Friday, March 30, 2012

Changes to CT 231-March 2012

Caltrans has released a March 2012 version of CT 231: Method of Test for Relative Compaction of Untreated Soils and Aggregates Using Nuclear Gauges.  In general they have formatted and re-worded the majority of the test method to make it clearer but the following is a list of the major changes:

  • It now defines the nuclear gauge and standardizing block.
  • It no longer defines the exact dimensions of the guide plate but specifies that it should be at least as big as the footprint of the nuclear gauge.  It also now specifies a tolerance for how flat it must be (1/16in).
  • It no longer defines the exact dimension of the pin but specifies that it should meet manufacturer’s specifications.
  • To standardize your nuclear gage for wet density and moisture the test method now tells you to take 1 four minute count instead of 4 one minute counts.  I think this is a mistake but that’s how the method reads.  It refers you to record the counts on the form in the back of the test method and there is still room for multiple counts so I believe you should still take 4 one minute counts. 
  • When preparing the site, it is no longer specified that you should remove loose surface material to a depth of not less than 50 mm below the deepest penetration by the roller.  It is now more general and only requires that you remove the material until you are blow the deepest penetration.
  • It now tells you what position the gage should be in for each test: Direct transmission for wet density and backscatter for moisture content.
  • It now expands on what the direct transmission depth of the rod should be in the field test for wet density.
  • It now allows for gauges with direct readout capability to be used to determine density.
  • It is now noted that when testing for relative compaction, the tests should be conducted in areas free of debris, standing water, loose materials, and pumping conditions.
  • Under determination of wet test maximum density, it is no longer specified that “If the impact test result is to be used in a “common” composite control density, nuclear moisture, as well as a nuclear density must be taken for each test site in an area and be averaged”.
  • It now specifies and explains how to plot the correction for oversize material on the graph of the TL 2148.
  • The test method itself no longer explicitly points out that there are different calculations for relative compaction if there is 10% or more material retained on the ¾” Sieve (oversized material).  However, this calculation is still present on the example computations worksheet and TL-2148 and you still need to use different input variables in your equation if you have oversize material.
  • The directions for choosing a random sample plan are much more concise.  It no longer specifies how to choose a random sample plan, just that you should do it randomly. 
  • The appendices have been updated and moved around.  

If you use this method often you might want to read through it before your next venture out into the field.  The new version of this test method can be found on the Caltrans website and here.

Good luck!

Monday, March 26, 2012

CT 370-March 2012 Changes

Caltrans has posted a new version of CT 370-Method of Test for Determining Moisture Content of Bituminous Mixtures or Graded Mineral Aggregates using Microwave Ovens.

There have been no changes to the test method steps themselves.  This update seems to be solely formatting related.

You can find the new test method on the Caltrans website and here.

Tuesday, March 20, 2012

CT 227-March 2012 Changes

Caltrans is moving quickly through its test methods and has made a lot of changes this year.  This month they've posted changes to CT 227-Method of Test for Evaluating Cleanness of Coarse Aggregate.  There are not many changes to this one as you can see below.

  • The test method has changed from metric units to English units
  • You are no longer able to use tap water during testing, even if you can prove there is no difference in test results.  You must use distilled or deionized water.
  • If your water is not within 72± 5˚F you can now use a temperature correction factor.  You determine the correction factor by the same method as in CT 217.
  • The full formula for calculating CV is now present.  Before it only showed part of the equation.  The new equation is as follows: 

       That's all! The new test method can be found on the Caltrans website and here.

Thursday, March 15, 2012

CT 234 & 235 RSP Samples Announced

Today Caltrans announced that the next set of RSP samples will be testing labs' proficiency in CT 234 (Uncompacted Void Content of Fine Aggregates) and CT 235 (Percentage of Flat and Elongated Particle in Coarse Aggregate).  These samples will be distributed in May of 2012.  A check for $250 must be mailed to Caltrans by April 15, 2012 in order to register for the sample.  If you did not receive this announcement and have a laboratory that performs CT 234 and/or CT 235 you should contact the Caltrans RSP program at

Good luck!

Tuesday, March 6, 2012

Caltrans Revises CT 207 Again... March 2012 Changes

Many of us have expressed concerns with the new version of CT 207-Method of Test for Determining Specific Gravity and Absorption of Fine Aggregate that was released in September 2011. Specifically in regards to the major change in the test method where you would now need to wash the sample before testing. After a couple months it seems that Caltrans has now determined that this may actually be an issue. In recent communication, Joe Peterson, Caltrans' Chief of Roadway Materials Testing says:

"Our concern is that washing the fines produces an artificially low fine SPG and absorption value. Per AASHTO T 84 washing the fines over a #200 sieve can change the SPG value as much as 0.13 , depending on the percentage of P200's present. This in turn has a dramatic effect on the VMA of the mixture, driving the VMA value up 1-3 points. As a result of this we are starting to see a few JMF's that have adjusted their binder content down so their HMA meets minimum VMA requirements. This is producing an overly dry mix that could be subject to early age cracking, oxidation and premature failure. If the washing of the fines replicated production these would be valid values. To my knowledge most producers of HMA do not wash their fines prior to production."

Because of this, Caltrans has decided to change to using a hybrid version of the March 2000 test method and September 2011 test method of CT 207 for the immediate future while a task group reviews the test method and determines what changes would work best for California's roads.

The following changes can be seen between the September 2011 and March 2012 versions:
  • The mold sizes have returned to metric measurements although they are the same size molds.
  • The material is no longer washed over a #200 sieve before testing.
  • The material is now supposed to be soaked in water for a minimum of 15 hours (overnight) instead of 24hr±4 hrs. (The original wording from the Mach 2000 version)
  • After pouring off the free water, you can now dry the sample by spreading it on a smooth porous surface. In the Sept2011 version you were to spread it on a nonabsorbent surface. (The original wording from the Mach 2000 version)
  • The method for tamping is less strict. (The original wording from the Mach 2000 version)
  • The calculation for the bulk specific gravity reverted back to the original calculation that was used in the March 2000 version.
  • The rest of the test method has remained the same from the September 2011 version. 
You might be asking what you should do with all of the mix designs and tests you performed using the September 2011 version. For any projects that advertised during the period between September 2011 and February 2012 you will use the September 2011 version of CT 207. For any projects advertised starting in March 2012 you will use the March 2012 version.

This version is the March 2012 version and can be found on the Caltrans website and here.

*This entry was updated 8/22/12

Thursday, March 1, 2012

Bio Cells in Parking Lot Helps Storm Water Runoff

Here's an article by the Daily Commercial News that talks about an experimental parking lot in Canada. They are using Bio Cells to help retain, treat, and discharge storm water runoff and harmful pollutants.

Beamsville, Ontario carpool lot a test in asphalt innovation – Daily Commercial News

Asphalt Recycling Article

Here's a good article on asphalt recycling that addresses both recycling road and shingles from the American Recycler Newspaper.

"Asphalt recycling pulls material from roads and roofs"