350SUBBASE

350.1DESCRIPTION—This work is preparation of subgrade, as specified in Section 210, and construction

of a compacted aggregate subbase.

350.2MATERIAL—

specified in Sections 703.2 and 703.5.

350.3CONSTRUCTION—

Representative, if directed. Indicate the construction equipment and methods necessary to deliver and place the subbase in a manner that is not detrimental to the subgrade. Do not begin subbase operations until the Representative reviews the Subbase Delivery Plan. Prepare the subgrade as specified in Section 210 before placing subbase. Correct any deficiencies in the subgrade, as specified in Section 210, before placing the subbase. Do not place subbase material on soft, muddy, or frozen areas. If directed, correct unsatisfactory subbase conditions developing ahead of the base and paving operations by removing the subbase, correcting the subgrade problem, and replacing the subbase.

blend of materials from different sources only if allowed. Use material containing enough moisture to prevent segregation during stockpiling, hauling, and placing, and to minimize water added during compaction. Maintain subbase in a well-moistened condition from before placement to compaction.

Type A geotextile has been installed as specified in Section 210.3(b). Place the subbase before paving and as indicated. Control the subbase elevation and depth as specified in Section 210.3(c); except do not use templates if the subbase is trimmed using an automatic grading machine. Place the material on the subgrade and geotextile by back dumping then spreading the subbase ahead of all equipment. Spread, in a manner not causing segregation, to a uniform depth of the layer being placed. Do not make abrupt turns with tracked equipment that would result in pulling, folding, or tensioning of the fabric. Do not disturb or damage the geotextile during the installation of the overlying subbase. Repair any damaged geotextile at no additional cost to the Department. For rigid pavement and shoulders, place a course of No. 2A aggregate to a minimum compacted depth of 3 inches directly on the subgrade and place a course of No. OGS aggregate to a minimum compacted depth of 4 inches on top of the No. 2A aggregate. For flexible pavement and shoulders, place the indicated type of aggregate courses at the position and depth indicated for the pavement structure. Place each layer of No. 2A aggregate to a minimum compacted depth of 3 inches and place each layer of No. OGS aggregate to a minimum compacted depth of 4 inches. Construct subbase in layers not more than 8 inches in compacted depth; however, when granulated slag is used, limit each layer to not more than 4 inches in compacted depth. If allowed and when using granulated slag, the Contractor may place a maximum compacted layer of 6 inches when the full layer depth is compacted as specified in Section 206.3(b). If the subbase is constructed in widths less than the full pavement width, neatly trim the edge of completed subbase before placing the abutting subbase. For simultaneous construction of more than one pavement course, complete and maintain the subbase at least 1,500 linear feet in advance of placing the succeeding pavement course.

Compact from the sides to the center, with each pass uniformly overlapping the previous pass.

test hole to the full depth of the completed subbase. The Representative will measure the depth of the finished subbase. If the subbase depth is deficient by 1/2 inch or more from the depth indicated, the subbase is defective. The Representative may require additional test holes to determine the limits of the defective area. Scarify the subbase to a depth of 3 inches, blend in additional material, and recompact. After recompacting, the Representative may require test holes to verify the subbase depth is within 1/2 inch of the indicated depth. Backfill the test holes with subbase material and compact.

Do not allow traffic, including construction traffic, on a subbase constructed of No. OGS aggregate. If a subbase constructed of No. 2A aggregate is used as a haul road or if a subbase is exposed to weather in excess of 60 calendar days, retest for surface irregularities and depth and correct deficiencies as specified in Section 210.3(c) and 350.3(g). Do not leave subbase or subbase covered with treated permeable base course exposed during winter shutdowns. Place the required asphalt base course over all prepared subbase for flexible pavements and place the required reinforced or plain cement concrete over all prepared subbase (with or without treated permeable base course) for rigid pavements, before the shutdown of paving operations for the construction season. If subbase is in place over winter without a protective layer ( asphalt base course for flexible pavements or cement concrete for rigid pavements), proof roll as specified in Section 206.3(a)1 before placement of flexible or rigid pavement. Remove subbase in any areas indicating instability and remove and replace or repair the subgrade. Replace the subbase after repairs are completed on the subgrade. If the majority of or all subbase exhibits instability during the proof rolling, remove subbase and repair subgrade. Replace subbase in its entirety. Remove subbase, repair subgrade, and replace subbase at no additional cost to the Department.

350.4MEASUREMENT AND PAYMENT—

The Department will not pay the entire quantity of subbase complete in place until the base course or pavement is constructed over the subbase. However, the Department will pay for up to 75% of the estimated quantity of subbase placed in advance of the succeeding operations, if the Contractor satisfactorily completed and is properly maintaining the subbase.