Particle Size Analysis
The Particle Size Analysis (PSA) is one of the most descriptive analyses performed on soil materials.  The PSA analysis is composed of two distinct phases.  One phase of the PSA is the textural analysis of a soil where the sand, silt, and clay contents are determined.  Another phase of the PSA is the sand grain distribution analysis.  The silt and clay content are determined using a pipette method.  The sand grain distribution is determined via the use of a stack of sieves with decreasing sized openings from the top sieve to the bottom, and it is based on the United States Department of Agriculture (USDA) sand distribution definition.  Sand grain distributions should be determined on the sand component that has had all of the silt and clay removed.
 

Parameters such as the D15 (particle diameter at which 15% of the particles present are finer) and D85 (particle diameter at which 85% of the particles present are finer) are determined.  A textural classification, based on the USDA definition, can also be provided.

Gravel Distribution
Gravel is used to aid the drainage and/or water holding capabilities of a turf system.  The gravel is usually at the bottom of the turf system, with the rootzone media on top.  The gravel distribution test is analogous to the sand grain distribution.  It is a measurement of the size distribution of gravel particles.  Gravel used in turf systems is typically spread over a size range of  1 mm to 6 mm.

Drainage gravel is often chosen after selecting the rootzone materials.  This is because of concern about the “bridging and permeability” between the rootzone material and the gravel.  Bridging refers to using rootzone material and gravel of the proper sizes, so that the rootzone will stay suspended over the gravel.  If the rootzone particles are too small in comparison to the size of the gravel, there is a potential for these materials to migrate down in to the gravel over time.  Permeability also refers to using rootzone material and gravel of the proper sizes.  However, the goal of proper permeability is to ensure that there is a distinct difference in sizes between the gravel and rootzone layers.  This difference in sizes is required in order to have proper water movement in a USGA style turf system.  The calculations for checking the bridging and permeability are:

A Couple Thoughts
To properly evaluate construction materials, one should take in to account all of the physical data that is reported.  This data should then be compared to the goals of the project when making material selection and usage decisions.  Remember that natural materials, such as sand and gravel, are not always the same from lot to lot.  Just because a material “worked” or met specs in the past doesn’t guarantee it will in the future.  A good testing program will help to ensure quality materials are used, and provide for consistency throughout the site.

The next time you’re asked to use a different lab, tell them you want the fastest turnaround and highest quality data.  Tell them, I’d rather use Turf Diagnostics and Design!

We’ll make sure that both you and your clients are happy that you chose our services.

Turf Diagnostics and Design serves the golf course, sports field, and landscape industries.  We have performed testing and/or consulting on over 1,000 golf courses and hundreds of sports field and landscape projects.  Our services have been instrumental in ensuring that our clients utilize quality building materials and maintain healthy turf systems.

Our web site, www.turfdiag.com has more detailed information on our cost effective services.

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