Granular Base and Subgrade Prep

Subgrade is the prepared soil or engineered fill beneath the pavement or slab system. Granular base is processed aggregate placed above it to distribute load, provide a stable working surface, and support drainage or final construction. Harrowgate accepts and records both surfaces because a strong aggregate layer cannot permanently compensate for yielding soil below.

The cause and depth are confirmed before correction. Approved options can include drying and recompaction, undercut and replacement, drainage, lime or cement stabilization, geogrid, geotextile separation, or a thicker engineered section. Harrowgate maps the area, completes the directed repair, and repeats proof or geotechnical review before placing ordinary base material.

The design may specify Granular A, a Granular B type, select subgrade, clear stone, crushed concrete meeting an approved specification, or a project-specific blend. The correct choice depends on drainage, frost, load, confinement, and owner standards. Harrowgate verifies source and material designation against OPSS and project documents before placement.

Field density is compared with the specified laboratory reference at locations and depths defined by the testing plan. Moisture, lift thickness, aggregate variability, and confinement affect results. Harrowgate ties tests to a work lot and elevation, reworks the full affected zone after a failure, and obtains acceptance before the next layer prevents correction.

Repeated handling, high free-fall, end dumping, long grader carries, and pushing dry aggregate can separate coarse particles from fines. Segregated pockets compact and drain differently. Harrowgate controls loading and dump spacing, spreads in short consistent passes, maintains suitable moisture, and remixes or removes visibly separated material rather than covering it with a fine grading pass.

Tolerance comes from the project specification and the material placed above. Asphalt, curb, and high-tolerance industrial slabs can demand different control. Harrowgate establishes a survey grid concentrated at crowns, edges, drains, doorways, structures, and transitions, then corrects the base without creating loose skin or local segregation. Average elevation does not excuse thin points.

Provide subgrade and top-of-base elevations, pavement or slab sections, aggregate specifications, compacted thicknesses, geotechnical report, proof and testing criteria, undercut allowances, geosynthetic details, drainage and subdrains, utility and structure locations, survey tolerance, source restrictions, construction traffic, seasonal conditions, and responsibility for protecting the accepted surface before paving or concrete.