The results of a survey of recent literature on the topic of dust palliatives for unsealed roads are presented, and an investigation is described that was conducted during 1994, using a number of palliative products in road test sections constructed and monitored by the Far North District Council (FNDC) and the Western Bay of Plenty District Council (WBPDC), North Island, New Zealand.
Both investigations trialled proprietary products, Weslig 120 and Borresperse CA, as well as bituminous emulsion. In addition, the WBPDC trial included one test section using waste oil (which could be trialled because the Council had an existing Consent under the Resource Management Act 1991). The FNDC test sections were constructed using both stabilisation and surface dressing techniques, while the WBPDC test sections used the surface dressing technique only.
The test sections were monitored by photographing the dust plume generated by a test vehicle trafficking each test section at regular intervals, over a period of five to eight weeks. The results showed that waste oil was the most effective and economical dust palliative. The other palliatives appeared to be effective to varying degrees but only for a relatively short duration. The stabilisation construction technique was found to be the most effective, except for bituminous emulsion which appeared to give a similar result for both construction techniques.
The economics of dust control depend on the situation, e.g. traffic type and frequency, aggregate type, road maintenance practices, and cost of available palliatives. Use of waste oil (subject to a consent under the Resource Management Act 1991) could result in savings in annual maintenance costs of $360/km. Use of the other dust palliatives could involve increases to annual maintenance costs of around $800/km.
The photographic monitoring technique provided reasonable results in the FNDC investigation. However some inconsistencies were identified in the WBPDC results. further research of dust monitoring techniques is recommended.
Keywords: Bitumous emulsion, Borresperse CA, dust, dust palliative, lignosulphonates, New Zealand, roads, unsealed roads, waste oil, Weslig 120