May 15, 2015 · Subgrade shall be compacted to 90-92% of maximum dry density according to standard proctor (ASTM D698) and shall be firm and unyielding prior to placing pavement section material. Subgrade preparation density tests shall be conducted at a rate of 2 tests per 5000 square feet, and 4 tests per 200 lineal feet of roadway.

This section governs the performance of all work connected with subgrade preparation, prior to constructing pavements, sidewalks, drive approaches and concrete curb and gutters.

Subgrade preparation shall be measured in square metres based on the surface area of compacted and accepted subgrade actually completed in accordance with the Specifications, to the lines, levels, grades and cross sections required as directed by the Engineer.

To achieve high-quality subgrade, proper understanding of soil properties, proper grading practices, and quality control testing are required. However, pavement design requirements and the level of engineering effort should be consistent with relative importance, size, and cost of design projects.

The sub-grade course, including an area two (2) feet back of the proposed curb line, shall be sprinkled as required and rolled as directed until a uniform compaction and required density is obtained.

This manual has been developed to help Iowa highway engineers improve the design, construction, and testing of a pavement system’s subgrade and subbase layers, thereby extending pavement life.

Subgrade preparation work, when so ordered by the Consultant, will be performed according to the specified requirements of Section 3.1.2.3, Preparing Subgrade Surface.

This document describes specifications for subgrade preparation for road construction. It details requirements for compacting existing ground below subgrade level, breaking up and recompacting existing pavement, and shaping the subgrade surface to meet tolerances.

The work covered by this section includes furnishing all labor, materials, and equipment necessary for the preparation and compacting of the sub-grade on the streets in the various areas as shown on the drawings, as hereinafter specified, or as directed by the Engineer.

The Contractor shall accurately grade and prepare the subgrade section to the lines and grades called for on the plans and detail drawings, with due provision for future surface improvements and in accordance with SS Section 19-2, "Roadway Excavation" and Section 40-1.03C, "Subgrade Preparation".