<p><p><figure id='attachment_3335' style='max-width:430px' class='caption aligncenter'><img class="wp-image-3335 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of bridge, the Storrow Drive Connector, part of the Boston Central Artery Project." width="430" height="266" /><figcaption class='caption-text'> Storrow Drive Connector, Boston Central Artery/Tunnel Project, Massachusetts. (Photograph from EPA-530-K-05-002 (2005), courtesy of U.S. Environmental Protection Agency.)</figcaption></figure></p><p><div><h2>Project Summary/Scope:</h2>Approximately 3.8 million yards of concrete containing a 30% coal fly ash mix were used in the sprawling Boston Central Artery/Tunnel project. This was one of the largest and most technologically challenging highway projects in the United States.</p><p>The project consisted of the replacement of a six-lane elevated highway with an eight- to 10-lane underground expressway directly beneath the existing road, culminating in a two-bridge crossing of the Charles River. It also included the extension of Interstate 90 (the Massachusetts Turnpike) from its current terminus south of downtown Boston through a tunnel beneath South Boston and Boston Harbor to Logan Airport.</p><p>Coal fly ash was used as part of the concrete design and specification because of its resistance to alkali reactivity and low heat of hydration.</p><p>Using these mix-designs allowed for the elimination of construction joints, which in turn helped the construction schedule and allowed for very large placements - up to 1,400 cubic yards in a single pour. At the same time, the fly ash used in place of cement will prevent the generation of approximately 335,000 tons of greenhouse gases.</p><p></div><h2>Project Technical Paper:</h2>EPA (2005) Report No. EPA-530-K-05-002<br><h2>Date Case History Prepared:</h2>November 2012</p><p>&nbsp;</p></p>