Evaluation of Dust Suppressants for Gravel Roads: Methods Development and Efficiency Studies

Abstract: Application of the proper dust suppressant to a gravel road ensures road safety and riding comfort as well as creating a cleaner and healthier environment for residents in buildings adjacent to the road. It also reduces the need and cost for vehicle repair, road maintenance activities, and aggregate supplementation. Both field-based and laboratory research, using newly developed methods, were performed to evaluate the efficiency of various suppressants and the influence such factors as product concentration, leaching, and fine material content have on the efficiency of different products. A significant problem when using dust suppressants is their tendency to leach during rainfall due to their soluble properties. Residual chloride could be detected in the gravel wearing course over a longer period of time than lignosulphonate and, therefore, showed more effective long-term performance. Optimal percentages of fine material for minimal lignosulphonate and chloride leaching were found to be 15 percent by weight and 10-16 percent by weight, respectively. By applying a calcium- or magnesium chloride solution instead of traditionally used solids, the cost for annual dust control, as well as the environmental impact from the release of these chemicals in the environment, can be reduced by 50 percent. Ions of calcium chloride seemed to initiate flocculation of clay particles, thereby preventing them from leaching. Still, the fine material in gravel wearing courses has to be replenished regularly as indicated by studies of the longevity of fine material. Loss up to 80 percent was found after two years. Toxicity tests show that dust suppressant application for dust control purposes, at traditionally used application rates, does not constitute a threat to sensitive aquatic life. Tests on subsoil water samples indicated elevated chloride levels, which possibly could cause corrosion to pipes, but not high enough to flavour drinking water.