Concrete Pump Line Pressure and Reach Limit

A concrete pump line has a pressure limit and a concrete mix has a pumpability, and where they meet decides whether the pour runs or the line plugs. THE STATIC TERM IS THE EASY ONE AND OFTEN THE LARGER ON A HIGH POUR. A unit weight in pounds per cubic foot divided by 144 square inches to the square foot is the pressure gradient in pounds per square inch per foot of rise, which for normal weight concrete is 1.04 -- so a fifteen storey lift is more than 150 psi before any friction at all. Horizontal friction depends most on slump and line diameter, and it is where a mix change shows up: a stiffer mix can double the friction per hundred feet, and a line that ran fine on a five inch slump plugs on a three inch one. BENDS AND REDUCERS ARE THE QUIET KILLERS, and they are handled here the way the field handles them -- as equivalent feet of straight line. Each 90 degree bend is worth several feet, flexible hose is worth several times its own length, and a reducer at the pump outlet can be worth more than a long run. That is why a line threading a congested site can hit the pump's limit at a fraction of its nominal reach, and why the equivalent length rather than the measured length is the number that matters. The limit to compare against is the pump's rated CONCRETE pressure, not its rated hydraulic pressure, and those are different numbers on the same data plate. The output worth having is the additional line length still available: a crew that knows it has forty feet of margin can plan the last placement, where a crew that discovers the limit by plugging the line loses the pour and spends the afternoon breaking couplings. THE FRICTION VALUE IS AN INPUT AND NO CHART IS SHIPPED. Friction loss in a concrete line is not a simple function of anything: it depends on slump, aggregate size and shape, sand content, fines, admixtures, temperature, and the condition of the line itself, and published charts give broad ranges rather than values. A mix's pumpability is a mix design question, and a marginal mix will block regardless of what any pressure calculation says -- blockages are usually a mix or segregation problem, not a pressure problem, and the correct response to a stiff mix is to fix it at the truck rather than push harder. This does not design a pump setup, size a pump, or address line restraint, which is a safety requirement rather than a preference: a line under pressure that separates whips, and couplings, restraints, and the exclusion zone are governed by the equipment manufacturer and by OSHA. Boom reach, setup, and outrigger ground bearing are separate. ACI 304.2R for pumping, the pump manufacturer's ratings, the concrete supplier's mix design, and the contractor's competent person govern.

total pressure = static + friction. Static gradient = unit weight (pcf) / 144, so normal weight concrete is 1.04 psi per foot of rise; friction = equivalent length x the entered loss per 100 ft, with bends counted as an equivalent length each and flexible hose as a multiple of its own length.

The static and friction components of a concrete pump line by name, with ACI 304.2R for pumping and the pump manufacturer's ratings named. NO FRICTION CHART IS SHIPPED: the loss per 100 ft depends on slump, aggregate, fines, admixtures, temperature and line condition, and published charts give ranges. The limit compared against is the pump's rated CONCRETE pressure, not its hydraulic pressure. ACI 304.2R, the pump manufacturer's ratings, the concrete supplier's mix design, and the contractor's competent person govern.

A division and a multiplication on a friction value the reader takes off a pumping chart; no chart is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: horizontal_length_ft, vertical_lift_ft, unit_weight_pcf, friction_psi_per_100ft, bend_count, bend_equivalent_ft, hose_length_ft, hose_friction_multiple, pump_rated_psi, static_psi, friction_psi, equivalent_length_ft, total_psi, margin_psi, additional_line_ft

• The friction value is entered it depends on slump, aggregate, fines, admixtures, temperature and line conditiona pumping chart for the mix and line
• Pumpability is a mix question a marginal mix blocks regardless of calculated pressurethe concrete supplier's mix design
• Line restraint is not addressed a line under pressure that separates whips; couplings and exclusion zones are safety requirementsthe equipment manufacturer and OSHA