Procedures for Bench-Scale Tests

Procedures used by EarthFax Development were developed based on the extensive experience  of EarthFax Engineering geotechnical engineers in the performance of bench-scale tests. Results of these tests have been used to successfully design projects for the solidification/stabilization of over 400,000 yd3 of sludges and contaminated soils.

EarthFax has found that it is convenient to conduct bench-scale tests in plastic cylinder molds. Typically, each phase of bench-scale testing requires 8 to 10 weeks, depending on the need to evaluate pre- solidification. This allows sufficient time to cast and cure the cylinders and perform the physical and chemical laboratory tests. As a result, bench-scale tests need to begin at least 2 to 3 months before the specifications are due, depending on the scope of testing.

If time and budget permit, bench-scale tests should be conducted in two phases. The first phase involves using 2 or 3 of the most cost-effective reagents with 2 or 3 reagent contents. After these cylinders have been tested, the effectiveness of each mix design can be evaluated and the most effective 1 or 2 conditions can be selected for additional testing. Although this approach requires additional time, the resulting conclusions are generally better optimized for the site.

Bench-scale testing should be designed on a project-specific basis. However, typical
procedures followed by EarthFax include:

• Determine the chemical characteristics of the untreated waste.
• Mix the waste types as appropriate and determine unit weight.
• Pre-solidify the waste if necessary.
• Mix the waste with the appropriate reagents and cast sufficient cylinders for physical and chemical tests (typically 8 cylinders per reagent mix).
• Conduct pocket penetrometer tests to determine the daily strength gain.
• Submit selected cylinders for unconfined compression tests and leachate chemical tests.
• Prepare a report of findings.