A laboratory experiment was conducted to evaluate the stabilization of low- and high-plasticity clay soils with nontraditional chemical or liquid stabilizers. Clay soil specimens were mixed with various stabilization products and compacted using a gyratory compaction machine to approximate ASTM D1557 moisture–density compaction. Each specimen was subjected to wet and dry testing following a 28-day cure. Twelve nontraditional stabilizers were evaluated, including an acid, enzymes, a lignosulfonate, a petroleum emulsion, polymers, and a tree resin. Additional specimens were stabilized with Type I portland cement and hydrated lime for comparison with traditional stabilizers under the same mixing, compaction, and curing conditions. Analysis of the test data consisted of determining the average strength, in terms of unconfined compressive strength, of three replicate specimens of each mixture. The average strength of the three replicates of each additive was compared with the average strength results of the remaining nontraditional additives, the traditional stabilization results, and a series of control specimens that were not stabilized. The experiment results indicate an increased strength of some nontraditionally stabilized specimens when compared with that of both the control series and the traditional stabilization alternatives. Other nontraditional stabilizers did not demonstrate significant increased strength compared with that of the control series for the conditions of this experiment. Many of the stabilized specimens were highly susceptible to moisture, indicating the potential for poor performance when exposed to adverse environmental conditions, whereas a few specimens demonstrated excellent performance when exposed to moisture. Specific product categories are recommended for stabilizing low- and high-plasticity clay soils.

Because of the high cost of quality construction materials, transportation engineers are often forced to seek alternative designs using substandard materials, commercial construction aids, alternative pavement materials, and innovative design practices. Nontraditional soil stabilization additives are being marketed as viable solutions for stabilizing marginal materials as a low-cost alternative to traditional construction materials. Nontraditional additives are diverse in their composition and the way they interact with soil. Unfortunately, little is known about their interaction with geotechnical materials and their fundamental stabilization mechanisms. The objective of this research was to advance current understanding of the chemical and physical bonding mechanisms associated with selected non-traditional stabilizers. The research consisted of conducting qualitative analyses of hypothesized stabilization mechanisms, examining historical literature for supporting documentation, and performing laboratory experiments to improve the understanding of how these nontraditional additives stabilize soils. Laboratory experiments included image analyses, physical characterization, and chemical analyses to determine the primary constituents of the mineral, soil, stabilizer, and stabilized soil composite. The focus of this effort was to provide insight into the proposed mechanisms by using the laboratory data to examine proposed mechanisms from the historical literature and to provide additional hypotheses for the interaction between nontraditional additives and different soil types.

A laboratory experiment was conducted to evaluate the stabilization of a silty-sand (SM) material with nontraditional chemical or liquid stabilizers. SM soil specimens were mixed with various stabilization products and compacted using a gyratory compaction machine to approximate ASTM D1557 moisture-density compaction. Each specimen was subjected to wet and dry testing following the designated cure period. Twelve nontraditional stabilizers were evaluated in this experiment, including acids, enzymes, lignosulfonates, petroleum emulsions, polymers, and tree resins. Additional specimens were stabilized with an asphalt emulsion, cement, and lime to provide a comparison with traditional stabilizers under the same mixing, compaction, and curing conditions. The analysis of the test data consisted of determining the average strength, in terms of sustained load, of three replicate specimens of each mixture. The average strength of the three replicates of each additive was compared with the average strength results of the remaining nontraditional additives, the traditional stabilization results, and a series of control specimens that were not stabilized. The results of the experiment indicate increased strength of some nontraditionally stabilized specimens compared with that of both the control series and the traditional stabilization alternatives. Other nontraditional stabilizers did not demonstrate significantly increased strength compared with the control series for the conditions of the experiment. Many of the stabilized specimens were highly moisture susceptible, indicating the potential for poor performance when they are exposed to adverse environmental conditions, whereas a few specimens demonstrated excellent performance when exposed to moisture. Specific product categories are recommended for stabilizing SM soils.

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Abstract:In support of the U.S. Air Force Air Combat Command, the U.S. Army Engineer Research and Development Center (ERDC) was tasked to develop and test innovative techniques, materials, and equipment for expedient and sustainment repairs of small bomb craters in airfield pavements. This airfield damage repair (ADR) investigation consisted of laboratory testing of selected crater fill and capping materials, as well as full-scale field testing of small crater repairs to evaluate field mixing methods, installation procedures, and repair performance. After 3 hr of cure, each crater was trafficked under controlled traffic conditions to determine the ability of the repairs to support the gross load of an F-15E aircraft. Results of the traffic tests identified multiple repair materials that can be used for expedient and sustainment repairs of concrete airfield pavements. Both the laboratory and full-scale traffic tests were conducted at the ERDC in Vicksburg, MS, from February to November 2006. Experimental results were used to develop ADR criteria for rapidly repairing small craters.

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A laboratory experiment was conducted to evaluate the effect of two products used to accelerate strength improvement of a silty sand (SM) material stabilized with nontraditional stabilizers. SM soil samples were mixed with selected products and tested under both “wet” and dry conditions after 1- and 7-day cures. Nine nontraditional stabilizers, including lignosulfonates, polymers, silicates, and tree resins, were evaluated in this experiment. Two accelerator products, an acrylic polymer and Type I portland cement, were evaluated. Samples were also stabilized with either an asphalt emulsion or cement to provide a comparison for traditional stabilizers under the same conditions. The average unconfined compressive strength (UCS) of three replicates of each mixture was compared with the results of the remaining mixtures, the traditional stabilization results, and a series of untreated control samples. The results indicate increased UCS of samples stabilized with Silicate 1 and Polymer 3 compared with both the untreated control series and the traditional stabilization alternatives. Lignosulfonate 1; Polymers 1, 2, 4, 5, and 6; and Tree Resin 1 did not demonstrate significant increased strength over the control series for the conditions of this experiment. The UCS following the 7-day cure provided the maximum UCS of the samples evaluated in both wet and dry conditions. One accelerator, cement, in combination with a nontraditional stabilizer did show significant improvement in early strength gain when compared to the control series.

A laboratory research program designed to investigate geotextile and geogrid reinforcement of the aggregate layer in unbound pavement sections was performed by the U.S. Army Engineer Research and Development Center. The investigation's objective was to evaluate the performance of geosynthetic-reinforced aggregate road sections over a very soft subgrade. Standard construction materials were used to construct six aggregate road sections in a large steel box. Each instrumented road section was subjected to cyclic plate load tests to evaluate the performance of the model pavement sections under simulated truck traffic. The mechanistic response and permanent deformation of each instrumented pavement section were monitored periodically during each test. Analysis of the experiment data indicated that the geosynthetics improved the performance of the reinforced pavement sections compared with the unreinforced section in terms of improved load distribution and reduced permanent deformation or rutting. Additional information regarding the reinforcement mechanisms is summarized.