Concrete Glossary

Autoclave A chamber in which various cement based products are subject to an environment of high pressure steam to speed up the hardening and curing. Typically the design strength can be achieved in 24 hours or less. Autoclaved Aerated Concrete (A.A.G.) A lightweight form of concrete manufactured from sand, cement, recycled material, lime, gypsum and an aerating agent, aluminium paste. Used in pre-cast products such as building blocks and panels. Back-Fill The fill material or the process of filling and compacting excavations when the work has been completed. Bar Chairs Plastic, metal or cement products used for supporting reinforcing steel and maintaining the correct amount of concrete cover in reinforced concrete construction. Bleed Water Water that rise to the surface of concrete of freshly poured concrete during the process of laying, vibrating and screeding. Blistering on Concrete Faults on finished concrete, caused by entrapped air or bleed water below the surface. Broom Finish Concrete A simple and basic non-skid finish to concrete paved areas created by drawing a stiff brush or broom over the surface. Building Foundation The part of a building that sits immediately on the natural ground, rock or compacted fill. The base that supports the building. A base for machinery. Usually all or part is below ground level. Bush Hammered Concrete Concrete that has the surface textured with a bush hammer. Cast in-situ Concrete Concrete that is cast in place. Formwork is used to hold the wet concrete in place Cement Types A list of the various types of cement most commonly used in building construction. Cold Joints An unplanned joint that should never happen. When one batch of concrete in a continuous pour starts to go off before the next batch is available Compression test A laboratory test of the compressive strength of concrete samples. Concrete Screed A machine or a hand tool for doing the primary leveling of a freshly poured concrete slab. Concrete Vibration A method of consolidating wet or plastic concrete by applying either internal or external vibration to the concrete to remove gross voids and entrapped air pockets. concrete additives Admixtures added to a normal concrete mix either before or during the mixing process to alter the characteristics of the concrete. Concrete Batching Plant Usually situated in an industrial area a plant that delivers all the ingredients of a concrete mix into concrete trucks for delivery of fresh concrete to construction sites. Concrete Bullfloat A concrete finishing tool. Used after screeding to level the surface and to bring the fat to the surface prior to troweling, Concrete Corefill A concrete mix designed for filling the hollow cores of reinforced CMU blocks Concrete Cover The amount of concrete that covers and protects the rebar or reinforcing steel in reinforced concrete. Concrete Fill A mix of concrete designed to fill the cavity of cavity brick walls from the foundation to the damp proof course level. Concrete Finishing The process of bringing freshly poured concrete to it's completed surface finish. Concrete Kibble A hopper like receptacle for lifting concrete and positioning concrete it by crane. The size of the kibble is goverened by the lifting capacity of crane available. The discharge is either from the bottom or side. Concrete Masonry Unit CMU A hollow concrete building block. The CMU system allows for masonry walls to be built in a range of sizes and applications including the use of reinforced concrete vertical cores and horizontal and sloping beams. Concrete Mixer A machine for mixing concrete and mortar. Concrete Pavement A horizontal layer of concrete laid on the ground outdoors as a pavement. Ranges from highway construction to footpaths. Concrete Pavers Factory made products in all shapes and sizes for creating paved areas. Usually in the open and on the ground. Concrete Pump A machine for pumping wet concrete. In most cases they are mobile being truck or trailer mounted. Larger projects use fixed pumps. Concrete Rebar Steel reinforcing bars of various diameters, patterns and steel grades used for reinforcing concrete. Concrete Rebar Ligatures Made up rebar fitments for forming cages to increase the compressive strength of reinforced columns and beams. Also they contribute to accurately positioning the main reinforcing bars. Concrete Saw A saw with a diamond blade that will cut concrete and bitumen pavements. Ranges from hand tool eclectic driven to petrol or diesel engined self propelled models. Concrete Suspended Slab A slab spanning between walls, columns or other supports. Distinct from a slab on the ground. Concrete Testing The process of testing concrete to see that it conforms to the specifications and standards governing its use. Concrete Transit Mixer Usually a road registered truck that brings concrete from a batching plant to the job site. When it is traveling (in transit) the bowl is turning and the concrete is being mixed. Continuous Mixer A mixer that is used for concrete or mortar in production processes that produces an uninterrupted source of concrete in contrast to a batch mixer Control Joint Grouting The injection of grout or mastic into control joints Control Joints A purpose made groove in a concrete slab that is made to control unsightly cracking in concrete slabs. Curing Concrete Keeping freshly poured concrete in a condition that it does not dry out too soon and so weaken the finished product. Cyclopean Concrete Mass concrete that also contains large stones or rocks. Typically not less than football size, but they can a lot larger in civil engineering work. Decorative Concrete Concrete pavements and floors that have the surface modified in some way to provide a decorative effect. Deformed Bars Steel reinforcing bars for concrete that are manufactured with deformations on the surface that aid in creating a bond between the bar and the concrete. In addition the various patterns can be a guide for inspectors and others in identifying the grade of the bars. Dowel Bars Reinforcing bars set across an expansion joint or construction joint that allow movement horizontally but keep the vertical movement across the joint in a minimum Expansion Joints Joints in concrete between different parts of a building to accommodate varying degrees of movement Exposed Aggregate Concrete Concrete pavements that have the surface washed before the final set to provide a decorative effect. External Concrete Vibrators Vibrating machines that are fixed to formwork or casting tables and the like to consolidate wet concrete. Fly-Ash Concrete A lightweight concrete using a by product of coal fired power stations, pelletized fly-ash as an aggregate. When used in lightweight masonry blocks the name cinder blocks is often used. Granolithic Concrete A concrete suitable for conditions of hard surface wear and heavy traffic areas. Granolithic Concrete Topping A concrete topping layer added to standard concrete, when it is either hard, green or still semi-plastic. To make the surface suitable for conditions of hard wear and heavy traffic areas. Hand Screed A length of aluminium box section with a handle attached that one man can use to level freshly poured concrete. Or a larger section of aluminium or timber that two men can use to straddle the work. Internal Vibrators Machine driven oscillating probes that are placed into wet concrete to vibrate it. Laitance A layer of weak powdery material on the surface of hardened concrete, that is caused too much water for any reason, segregation, or over vibration. Lime Mortars Traditional mortars for brickwork and masonry that derive from crushed and heated limestone. Mass Concrete Concrete without reinforcement. Often poured in large quantities. Modern Concrete Said to be the most common of all man made materials. It an artificial stone made by combining water with various aggregates and a binding material which most commonly is Portland Cement. No-Fines Concrete Concrete that contains little or no fine aggregate or sand. Non-cement Binders Materials other than Portland cement that can be used as binders for concrete, grouts and mortars. Off Form Concrete Concrete that has no particular finish added to it after the removal off the formwork. In many cases the formwork is designed to create a certain finish purely for effect. Pad Foundations Also known a pier foundation. A foundation designed to carry a point load from a column, post or a pier. Often square, rectanglular or circular in plan. Placing Concrete Also called pouring concrete. The filling of concrete formwork with plastic concrete. Plain Concrete Concrete containing no more than 0.2% of reinforcing. Polished Concrete Concrete pavements or floors that have the surface ground and polished to provide a decorative effect. Portland Cement Portland Cement Post Tensioned Concrete Concrete elements that have their tendons tightened after the concrete has been poured. Power Float. A machine for applying the final finish to concrete slabs by means of rotating steel floats. Power Screed In it's simplest form an aluminium frame that duplicates the size and action of hand screed, to larger double beam and truss screeds that sit on the formwork either side and spanning the slab being leveled. They have a motorised vibrator mounted on it and drawn from one end of the slab to the other by two men, or by a vehicle mounted winch. They performs the function of an external vibrator and screed. Pozzolanic Concrete A concrete using volcanic ash as an aggregate. From the Roman name for the ash Pozzolana. More often today it would consist of fly ash. Pre Tensioned Concrete Concrete elements that have their tendons tightened before the concrete has been poured. Precast Concrete Prefabricated concrete building elements that are made or manufactured elsewhere than their final position in the structure. The Opposite of cast in-situ. Cast in place. Prestressed Concrete Reinforced concrete in which internal stresses are introduced deliberately by using tensioned steel wire tendons to conteract the calculated tensile forces that the finished element will be subjected to. Prestressed Concrete Wire Steel wire that has a very high tensile strength used for prestressing concrete. Raft Foundation, Raft Slab A continuous concrete slab foundation usually reinforced. With perimeter beams and slab thickenings under internal load bearing walls. Used in poor ground conditions. Ready-Mixed Concrete Concrete that is not mixed on site, but which is batched at a central plant and delivered to the site by transit mixers. Reinforced Concrete Concrete that has been strengthened by the addition of other materials, usually steel to increase it's strength to resist tensile forces. Reinforcing Mesh Steel welded mesh sheets using bars of various diameters, patterns and steel grades used mainly for reinforcing concrete slabs. Roman Concrete The first form of concrete. Devised by the Romans over two thousand years ago some of their concrete structures and buildings are still standing so it is also the longest lasting form of concrete. Seeded Finish Concrete A concrete finish having a layer of decorative chips of stone, pebbles or the like scattered over the wet surface of the main concrete mix. Shrinkage Cracks Unsightly and unplanned cracks in a concrete slab. Can be caused in an otherwise good slab by lack of control joints or because of faults and bad concreting technique Slab Vapor Barrier A layer of plastic film laid under concrete slabs to stop water vapour entering the concrete. Mandatory in many jurisdictions for habitable rooms. Slump A distance measurement that gives an on site indication of the wetness of a mix of concrete. A standard sized steel cone is filled with wet concrete and compacted. It is then removed and the amount that the concrete sags or slumps is an indication of the amount of water in the mix. Slump Test An on site method of testing fresh concrete to determine if it has the correct amount of slump. Sponge Finish Concrete A simple and basic non-skid finish to concrete paved areas created by the surface with a sponge. Stairs in Concrete Stairs that are formed and poured with cast in-situ concrete or precast elements that are used to form stairs and stair flights. Stamped Concrete Concrete pavements that have the surface stamped before the final set to provide a decorative effect. Starter Bars Steel reinforcing bars cast into two separate pours of concrete. With lap joints to main bars they continue the reinforcement through the concrete joint. Stenciled Concrete Concrete that has the surface textured and patterned with a stencil process. Strip Footing A footing that is longer in one direction than the other. Typically under walls. Tempcore Rebar Bars that are made with this process have a core of high grade steel for strength while retaining an outer ring of more ductile steel for ease of bending and welding. Tools for Concrete Hand finishing tools for concrete, edger, jointer, wood float, steel float, magnesium float etc. Trench Mesh Narrow welded mesh sheets using heavy bars for the long bars and lighter bars for the cross bars. Used in strip footings and beam sections in raft slabs.