed that NaCl/sugar 50/50 had an amount of residual salt after first rinse that wasonly 16% higher than NaCl with no sugar. However, compared to tests performed inroom temperature, there was a difference after five rinses. NaCl/sugar 50/50 had atthis stage 24% more residual salt left on the substrate than NaCl with no sugar. Onepossible hypothesis that explains the results might be that the dissolution rate isslowed down when sugar is added. The experiment should be performed in an ice laboratory to ensure that it has thesame temperature as out on the roads in the winter. Further development of theexperiment should focus on how the water is applied and how to make it run off. Theexactly same procedure for these operations is not possible for a human to repeatseveral times. To get a more reliable experiment the operations mentioned should be done in other ways.