Predicting Dust Palliative Effectiveness on Unpaved Roads Using a Simple Laboratory Procedure

Abstract The effectiveness of palliatives such as hygroscopic salts and synthetic fluids in reducing dust emissions from unpaved roads and surfaces is well established. However, the performance of various products designed to minimize the loss of fine aggregate particles has primarily been assessed by observing the intensity of dust plumes generated by moving vehicles. Currently, there is no standardized laboratory test available to predict the performance of dust palliatives. This study presents a laboratory methodology capable of evaluating the effectiveness of palliatives applied to unpaved aggregate surfaces. The methodology assesses the ability of palliatives to retain dust size particles by measuring the total mass of PM 10 (particulate matter less than 10 μm in diameter) present in material abraded from the treated aggregate surface. Total mass is determined by analyzing PM 10 concentrations in settling dust produced when a sample is propelled into a column. PM 10 concentrations in the column are measured using a commercially available nephelometer. Five different commercially available palliatives are assessed using this methodology: two types of synthetic fluids, two emulsion products, and calcium chloride. Results demonstrate that the proposed test methodology can effectively differentiate between the PM 10 retention capabilities of various palliatives applied at identical application rates. Additionally, the methodology is capable of distinguishing PM 10 retention at different application rates for the same palliative. Among the five products evaluated, one of the emulsion products marginally outperformed the others in terms of retaining dust-sized particles. Most tested products reduced dust-sized particle emissions by 99% or more. The test methodology is straightforward and provides repeatable results. Furthermore, its ability to differentiate PM 10 retention capabilities between different products and application rates highlights its high resolution. Minor limitations exist within the methodology due to the inherent heterogeneity of compacted aggregates; however, these can be mitigated through careful sample preparation.