base course aggregate compaction
base course aggregate compaction
(OP)
Dear All,
How many passes a 14 Tonne vibratory roller should make to achieve 100% compaction for base course aggregate? The MDD is 2.315 T/cum, OMC = 7%. Please help as the site is facing serious delays because of less compaction achieved even after 5-6 full passes. The maximum compaction achieved is only 85%!!
Hope somebody can help me out of this anamoly....
Regards
How many passes a 14 Tonne vibratory roller should make to achieve 100% compaction for base course aggregate? The MDD is 2.315 T/cum, OMC = 7%. Please help as the site is facing serious delays because of less compaction achieved even after 5-6 full passes. The maximum compaction achieved is only 85%!!
Hope somebody can help me out of this anamoly....
Regards





RE: base course aggregate compaction
RE: base course aggregate compaction
was the subgrade tested/proofrolled? what was the requirements for that? also as cvg asks, you referring to standard/modified Proctor or relative?
RE: base course aggregate compaction
RE: base course aggregate compaction
RE: base course aggregate compaction
RE: base course aggregate compaction
2. Normally, in my experience, base courses are compacted to 98 to 100% of the maximum dry density (MDD) Modified Proctor.
3. GeoPaveTraffic indentifed several aspects that are important.
4. 7% OMC (optimum moisture content) seems a bit on the high side for pavement base courses I have used. It would suggest that you are not using crushed stone aggregate and that your base course material is a bit on the sandy side - or, forbid, the base course has significant fines that might be clayey in nature (high PI).
5. 85% is very much on the low side - especially since end dumping into a pile will be in the order of 85% (standard proctor). So any passes you are making should improve considerably this number. Sands I have used in the past would gain 95% standard Proctor under 4 passes.
6. I would doubly check your proctor values if after all those passes you are getting such low results. I might suggest that you carry out a relative compaction check using the old Ontario's Ministry of Transportation and Communication (MTC)-or whatever they call themselves these days. I've explained it fully in previous threads - but basically, you dig a hole, use a sand cone or rubber balloon to determine the volume of the hole. you take ALL the material from the hole and compact, on site, into a proctor mould at "about" the optimum moisture content(depends on how good your field tech is - but if they do this a lot, they would have a good feel). Adjustments in the number of blows per layer are made for holes that are not of the "standard" volume. You then determine the volume of the compacted material in the mould. Compare the volume in the dug hole with the volume in the compacted mould to get the approximate relative compaction. It is a good test - takes time but as a check on the lab proctor values would be reasonable.
Sorry it is long reply . . . Cheers
RE: base course aggregate compaction
How are you determining the density in the field? That is the first thing to check when you are that far off of what might be expected. Do you have equipment to do the test by old stand-by methods such as the sand cone (large enough size also). A 2 mm loosening error on hole sides even for that method can make a major goof in the result. Is sand calibrated in the lab?
Accumulating errors in the wrong direction also may be your problem.
If you are using nuke methods, there can be some big errors present due to technique and no on-site calibration (not a lab calibration).
Then comes the proof of the pudding. What does a full load of heavy vehicle tire load cause in the way of visual appearance of the job? Any ruts? Deflection in the base?
RE: base course aggregate compaction
This material has a MDD of about 142 pcf, so 7% is not out of the ballpark. I would expect that the shape of the proctor curve is steep and therefore the material is very moisture sensitive. Maybe they're not controlling the moisture well enough to achieve compaction. If they are on the dry side, then they can pound on it forever and not get anywhere.
GPT, BigH, and oldestguy have laid it out nicely...no point in repeating.
RE: base course aggregate compaction
RE: base course aggregate compaction
RE: base course aggregate compaction
A thorogh mixing is very important.
Next time please check compaction and see the corresponding moisture. What is the gap in moisture against lab moisture.
If you do not achieve compaction with 7% moisture, u need to request a recheck on proctor density and moisture
RE: base course aggregate compaction
RE: base course aggregate compaction
RE: base course aggregate compaction
and the material is a crushed stone mix with fines...
85% sounds like you're not getting it wet enough, or at least that's what would be the case if what you described happened in my regional area. Most paving contractors i know inundate the stone with water right before compaction. The excess water is squeezed out to the top and evaporates after a day or two. Road base done right looks like concrete around here.
5-6 passes of a 14 ton smooth drum roller should get much better than 85% of either the Standard or the Modified Proctor. but don't count the passes... keep compacting until it feels and looks right. Rolling patterns are appropriate for asphalt paving construction.
i get 144.5 pounds per cubic feet for the conversion... 7% does seem a little high, but there is no telling that you don't have parent bedrock with a higher specific gravity than i'm used to.
if your crew is wet-setting the stone and you're still getting less than 95% Modified Proctor...i'm guessing your soil subgrade may not be as stiff as you need.
RE: base course aggregate compaction
RE: base course aggregate compaction
Then again, the problem could be as also described.
f-d
¡papá gordo ain't no madre flaca!
RE: base course aggregate compaction
is that normal or not ?
& why ?
RE: base course aggregate compaction
RE: base course aggregate compaction
RE: base course aggregate compaction
a) are the roller operatory putting the roller in a high gear(vibrating gear)during this operation?High gear normally uses more diezel,most probably they may use a low gear to serve or to sell diezel.By using a lower gear you will not achieve the compaction required.It will be just as rolling the base coarse material.Remember the crushed stone base are cohesionless materials and inorder to bring the particles close require vibration gear.
b)Yuo should use a lot of water after spreadingand greading the materials prior to compaction.So you need to have a lot of water buozer on site.Similarly you need to slush thhe section after compaction to bring all fines to the surface.Hopefully if you follow cosely this procedure you shall achive the required compaction not more than six passess.
RE: base course aggregate compaction
RE: base course aggregate compaction
BMP's on rock. I found that by flooding the rock, we use a lot of limstone, and then vibration heavy, it will go to pumping. This movement is needed with the lubication of the extra water to bring the fines to the surface and interlock with the large aggregates. yes it will be wet, pumping and soggy, but a day later after the water has evaporated out it will be over 100%. Rock is only going to absorb so much water, You cannot get rock too wet. the excess water is surface saturated water, it be gone in couple hours.
so knock to grade, flood it, vibrate it and cut to grade. If you cut after the water drys the dozer will not cut the rock, it will slide on top.
RE: base course aggregate compaction
If you are routinely achieving 100% of modified with pumping, I'd question your tests.
RE: base course aggregate compaction
RE: base course aggregate compaction
The method(s) of setting it up, finishing it, curing it, and continuing with the next layer is I think very dependent on the local availability (spec's are usually tailored to weed out the bad "local" sources) or pits.
Where I have worked (SW US) some materials that meet specifications cannot be slushed and others can.
If the type of material can be slushed I prefer it, as it produces a more homogeneous/smoother course. I have seen folks bring up the (very fine) fines using a vib. stl. whl. compactor, and have also seen them "make" fines with a small windrow and the same stl. whl. compactor.
I disagree that the bringing of fines to the surface is a poor practice....it has be a good method of helping to seal off the surface so as to properly cure and prime the base course. It has been a proven practice for years around my areas.