Caltrans Specifications for Aggregate Base and Subbase

The California Department of Transportation (Caltrans) provides specifications for the use of recycled aggregate, sometimes referred to as crushed miscellaneous base (CMB), as base (section 26) or subbase (section 25) on road projects. This Department of Resources Recycling and Recovery (CalRecycle) webpage is a selective list of Caltrans specifications for the use of recycled aggregate “which may include material processed from reclaimed asphalt concrete, Portland cement concrete (PCC), lean concrete base (LCB), cement treated base (CTB), or a combination of any of these materials” for aggregate base (AB)  and aggregate subbase (AS).  Please refer to the appropriate specification for the requirements the material must meet for use.

The following specifications can be found on the Caltrans Construction Contract Standards webpage:

1. 2010 Standard Specifications allowed up to 100 percent use of recycled aggregate for both base and subbase.
2. 2006 Standard Specifications originally only allowed up to 50 percent use of recycled aggregate for subbase or base, but were amended in 2007, see below. These specifications can only be used for projects until Dec. 1, 2012.
3. Section 25 and 26 Updates to 2006 Standard Specifications. In February 2007, Sections 25 and 26 of the 2006 Standard Specifications were amended to allow, for Class 1, 2, 3, or 4 aggregate subbase and Class 2 or 3 aggregate base, up to 100 percent of any combination of:
   • Processed asphalt concrete
   • Portland cement concrete
   • Lean concrete base
   • Cement treated base
4. Standard Special Provisions (SSP), Sections 25 and 26 in Division IV, updated in February 2007, allow for the use of processed glass for some base and sub-base applications.