Self-Consolidating Concrete for Cast-in-Place Bridge Components (2016)

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59 Glossary Admixture: A material other than water, aggregates, cementi- tious materials, filler, and fiber reinforcement that is used as an ingredient of a cementitious mixture to modify its freshly mixed, setting, or hardened properties and that is added to the batch before or during its mixing. Aggregate blocking: The situation in which coarse aggregate particles jam between reinforcing steel bars or other obsta- cles within the form and prevent free flow of SCC. Air content: The volume of air voids in cement paste, mortar, or concrete, exclusive of pore space in aggregate particles, usually expressed as a percentage of total volume of the paste, mortar, or concrete. Angularity: The sharpness of the corners and edges of a particle (shape describes a particle on the coarsest scale, angularity on an intermediate scale, and texture on the finest scale). Bleeding: The autogenous flow of mixing water within, or its emergence from, newly placed concrete or mortar that is caused by the settlement of the solid materials within the mass, also called water gain. Bulk specific gravity (saturated surface dry): The ratio of the mass of a volume of a material including the mass of water within the pores in the material, (but excluding the voids between particles) at a stated temperature, to the mass of an equal volume of distilled water at a stated temperature. Cement: A binding material that sets and hardens by chemical reaction with water and is capable of doing so underwater. Chloride penetrability: The rate of ingress of chloride ions into concrete, which depends on the pore structure of concrete Concrete, conventionally vibrated (CVC): A composite material that consists essentially of a binding medium within which are embedded particles or fragments of aggre- gate; in hydraulic cement concrete, the binder is formed from a mixture of hydraulic cement and water and is con- solidated using mechanical vibration. Concrete, self-consolidating (SCC): Fresh concrete that can flow around reinforcement and consolidate within formwork under its own weight without vibration and that exhibits no defect due to segregation or bleeding. Consolidation: The process of inducing a closer arrangement of the solid particles in freshly mixed concrete or mortar during placement by the reduction of voids—usually in non-SCC by vibration, centrifugation, rodding, tamping, or some combination of these actions. In SCC, consolida- tion is achieved by gravity flow of the material. Creep coefficient: The ratio of the creep strain at a certain age after loading to the elastic strain at loading. Filler: Finely divided inert material, such as pulverized lime- stone, added to portland cement to reduce shrinkage and improve workability. Filling ability: The ability of SCC to flow into and fill com- pletely all spaces within the formwork, under its own weight, also referred to as deformability or non-restricted flowability. Filling capacity: The ability of SCC to flow into and fill completely all spaces within intricate formwork contain- ing obstacles such as reinforcement. Fly ash: The finely divided residue that results from the com- bustion of ground or powdered coal and that is transported by flue gasses from the combustion zone to the particle removal system. Because of its spherical shape and fineness, fly ash can improve the rheology of SCC. Ground granulated blast-furnace slag (GGBFS): A fine, gran- ular, mostly latent, hydraulic binding material that can be added to SCC to improve workability of the material. GGBFS is also referred to in some cases as slag cement (a waste prod- uct in the manufacture of pig iron and chemically a mixture of lime, silica, and alumina). Hardened visual stability index (HVSI): A test that involves the visual examination of aggregate distribution in sections made by longitudinal saw cuts of test cylinders. High-range water-reducing admixture (HRWRA): A water- reducing admixture capable of producing large water reduc-

60 tion (>12%) or greater flowability of a concrete mixture without causing undue set retardation or excessive entrain- ment of air. J-ring: An apparatus consisting of a rigid ring supported on 165⁄8 in. [16 mm] diameter rods equally spaced on a 12 in. [300 mm] diameter circle 4 in. [100 mm] above a flat surface. J-ring, D: The difference between the J-ring flow (confined) and slump flow (unconfined) rounded to the nearest ¼ in. J-ring, H: An indicator of the difference in height of the SCC patty between the inside and the outside of the ring rounded to the nearest ¼ in. Laitance: A layer of weak material derived from cementitious material and aggregate fines either (1) carried by bleeding to the surface or to internal cavities of freshly placed mixture or (2) separated from the mixture and deposited on the surface or internal cavities during placement of the mixture. Limestone powder (LSP): Finely crushed limestone with particle sizes passing the No. 100 sieve (0.15 mm) that may be used as a filler to increase the amount of powder in SCC mixes. Mortar: a mixture of cement paste and fine aggregate; in fresh concrete, the material occupying the interstices among parti- cles of coarse aggregate; in masonry construction, joint mor- tar may contain masonry cement or may contain hydraulic cement with lime (and possibly other admixtures) to afford greater plasticity and workability than are attainable with standard portland cement mortar. Nominal maximum size of aggregate (NMSA): The smallest sieve size through which the major portion of the aggregate must pass. The nominal maximum size sieve may retain 5% to 15% of the aggregate, depending on the size number. Passing ability: The ability of SCC to flow under its own weight (without vibration) and completely fill all spaces within intricate formwork containing obstacles such as reinforcement. Paste: The fraction of the concrete comprising powder, water and air, plus admixture, if applicable. Plastic viscosity: The resistance of the plastic material to undergo a given flow. Plastic viscosity is computed as the slope of the shear stress versus shear rate curve measurements. Mixtures with high plastic viscosity are often described as “sticky” or “cohesive.” Concrete with higher plastic viscosity takes longer to flow. Plastic viscosity is closely related to T50. Powder: Includes cement, fly ash, GGBFS, limestone fines, material crushed to less than 0.125 mm (No. 100 sieve), or other non-cementitious filler. Pozzolan: A siliceous or silico-aluminous material that will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary tem- peratures to form compounds having cementitious prop- erties (there are both natural and artificial pozzolans). Pumpability: The ability of an SCC mix to be pumped without significant degradation of its fresh SCC properties. Rheological properties: Properties dealing with the deforma- tion and flow of the fluid fresh SCC mixture. Rheology: The science of dealing with flow of materials, including studies of deformation of hardened concrete, the handling and placing of freshly mixed concrete, and the behavior of slurries, pastes, and the like. In the context of SCC, rheology refers to the evaluation of yield stress, plastic viscosity, and thixotropy to achieve desired levels of filling ability, passing ability, and segregation resistance. Rheometer: An instrument for measuring the rheological properties of a substance. Segregation: The differential concentration of the compo- nents of mixed concrete, aggregate, or the like, resulting in non-uniform proportions in the mass. In the case of SCC, segregation may occur during transport, during flow into the forms, or after placement when the concrete is in a plas- tic state. This results in non-uniform distribution of in-situ properties of the concrete. Setting: The process occurring due to chemical reactions after the addition of mixing water, which results in a gradual development of rigidity of a cementitious mixture. Silica fume: Very fine non-crystalline silica produced in electric arc furnaces as a byproduct of the production of elemental silicon or alloys containing silicon. Slump flow: The average diameter of the SCC patty after con- ducting the slump flow test using the slump cone (upright or inverted) to measure mixture filling ability. Spacing factor: An index related to the maximum distance of any point in a cement paste or in the cement paste fraction of mortar or concrete from the periphery of an air void (also called Powers’ spacing factor). Specific surface: The surface area of particles or of air voids contained in a unit mass or unit volume of a material. Stability, dynamic: The resistance to segregation when exter- nal energy is applied to concrete, namely during placement. Stability, static: The resistance to segregation when no exter- nal energy is applied to concrete, namely from immediately after placement and until setting. Supplementary cementitious material: An inorganic material such as fly ash, silica fume, metakaolin, or slag cement that reacts pozzolanically or hydraulically. T50: Also referred to as the T-20 in. time in North America. That is the amount of time for the concrete to reach the 500 mm (20 in.) diameter circle drawn on the slump plate, after starting to raise the slump cone. Thixotropy: A property of a material to thin upon isothermal agitation and to thicken upon subsequent rest. Time of initial setting: The amount of time required for a freshly mixed cement paste, mortar, or concrete to achieve initial setting.

61 Viscosity-modifying admixture (VMA): An admixture used for enhancing the rheological properties of cement-based materials in the plastic state to reduce the risk of segregation. Visual stability index (VSI): A test that involves the visual examination of the SCC slump flow spread resulting from performing the slump flow test. Void, air: A space in cement paste, mortar, or concrete filled with air; an entrapped air void is characteristically 1 mm or more in width and irregular in shape; an entrained air void is typically between 10 and 1,000 µm in diameter and spherical or nearly so. Water-cementitious materials ratio (w/cm): The ratio of the mass of water, exclusive only of that absorbed by the aggre- gates, to the mass of cementitious material (hydraulic) in concrete, mortar, or grout, stated as a decimal. Water-to-powder ratio (W/P): The ratio of the mass of free water to the mass of solids composing the paste (material passing the No. 100 [0.15 mm] sieve) in a concrete or mortar mixture. Workability: That property of freshly mixed concrete or mor- tar that determines the ease of it being mixed, placed, consol- idated, and finished to a homogeneous condition. For SCC, workability encompasses filling ability, passing ability, and segregation resistance. Workability is affected by rheology. Yield stress: The minimum shear stress required to initiate (static yield stress) or maintain (dynamic yield stress) flow. The yield stress is closely related to slump flow (lower yield stress results in higher slump flow); yield stress is calcu- lated as the intercept of the shear stress versus shear rate plot from rheometer flow curve measurements.