Instantly estimate pipeline pressure loss when pumping fresh concrete to high floors or over long horizontal runs, using a Buhrau-style empirical formula. Vary slump, pipe diameter, horizontal length and vertical lift to see required pump head and recommended boom-truck class (M28-M70) update in real time — useful for pre-pour method statements.
Parameters
Slump (workability)
Drives the friction coefficient f (smaller = stiffer, higher viscosity)
Pipe diameter D
mm
Horizontal length L_h
m
Vertical lift H
m
Vertical height to the slab being poured
90° bends
25 kPa local loss per bend
Reducers
80 kPa each — biggest blockage risk
Delivery rate Q
m³/h
Piping material
Wear roughens the internal wall and raises friction
Results
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Pipe area (cm²)
—
Flow velocity (m/s)
—
Horizontal friction (kPa)
—
Vertical lift loss (kPa)
—
Total drop (MPa)
—
Pump head required (MPa)
—
Pump truck and pipeline schematic
Pipeline path from boom truck to pour spot: horizontal run, 90° bends, vertical riser. Colour and animated flow reflect the verdict.
Horizontal friction loss ΔP_h (kPa) and pipe velocity v (m/s). f is the slump-dependent friction coefficient, L_h horizontal length, Q delivery rate (m³/h), A pipe cross-section (m²).
Required pump head P_pump (MPa). n_b: 90° bends, n_r: reducers, k_m: material factor (1.0 / 1.15 / 1.5), 1.3: safety factor for start-up, blockage and hose fatigue.
Concrete Pump Pipe Pressure Drop — Buhrau Formula for High-Rise
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I watched a tower-block site pumping concrete up to the 30th floor from a truck at street level. What kind of pressure does that take? It looks much harder than a water pump.
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Great question. Concrete has a density of about 2,400 kg/m³ — 2.4× water. Just lifting it 100 m gives you a static head of 2.4·9.81·100/1000 ≈ 2.4 MPa. Add pipe friction and the bend losses and a typical 30th-floor pour (about 90 m) needs 3–5 MPa at the pipe outlet, 5–7 MPa at the pump discharge. That is why those boom trucks carry hydraulic cylinders 200 mm or larger across the bore, and the top models can deliver up to 25 MPa.
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Switching to 210 mm SCC slump halves the pressure loss. Why don't we just pump SCC everywhere?
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In principle yes — SCC has a friction coefficient around 0.005 and pumps very easily. In practice three things stop you: cost is roughly 50% higher than normal mix; SCC is prone to segregation over long pump runs (water and aggregate separate); and the high pour rate raises formwork pressure, so the moulds need extra bracing. So even on high-rise jobs the workhorse is 120 mm normal-slump concrete with high-range water reducers tuned for pumpability. SCC is reserved for congested sections like columns and beam bottoms where a vibrator cannot reach.
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A single 90° bend costs 25 kPa? With eight bends that is already 0.2 MPa. Can you avoid them?
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Bend count is the hidden driver of pressure loss. Layout strategies are: (1) build a 90° turn from two 45° bends, (2) keep curvature radii at least 3× pipe diameter, and (3) move the pump truck so fewer bends are needed at all. Just as important is blockage — at a bend the velocity vector shifts abruptly, pushing aggregate against the wall and creating jam risk. Inspect 5 m either side of every bend. Reducers are even more sensitive; only concentric, gradual reducers should be used in pumped concrete.
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The tool suggests "M52/M58" and "M62/M70" as boom-truck classes. What do the numbers mean?
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They are model names from Putzmeister (Germany) and Schwing — the number is the boom reach in metres. M28 reaches 28 m, M70 reaches 70 m. In Japan the 28–52 m range covers most jobs; for very tall buildings sites switch to a relay pump or a ground-based stationary pump feeding a riser pipe. If this calculator says "above 25 MPa", treat it as a signal to consider a relay configuration rather than a bigger truck. Relay pumps cost more up front but spread the pipeline wear, so they pay back on long-duration mega-projects.
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Last question — how accurate are these numbers in the field?
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Honestly, ±20–30 %. Concrete is a Bingham fluid; its viscosity varies with temperature and elapsed time, the slip layer at the pipe wall has unstable thickness, and pump pulsation adds dynamic peaks. So treat the output as a first-pass model for boom-truck class selection and pre-pour planning, and confirm with the pumping contractor before mobilisation. It is still genuinely useful — you can see at a glance whether an M28 has any chance, or whether the bend count needs surgery before going further.
FAQ
We use a simplified version of the Buhrau empirical family: horizontal friction loss is ΔP_h = f·L_h·v^1.5·g, where f is a slump-dependent friction coefficient (about 0.018 for 80mm stiff SCC, 0.012 for 120mm normal, 0.008 for 180mm fluid, 0.005 for 210mm SCC). Vertical lift loss is ΔP_v = ρ·g·H with ρ = 2400 kg/m³ converting directly into a pressure head. Each 90° bend adds 25 kPa and each reducer adds 80 kPa.
We multiply the total pipeline pressure drop by a 1.3 safety factor for start-up, blockage risk and hose fatigue. M28-4 (small) boom trucks deliver up to 7 MPa, M36-5 (mid) up to 14 MPa, M52/M58 (high-rise) up to 25 MPa; above that you need M62/M70 flagship machines. Calculations exceeding 25 MPa should consider larger pipe, a relay pump or ultra-high-pressure equipment.
Concrete is rigorously a Bingham fluid with yield stress τ_y and plastic viscosity η_p. A higher slump means lower τ_y and a thinner cement-paste slip layer along the pipe wall, both of which reduce friction. The downside is increased risk of segregation (bleeding and aggregate settling), so high-rise SCC mixes typically include anti-segregation admixtures.
With new steel pipe as 1.0, used steel with a rough internal surface adds about 15% (1.15×) and the rubber end hose typically adds 50% (1.5×). Many sites use rubber hose only on the last few metres, but if the hose run exceeds 10 m the correction becomes significant and should be included in the calculation. Replace worn pipes when the internal wall thickness drops below 2 mm.
Real-world Applications
Super-tall residential towers: on 200 m-plus towers in Tokyo and Osaka, the standard arrangement is a ground-based stationary pump (e.g. Putzmeister BSA-class) feeding a vertical riser pipe. Plug 300 m of vertical lift into this simulator and the required pump head exceeds 25 MPa, forcing a relay-pump or ultra-high-pressure (35 MPa) decision. The tool gives the planning team an early estimate of pump position, pipe routing and pour sequence.
Tunnel and deep-basement pours: shield-tunnel backfill grouting and deep foundation pits can easily exceed 300 m of horizontal run. Because horizontal loss scales as L_h·v^1.5, going from 125 mm to 150 mm pipe pays off strongly on long runs. Run the two diameters through the tool side-by-side and the benefit becomes obvious for any project past ~150 m.
Mass concrete on dams and foundations: RCC dams and large mat foundations use 120 m³/h-class pumps. Combining Q = 150–200 m³/h with 125 mm pipe drives the velocity above 6 m/s, accelerating pipeline wear. The simulator gives a quick first sanity check on the balance between throughput, pipe size and machine class.
BIM and construction simulation: with the pipe route modelled in BIM you can feed segment lengths and bend counts straight into this simulator to test pump-ability during planning. Combine that with a lift plan (how the pour is split vertically over a day) and you have a first estimate of daily concrete volume and required pump count.
Common Pitfalls
The most frequent mistake is assuming "bigger pipe always helps". Yes, increasing diameter drops the velocity and the friction loss, but you pay for it: pipe self-weight pressures the boom envelope; bend and coupler costs jump; and the priming volume (the leading mortar slug) grows with pipe volume. 150 mm pipe is overkill outside super-tall or super-long runs, which is why 125 mm is the de-facto standard. Sizing pipe on pressure drop alone often shifts the problem to boom-reach limitations.
Second, do not over-trust the absolute number. Our accuracy is around ±20–30 %, because Bingham rheology lumps three big uncertainties into a single empirical constant: temperature (viscosity roughly doubles between summer 35 °C and winter 5 °C), pump pulsation (peak about 1.4× mean), and unstable slip-layer formation. If the simulator outputs 7.5 MPa, plan for a 10 MPa-class machine in real procurement. For winter pours or long-duration sites, always confirm with the pump manufacturer's own pumping tests.
Finally, pressure-drop math is necessary, not sufficient. A real pour is constrained by per-cycle batch volume and pour rate, ready-mix truck rotation, cold-joint windows and vibration capacity. Even if the simulator says "pump-wise OK", a site that can only land three ready-mix trucks per hour will never actually deliver 80 m³/h. Use pumping calculations as one input to a wider compatibility check with supply chain and crew planning.
How to Use
Enter pump pipe internal diameter (mm) — typically 100–160 mm for ready-mix delivery
Input horizontal run length (m) and vertical lift height (m) for your placement route
Specify number of 90° bends in the pipeline — each adds friction equivalent to 1–2 m of straight pipe
Run simulation to compute friction losses, hydrostatic head, and total pump pressure required in MPa
Verify pump capacity exceeds calculated head; pressure drop scales with concrete slump and aggregate size
Worked Example
Pumping 8 m³/h through a 125 mm diameter pipe: 50 m horizontal + 35 m vertical lift with four 90° bends. Pipe cross-section = 122.7 cm². Flow velocity = 1.82 m/s. Horizontal friction loss (Darcy-Weisbach, f≈0.032 for fresh concrete) = 8.4 kPa. Vertical hydrostatic loss = 35 m × 24 kN/m³ ÷ 1000 = 0.84 MPa. Bend losses ≈ 0.15 MPa. Total pressure drop = 1.05 MPa. Pump must deliver ≥1.1 MPa at delivery hose coupling to overcome pipeline resistance.