Acid numbers – a criterion for the suitability of bitumen for wearing courses for slurry surfacing

Abstract

The article explores the dependence between the acid number of bitumen binders and the cohesive strength of Slurry Surfacing. To produce cationic bitumen emulsions and Slurry Surfacing, paraffinic binders from the Polish company PKN Orlen and domestic bitumen from PJSC Ukrtatnafta (Kremenchuk Refinery) were tested. Naphthenic bitumen was sourced from the Swedish company Nynas, the world’s largest producer of naphthenic bitumen. To create the cationic bitumen emulsions for Slurry Surfacing, bitumen, a cationic emulsifier (amine-based), hydrochloric acid, and drinking water were used. Emulsions were prepared in a laboratory setting using a colloidal mill. Slurry Surfacing was designed and tested following the technical bulletins of the International Slurry Surfacing Association. In addition to emulsions, the Slurry Surfacing mix included a granite crushed stone-sand mixture (0-10 mm fraction), water, portland cement, and a decomposition regulator in the form of a 10% emulsifier solution.

It was found that high-acid bitumen binders are optimal for Slurry Surfacing in terms of cohesive strength. The study confirmed that naphthenic bitumen exhibits significantly higher acid numbers than paraffinic bitumen. Additionally, Slurry Surfacing compositions based on naphthenic and paraffinic bitumen require different amounts of decomposition regulator to achieve the desired decomposition time. Specifically, formulations with naphthenic bitumen require 0.5 parts more degradation agent than those with paraffinic bitumen. Despite this increased need for degradation agent, the rate of cohesive strength gain in Slurry Surfacing samples with naphthenic bitumen is 12 times higher than that of unmodified paraffinic samples and 10 times higher than that of polymer-modified paraffinic samples.