Lightweight aggregate soil mechanics: properties and applications

Abstract

Structural grade lightweight aggregates have been extensively used throughout North America for more than 70 years in cast-in-place structural lightweight concretes for high-rise buildings and bridges and are now being widely used for geotechnical applications. Structural grade lightweight aggregates, when used in backfills and over soft soils, provide geotechnical physical properties that include reduced density, high stability, high permeability, and high thermal resistance. These improved physical properties result from aggregates with a reduced specific gravity and a predictable stability that results from a consistently high angle of internal friction. The open texture available from a closely controlled manufactured aggregate gradation ensures high permeability. High thermal resistance results from porosity developed during the production process. Physical properties of structural grade lightweight aggregate and geotechnical engineering properties of lightweight aggregate backfills are illustrated, along with references to extensive testing programs that developed data on shear strength, compressibility, durability, and in-place density. Representative case studies are reported from the almost 100 projects that illustrate completed applications of structural grade lightweight aggregate fills over soft soils and behind retaining walls and bridge abutments.