Ma s s i ve base mat pours or high-rise projects mayinclude pump placements of thousands of cubicy a rds of concre t e. These re c o rd-setting projects some-times obscure the fact that pumps are used on manysmall- to medium-sized pours as well. Because of tech-nological improvements in recent years, the pumps aremore reliable and line systems or placing booms can bemore quickly put into operation at the jobsite.

Co n t ractors choose to hire a pumping service or tobuy their own pump for a number of re a s o n s. On some

jobs access is a problem and pumping is the only waythat concrete can be placed. One pumper tells of bre a k-ing a hole in the sidewalk outside of a university build-ing, and running line into the subbasement for a 30-cu-b i c - y a rd pour. On another occasion a contractor waswilling to pay the pumper a $400 minimum charge toplace only 12 cubic yard of concre t e. There was no otherway to get the job done. Pumping is well-suited for plac-ing concrete for mez z a n i n e s, balconies, fre e - s t a n d i n gcolumns and many types of repair work inside existingb u i l d i n g s. When the pour is accessible by crane but thec rane must be pulled from other work or doesnt havethe needed capacity for fast concrete placement, pump-ing is often the most economical placing method.

On jobs where access isnt a problem, pumping can

still save time and money. In narrow walls the pump dis-c h a rge hose can eliminate the need for drop chutes andelephant tru n k s. And because concrete can be placedcloser to its final position in the form, less shoveling ord ragging is necessary to move the concre t e. On pours forf o u n d a t i o n s, slabs on ground, and multistory stru c t u ra lf rames as well, faster placement rates reduce the num-ber of man-hours needed and cut down on ove rt i m e. La-bor savings will frequently offset the costs of pumpinge ven on smaller pours.

PUMPS FOR THE BREAD-AND-BUTTER JOBS

Pumps mounted on trailersTra i l e r-mounted pumps can be used on smaller jobs

to move concrete through placement lines with diame-ters anywhere from 2 to 5 inches. The smallest pumps,equipped with 2- or 212-inch placing hoses, are suitableonly for concretes made with pea gra vel (38 -inch maxi-mum size) aggre g a t e s. Users of these pumps shouldk n ow that considerably more water is needed to get ad e s i red slumpand more cement to get a desire ds t rengthwhen small-aggregate concretes are used.The big advantage is that smaller hoses are easier tom ove around. Ten feet of 212-inch hose filled with con-c rete weighs only about 50 pounds.

Concrete pumpingBoom or line pumps can be used profitably on many smaller jobs

Small, trailer-mounted pumps are particularly useful onrepair or rework projects. For the job shown here, newpatios were being built in the courtyard of an existingcondominium. Only 8 to 12 cubic yards of concrete wereneeded for each pour and pumping was the only feasibleway to place the concrete.

Reach of a truck-mounted boom was extended here by usingadditional lengths of steel line.

Many of the smaller tra i l e r-mounted pumps havingcapacities from 20 cubic yards per hour and up canpump concrete with up to 112-inch maximum size ag-g regate if the line size is adequate. These pumps aresmall enough to be towed by a pickup truck and a majora d vantage is lower cost than for truck-mounted unitswith booms. Prices for single-cylinder pumps of thistype start at about $20,000 while two-cylinder pumpswill cost anywhere from $30,000 to $45,000.

The amount of pre s s u re a pump can generate is a ma-jor factor in determining how far the pump can movec o n c re t e. Maximum ve rtical pumping ability for thesmaller tra i l e r-type models is typically between 100 and300 feet while maximum hori zontal distances that arepossible may range from 500 to over 1200 feet. The ve r-tical and hori zontal limits cant be achieved simultane-o u s l y.

Smaller trailer pumps are used advantageously toplace concrete for patios, swimming pools, sidewalksand similar projects in residential neighborh o o d s. Inru ral are a s, where tra vel time costs for a pumping serv i c ecould be pro h i b i t i ve, applications have included ra i s e dsilo bases, manure holding tanks and floors for auctionri n g s. The pumps are also useful on projects where sev-e ral smaller pours are to be made on seve ral differe n td a y s. On these jobs, the ve rtical pumpline can be tiedd own and left in place, saving setup time.

One disadvantage of trailer pumps is the time re-q u i red to set up the line system. Also, on muddy sites thepump and pickup truck are more likely to get stuck thanis a larg e r, more powe rful truck-mounted unit. And ifhigh production rates in cubic yards per hour are re-q u i red, the smaller pumps may not have enough capac-i t y. One contractor uses his trailer pump for jobs under50 cubic yards but goes with a bigger truck and boom forjobs with more yard a g e.

Truck-mounted pumps with placing boomsUsing a truck-mounted concrete pump with placing

boom, a pump operator can dri ve to the jobsite and beready to pump soon after he arri ve s. Ve ry little bre a k o u tand setup time is needed. He can boom up and out,quickly delive ring concrete to most hard - t o - reach spots.

Nearly eve ry major pump manufacturer makes lowe rcapacity truck-mounted pumps with placing boomsthat are well suited for smaller pours. Many are mount-ed on a two-axle truck which is less expensive and morefuel efficient than tandem-axle models. New and usedunits are available with piston or squeeze - p re s s u repumps having theoretical capacities starting at 25 cubicy a rds per hour. The actual capacity or output in cubicy a rds per hour for any pump will va ry with how far thec o n c rete is being pumped and with mix chara c t e ri s t i c saffecting pumpability. Pumps can be designed to deliv-er either greater volume or greater distance.

Pumping booms have ve rtical reaches of 60 feet andup and line diameters of 3, 4 or 5 inches. Some will ro t a t e

t h rough a 360 degree arc while others are limited to asmaller slewing ra n g e. Articulating or telescoping de-signs allow the boom to unfold and to place concre t es t raight out, straight up or dow n w a rd. Remote control ofthe boom functions is a feature of many models.

The reach of boom pumps can be further extended byattaching the boom to a pipeline system set up at thej o b s i t e. Pump capacity then determines maximum hor-i zontal and ve rtical distances that can be achieve d .

SELECTING THE RIGHT PUMPCo n c rete pump manufacturers usually list a maxi-

mum theoretical output or pump capacity in cubic yard sper hour for the models they manufacture. But for anyc o n c rete pump, this maximum attainable output in cu-bic yards per hour will decrease as line resistance in-c re a s e s. Factors that increase line resistance include: longer lengths of hori zontal line

line that rises ve rt i c a l l y

smaller line diameters

changes in line diameter (re d u c e r s )

bends, especially sharp bends, in the lineSlump and other concrete pro p e rties also affect line

re s i s t a n c e. Ge n e ra l l y, more pumping pre s s u re is neededto push low-slump concretes through straight lines ort h rough bends and reducing sections.

The pump manufacturer or distributor can be con-sulted for help in selecting appro p riate equipment. Thec o n t ractor knows how much concrete he needs to placeper hour, but the pump will seldom be in operation for60 minutes out of eve ry hour. De l i ve ry output for thepump must be approximated, based upon estimatedd ow n t i m e. This output, plus the size pipe to be used, jobl a yout and concrete pro p e rties are taken into accountin calculating the re q u i red pumping pre s s u re. Then thecombination of output and re q u i red pumping pre s s u recan be used to choose the best pump for the job.

GETTING MAXIMUM BENEFITS FROM DOLLARS SPENT ON PUMPING

The basic re q u i rements for a fast-moving, smooth-running pump pour are a level site for the pump, withroom to get ready mix trucks in and out; timely delive ryof a pumpable concrete; and enough people on the plac-ing and finishing crews to handle the concre t e.

Spotting the pumpBoom pumps must be set up so that they are within a

few degrees of being level. That means you need not on-ly a level site but also one where the surface is firmenough to support the weight of the truck and the pre s-s u re beneath the outri g g e r s. A level surface isnt as cri t i-cal for trailer pump operation. The trailer pump shouldbe positioned as close as possible to the forms or area tobe concreted last.

Id e a l l y, there should be enough room at the pump to

h a ve two concrete trucks at the hopper so pump timei s nt wasted while trucks are maneuve ring. On slow - m ov-ing pours with a small capacity pump you may be able toget by with room for only one truck, but you wont bemaking the most efficient use of the equipment.

Check the location of ove rhead lines, too, when yo urespotting a boom pump. Powerlines are a safety hazardand many pumpers wont operate a boom pump neart h e m .

Fi n a l l y, measure the distance between where yo ure go-ing to set up the pump and the farthest point you need toreach. That will determine how much line is needed orh ow long the boom has to be. When yo ure deciding whatlength boom to order remember that the maximum hor-i zontal reach of a boom will be about 10 to 20 feet short e r

than the stated length. If you order a 100 foot boom yo ul lbe able to reach about 85 feet straight ahead of the fro n tb u m p e r.

Ordering and scheduling the concreteTell the pump operator ahead of time what kind of con-

c rete hell be pumping. The coarse aggregate maximums i ze affects the line diameter re q u i red; 5-inch-line sys-tems are needed for 1 1/2-inch aggregate and 4-inch-linesystems are usually adequate for 1-inch or smaller aggre-g a t e. The operator will need to know whether hard rock orl i g h t weight concrete is to be pumped and hell pro b a b l ywant to look at the mix design if its for a concrete mix thathe hasnt pumped pre v i o u s l y. Sl u m p, cement content, ad-m i x t u res used, sand grading and type of coarse aggre-gate used will all affect pumpability.

So that pump time isnt wasted, schedule concrete de-l i ve ry to start about 15 minutes after the pump arri ves onthe jobsite. Long delays on concrete delive ry will sub-stantially increase the cost of pumping and the biggerthe trailer pump or boom truck being used, the morecostly the delays will be.

Having enough workers on handTo take full advantage of the faster placing rates for

pumped concre t e, have enough workers on hand. Di s-c h a rge hoses on line systems and booms on tru c k -mounted pumps are ve ry maneuve ra b l e, so fewer peoplemay be needed to get the concrete in place. But on flat-w o rk jobs you might have to use more finishers. For slabpours on metal decks or thin toppings for repair applica-t i o n s, the amount of concrete that can be pumped perhour will depend mainly on how fast it can be finished.

Smaller pumps can be used effectively when thin concreteoverlays are placed because the rate at which concrete canbe finished will frequently dictate the pump capacityneeded.

PUBLICATION #C850177Co py right 1985, The Ab e rdeen Gro u p

All rights re s e rve d