Large amounts of soil are excavated, piled and exposed during the construction of roads and buildings. Dry conditions and even light winds can carry away exposed portions of the soil to create airborne dust that contributes to atmospheric pollution. Regulatory bodies charged with controlling environmental pollution, including the U.S. Environmental Protection Agency, are requiring stricter pollution controls to reduce the levels of airborne dust generated by exposed construction soil.
One dust suppression method is to cover the exposed soil with a plastic tarp. This method has a number of drawbacks, including the cost of materials and the labor involved in covering and uncovering the soil with the tarp. Tarps are especially impractical for covering large areas of exposed soil typically created by road construction. Tarps are also generally inappropriate for soil being actively worked during the construction.
Another dust suppression method is to wet the exposed soil with water. The water acts as a temporary binder that holds together loose soil aggregates that may otherwise become airborne. However, water can quickly leave the exposed dirt surface through a combination of soil absorption and surface evaporation. Thus, water must be frequently applied to the dirt for dust suppression. In hot, dry environments where water quickly evaporates, the dirt may have to be wetted on an almost continuous basis.
One technique to reduce the rate at which the water evaporates from the soil is to provide a dissolved salt in the water. The salt reduces the vapor pressure of the aqueous salt water solution, which reduces the rate at which the solution evaporates from the soil. The lower evaporation rate permits less frequent applications of the solution on the exposed soil. However, salt water solutions also have a number of drawbacks as dust suppression compounds. The salt introduces an additional environmental pollutant that can harm the surrounding environment, especially surrounding vegetation. Water soluble salts are also easily washed away from the exposed soil surface by rainfall, which can carry them to nearby water resources. Thus, there is a need for new methods and compositions to suppress dust from construction site soil. This and other topics are addressed below.