AS 1289.3.8.1:2017 pdf free

AS 1289.3.8.1:2017 pdf free.Methods of testing soils for engineering purposes
If the soil does not disperse after two hours, obtain a few grams of air-dried soil passing the 0.425 mm sieve and add distilled water to bring the soil to approximately the plastic limit. Use the spatula to remould at this moisture content for 2 min. Do not mould the soil to the plastic limit by hand as this will influence the test result. Mould three balls of this soil approximately 3 mm in diameter.
NOTE: For some soils there is a minimum initial moisture content at which they just start to show dispersion when immersed in water. This moisture content is intermediate between the maximum water uptake of an initially dry soil and that corresponding to a suspension. In engineering laboratories, it is convenient to wet to the plastic limit or up to 2% wet of the plastic limit. At this moisture content, the bonds between the clay particles are loosened by the water layers and dispersion is easier. The action of remoulding or shearing the soil tends to further break up the clay domains and establish a more random orientation with a predominance of edge-to-face contacts. Dispersion is easier from this condition than from the oriented face-to-face condition. Thus, the 2 min of mechanical work with the spatula to bring the soil to the required moisture range is an important part of the operation. After the balls have been rolled, immerse them in the water immediately to avoid thixotropic regain of strength.
If the soil still does not disperse, check chemically for presence of calcium carbonate (calcite) or calcium sulfate (gypsum) using the applicable procedure in Appendix A. If the calcium carbonate or calcium sulphate is present, classify the soil as Class 4.
NOTE: The clay present in the soil may still not be dispersive if there are minerals in the crumbs or balls that dissolve rapidly enough to maintain the ionic concentration above the flocculating concentration. As the soluble salts diffuse out of soils containing calcium, the percentage of exchangeable sodium on the as yet undispersed clay is gradually reduced by exchange of sodium ions for calcium ions derived from the calcium-bearing minerals [usually calcium carbonate (calcite) or calcium sulfate (gypsum)] present, and the soil becomes less and less dispersive. Thus, it is necessary to determine whether calcium-rich minerals are present in soils that do not disperse from the moist state.AS 1289.3.8.1 pdf free download.