Soil Cement Volume Needed 2

[DirtDelight]

Need some help please....

We have a 122 foot diameter structure with a 5 foot removal of existing soil under the proposed slab ( ox ). We are planning to remove 1/2 the diameter for the full 5 foot depth, stockpile the material, and then process and compact the sub grade. We need to add 3% cement back to the soil and plan on placing fill back in 1 foot +- lifts to the OX'd area and re compact the 5 feet. The 3% is based on dry weight with the soil at 98 lb ft3. My question is the formula needed to determine how much cement to add to the 5 feet of material to achieve 3 % by weight. I then figured to divide that weight by 5 to achieve the required amount of cement for each lift ( 1' ) ? Can someone please help me break this down ?

Thanks for the help ...

 

[Ron]

(((pi*d^2)/4)/2)*0.03*98=weight of cement for 1 foot lift

That should be about 17,184 lb of cement per lift or about 182 standard sacks of cement (94 lb/sack).

 

[amraam35]

assuming you are talking about a 122-ft diameter CIRCLE, 5-ft deep, that works out to 11690 cubic feet of excavated soil (neat volume). This equals 2338 cubic feet per lift (11690/5). Assuming a dry soil unit weight of 98pcf, the weight of the excavated soil is 1,145,620 lbs. (229,124 lbs per lift). Adding 3% cement by weight will give you a total weight of cement of 34368 lbs (6874 lbs of cement per lift).

 

[amraam35]

if you are only excavating half the footprint at a time, divide the answers by 2. (i.e. 34368lbs/2 equals 17184lbs)

 

[DirtDelight]

Sir,
Thanks for the response.

If you get a chance , can you please explain what the /4)/2) portion of the formula is ?

I'm getting the pi * d ^ 2 portion, as well as * 0.03 * the dry weight of the soil.

Are you saying then that the 17,000 + lbs represent ( 1 ) one foot lift for 5 vertical feet of fill over 1/2 the tank ?

If this is the case, we are looking at approx 1820 94 lb standard sacks for the total job ? As we will do the same removal and re compact for the other 1/2 of the tank bottom.

"((pi*d^2)/4)/2)*0.03*98=weight of cement for 1 foot lift "

Thanks again sir. Really appreciate the help .

peace....

 

[DirtDelight]

Thanks guys for the help with this. The light is starting to blink a little bit and the numbers make sense.

Now the challenge will be to get that cement properly mixed into each lift for proper uniformity and the compaction

Thanks again for the help guys.

peace...

 

[Ron]

You have a large quantity of mixing to do. I would suggest that you buy or rent a portable pugmill mixer for this job.

If you don't do that, you'll be looking at trying to uniformly spread cement to a depth of less than 1/4-inch over the area of each lift, then mixing that into the existing soil for each lift. Generally we put a limit of 2 hours from time of first introduction of moisture into the cement to final compaction for such mixing and compacting operations. That works ok for road work, but for confined area, non-linear sections, it can be very difficult.

With a pugmill mixer, you can work at whatever pace you want and you'll have ready supply of material there that is fresh and has not started to hydrate.

Check with local aggregate or asphalt suppliers. They might have a portable pugmill mixer they will rent or will do the job for you.

good luck.

 

[BigH]

I agree with Ron - a small pugmill is essential. I have seen several "site" mixings tried and none, in my opinion, match the results we have had when using a pugmill.

 

[cvg]

get the pugmill, but if you insist on mixing "insitu" I would increase the cement content beyond the 3% in order to get the performance you want with poor mixing

 

[kiwicroc]

We do portable pugmill mixing throughout US. Contact me.