Evaluation of a Roller Method for Geochemical Leach Testing
Currently, multiple tests are being used when evaluating an MSE wall backfill material for pH, conductivity, chloride concentration, and sulfate concentration. There is no one test to measure all four characteristics when testing a soil. Texas Department of Transportation (TxDOT) uses four different tests to measure these characteristics. The goal of this research was to refine a simplified test procedure that was created by David Borrok et al., the Tex-620-M. The method that was developed to replace the current TxDOT test procedures Tex-620-J, Tex-128-E, and Tex-145-E test procedures is the Tex-620-M2. Leaching kinetics were analyzed for gravel and fines by performing 24-hour tests, and a duration of one hour was selected for the Tex-620-M2 method. The results from tests carried out as per Tex-620-M2 were compared to current TxDOT test procedures. Each TxDOT test was compared based on the respective analyte (i.e., pH, electrical conductivity, chloride concentration, and sulfate concentration). Finally, the results from Tex-620-M2 were compared to the results from the current standards used by other agencies. Comparison of results of the Tex-620-M2 test procedure to the current TxDOT standards for soils passing a No. 40 sieve showed that the Tex-620-M2 method generally leached more chloride and sulfate and resulted in greater conductivity than the current TxDOT standards. Comparison of results from Tex-620-M2 analysis of TxDOT AS, BS, and DS size distributions against results from current standards showed that the current standards are biased to show greater conductivity and chloride and sulfate concentrations because the current methods specify using a finer material. Overall, the proposed test procedure Tex-620-M2 seems to be a simple, comprehensive, and reliable test for highway agencies to consider.
Svede, Troy Allen, "Evaluation of a Roller Method for Geochemical Leach Testing" (2017). ETD Collection for University of Texas, El Paso. AAI10620215.