Monday, September 17, 2012

CT105 Changes-July 2012

Sorry for the hiatus from updates, its been an extremely busy month for me!  

If you hadn't heard, CT 105: Calculations Pertaining to Gradings and Specific Gravities was updated in July 2012.  Most of the update is reformatting and all of it has made this difficult to learn test method into a much more useful reference tool.  There have been no major changes to the meat of this test method but here are a list of what I noticed as actual changes:

  • There is better definition of what each adjustment is for. 
  • The calculations shown in each example are easier to follow and understand where the final value comes from because they show the calculation and what each calculation equals instead of only showing the calculation.  It also shows the answer to the hundredth decimal place so that you can see how it’s been rounded in the “as used” column.
  • Most of the adjustments’ wordings have been made broader.  Instead of referring to “a portion of the passing 4.75mm material”, it refers to “the portion of the material passing a designated sieve”.
  • The diagrams are more explanatory.
  • The adjustments are now broken down into four parts: A definition section which explains when this particular adjustment is used, Procedure which is a summary of the adjustment, Example, and Calculations/Adjustments which explains the calculations used.  This defines the adjustment better and makes each one easier to understand and refer to.
  • In Adjustment 5, the calculation for determining the total amount of material before wasting has been corrected by changing 10,000 / (100-3)=10,309 g  to  10,000 / [(100-3)/100]=10,309 g.  This same type of correction was made in adjustment #10.
  • The equation in Adjustment 5 for determining the amount of material passing No. 4 sieve that will be needed before screening out the passing No. 200 material now uses 54% in the example instead of 55%.
  • When moving from section to section, the adjustment numbering system does not restart.  There are now a total of 11 adjustments covered over 3 sections.

The July 2012 version of CT 105 can be found on the Caltrans website and here.

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