<p><p><h2>Preferred QC/QA Procedures</h2>Currently, there is no FHWA or other methodology that addresses QC/QA procedures or provides guidelines to use in conjunction with bio-treatment technology. This technology is in the research phase. Most experiments are confined to laboratory studies, and there is some, but limited, field use. All of the QC/QA procedures refer to lab tests on field samples. Different types of lab testing methods have been used to measure engineering properties of bio-treated soils and can be broadly categorized into the following:<br><ul> <li>Shear wave velocity test</li> <li>Laboratory triaxial tests</li> <li>Scanning electron micrographs and X-ray compositional mapping</li> <li>Compression wave velocity tests</li> <li>Resistivity measurements</li> <li>Microorganism physiological classification</li> <li>Oedometer experiments</li> <li>Urease activity monitoring</li></ul>Since some bio-treatment methods are similar to chemical stabilization, QC/QA procedures used for chemical stabilization can be used for bio-treatment. Please refer to the <em>QC/QA Procedures </em>document for chemical stabilization of subgrades and bases for additional QC/QA procedures that are not specific to this technology.</p><p>Construction quality is achieved by meeting established requirements, as detailed in project plans and specifications, including applicable codes and standards. Quality Control (QC) and Quality Assurance (QA) are terms applied to the procedures, measurements, and observations used to ensure that construction satisfies the requirements in the project plans and specifications. QC and QA are often misunderstood and used interchangeably. Herein, Quality Control refers to procedures, measurements, and observations used by the contractor to monitor and control the construction quality such that all applicable requirements are satisfied. Quality Assurance refers to measurements and observations by the owner or the owner's engineer to provide assurance to the owner that the facility has been constructed in accordance with the plans and specifications.</p><p>The components of QC/QA monitoring programs for bio-treatment for subgrade stabilization are listed in Tables 1, 2, and 3. The entries in the tables are a list of typical items, not a list of all methods that could be used for QC/QA. Some QC procedures and measurement items may also serve as QA procedures and measurement items.<br><h3><strong>TABLE 1. TYPICAL EXISTING QC/QA PROCEDURES AND MEASUREMENT ITEMS</strong></h3><table class='tablepress' id='tablepress-1918'><thead><th><center>QC or QA</th><th><center>Material or Process</th><th><center>Items</th></thead><tbody><tr><td ><center>QC</td><td ><center>Material Related</td><td >•Subsurface conditions
•Wave velocity
•Resistivity
•Micro-structure
</td></tr><tr><td ><center>QC</td><td ><center>Process Control</td><td >•Curing time
•Microorganism selection
•SEM
•Compositional mapping
</td></tr><tr><td ><center>QA</td><td ><center>Material Related</td><td >•Subsurface conditions
•Wave velocity
•Resistivity
•Micro-structure
</td></tr><tr><td ><center>QA</td><td ><center>Process Control</td><td >•Curing time
•Microorganism selection
•SEM
•Compositional mapping
</td></tr></tbody></table><br><h3><strong>TABLE 2. PERFORMANCE CRITERIA USE IN QC/QA MONITORING PROGRAMS </strong></h3><table class='tablepress' id='tablepress-1919'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Parameters</td><td >•Unconfined strength with time
•Mass change
•Bearing capacity
•Stiffness/modulus
</td></tr><tr><td ><center>System Behavior</td><td >•Settlement
•Uniformity
</td></tr></tbody></table><br><h3><strong>TABLE 3. EMERGING QC/QA PROCEDURES AND MEASUREMENT ITEMS</strong></h3><table class='tablepress' id='tablepress-1920'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Related</td><td >•Resilient modulus of stabilized samples</td></tr><tr><td ><center>Process Control</td><td >•Intelligent compaction and intelligent mixers</td></tr></tbody></table></p></p>
<p><p><h2>QC/QA Guidelines</h2>Inspections, construction observations, daily logs, and record keeping are essential QC/QA activities for all technologies. These activities help to ensure and/or verify that:<br><ul> <li>Good construction practices and the project specifications are followed.</li> <li>Problems can be anticipated before they occur, in some cases.</li> <li>Problems that do arise are caught early, and their cause can oftentimes be identified.</li> <li>All parties are in good communication.</li> <li>The project stays on schedule.</li></ul>Additional technology-specific details for inspections, construction observations, daily logs, and record keeping QC/QA activities are provided in the <em>Individual QC/QA Methods </em>section below.</p></p>
<p><p><h2>References</h2>DeJong J.T., Fritzges M.B., and Nusslein K. (2006). “Microbially induced cementation to control sand response to undrained shear”. <em>Journal of Geotechnical and Geoenvironmental Engineering, </em>132(11): 1381-1392.</p><p><a href="http://ascelibrary.org/doi/abs/10.1061/%28ASCE%2910900241%282006%29132%… J.T., Mortensen B.M., Martinez B.C., and Nelson D.C. (2010). “Bio-mediated soil improvement”. <em>Ecological Engineering</em>, Volume 36, Issue 2, pp. 197-210.</p><p>Ivanov V. and Chu J. (2008). ‘Application of microorganisms to geotechnical engineering for bioclogging and biocementation of soil in situ”. <em>Rev Environ Sci Biotechnol, </em>7:139–153.</p><p>Neumeier U. (1999). “Experimental modeling of beachrock cementation under microbial influence.” <em>Sedimentary Geology</em>, 126, 35–46.</p><p>Perkins, S.S., Gyr, P., and James, G. (2000). “The influence of biofilm on the mechanical behavior of sand.” <em>ASTM Geotechn. Testing J.</em> 23 (3), 300–312.</p><p>Whiffin V.S., van Paassen, L.A., and Harkes M.P. (2007). “Microbial carbonate precipitation as a soil improvement technique”. <em>Geomicrobiol. J.</em> 25 (5), 417–423.</p><p> </p></p>