construction and refurbishment of earthen irrigation channel banks

16.12 Density Control Tests and ProceduresConstruction Control of Density occurs in four steps:1. Establish a Maximum Dry Density (also referred to as a Reference Density)2. Determine Field Density3. Determine Relative Density4. Check relative density conforms with the specification16.12.1 Establishment of Maximum Dry Density for calculation of relative compactionThe Maximum Dry Density is also referred to as the Reference Density.To permit relative compaction to be calculated, it is necessary to establish amaximum dry density. Procedures for establishing such maximum dry densitieshave been developed empirically over many years and standardised with theAustralian Standard test procedures of:AS 1289.5.1.1-1993 Determination of the dry density/moisture content relation of asoil using standard compactive effortAS1289.5.2.1-1993 Determination of the dry density/moisture content relation of asoil using modified compactive effortAS1289.5.7.1-1993 Compaction control test – Hilf density ratio and Hilf moisturevariation (rapid method)AS1289.5.5.1-1998 Soil compaction and density tests – Determination of theminimum and maximum dry density of a cohesionless material– Standard methodIn each of the above procedures, a maximum dry density is obtained. It must beappreciated that these do not represent the maximum achievable, but that which canbe achieved using the test procedures outlined.A sample of soil is required to determine the maximum dry density for thatparticular soil at Standard Compaction. This is achieved in the laboratory bydetermination of the Dry Density/Moisture relation of a soil (AS1289.5.1.1-1993).This is also known as a Proctor Test. This standard impact compaction testdetermines the moisture content at which the soil will achieve maximum drydensity (reference density) with the minimum compactive effort. In this test at leastfive samples of a soil are mixed with a varying amount of water. Each sample isthen compacted with 25 blows of a standard hammer. The density of each sampleis then measured.A graph plotting final density against moisture content is plotted and a curveapplied as shown inFigure 16.2. The top of the curve corresponds to the Maximum Dry Density andOptimum Moisture Content for that sample. The disadvantage with this procedureis that the conditioning and testing can take up to a week. This is obviouslyimpracticable for control of construction.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 16-21