<p><p><figure id='attachment_2538' style='max-width:448px' class='caption aligncenter'><img class="wp-image-2538 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of a mixer incorporating lime into a subgrade soil." width="448" height="323" /><figcaption class='caption-text'> (Photograph courtesy of Carmeuse Lime &amp; Stone, from www.carmeusena.com)</figcaption></figure><h2>Basic Function:</h2>Chemical stabilization with admixtures of subgrades and base courses can be used to control swelling and frost heave and improve the strength and deformation characteristics of soils.<br><h2>Advantages:<em> </em></h2><ul> <li>Applicable to all soil types</li> <li>Reduces plasticity index, water absorption, swelling potential, compressibility, and increases strength with time</li> <li>Speeds up construction</li> <li>Improves durability</li> <li>Increases stiffness of subgrades and base courses</li></ul><h2>General Description:</h2>Admixtures such as lime, cement, fly ash, and asphalt are mixed with subgrade soils to reduce swelling and frost heave. Admixtures are also used to improve strength, deformation characteristics, and stability of soils.<br><h2>Geologic Applicability:</h2><ul> <li>Cementing coal fly ash is suitable for cohesive and granular materials.</li> <li>Lime and cement mixtures are applicable to high plasticity clay soils.</li> <li>Fly ash is suitable for soils that contain little or no plastic fines.</li> <li>Asphalt stabilization is suitable for silty, sandy, and granular materials.</li> <li>Cement Kiln Dust (CKD) stabilization and lime stabilization are applicable to treat expansive clays.</li> <li>A high water table in silts and very fine subgrades may cause compaction operations to pump water to the surface.</li></ul><h2>Construction Methods:</h2>Specific chemicals and methods are recommended for different soils types. Hydrated lime is used to stabilize cohesive soils and granular soils. Lime should be considered with the plasticity index of the soils is greater than 12. The lime can be used to help create a construction working platform. Portland cement is generally used in non‑plastic soils. Chemical stabilization is generally performed to a depth of 6 to 12 inches (150 to 300 mm). To complete stabilization of soils to depths greater than 12 inches (300 mm), removal and pugmill mixing is generally required.<br><h2>Additional Information:</h2>Lime reduces the plasticity index and reduces the sensitivity of clay soil to moisture change. Chemical stabilization is marginal in helping New Embankment and Roadway Construction over Unstable Soils. Changing the physical properties of a soil through chemical stabilization may make the soil susceptible to frost heave.<br><h2>SHRP2 Applications:</h2><ul> <li>New Embankment and Roadway Construction over Unstable Soils</li> <li>Roadway and Embankment Widening</li> <li>Stabilization of Pavement Working Platforms</li></ul><h2>Example Successful Applications:</h2><ul> <li>Kentucky Route 11 – KY</li> <li>Washington Dulles International Airport – VA</li> <li>State Highway 32 – Port Washington, WI</li></ul><h2>Complementary Technologies:</h2>Mechanical stabilization<br><h2>Alternate Technologies:</h2>Combination of geotextiles and geogrids, mechanical stabilization through mixing aggregate with fine-grained subgrade, dynamic compaction, paper sludge, and blast densification.<br><h2>Potential Disadvantages:</h2><ul> <li>The absence of an allowance for stabilized subgrade support in current pavement design codes.</li> <li>Dust is produced by some processes in construction.</li> <li>No long-term performance data.</li></ul><h2>Key References for this technology:</h2>Christopher, B.R., Schwartz, C., and Boudreau, R. (2006). “Chapter 7 in Geotechnical Aspects of Pavements.” Rep. No. FHWA-NHI-05-037, U.S. Department of Transportation, Federal Highway Admin., Washington D.C.</p><p>Rollings, M.P., and Rollings, R.S. Jr. (1996). Geotechnical Materials in Construction. McGraw-Hill, New York, NY, 249-312.</p></p>