grading specifications 1

[bbakk]

Would one of you experts out there give me the low down on the various compaction requirements such as aashto t99/t180 (the maximum density and optimum moisture test) and the inplace density and moisture test AASHTO T-310. I guess my question is if I instruct the contractor to compact the granular base to 95% of maximum dry density per aashto T-180, is it the same as specifying 95% of maximum density per AASHTO T-310 (the inplace density and moisture test)?

an example specification (is this conflicting and or redundant?):


1. IMMEDIATELY FOLLOWING FINE GRADING OPERATIONS PROOF ROLL SUBGRADE OF NEW PAVED AREAS TO ACHIEVE AT LEAST 95% OF THE MAXIMUM DENSITY FOR A 12" DEPTH PER AASHTO T-310. MOISTURE CONTENT AT THE TIME OF COMPACTING THE MATERIALS SHALL BE PREPARED TO WITHIN MINUS 4% TO PLUS 2% OF OPTIMUM MOISTURE CONTENT PER AASHTO T-180. EMBANKMENTS OR FILLS ARE TO BE CONSTRUCTED IN 6" MAXIMUM LIFTS, WITH EACH LIFT BEING COMPACTED TO 95% OF MAXIMUM DENSITY PRIOR TO PROCEEDING WITH THE NEXT LIFT. AREAS RECEIVING STRUCTURAL FILL ARE TO BE TESTED BY A QUALIFIED TESTING LAB.

Thanks in advance.
brb

 

[Ron]

No. Specify to achieve 98% of the maximum dry density per AASHTO T-180. You can then specify a method of density testing if you want, but that's not necessary. The in-place density test (AASHTO 310) is just a method of determining the in-place density, not its comparison to the laboratory standard test (AASHTO T-180). Don't confuse the two. They are different.

Your spec is not the clearest, but is adequate; however, I would phrase it this way...

"Immediately following fine grading operations, proof-roll the subgrade of proposed pavement areas with at least 6 overlapping passes of a vibratory compactor having a static, at-drum weight of at least 10 tons. Soft or yielding areas shown during proof-rolling shall be over-excavated and replaced with select fill material.

Compaction shall be checked by performing in-place density tests in each 12-inch or less lift, at the rate of one test per 500 square yards of pavement area. In-place density tests shall be done using AASHTO T310 and shall achieve at least 98 percent of the maximum dry density as determined by AASHTO T180. All testing shall be done by a commercial testing laboratory meeting the requirements of ASTM E329."