Atterberg limits Test
The Atterberg limits test consist of the following key values of moisture content:
The Plastic Limit (PL) is the moisture content at which a fine-grained soil can no longer be remolded without cracking.
The Liquid Limit (LL) is the moisture content at which a fine-grained soil no longer flows like a liquid.
The Shrinkage Limit (SL) is the moisture content at which a fine-grained soil no longer changes volume upon drying—any loss of moisture is compensated by the entry of air into the pores.
Remark: Whereas the LL and PL limits are arbitrary limits, the SL is a definite limit for a given soil.
Remark: The SL is useful for determining the swelling and shrinkage capacity of soils. In general, “soils that swell a lot will also shrink a lot.”
Remark: Since the Atterberg limit tests are performed on remolded samples, the previous stress history of the soil is completely removed.
The Atterberg limits test are useful in that they allow for soil behavior to be inferred. For example, soil having similar LL and plasticity index (PI) will typically have similar strength/water content relationships. Thus, if such a relationship is known for one soil, it can be inferred for a soil with similar Atterberg limits.
Testing of Atterberg limits is performed only on the soil fraction passing through a No. 40 sieve, according to ASTM D4318-00 (ASTM, 2003). Therefore, mixtures of cohesive clayey soil and fine rubber particles (< 0.425 mm size) have been studied and results showed that as the percentage of tyre rubber increased, the clay content decreased and consequently Atterberg limits also decreased. In particular, the liquid limit stayed unchanged until levels of waste tyre reached 30%, and then it started to decrease; the plastic limit stayed about the same up to 10% waste tyre inclusion levels, started to decrease at levels of 20% and then stayed the same (Cetin et al., 2006). The plasticity index was found to stay the same for rubber chips up to 10% inclusion levels, while according to N. Oikonomou and S. Mavridou (unpublished observations, 2008) this was found to slightly decrease as the percentage of rubber increased to 10%.See other soil testing methods here Check us out on Facebook here