Sand replacement density (SRD) tests are used to measure the in-situ density of natural or compacted soils using sand pouring cylinders. The in-situ density is normally used for highway or pavement design purposes to estimate the relative density of road-base or sub-grade materials.
The test method is described in BS 1377: Soils for civil engineering purposes: Part 9. The test can be carried out using either a small or large sand pouring cylinder. Unless otherwise specified the large pouring cylinder method is normally used. The tests are typically undertaken at ground level or the prepared formation level. In some circumstances the test may be carried out in shallow trial pits or trenches excavated up to approximately 1m deep, if the side walls of the excavation are prevented from collapse either by digging a safe angle or by shoring with timber or support systems.
A cylindrical, flat bottomed, hole is excavated from the surface, approximately 200mm deep by 200mm. diameter. All material excavated is carefully saved in a moisture retaining container, and weighed. Sand of a known density is poured into the hole using a calibrated pouring cylinder, from the weight of the sand taken to fill the hole the volume of the hole can be determined. The bulk density is calculated and after determining the moisture content, the dry density and air voids can be established.