Laboratory investigation of CDG soil as source of fine aggregates for Portland cement concrete

Completely decomposed granite (CDG) soil is a typical and abundant in-situ weathered soil on the ground around the world. This paper investigates the possibility of CDG soil as fine aggregates for production of Portland cement concrete. It first develops a washing and sieving method to separate the CDG soil into its constitutional particles including gravel, sand, silt, and clay. It further examines the properties of the CDG sand using Hong Kong and other standards of fine aggregates for concrete. The first type of the property is the geometrical property including the size gradation, stereomicroscope observation, SEM observation, and shape statistical analysis of the sand particles. The second type is the physical property including magnesium sulphate soundness, compacting bulk density, relative density, and water absorption. The third type is its chemical property including chemical elements, acid-soluble chloride content, water-soluble chloride content, acid-soluble sulphate content, total sulphur content, and presence of humus. The fourth type is the mechanical property including drying shrinkage, effect of organic substances, and alkali silica reaction potential. These test results show that all the properties of the CDG sand well meet the standard requirements and can be used as fine aggregates in Portland concrete.