Laboratory Testing of Nontraditional Additives for Stabilization of Roads and Trail Surfaces

Recently the Pacific Northwest Region of the U.S. Department of Agriculture Forest Service conducted laboratory tests evaluating the expected field performance of various additives on dense-graded aggregate. Additives used in the laboratory analysis included chlorides, clay, enzymes, lignin sulfonate, synthetic polymer emulsions, and tall oil emulsions. Laboratory analysis included indirect tensile strength and durability testing on AASHTO T 99 fabricated samples. Durability was evaluated after a number of wet-dry and freeze-thaw cycles. Other variables in the study included the amount of additive and the cure (temperature and time) before testing. Findings and observations include the following: (a) Untreated dense-graded aggregate provides little tensile strength in warm dry climates, (b) Chlorides, clay additives, enzymes, and sulfonate provide some tensile strength in warm dry climates. With increasing moisture contents they lose their tensile strength, (c) Once cured, synthetic polymer and tall oil emulsions provide significant tensile strength in warm dry climates. In wet climates these additives would tend to break down with increased exposure to moisture or freezing. (d) Increasing the percent residual (solids) of the synthetic polymer emulsions and tall oil emulsions increases the tensile strength and durability of the treated material, (e) Cure temperature has a dramatic impact on tall oil emulsions’ tensile strength and durability resistance. (f) The use of nontraditional additives can be cost-effective depending on the projects’ objective, the type of in-place material, and the cost of the additive.