208— Subgrade

200-35 Section 208 — Subgrade

208.1 Description 1 Shape and compact s ubgrade before placing a base or surface course. 208.2 Materials 1 None specified. 208.3 Construction 208.3.1 General 1 Remove all soft, unstable, or unsuitable material that does not compact readily. Replace this material with satisfactory material as directed by the RCE. Remove or break off all objectionable loose rock or boulders to a depth of not less than 6 in. below the surface of the subgrade. Fill all holes, ruts, or depressions in the subgrade with approved material, elevate the subgrade to the required line and grade, and properly compact. If the subgrade is too dry to compact properly, sprinkle with w ater to wet, if determined necessary by the RCE, for proper compaction. 2 Compact the subgrade between lines 18 in. outside the area occupied by the pavement structure, including curb and gutter and sidewalk as applicable, to not less than 95.0% of maximum density. Accomplish the compaction by using suitable construction procedures while the subgrade is at suitable moisture content. Maximum densities are determined by either SC-T-25 (Method A or C as applicable) or SC -T-29. 3 Where the base and pavement are constructed under a later contract, compact the subgrade as specified above to not less than 95.0% density. 4 When any portion of the subgrade is constructed on an old roadbed that conforms to or approximates the elevation of the subgrade, scarify and grade the existing surface as directed by the RCE so that the subgrade has a uniform density when compacted. 208.3.2 Protection and Maintenance 1 Maintain the subgrade in a smooth and fully compacted condition, free from ruts and depressions, and adequately drained. Do not store or stockpile materials directly on the subgrade without the prior approval of the RCE. 2 Do not place any base, surface course, or pavement before the subgrade is checked and approved by the RCE. 3 Do not place any base, surface course, or pavement on frozen, muddy, or unstable subgrade.