<p><p><figure id='attachment_946' style='max-width:1200px' class='caption aligncenter'><img class="wp-image-946 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Micro-photographs of untreated sand and sand treated with iron based biocement." width="1200" height="473" /><figcaption class='caption-text'> Left: Light microscope photos of untreated sand. Right: sand treated with the iron based biocement (Photos courtesy of Chu et al. 2011, with permission from ASCE).</figcaption></figure></p><p>Bio-treatment for subgrade stabilization involving chemical and biological reactions can modify and enhance the physical and mechanical properties of earth materials. Unstable soils can be made sufficiently strong and durable, and also improve the sustainability and stability of geotechnical engineering practices. This technique is applicable to stabilization of the pavement working platform and embankment widening.</p><p>