Concrete & Cement

Start here: ten words every newcomer needs

Overheard on the job

Real-sounding lines from the floor, translated into plain English.

• Hot load on the street and the east end's already kicking, skip the second bull float and get the pans on.

  TranslationA truck has arrived with concrete that is setting fast and part of the slab is already stiffening, so the crew should skip a finishing step and start machine floating right away.

• Ticket shows ten gallons added and the 7-day breaks were already light, so no more water in that drum, I don't care if it's rocky.

  TranslationThe driver already added water on site and early cylinder results were low, so no further water may go into the load even if it is stiff and hard to work.

• Burn the warehouse floor but leave the dock apron at a broom finish, that's the air-entrained mix.

  TranslationGive the interior slab a hard, glossy trowel finish, but give the outdoor apron, which contains entrained air, a textured broom finish instead.

• We plugged at the reducer, so the slick line's down and three trucks are stacking up on the street.

  TranslationThe pump line is blocked at the fitting where pipe size changes, placement has stopped and delivery trucks are waiting with concrete aging in their drums.

• Rod busters ran out of dobies, half the bottom mat is laying on the Visqueen with no cover.

  TranslationThe rebar crew ran short of concrete bar supports, so much of the lower reinforcement is resting on the plastic vapor retarder and would end up without its required concrete cover.

• Get the early-entry saw on it tonight or we'll have wild cracks by morning.

  TranslationCut the control joints within hours of finishing, or early shrinkage and overnight cooling will crack the slab in random places before conventional saws can get on it.

• Strip came off with bugholes and some honeycomb at the base, sack rub the face and get the engineer to look at that column.

  TranslationRemoving the forms revealed small surface voids and a zone of poorly consolidated concrete at the bottom, so the surface needs cosmetic patching and the column needs a structural review.

Portland cement, supplementary cementitious materials, aggregates and the admixtures that tune a mix.

• Acceleratoralso calcium, calcium chloride
  An admixture that speeds up setting and early strength gain, mostly used in cold weather.
• Admixturealso admix, chemicals
  A product dosed into a concrete batch, usually by the ounce, to change its flow, set time, air or durability.
• Aggregatealso agg, rock
  The sand, gravel and crushed stone that make up 60 to 75 percent of a concrete mix by volume.
• Fly ashalso ash, Class F ash
  Fine powder captured from coal-fired power plant exhaust, used to replace part of the cement in concrete.
• HRWRalso superplasticizer, super
  High-range water reducer, the superplasticizer that makes concrete flow without adding water.
• Mudalso concrete, crete
  Jobsite slang for fresh concrete, used by finishers, pumpers and ready-mix drivers alike. Shop talk
• Pea gravel mixalso pea rock, pump mix
  Concrete made with 3/8 in pea gravel instead of standard coarse stone, so it moves through small pump hoses. Shop talk
• Portland cementalso cement, OPC
  The gray powder that reacts with water to bind sand and stone together into concrete.
• Retarderalso set retarder, Type B admixture
  An admixture that delays setting, used in hot weather, on long hauls and for big continuous placements.
• Sackalso bag, six-sack
  A 94 lb bag of portland cement, used as shorthand for how much cement goes into each cubic yard. Shop talk
• SCMalso SCMs, supplementary cementitious materials
  Supplementary cementitious material: fly ash, slag cement or silica fume used alongside portland cement in a mix.
• Silica fumealso microsilica, condensed silica fume
  Ultrafine silica dust from silicon smelting that makes concrete much denser, stronger and less permeable.
• Slag cementalso slag, GGBFS
  Ground granulated blast-furnace slag, an ironmaking byproduct that replaces part of the portland cement in a mix.
• Type I/II cementalso Type I-II, dual-certified cement
  The everyday portland cement, certified to meet both general-purpose Type I and moderate sulfate-resistant Type II limits.
• Type III cementalso high-early cement, HE cement
  High-early-strength portland cement, ground finer so concrete gains strength in days instead of weeks.

Mix design, water ratios, slump, air, bleeding, setting and the words crews use for a load's behavior.

• Air entrainmentalso air, AE
  Deliberately building billions of microscopic air bubbles into concrete so it survives freezing and thawing.
• Bleed wateralso bleeding, bleed
  Water that rises to the surface of fresh concrete as the heavier solids settle.
• CLSMalso flowable fill, slurry
  Controlled low-strength material, the soupy flowable fill poured into trenches and voids instead of compacted soil.
• Creamalso juice, paste
  The cement paste and fine sand that finishing tools bring to the surface, giving finishers something to work. Shop talk
• Green concretealso green, young concrete
  Concrete that has set but is only hours or days old, still weak enough to cut, mark or damage easily. Shop talk
• Hot loadalso hot truck
  A truckload of concrete that is setting faster than it should, from heat, delay or leftover concrete in the drum. Shop talk
• Hydrationalso cement hydration
  The heat-releasing reaction of cement with water that turns the paste into solid binder.
• Initial setalso set, time of set
  The point at which fresh concrete stops being workable and begins to stiffen into a solid.
• Kickalso kick off, go off
  To start setting, usually sooner than the crew expected; a load that kicks stiffens fast. Shop talk
• Mix designalso mix, mix submittal
  The recipe for a concrete mix: the weights of cement, SCMs, water, aggregates and admixtures per cubic yard.
• SCCalso self-consolidating concrete, self-compacting concrete
  Self-consolidating concrete, a highly fluid mix that fills forms and wraps rebar under its own weight.
• Segregationalso separation
  Separation of coarse aggregate from the mortar in fresh concrete, leaving rock-heavy and paste-heavy zones.
• Slumpalso slump test, cone
  How far a cone-shaped sample of fresh concrete sags, the standard field measure of consistency.
• Soupalso soupy, slop
  Concrete so wet it runs like liquid, usually because too much water went into the truck. Shop talk
• w/cmalso w/c, water-cement ratio
  Water-to-cementitious-materials ratio: the weight of mix water divided by the weight of cement plus SCMs.

Trucks, tickets, pumps, vibrators and the work of getting concrete into the forms without joints or voids.

• Batch ticketalso ticket, delivery ticket
  The delivery ticket that travels with every ready-mix truck, showing mix, quantity, time batched and water allowed.
• Blowoutalso form failure, blew out
  A form failure where formwork bursts open or shifts under the pressure of fresh concrete. Shop talk
• Boom pumpalso pump truck, the pump
  A truck-mounted concrete pump with a folding hydraulic boom that places concrete right where it is needed.
• Buggyalso power buggy, Georgia buggy
  A small motorized or push cart that carries concrete from the truck to spots the chute and pump cannot reach. Shop talk
• Cold jointalso cold seam
  An unplanned seam left where fresh concrete was placed against concrete that had already begun to set.
• Cold weather concretingalso winter concreting, cold weather protection
  Placing and protecting concrete when air temperatures are at or expected to drop below 40 F.
• Consolidationalso vibration, vibrating
  Working fresh concrete, usually by vibration, so it fills the form completely and releases trapped air.
• Drumalso barrel, mixer drum
  The rotating mixing barrel on a ready-mix truck, turning one way to mix and the other to discharge.
• Liftalso layer, pour lift
  One layer of concrete placed in a wall, column or mass pour, or the height cast between horizontal joints.
• Plugalso pack-off, blockage
  A blockage that jams a concrete pump line or hose, stopping placement until it is cleared. Shop talk
• Pouralso placement, placing
  The act of placing concrete, or one placement itself, in everyday jobsite speech. Shop talk
• Short loadalso short-load fee, small-load charge
  A concrete delivery smaller than the plant's minimum, which brings an extra per-yard or flat fee. Shop talk
• Shotcretealso gunite, sprayed concrete
  Concrete shot from a nozzle by compressed air and built up in layers on walls, slopes, pools and tunnels.
• Slick linealso slickline, pipeline
  Rigid steel pipeline that carries pumped concrete from the pump to a distant or elevated pour area. Shop talk
• Stingeralso vibe, vibrator
  An internal concrete vibrator, or specifically the vibrating head on the end of its flexible shaft. Shop talk
• Tremiealso tremie pipe
  A vertical pipe that places concrete underwater or deep in a shaft without letting it free-fall or wash out.
• Washoutalso washout pit, washout area
  Rinsing concrete residue from a truck's chutes and hopper, and the contained pit where that wash water goes.
• Yardalso yd, yds
  One cubic yard of concrete, 27 cubic feet, the unit used for every US ready-mix order and invoice. Shop talk

Screeding, floating, troweling and texturing a slab, plus the tools and slang of the finishing crew.

• Bird bathalso birdbath, puddle
  A low spot in a finished slab or pavement where water collects and sits after rain or washing. Shop talk
• Broom finishalso broom, broomed finish
  A textured surface made by dragging a broom across fresh concrete, giving slip resistance outdoors.
• Bull floatalso bull floating, bull
  A wide flat float on a long handle, pushed across a fresh slab right after screeding to smooth and close it.
• Burnalso burnish, hard trowel
  To steel-trowel a slab again and again at high blade pitch until it turns hard, dark and glossy. Shop talk
• Edgeralso edging tool
  A hand tool that rounds and compacts the edges of a slab along its forms so they resist chipping.
• Evaporation retarderalso evap retarder, monomolecular film
  A film-forming liquid sprayed on fresh concrete to slow moisture loss between finishing passes.
• F-numbersalso FF/FL, FF
  FF and FL, the paired numbers that measure how flat and how level a concrete floor is.
• Floatingalso float finish, mag float
  The finishing step that levels, compacts and opens the surface of a slab once the bleed water is gone.
• Fresnoalso fresno trowel, long-handled trowel
  A long-handled steel trowel finishers swing across a slab from its edge to smooth it without walking on it. Shop talk
• Kneeboardsalso knee boards, kneelers
  Flat boards finishers kneel on to spread their weight while working a fresh slab by hand. Shop talk
• Panalso float pan, panning
  A round steel float disc clipped onto a power trowel's blades for the first, flattening machine passes. Shop talk
• Power trowelalso helicopter, machine
  A gas or electric machine with rotating blades that floats and trowels large concrete slabs.
• Screedalso strike off, screed board
  To strike off fresh concrete to the right height, or the straightedge, board or machine that does it.

Keeping concrete moist and warm, and the cylinders, cores and field tests that prove its strength.

• Air meteralso pressure meter, air pot
  A sealed pressure vessel used at the truck to measure the air content of fresh concrete.
• Breakalso breaks, cylinder break
  A cylinder strength test result, or the crushing of cylinders in the lab. Shop talk
• Compressive strengthalso strength, comp strength
  The crushing load concrete can carry per unit area, the main property specified and tested for concrete.
• Corealso core sample, drilled core
  A cylinder of hardened concrete drilled out of a structure to test its strength or inspect its condition.
• Curingalso cure, wet cure
  Keeping fresh concrete moist and warm enough, for long enough, that the cement keeps hydrating.
• Curing compoundalso cure and seal, membrane cure
  A sprayed liquid membrane that seals moisture into newly finished concrete.
• Cylinderalso cylinders, test cylinder
  A cast concrete test specimen, usually 4 by 8 in or 6 by 12 in, crushed to measure compressive strength.
• f'calso f prime c, specified strength
  Symbol for specified compressive strength, the design strength the engineer requires, usually at 28 days.
• Flexural strengthalso modulus of rupture, MR
  The bending strength of plain concrete, measured by breaking an unreinforced beam and used for pavement design.
• Maturity methodalso maturity sensors, maturity meter
  Estimating in-place concrete strength from its temperature history, recorded by sensors cast into the pour.

Rebar, mesh, post-tensioning, formwork and the joints that control where concrete moves and cracks.

• Chairalso bar chair, bar support
  A wire or plastic stand that holds rebar or mesh at the right height inside the form.
• Construction jointalso CJ, pour joint
  A planned stopping point between two placements, prepared so the next pour bonds to it or transfers load across it.
• Control jointalso contraction joint, sawcut
  A planned groove or sawcut that makes a slab crack in a straight line exactly where the crew wants it.
• Coveralso concrete cover, clear cover
  The depth of concrete protecting the outermost bar, measured from the bar to the nearest face.
• Dobiealso dobe, dobie brick
  A small precast concrete block, often with tie wire cast in, used to hold rebar up off the ground. Shop talk
• Dowelalso dowel bar, plate dowel
  A smooth steel bar across a slab joint that transfers load while letting the joint open and close.
• Early-entry sawalso Soff-Cut, early entry
  A lightweight saw that cuts control joints within hours of finishing, before shrinkage cracks can start.
• Embedsalso embed, embedded items
  Steel plates, anchor bolts, sleeves and inserts cast into concrete for connections made later. Shop talk
• Formworkalso forms, forming
  The temporary molds, supports and bracing that hold fresh concrete in shape until it can carry itself.
• Green baralso epoxy bar, epoxy-coated rebar
  Epoxy-coated rebar, named for its usual green coating, used where salt and chlorides threaten corrosion. Shop talk
• Isolation jointalso expansion joint
  A full-depth separation between a slab and a fixed element, so each can move without cracking the other.
• PTalso post-tensioning, post-tensioned concrete
  Post-tensioning: reinforcing concrete with steel tendons that are stretched tight after the concrete hardens.
• Rat slabalso mud slab, mud mat
  A thin layer of lean concrete over dirt that gives a clean working surface or seals a crawlspace floor. Shop talk
• Rebaralso reinforcing steel, bar
  Deformed steel bar cast into concrete to carry the tension that plain concrete cannot.
• Rod busteralso rodbuster, reinforcing ironworker
  An ironworker who places and ties the reinforcing steel on concrete jobs. Shop talk
• Tendonalso strand, PT cable
  The steel strand assembly in post-tensioned concrete that is pulled tight to precompress the member.
• Vapor retarderalso vapor barrier, Visqueen
  A plastic sheet under a slab on grade that slows ground moisture from rising into the concrete.
• Wet setalso wet-setting, stabbing
  To push anchor bolts, dowels or embeds into concrete after placing it, instead of fixing them in place beforehand. Shop talk
• WWRalso welded wire reinforcement, welded wire fabric
  Welded wire reinforcement, a grid of steel wires welded at every crossing and sold in sheets or rolls.

Cracks, surface failures and chemical attacks, and what each one says about how the concrete was made.

• ASRalso alkali-silica reaction
  Alkali-silica reaction, a slow internal reaction between cement alkalis and certain aggregates that cracks concrete.
• Blisteringalso blisters
  Hollow bumps that form on a troweled slab when air or bleed water gets trapped under a sealed surface.
• Bugholesalso bug holes, surface voids
  Small surface pits on vertical formed concrete left by air bubbles trapped against the form face. Shop talk
• Crazingalso craze cracks, checking
  A fine, shallow network of hairline cracks on a concrete surface, often in a rough hexagon pattern.
• Curlingalso curl, warping
  Upward warping of slab edges and corners, caused by the top drying and shrinking faster than the bottom.
• Delaminationalso delam, delams
  A surface layer that has split away from the concrete below it, found by the hollow sound it makes when tapped.
• Drying shrinkagealso shrinkage
  The volume loss of hardened concrete as it gives up moisture over months and years.
• Dustingalso dusty slab, chalking
  A soft, powdery concrete surface that rubs off under traffic or a scraped fingernail.
• Efflorescencealso bloom, lime bloom
  The white powder or crust that appears where water seeps out of concrete or masonry and leaves its salts behind.
• Honeycombalso honeycombing, rock pocket
  Patches of bare, loosely bound stone with open gaps, left where paste never worked in around the coarse rock.
• Laitancealso surface laitance, scum
  The soft, chalky skin of fines that bleed water leaves on top of concrete, too weak to bond to.
• Plastic shrinkage crackingalso plastic cracking, plastic shrinkage cracks
  Cracks that open in fresh concrete before it sets, when the surface dries faster than bleed water replaces it.
• Popoutalso pop-out, pop-outs
  A small conical crater where a swelling stone just under the surface pushed out a chip of concrete.
• Scalingalso scale, surface scaling
  Thin patches of surface mortar coming off a slab, usually after freeze-thaw cycles with deicing salt.
• Spallingalso spall, spalls
  Chunks or flakes breaking away from a concrete surface or edge, often from corroding rebar beneath.
• Sulfate attackalso sulfate exposure, external sulfate attack
  Deterioration of concrete by sulfates from soil, groundwater or seawater reacting with the cement paste.
• Wild crackalso random crack, uncontrolled crack
  An uncontrolled crack that wanders across a slab panel instead of forming under a control joint. Shop talk

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