Concrete pumping terms, defined

Plain-English definitions of 87 concrete pumping terms: booms, outriggers, valves, slump, priming, line pumps and more.

• Accumulator — A pressure vessel in the hydraulic circuit that stores energy and smooths out pressure spikes. Because it holds charge, it must be correctly discharged before work on hydraulic lines.
• Admixture — A chemical added to concrete to change its behaviour, such as a plasticiser to improve flow or a retarder to slow setting. Admixtures can make a mix easier to pump.
• Aggregate — The gravel, crushed stone and sand that make up most of a concrete mix by volume. Aggregate size and grading strongly affect whether a mix pumps smoothly or blocks.
• Agitator — A slow-turning paddle shaft inside the hopper that keeps the concrete moving and feeds it towards the pumping cylinders. It stops the mix from bridging over the intake.
• Air lock — A pocket of trapped air in a delivery line or cylinder that makes the pump stroke feel spongy and can cause slow or erratic flow. Air in the line also stores energy that can be released violently when a blockage or joint lets go.
• Bend radius — How tight a pipe bend is. Tighter bends cause more resistance and more wear, so wide-radius elbows are preferred where pressure is high.
• Bleed water — Water that rises to the surface of freshly placed concrete as the solids settle. Excessive bleeding in a mix can also signal that water is separating under pumping pressure.
• Blockage — A plug of concrete that stops moving in the line, usually caused by a harsh or segregated mix, a dry line, a damaged coupling or air in the system. A blockage must be treated as a pressurised hazard and the pressure relieved before anything is opened.
• Boom lock — A mechanical or hydraulic lock that holds the boom sections folded for travel. It must be engaged before the truck drives off and released only once the machine is properly set up.
• Boom pump — A concrete pump mounted on a truck chassis with a folding, remotely controlled boom that carries the delivery line to the placement point. It suits jobs needing fast placement, high reach or where ground lines are impractical.
• Boom sections — The individual folding arms that make up a placing boom, joined by hinges and moved by hydraulic rams. Booms are commonly described by their number of sections, such as a 4-section or 5-section boom.
• Boom tip — The outer end of the last boom section, where the end hose is attached. The tip position is what the operator steers when placing concrete.
• Call-out fee — A fixed charge for sending a pump and operator to site, covering travel and setup. It is separate from the pumping time charge.
• Cleanout — The process of clearing concrete out of the pump and line at the end of a pour, usually with a wash-out sponge pushed by water or air. A planned cleanout stops concrete setting hard inside the equipment.
• Concrete pump — A machine that moves wet concrete through a pipe or hose to where it is needed, using hydraulic cylinders to push the mix. Pumps are made as truck-mounted boom pumps, line pumps and stationary pumps.
• Coupling — A clamp that joins two sections of delivery pipe or hose and seals them against the high pressure inside. Couplings need a good gasket and a fully closed latch to avoid leaks and blow-outs.
• Cube test — A strength test where concrete samples are cast in cube moulds, cured and crushed at a set age. It confirms the delivered mix reached its specified compressive strength.
• Cutting ring — A hardened ring set against the wear plate that shears the concrete as the valve swings. When worn, it lets grout bypass and cuts output.
• Cylinder wear — Gradual loss of the smooth bore surface inside a pumping cylinder, usually checked by measuring the clearance around the piston seal. Worn cylinders let slurry past the piston and reduce output.
• Delivery line — The pipe and hose run that carries concrete from the pump outlet to the placement point. It can be steel pipe, flexible hose or a mix of both, and its length and diameter determine the pressure the pump must develop.
• Delivery pressure — The pressure the pump develops to push concrete through the line, set by line length, height, bends and the mix itself. It must stay within the lowest pressure rating of any component in the line.
• Downhill pumping — Pumping concrete to a level lower than the pump. Gravity can pull the concrete down faster than the pump supplies it, which leaves an air gap, so the line needs special care.
• Dry run — Moving the boom or cycling the machine's functions without concrete, such as when checking everything works before the first truck arrives. Running the pistons on an empty hopper for long is avoided, because the seals depend on the mix for lubrication.
• Dump valve — A valve that releases stored hydraulic pressure from the pump system, used when shutting down or when the circuit needs to be made safe to work on.
• Elbow — A curved pipe section that changes the direction of the line. Each bend adds friction, and bends are wear points that are checked regularly.
• Emergency stop — A red stop button, on the pump and on the remote, that cuts the machine's movement and power. Operators test it as part of pre-start checks.
• End hose — The flexible rubber hose fitted at the boom tip that the placing crew guides to the formwork. It is usually three to four metres long, and it can whip when concrete surges, so it must be handled with care.
• Exclusion zone — An area around the pump and boom that people are kept out of while the machine works, to guard against falling concrete, whipping hoses, boom movement and electrical hazards. Its size depends on the machine, site rules and local regulation.
• Flow rate — The volume of concrete the pump moves per hour, usually quoted in cubic metres per hour. Real output is lower than the rated maximum and depends on the mix, the line and the pressure needed.
• Gasket — A rubber seal inside a coupling that stops grout and water leaking from the joint. A worn or missing gasket is a common cause of leaks and lost pressure.
• Grate — A steel mesh or bar screen over the hopper that stops oversized lumps, tools and debris falling into the pump. It also acts as a guard so people cannot reach the moving agitator.
• Ground bearing pressure — The load that the ground under an outrigger must carry. Soft fill, fresh trenches and buried services can fail under a loaded outrigger.
• Grout — A fine cement-and-sand slurry. In pumping it usually means the lubricating slurry pushed through the line first, or the paste that leaks out of poor joints.
• Hopper — The steel receiving bin at the back of the pump where the ready-mix truck discharges its load. The agitator sits in the hopper and the pumping cylinders draw concrete from it.
• Hose whip — Sudden violent movement of the end hose, caused by air pockets, changing flow or a start-stop surge in the line. It is a recognised injury hazard for anyone standing near the end hose.
• Hydraulic oil — The fluid that carries power through the pump's hydraulic circuit. Oil level, cleanliness and temperature are checked regularly because contamination and overheating shorten component life.
• Hydraulic system — The pumps, valves, rams, hoses and oil that power the concrete cylinders, agitator, outriggers and boom. Its condition is critical to both output and safety.
• Line pump — A smaller concrete pump, usually trailer or truck mounted, that pushes concrete through ground-laid pipe and hose rather than a boom. It suits residential slabs, basements, tight access and jobs where lines are laid by hand.
• Mix design — The recipe for a concrete mix: cement, water, aggregates and admixtures in set proportions to hit a target strength and workability. A pumpable mix design usually carries more fines than a mix designed to be placed by chute.
• Oil cooler — A heat exchanger that keeps hydraulic oil at a workable temperature during long or high-pressure pours. A blocked cooler is a common cause of overheating.
• Operator — The trained person who sets up the pump, runs it and places concrete. Operators typically hold the licence or ticket required where they work.
• Outrigger — A hydraulic support leg that extends out and down from the truck to stabilise it while the boom is working. Outriggers must be set on firm, level ground or spreader pads, in line with the manufacturer's setup rules.
• Overhead power lines — Live electrical lines above or near the work area. A boom, hose or concrete stream can create a fatal path to the line, so the clearance distances set by regulation must be known before setup.
• Pipeline — A fixed or semi-fixed run of steel pipe, often used on high-rise buildings or tunnels, that carries concrete over long distances or heights. It is laid in lengths joined with couplings.
• Piston — The plunger inside a pumping cylinder that pushes concrete forward on the delivery stroke and draws it in on the return stroke. Its seals are a wear item.
• Placing boom — The hydraulic folding arm on a boom pump that carries the delivery pipe up and out to the pour. It is controlled by the operator from a remote and is rated for specific reach and load limits.
• Placing crew — The workers at the pour who guide the end hose, level the concrete and communicate with the operator. They work close to the end hose, so clear signals matter.
• Plasticiser — An admixture that makes concrete flow more easily without adding extra water, helping a pump push it with less pressure.
• Pre-pour inspection — The checks made on the pump and boom before concrete goes in: structure, hydraulics, controls, wear parts and setup. Doing it every time catches faults before they cause a stoppage or an injury.
• Pressure gauge — A gauge that shows hydraulic or concrete pressure so the operator can see the load on the pump. A climbing reading can warn of a developing blockage.
• Pressure rating — The maximum working pressure a pipe, hose, coupling or clamp is designed to carry. Every part in a line must be rated for at least the pressure the pump can deliver.
• Pressure relief — Releasing stored pressure from the line and hydraulics before opening a coupling or working on a blockage. Skipping this step is a classic route to a serious injury.
• Priming — Coating the inside of a clean, dry delivery line with a lubricating slurry or grout before the first load of concrete, so the main mix does not stick and block the line. How it is done depends on the line length and the site's rules for disposing of the slurry.
• Pump hire — Hiring a concrete pump with an operator, usually priced as a call-out charge plus an hourly rate and sometimes a per-cubic-metre rate. Rates vary by pump size, location and job.
• Pumpable mix — Concrete with the cohesion, fines and workability to flow through a line without separating or blocking. Mixes that are too dry, too wet or too harsh cause problems in the pump.
• Pumping cylinder — One of the two material cylinders in the pump, each holding a piston that draws concrete from the hopper and pushes it out into the line. They work alternately to give a near-continuous flow.
• R-fold — A boom folding layout where the sections roll up on themselves. It allows a low unfolding height under obstacles such as ceilings or power lines.
• Reach — How far a boom can place concrete, given as a vertical height and a horizontal distance from the turret. Quoted reach figures are maximums and assume the boom is fully extended.
• Reducer — A tapered pipe fitting that steps the line down from a larger to a smaller diameter, such as 125 mm to 100 mm. It raises the pressure needed because the same flow now passes through a smaller bore.
• Remote control — A handheld transmitter, radio or cabled, the operator uses to move the boom and run the pump from a safe position with a view of the pour. Controls include an emergency stop.
• Retarder — An admixture that slows the setting of concrete. It is used in hot weather or on long hauls so the concrete stays workable until pumped.
• Reverse pumping — Running the pump so it draws concrete back out of the line into the hopper, which can relieve pressure and help clear a blockage. It is done before the line is opened up.
• Rock valve — A rotating cylindrical valve that directs concrete from the cylinders to the outlet. It is common on trailer line pumps and suits higher-pressure pumping.
• S-valve — An S-shaped swinging tube that connects each pumping cylinder to the outlet in turn. It is the most common valve type on boom pumps and handles large-aggregate mixes well.
• Segregation — The separation of a mix into its parts, with heavy aggregate dropping out of the paste or water drifting away. Segregated concrete is a leading cause of blockages and poor finished work.
• Shotcrete — Concrete projected at high speed onto a surface through a nozzle, used for tunnels, slopes and pools. It needs specialist equipment but is fed by a pump.
• Slew — The sideways rotation of the boom around its turret. Slewing is limited when outriggers are only partly extended.
• Slump — A simple measure of concrete workability: how far a standard cone of fresh concrete settles when the cone is lifted away. It is used as a quick check that the delivered mix is within the specified range for pumping and placing.
• Slump test — The on-site test that measures slump by filling a cone with concrete, lifting it off and measuring the drop in height. It is carried out on delivery to check the mix before it is pumped.
• Slurry — A wet cement-and-water mixture. In pumping, a slurry or grout slug is often used to coat the inside of a dry line before the main mix goes through.
• Sponge ball — A soft foam ball pushed through the line by water or air during cleanout to scrub concrete off the pipe wall. It is sometimes also used to separate the first slurry from the following concrete.
• Spotter — A second person who watches the boom path, the hose and the surroundings and signals to the operator. Used where the operator cannot see everything.
• Spreader pad — A flat plate or timber placed under an outrigger foot to spread the load over a larger area of ground. It reduces the risk of the ground giving way under the leg.
• Stability — The machine's resistance to tipping while pumping. It depends on outrigger setup, ground conditions, boom position and the weight of concrete in the line.
• Standing time — Time the pump and crew wait on site for concrete to arrive or the pour to be ready. Many hire quotes charge for it after an agreed allowance.
• Stationary pump — A general term for any pump that sits in one spot and pumps through a pipeline, as opposed to a boom pump that places concrete with its own boom. Trailer-mounted line pumps are the most common kind.
• Stroke — One complete push of a piston through a pumping cylinder. Strokes per minute and cylinder size together set the output.
• Theoretical output — The maximum flow a pump could deliver under ideal conditions, based on cylinder size and stroke rate. In practice, actual output is lower.
• Tip-over — A pump overturning, usually from outriggers on poor ground, incorrect setup or boom use outside its limits. Prevention comes from site assessment and following the setup rules.
• Trailer pump — A pump mounted on a towable trailer. It is the usual form of line pump and works with a ground-run pipe or hose.
• Tremie — A pipe used to place concrete under water or in deep piles so it does not fall freely and separate. A pump can feed a tremie pipe.
• Truck-mounted pump — A pump built onto a truck chassis, often with a placing boom. It drives itself to site and sets up on its outriggers.
• Turret — The rotating base on which the boom sits, allowing the whole boom to swing round. Slew range depends on how the outriggers are deployed.
• Vertical pumping — Pumping concrete up a rising line, such as on a high-rise. The weight of the column in the line adds substantial pressure the pump must overcome.
• Wash-out pit — A contained area or bin on site where the pump's washing water and leftover concrete are discharged. Disposal rules are set by the site and local environmental law.
• Wear plate — A hardened steel plate that the swinging valve slides against. Together with the cutting ring it is a replaceable wear part that must be kept within tolerance to hold pressure.
• Z-fold — A boom folding layout where the sections fold in a zigzag, like the letter Z. It packs a long boom into a compact travel length.

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