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OCR for page 29
29 Glossary Some of the following definitions are general and apply to con- Deformability--The ability of SCC to flow under its own mass and fill ventional concrete, while others are specific to self-consolidating completely the formwork. concrete. Some of these definitions are based on definitions given in Drying shrinkage--Shrinkage occurring in a specimen that is exposed American Concrete Institute (ACI) and Precast/Prestressed Concrete to the environment and allowed to dry (ACI 209). Institute (PCI) technical documents. Fillers--Finely divided inert material, such as pulverized limestone, sil- ica, or colloidal substances, sometimes added to portland cement Admixture--A material, other than water, aggregates, hydraulic ce- paint or other materials to reduce shrinkage, improve workability, ment, and fiber reinforcement, used as an ingredient of a cementi- or act as an extender or material used to fill an opening in a form tious mixture to modify its freshly mixed, setting, or hardened (ACI 116). properties and that is added to the batch before or during its mix- Filling ability--The ability of SCC to flow into and fill completely all ing (ACI 116). spaces within the formwork, under its own weight, also referred to Autogenous shrinkage--The shrinkage occurring in the absence of as deformability or non-restricted deformability (ACI 237). moisture exchange due to the hydration reactions taking place in- Filling capacity--The ability of SCC to flow into and fill completely all side the cement matrix (ACI 209). spaces within the formwork. Binder--A cementing material, either a hydrated cement or reaction Flowability--The ability of fresh concrete to flow in confined or un- products of cement or lime and reactive siliceous material; also, confined form of any shape, reinforced or not, under gravity and/or materials such asphalt, resins, and other materials forming the external forces, assuming the shape of its container (PCI 2003). matrix of concretes, mortars, and sanded grouts. Fluidity--The ease by which fresh concrete flows under gravity (PCI Bingham fluid--A fluid characterized by a yield stress and a constant 2003). Fluidity is the reciprocal of dynamic viscosity. plastic viscosity, regardless of flow rate (PCI 2003). Fly ash--The finely divided residue that results from the combustion Bleed water--The water that rises to the surface subsequent to the of ground or powdered coal and that is transported by flue gasses placing of the concrete. The rise of mixing water within, or its emer- from the combustion zone to the particle removal system (ACI gence from, newly placed concrete, caused by settlement and con- 116). Because of its spherical shape and fineness, fly ash can im- solidation of the plastic concrete (PCI 2003). prove the rheology of SCC. Bleeding test--The standard test for determining the relative quantity Formwork pressure--Lateral pressure acting on vertical or inclined of mixing water that will bleed from a sample of freshly mixed con- crete (ASTM C 232). formed surfaces, resulting from the fluid-like behavior of the un- Blocking--The condition in which coarse aggregate particles combine hardened concrete confined by the forms (ACI 116). to form elements large enough to obstruct the flow of the fresh con- Ground granulated blast-furnace slag (GGBFS)--A fine granular, crete between the reinforcing steel or other obstructions in the mostly latent hydraulic binding material that can be added to SCC concrete formwork (PCI 2003). to improve workability of the material (PCI 2003). GGBFS is also Cohesiveness--The tendency of the SCC constituent materials to stick referred to in some cases as slag cement (a waste product in the together, resulting in resistance to segregation, settlement, and manufacture of pig iron and chemically a mixture of lime, silica, bleeding (PCI 2003). and alumina). Consistency--The relative mobility or ability of freshly mixed concrete High-range water-reducing admixture (HRWRA)--A water-reducing or mortar to flow (ACI 116). admixture capable of producing large water reduction or greater Consolidation--The process of inducing a closer arrangement of the flowability without causing undue set retardation or entrainment of solid particles in freshly mixed concrete or mortar during place- air in mortar or concrete (ACI 116). ment by the reduction of entrapped voids (ACI 116). In SCC, con- J-Ring flow--The distance of lateral flow of concrete using the J-Ring solidation is achieved by gravity flow of the material without the in combination with a slump cone (ASTM C 1621). need of vibration, rodding, or tamping. J-Ring test--Test used to determine the passing ability of SCC, or the Creep--Time-dependent deformation due to sustained load (ACI degree to which the passage of concrete through the bars of the 209). J-Ring apparatus is restricted (ASTM C 1621).

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30 L-box test--Test used to assess the confined flow of SCC and the extent Silica fume--Very fine non-crystalline silica produced in electric arc to which it is subject to blocking by reinforcement (ACI 237). furnaces as a byproduct of the production of elemental silicon or Metakaolin--Mineral admixture used as binding material (supple- alloys containing silicon (ACI 116). Silica fume can be added to SCC mentary cementitious material) in concrete (PCI 2003). to improve the rheological properties. Mixture robustness--The characteristic of a mixture that encompasses Slump flow--Test method used (upright or inverted) to measure mix- its tolerance to variations in constituent characteristics and quan- ture filling ability (ASTM C 1611). tities, as well as its tolerance to the effects of transportation and Slump flow retention--The ability of concrete to maintain its slump placement activities (PCI 2003). flow over a given period of time. Passing ability--The ability of SCC to flow under its own weight (with- Slump flow spread--The distance of lateral flow of concrete during the out vibration) and completely fill all spaces within intricate form- slump-flow test (ASTM C 1611). Slump flow spread is the numer- work, containing obstacles, such as reinforcement (ASTM C 1621). ical value in inches (mm) of flow determined as the average diam- Paste volume--Proportional volume of cement paste in concrete, mor- eter of the circular deposit of SCC at the conclusion of the slump tar, or the like, expressed as volume percent of the entire mixture flow test. (ACI 116). Stability--The ability of a concrete mixture to resist segregation of the Plastic viscosity--The resistance of the plastic material to undergo a paste from the aggregates (ASTM C 1611). given flow. It is computed as the slope of the shear stress versus Stability, Dynamic--The resistance to segregation when external en- shear rate curve measurements. Mixtures with high plastic viscos- ergy is applied to concrete, namely during placement. ity are often described as "sticky" or "cohesive." Concrete with Stability, Static--The resistance to segregation when no external en- higher plastic viscosity takes longer to flow. It is closely related to ergy is applied to concrete, namely from immediately after place- T-50 and V-funnel time (higher plastic viscosity: higher T-50 and ment and until setting. V-funnel time). T-50 measurement (also referred to as the T-20 in. time in North Powder (also referred to as graded powder)--Includes cement, fly ash, America)--The time for the concrete to reach the 500 mm GGBFS, limestone fines, material crushed to less than 0.125 mm (20 in.) diameter circle drawn on the slump plate, after starting to (No. 100 sieve), or other non-cementitious filler (ACI 237). raise the slump cone (ASTM C 1611). Powder-type SCC--SCC mixtures that rely extensively on the amount Texture--The pattern or configuration apparent in an exposed surface, and character of the fines and powder included in the mixture for as in concrete and mortar, including roughness, streaking, striation, meeting workability performance requirements (stability) (PCI or departure from flatness (ACI 116). 2003). Thixotropy--The property of a material that enables it to stiffen in a Pumpability--The ability of an SCC mixture to be pumped without short period while at rest, but to acquire a lower viscosity when me- significant degradation of workability (PCI 2003). chanically agitated, the process being reversible, a material having Rheological properties--Properties dealing with the deformation and this property is termed thixotropic or shear thinning (ACI 116). flow of matter (PCI 2003). Thixotropy indicates formwork pressure and segregation resistance Rheology--The science of dealing with flow of materials, including of SCC. studies of deformation of hardened concrete, the handling and Transportability--The ability of concrete to be transported from the placing of freshly mixed concrete, and the behavior of slurries, mixer to the placement site while remaining in a homogeneous pastes, and the like (ACI 116). In the context of SCC, rheology condition (PCI 2003). refers to the evaluation of yield stress, plastic viscosity, and thixotropy to achieve desired levels of filling ability, passing ability, V-funnel--Device used to determine the time for a given volume of and segregation resistance. concrete to flow out through a funnel opening (PCI 2003). Segregation--The differential concentration of the components of Viscosity--The resistance of a material to flow under an applied mixed concrete, aggregate, or the like, resulting in non-uniform shearing stress (ASTM C 1611). proportions in the mass (ACI 116). In the case of SCC, segregation Viscosity-modifying admixture (VMA)--An admixture used for en- may occur during transport, during flow into the forms, or after hancing the rheological properties of cement-based materials in the placement when the concrete is in a plastic state. This results in plastic state to reduce the risk of segregation and washout (ACI 237). non-uniform distribution of in-situ properties of the concrete. Visual Stability Index (VSI)--A test that involves the visual examina- Segregation resistance--The ability of concrete to remain uniform in tion of the SCC slump flow spread resulting from performing the terms of composition during placement and until setting (PCI slump flow test (ACI 237). 2003). Segregation resistance encompasses both dynamic and static Water-cementitious material ratio (w/cm)--The ratio of the mass of stability. water, exclusive only of that absorbed by the aggregate, to the mass Self-consolidating concrete (SCC) (also self-compacting concrete)--A of cementitious material (hydraulic) in concrete, mortar, or grout, highly flowable, non-segregating concrete that can spread into place, stated as a decimal (ACI 116). fill the formwork, and encapsulate the reinforcement without any Workability--That property of freshly mixed concrete or mortar that mechanical consolidation (ACI 237). determines the ease with which it can be mixed, placed, consoli- Service life--The time during which the structure performs its design dated, and finished to a homogenous condition (ACI 116). For functions without unforeseen maintenance or repair. SCC, workability encompasses filling ability, passing ability, and Settlement--The condition in which the aggregates in SCC tend to sink segregation resistance, and it is affected by rheology. to the bottom of the form resulting in non-homogeneous concrete Yield stress--The minimum shear stress required to initiate (static (PCI 2003). Surface settlement can also be caused by bleeding of yield stress) or maintain (dynamic yield stress) flow (ACI 237). The free water and loss of air as well as movement of aggregate particles yield stress is closely related to slump flow (lower yield stress re- within fresh concrete (consolidation). sults in higher slump flow); it is calculated as the intercept of Shear stress--The stress component acting tangentially to a plane (ACI the shear stress versus shear rate plot from rheometer flow curve 116). measurements.