Performance-Based Testing of Chemical Stabilizers

Abstract

Chemical stabilizing agents have been introduced that have performed in field applications to improve the behavior of earth materials. The same agents and materials subjected to standardized laboratory tests have often resulted in no improvement. For example, the tests often require pulverization of materials to finer states than are needed in the field or may require remolding when field applications are done in situ, as with injection applications. Some of the physical tests do not place treated materials in a situation resembling conditions in the field, yet they are applied to determine the use of these agents. The experiences of the author in developing performance-based testing of chemical stabilizers that better simulate field conditions are described. The situations include a physical erosion test to determine dispersion of clays that have been treated, two swell test preparation sequences simulating injection of chemicals into clays, a wet-dry test sample preparation using field gradation specifications, and a three-dimensional swell test for stability of treated clays when subjected to wetting. Also, the standardized physical test results that did not adequately represent behavior are discussed. The applications and indications of successful testing are reviewed. Possible development processes for performance-based tests, involving parameters of variance, are included for consideration.

Measured Effects of Liquid Soil Stabilizers on Engineering Properties of Clay

“…Wellestablished testing protocols are needed to quantify how much a particular stabilizer product may improve the properties of specific project soils. Laboratory testing programs of this kind must include untreated control specimens prepared in the same manner, including water content, as the chemically treated samples (12,16).…”

“…• Positive or negative results obtained in the laboratory are sometimes questioned as predictors of field performance, because laboratory sample preparation may not completely simulate field conditions. For example, it is possible to achieve more complete mixing of the chemical agent in pulverized laboratory soil samples than is possible in the field (16). However, if a chemical does not exhibit positive results in a well-pulverized laboratory specimen, it is difficult to see how better results would be obtained from less complete mixing in the field.…”

“…• A principal concern is the lack of published, independent studies of non-calcium-based stabilizers (10). Test results provided by product suppliers are not necessarily unbiased (16) and are appropriately viewed with skepticism.…”

An Experimental Study on Partial Replacement of Clayey Soil with an Industrial Effluent: Stabilization of Soil Subgrade

“…The situations included a physical erosion test to determine dispersion of clays that have been treated, two swell test preparation sequences simulating injection of chemicals into clays, a wet-dry test sample preparation using field gradation specifications, and a three-dimensional swell test for stability of treated clays when subjected to wetting. Petry (1997) used Chemical stabilizing agents to improve the behavior of earth materials. Rao and Subba Rao (1994) have discussed the cause of ground heave of an inherently non-swelling, kaolinite-rich red soil (from Bangalore, India) due to prolonged spillage of concentrated (40%, weight/weight solution) caustic soda (sodium hydroxide) solution into the sub-soil through cracked drains in an industrial establishment.…”

Evaluation of Chemical Stabilizers: State-of-the-Practice Report

“…Additionally, two comprehensive studies on the use of chemical stabilizers were conducted at the University of Arizona (3) and Iowa State University (4). In addition, two recent papers have been published by TRB summarizing the procedures for evaluating chemical stabilizers and performance-based testing of stabilized soils (8,9). Potential users of any chemical stabilizer are encouraged to review these publications prior to embarking on the evaluation of a product.…”