AASHTO T288

Determining Minimum Laboratory Soil Resistivity

Applicability: AASHTO T 288 applies to soils, backfill materials, and geological materials where electrical resistivity is relevant to the design and protection of buried metallic structures including pipelines, cables, reinforced concrete foundations, and electrical earthing systems. It covers natural soils, compacted fill materials, and granular backfills across a range of moisture contents from air-dried to saturated. The method is used in geotechnical investigations for transportation infrastructure where soil corrosion potential must be assessed prior to construction.

Purpose: AASHTO T 288 determines the minimum electrical resistivity of a soil sample by measuring resistance across a standardized soil box cell at multiple moisture content levels and identifying the minimum value, reported in ohm-centimeters. Minimum resistivity is the critical design parameter for predicting soil corrosivity toward buried metals; soils with resistivity below approximately 1,000 ohm-cm are considered highly corrosive, and results are used by corrosion engineers to specify cathodic protection systems, protective coatings, and suitable backfill materials for transportation infrastructure projects.