Download or read book Pavement Subbases written by J. A. Crovetti and published by . This book was released on 1991 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the development of a complete pavement system which incorporates an open graded drainage layer to effectively remove infiltrated water. Candidate materials for use as open graded drainage layers were investigated using laboratory studies of flow characteristics and loading studies to measure accumulated deformations. The research team found that the required hydraulic conductivity of an open graded drainage layer must exceed 1,000 fpd for typical interstate design. For extreme conditions, hydraulic conductivity requirements may approach 5,000 fpd. Two standard Illinois DOT aggregate gradations, CA-7 and CA-11, were found to have hydraulic conductivities in excess of 5,000 fpd. Stability tests conducted on the open graded drainage layers indicate that stabilization with PCC cement or asphalt cement would be required if the materials were to be trafficked prior to final paving. Minimum PCC cement contents of 6% by weight of aggregate are required for adequate stabilization. Minimum asphalt cement contents of 2.5% are required. Observations of open graded drainage layer construction projects were made to document the practicality of construction. These observations indicate open graded drainage layers may be successfully placed if construction equipment specially suited to these materials is used.