Plasticity Index Plasticity Index ASHEAR (Civil/Environmental) (OP) 15 Jun 11 11:23 What is the meaning of a Plasticity Index "NP-4" ? RE: Plasticity Index cvg (Civil/Environmental) 15 Jun 11 13:43 NP means non-plastic so I would interpret this as PI ranges from 0 - 4 RE: Plasticity Index oldestguy (Geotechnical) 13 Jul 11 11:50 I'd interpret it to mean non plastic for the material smaller than the Number 4 sieve. RE: Plasticity Index jgailla (Geotechnical) 17 Jul 11 15:35 Plus one for cvg's response. RE: Plasticity Index TDAA (Geotechnical) 26 Jul 11 17:05 I would agree with cvg, as long as they were talking about a range for a few samples. RE: Plasticity Index fattdad (Geotechnical) 27 Jul 11 08:13 plasticity index, by definition is performed on the minus 40 sieve material. The lab is required to report NP if the sample is non-plastic. The ASTM does not acknowledge some range, like non-plastic to 4 as a range. Not saying that wasn't the lab's intent, it's just not a standard reporting method.I'd ask the lab. You have no idea how few folks actually read the ASTM methods for how to run the tests and what/how to report the test results.f-d ¡papá gordo ain't no madre flaca! RE: Plasticity Index ASHEAR (Civil/Environmental) (OP) 27 Jul 11 08:38 NP-4 IS HOW THE PLASTICITY INDEX IS REFERENCED IN THE USDA - NRCS ENGINEERING PROPERTIES REPORT FOR VARIOUS SOIL TYPES. RE: Plasticity Index fattdad (Geotechnical) 27 Jul 11 10:15 I WAS ASSUMING THE LAB WORK WAS DONE USING ASTM STANDARDS. YOUR ORIGINAL POST WAS NOT CLEAR THAT THE TESTING WAS PERFORMED USING USDA-NRCS STANDARDS, WHICH I HAVE NEVER EVEN SEEN (BEING AN ENGINEER AND SUCH).F-D ¡papá gordo ain't no madre flaca!