This report describes an investigation that took place at Aalto University commissioned by the Finnish Transport Agency about asphalt dust containing OKTO-aggregate. In the fall of 2013, Finnish newspaper headlines began to raise the issue of the occurrence of damaged timing belts in the Oulu region. It seemed to only concern certain models and was found in the form of a dust. The press reasoned that this "mysterious" dust must have originated from the aggregates abraded from the local Oulu roads. More specifically, it was attributed to the OKTO-aggregate used in surface wearing course mixtures on high traffic volume roads.
The OKTO-aggregate (OKTO-murske in Finnish) is a brand name for the man-made byproduct of the smelter slag from the Outokumpu Tornio ferrochromium plant. Natural rock aggregates are substituted by this material in high volume roads due to its excellent abrasion resistance against studded tire wear.
The conclusion is that the possible contribution of OKTO-aggregate to the mechanical breakage or abrasion of car parts was considered insignificant compared with the other fragments, such as corundum, that were also detected in the car dust. Furthermore, OKTO-aggregate was found to be much less reactive with deicing salts than the rock aggregate used in the Oulu region. Therefore, the OKTO-aggregate does not significantly contribute to the chemical corrosion of car parts
