Replies

1. 
   gstringe | Mar 17, 2005 04:29am | #1

   Plate compactor is cosmetic, looks good but worthless. Think about the fact that if the soil under your slab settles by only a sixteenth of an inch, you have lost support. Probably the worst practice I observe on construction sites is poorly compacted soil under slabs and walks. They usually just level with loose fill and slap it with a shovel and then wonder why a month later it cracks. Duh...

   every day of my life, I am forced to add another name to the list of those people who can just " kiss my arse"
1. 
   jhausch | Mar 17, 2005 01:43pm | #4

   Part of the problem with poor compacting usually comes from trying to compact a foot of fill rather than a couple of inches at a time, no?

1. 
   SamT | Mar 17, 2005 03:18pm | #5

   Jim,

   Specified Compaction, like you will find in civil and industrial work, will specify the soil mixture, moisture content, thickness of lift (added soil,) and compaction as a %.

   For residential work, "Eyeball" tolerance is usually "good'nuff." Eyeball tolerance would be as follows, assuming undisturbed soil. For a newly laid lift, compact a 3' square, then test the center of the square:

   Hold the Wacker in one place for 15 seconds;

   If the hole it punches is less than a couple inches deep, soil and moisture is ok

   If it buries itself, see a soil engineer.

   If it raises clouds of dust, moisture is too low.

   6" to 12" lifts.

   SamT

2. 
   averagejoe | Mar 17, 2005 03:32pm | #7

   The truth of the matter is it depends on what type of soil you are attempting to compact. I own a landscape contracting company that does a lot of paver work and have studied soil compaction like it was nuclear (or nukular for shrub) science.

   If the soil is cohesive (i.e. clay, partial clay, or loams with a clay base) then you definitly need a jumping jack. Because the soil particles will not separate when vibrated, the only way to compact these soils is through impact force.

   However, if the soil is very sandy or gravel-like (i.e. it will not stick together if you try to form it like a snowball), then a vibratory compactor is your best bet.  A jumping jack may work, but typically only very well in a confined trench. In a wide open area, it tends to displace the soil to the sides rather than truly compact it. (it re-loosens as it displaces) A vibratory compactor shakes the soil particles so that they separate slightly and rotate into a "best-fit" position relative to the particles next to them, removing void space and giving the soil a higher bearing capacity. An analogy would be to  take a cereal box with lots of different sizes of cereal in it (let's say corn flakes) and shake it gently for a while. The height of the cereal in the box will get lower until all the cereal fits together as efficiently as possible, with the small bits filling the voids between the larger bits.

   Neither type of compactor is inherantly better than the other, it just depends on the soil that you are working with. Match the right compactor and size to type and depth of soil, and Voila! Perfect compaction.

1. 
   reinvent | Mar 18, 2005 11:53pm | #32

   So what % of milk do you use to compact your corn flakes?

1. 
   averagejoe | Mar 19, 2005 03:34pm | #35

   2% if I'm trying to smash my cornflakes down with my spoon, 1% if I'm just gently shaking the bowl...

2. 
   paule38 | Mar 17, 2005 09:47pm | #16

   believe it or not, in this area of Oklahoma, on new house construction , most of them don't compact at all. They throw down some sand, dump a little water on it with a garden hose and then pour the same day. To further complicate matters, they start building on it within 2 days at best. I come from upstate NY and nothing gets done, either a commercial job or residential, without first compacting the soil, usually compacted crusher run on top of the compacted sub grade. Haven't seen a slab/sidewalk out here yet that isn't cracked early in it's life..the only guarantee they give a person out here is that it's "guaranteed" to crack. And...where I come from, the crete is covered with plastic and kept damp to allow curing...not here...pour a 9 or 10 slump, finish poorly and then leave exposed to those 110 degree days with no cloud cover........when I build my place I'll do my own crete, thanks...Hit 'em hard, hit 'em fast, SHOW NO MERCY!!!

1. 
   Heck | Mar 17, 2005 09:51pm | #17

   In Oklahoma, taking too long with the concrete would cut into the  huntin' and fishin' time.

   ;)Heck If I know....

1. 
   paule38 | Mar 17, 2005 10:07pm | #18

   you sound like you've been here before......I'll tell you a tale if you're interested....about not showing up...etc...Hit 'em hard, hit 'em fast, SHOW NO MERCY!!!

1. 
   Heck | Mar 18, 2005 12:36am | #20

   LOL.I have been there some, but I have a home-town buddy that moved there years ago that is a builder.

   We compare notes alot.Some of the things he tells me....

   Let's just say I know what you mean.

   Cheers!Heck If I know....

2. 
   paule38 | Mar 18, 2005 11:27pm | #30

   where is he building?? in the OKC metro area???Hit 'em hard, hit 'em fast, SHOW NO MERCY!!!

3. 
   Heck | Mar 18, 2005 11:48pm | #31

   Naw. Worse.

   He is a fairly small (but successful) operator living durn near to Arkansas, over there in Poteau.

   Does homes, mostly. Spends some time building dorms for the college there.

   We started in the trades together an awful long time ago before he moved to Ok.From what he has told me, and from what I have seen there myself, things are sure different there about what people will do and what people will accept.Heck If I know....

4. 
   paule38 | Mar 18, 2005 11:55pm | #33

   tell me about that!!! I can't believe the shoddy workmanship...and a majority of people would rather save a few bucks rather than have a quality job performed. I was at a 1/2 million dollar home the other day and the tile was so shoddy I can't believe it..needless to say, the owners are torked and it'll all have to be done again......the house is just over 6000 sq ft and the garage is 5000 sq ft......and the craftsmanship is ugly!!!!!Hit 'em hard, hit 'em fast, SHOW NO MERCY!!!

5. 
   BossHog | Mar 18, 2005 02:54pm | #27

   I spent a lot of time in Oklahoma. Was stationed at Ft. Sill for 2 years. I'll be perfectly happy if I never visit that state again.
   No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal live we'll ever see on this earth." [Ronald Reagan]

6. 
   paule38 | Mar 18, 2005 10:30pm | #28

   Yeah...I can't stand it myself.....I'm hurting to get back to where the air is pure and we have actual seasons...this state really sucks.......at least from what I'm used to........Hit 'em hard, hit 'em fast, SHOW NO MERCY!!!

2. 
   dIrishInMe | Mar 18, 2005 12:36am | #21

   While reading your post I wasn't surprized at anything I read until the end... "9 or 10 slump"!!!  Not much finishing required for that unless it's a windy day (think ripples across a pond of water).  Other than that, gravity would do most of the work!!!

   So how much water is needed for a 9 or 10 slump? - start with a 4 and then add 20 gallons of water to 10 yards - I'm guessing?

    

    Matt

1. 
   brownbagg | Mar 18, 2005 02:07am | #22

   rule of thumb. 1 gallon/ 1 yard / 1 inch

2. 
   paule38 | Mar 18, 2005 10:33pm | #29

   I don't have any idea how much is needed, but I do know that screeding is pretty easy.....you've got to wait awhile to get the whirlybird on it though..usually they wait too long and it seperates about a 1/4 inch below the surface......really crappy work......I'm not kidding about the slump, I've seen them pour it out of the truck looking like a thick soup...really bad workmanship......in upstate NY most of the commercial jobs I was on specified it at no more than a 4 slump (and they held us to it!!)Hit 'em hard, hit 'em fast, SHOW NO MERCY!!!

2. 
   BruceM16 | Mar 17, 2005 06:36am | #2

   Hal

   Not sure what your subsurface is, but I much prefer the JJ. A bit harder to navigate, and you gotta watch your toes and the edges of the footings....but it does a much beter job of actually tamping the soil/sand down than a plate compactor.

   BruceM

3. 
   SamT | Mar 17, 2005 07:22am | #3

   Wackers (JJs) are for compacting soil, vibrating plates are for smoothing it out after you compact.

   SamT

4. 
   BobKovacs | Mar 17, 2005 03:22pm | #6

   Hal-

   The truth is, it depends on the type of material you're working with.  Vibratory compactors (plates) are made for sands and stones, where the vibrating action works the particles together.   Jumping jacks are for clays and cohesive soils, they don't work as well on sands/stones.

   Bob

1. 
   averagejoe | Mar 17, 2005 03:34pm | #8

   Sorry bob, you must have posted while I was typing...what you said.

1. 
   brownbagg | Mar 17, 2005 03:39pm | #10

   jumpin jack

2. 
   901Hal | Mar 17, 2005 03:42pm | #11

   Thanks AverageJoe, I was also typing the same time you were. And your post answers it pretty well.
   -Hal

   Edited 3/17/2005 8:43 am ET by homeyhal

1. 
   pixburd | Mar 17, 2005 03:53pm | #14

   This site is also helpful:http://www.sunbeltrentals.com/library/reference/compaction/soil%20compaction.asp

2. 
   901Hal | Mar 17, 2005 03:38pm | #9

   Bob,
   Based on the other posts, I had pretty much settled on the wackerpacker until I saw your post. The force numbers for either machine are about the same, and I had planned on packing only a few inches at a time. My undisturbed base is medium-coarse sand, and I plan to fill with crusher run. Based on that, do some of you other JJ advocates still think the plate compactor is inferior?

1. 
   averagejoe | Mar 17, 2005 03:45pm | #12

   See above...For that situation, use a vibratory compactor. If it is a big enough area and your local rental place carries it, get a nice medium sized one with the hydostatic drive (it reverses or holds position). You need to smooth out each lift pretty well so that the plate contacts as much of the fill as possible.

1. 
   averagejoe | Mar 17, 2005 03:46pm | #13

   Again... simultaneous typing.

2. 
   BobKovacs | Mar 17, 2005 04:09pm | #15

   I never said the plate compactor was inferior- in fact, for the sand and gravel mixes you're using, it's the right piece of equipment.  I'd like to say "check with the staff at the rental yard to see what's the right piece of equipment to use", but that may give you the same mixed bag of correct and incorrect information that you're getting here.

   Bob

1. 
   brownbagg | Mar 18, 2005 02:11am | #23

   I never said the plate compactor was inferior- well, I can. The plate tamp is the worst piece of contruction equipment ever invented. it is more than inferior, it is a joke. and the bad thing is, everybody here knows I,m right. Nobody can touch me on this subject.The plate tamp is a waste of money and time......

1. 
   averagejoe | Mar 18, 2005 06:39am | #24

   No, everybody here DOESN'T know you are right...why does it seem that the more arrogant someone seems about their supposed knowledge, the more wrong they are?

   If your purpose in compaction is to attain a subsoil or base with the highest possible bearing capacity, then you had better understand your soil / base material and how it responds to different forces. The fact is that when compacting granular, non-cohesive materials, you will never be able to attain the same bearing capacity (ability to support and distribute loads) using a jumping jack as you can using a properly matched vibratory compactor.

   This is true in theory and it is true in the real world. I have installed tens of thousands of square feet of pavers, much of it exposed to vehicle traffic, and I own both types of compaction equipment. Both have their merits when used appropriately. I have often seen paver installations done by others with significant base failure issues, and I have never had a problem with one of my own. Most of my subsoil compaction is done with a jumping jack, ALL of my base compaction is done with a large "plate" compactor.

   I guess I've just been getting lucky all these years using the "worst piece of construction equipment ever invented."

    

2. 
   slykarma | Mar 18, 2005 07:23am | #25

   Bagger you are way out to lunch on this one. I do mostly commercial work and  compaction levels are specified for all engineered slab and footing prep. The engineer will also require that the work be tested to verify that compaction levels are met. I can tell you that vibratory tampers work just fine and we routinely meet required compaction levels using them. Admittedly, we typically use large diesel plate tampers and rollers, but that is because we have large areas to compact. I've also on occasion achieved good results using a small non-reversible plate tamper. Usually we use jumping jack for 'detail' work on confined areas.

   Both types of machine produce good results PROVIDED adequate moisture levels are maintained.

   Wally

    Lignum est bonum.

3. 
   SamT | Mar 18, 2005 02:42pm | #26

   Brown,

   I yoosta tink I was pretty good wit 'crete, till I met you.

   But, when it comes to compaction, you be fulla 'it.

   SamT

4. 
   brownbagg | Mar 19, 2005 02:48am | #34

   26 years with the testing lab, I am the one that test compaction and your concrete. I know what works and what doesnt. I have seen all the methods. I run the calculation and also the lab test. A plate tamp does not work, its only purpose is to make asphalt look pretty and vibrate sand into pavers. It doesnt have enough foot pound to work.

   Edited 3/19/2005 8:39 am ET by BROWNBAGG

5. 
   averagejoe | Mar 19, 2005 04:08pm | #36

   Before there is any more misunderstanding here, you should define what you mean by "plate compactor". If what you are trying to say is that something along the size of a Wacker 1550 isn't adequate for compacting 6" lifts of granular material, you are correct. In my business this machine is indeed only used for smoothing and firming up the final gravel screed (about 1" of material) and for compacting pavers into the bedding sand.

   Now, if what you are trying to say is that all plate compactors are a joke, including something along the size of a wacker BPU 3345 (which I use for most granular base compaction), then you are dead wrong. It works. Well. Better than a standard jumping jack.

   However, if I could only have 1 piece of compaction equipment, it would indeed be a jumping jack. It will compact a wider range of materials over a wider range of depths. There are few situations (if any) where a jumping jack would be completely inadequate for compaction, but there are many where a plate compactor (small or large) does't work well. But if I've got a large area of 6" deep, crushed, 3/4" minus limestone (that has been smoothed) to compact, you can't beat a large vibratory plate compactor with a jumping jack. For speed or compaction.

   Again, achieving proper compaction is a matter of understanding the type of material being compacted, and matching to it equipment that will impart the correct amount and type of force. To make a blanket statement that "plate compactors are a joke" shows a lack of understanding on your part. 

6. 
   averagejoe | Mar 19, 2005 04:13pm | #37

   I can't believe I'm getting so worked up about a stupid compaction arguement...Tell you what Brown... you whip out your jumping jack, I'll whip out my big plate compactor and we'll measure...

7. 
   SamT | Mar 19, 2005 04:19pm | #38

   We were talking about 6" lifts of gravel or sand. Right???

   In all other cases, I agree with you. Compact with Wacker, smooth with vibrating foot.

   Although, I do want to try pouring a drypak sidewalk or small slab with a vibrating foot.

   Just for science, ya know?

   Speekin' o' witch, You be interested in performing an experiment? According to my logic heehehehahahahahwahwahaw. . .Ahem, anyway. . .Concrete cures with moisture. Concrete loses stength with water. 

   Experimental procedure: Place dry mix in a high moisture content soil form, 3" lifts, tamp compact thouroughly, sprinkle top lightly (1/4" penetration,) cover with visqueen, let set for 60 days. Core and test at 60, 90, and 120 days.

   This is something I will do myself, iffin I kain't talk some foo... uh, friend into doing it first. But right now, I am broker than dropped crystal.

   SamT

5. 
   manimal | Mar 17, 2005 11:53pm | #19

   jumping jacks are for sure better for compacting,but you can get away with using a plate tamper if you have alot of time.adding a couple of inches of fill at a time and running the plate tamper over it layer by layer.now the best thing would be to get both and use the jumping jack all over and then finish it off with the plate,but using a jumping jack over a large area takes a long time.

6. 
   isahay | Oct 12, 2019 05:08pm | #39

   It's been a long and old post but I'm also looking for a plate compactor. Currently, there are two top choice on the market "Tomahawk" and "Multiquip". Want to choose one buy confused a bit. Read a review here, https://www.10machines.com/vibratory-plate-compactors/ but still can't make up my mind about which model to go with. I may also consider "Jumping Jack JXPC50H" but need some feedback on it.

7. 
   florida | Oct 13, 2019 09:39am | #40

   Are you going to use it on weekends when you aren't dropping sales links into forums?