Hey guys,

     I had to pull off a job this a.m. I was in my 39m schwing. I couldnt get the mud to pump. I have pumped this "same" mix from the same r.m. plant before with no probs. Today was the first time they added plastistizer. They dumped into me at a 6" slump and I got a 2" to trickle out my hose at max rpm and system psi. It was acting like a rock jam. The r.m. boss arrived and agreed the mix design is off but he dosent know what to change to make it a "pumpable mix".

  my urgent prob lies in the fact that I have to pour a bridge deck with the same r.m. co. in the a.m. but they cant bring anything wetter than a 3" slump. Does anyone know what they need to change??? Heres the mix i'm pumping tomorrow, only difference is the aggregate will be crushed granite.

3/4 rock     1800

sand           1420

portland       440

flyash           77

air                2.00 oz/cyl

water             242

Any help would be appreciated. I really need to get this co. on board with a pumpable mix as they have alot of work to send my way if I can pump it??

more cement, what type sand. man or natural

not really experienced with crushed granite but it seems as though they could use a little more cementuous material, and maybe drop the rock a 100 or so and go up on the sand,and make sure they have a 3" slump before the plasticizer is added if they are using it , have they thought of using a mid range this really helps with pumpability

send a putz if you have it,it will eat it up

allways six sack and change 300lb 3/4 rock to 3/8 as to blend the mix. also i would not want to tear up a perfictly fine putz.

Add 100 pounds of cement.  You have a Schwing so you know it's not the pump. That'll stir things up a bit on here!

I'm in awww. How did you get the r.m. boss to admit it was the concrete and not the pump?

Check your pressure spring and cutting ring. You might be blowing "fines" back into the hopper making it very hard to pump. I just had this problem. Changed my cutting and press. spring now it will pump anything.

typesdubs,

I like both just in my experiences here the putz will eat a little more junk,but both are very good machines

If you are pumping a B.D. in the a.m., you have little chance of getting the mix changed and aproved by the state or county in such a short time. If the R.M. boss said he had a problem, maybe the scales are off.  Lots of variables.  I agree on checking your Kidney Seal and Cutting Ring, but if the mix is off,  sometimes they just wont pump. 

It's simple,to much additive.My guess is a marginal mix (pumpable) but when additive added it became a lean mix.

been there done that

pudge its not the machine thats the problem , if he says its coming to his tip , its the mix. 

Thanks for the help. Got an engineer involved and he said the mix is marginal and when the plastisizer was added it got starved for water when I squeezed it in my SCHWING!! The r.m. manager is goging to settle up with the contractor and my name is cleared!!! as for in the a.m.??? we will see what they bring me. again, thanks for all the help.

disagree with you pumpon,some pumps pump harsher mixes than others maybe the mix is marginal but if the rock valve gets it to the tip the s-tube will put it out the hose but we are not gonna argue this because mixes are so different all over the world I have pumped mixes with a schwing putzs didnt like and viceversa not arguing what is the better pump just suggestions you have your opinions and I have mine,Good day 

UPDATE They lowered the rock and bumped up the sand and added 100 lbs of cement to the mix. It pumped great today!! Even at a 2" slump for the bridge deck. Or maybe it is the mighty SCHWING that chewed up the mix and spit it out !!! (for all you putz guys) seriously, thanks for all the replys and help. steve.

Glad to hear that !!.

Keep in mind the Kiss principle.Mix pumps great all the time,same mix enter "add mixtures".I can distinctly remember one incident that the same happend to me,which is why I knew.

For 30+ years the finger is pointed at the pump,a rattled operator only enhances the issue.Remember being the duck "stay calm on top of the water but palling to beat heck underneath".

Good to go

given you had a water cement ratio of .47, the clue is in the gradation of the aggregate, to say you had 3/4 rock and sand, i would bet the rock is gap graded with margins between seives not correct. This combined with a sand that may have a high FM 2.80 or higher. ( coarse ) or the same gradation faults.       

to make it a little easier to understand; too many gaps between particle spacing, so the addition of a fine material (portland cement) and the increase of sand fills in the spaces, so the mix is smooth.   

This happens more then you think, it is a true balancing act at a batch plant to produce a constant mix, every truck load of sand/stone can vary in so many ways.    Addition of portland cement is not the best solution as the cost of 6 +/- cents a pound if a producer adds say 50 lbs then thats 3 bucks a yard,in direct costs, ( who pays') so finding the right combination of the mix is very important.   

if you ever get the chance go by a batch plant when they are running daily gradations and moistures and you will understand how the process works.