ACI SCC Testing key terms

A highly flowable concrete that spreads under its own weight to fill formwork and encase reinforcement without mechanical vibration, while remaining cohesive enough to resist segregation during placement.

The capacity of fresh SCC to flow and deform under its own weight into all parts of a form, including corners and narrow sections, without applied vibration.

The ability of fresh SCC to flow through congested reinforcement and narrow openings without blocking, bridging, or segregating the coarse aggregate.

The ability of fresh SCC to keep its coarse aggregate uniformly distributed and suspended in the paste during transport, placement, and at rest, resisting static and dynamic separation.

A field test in which a slump cone filled with SCC is lifted and the resulting spread diameter is measured; the value indicates filling ability and is typically reported to the nearest 10 mm (0.5 in.).

The elapsed time for fresh SCC to spread to a diameter of 500 mm (20 in.) after the slump cone is raised, used as an indicator of viscosity and flow rate.

The average of two perpendicular measurements across the circular patty of SCC formed in a slump flow test, used to classify filling ability.

A test that places a ring of vertical bars around the slump cone so that the spread must pass between the bars; the difference in spread with and without the ring indicates passing ability.

An apparatus with a vertical channel and a horizontal channel separated by vertical reinforcing bars; the height ratio of SCC remaining in the two sections after flow indicates passing ability.

A condition in which coarse aggregate particles accumulate and bridge behind reinforcing bars or at a narrow opening, restricting flow and producing non-uniform filling of the form.

A qualitative rating from 0 to 3 assigned to the slump flow patty based on bleeding, mortar halo, and aggregate pile, used to judge segregation resistance in the field.

A laboratory test using a segmented vertical column of SCC allowed to rest; the difference in coarse aggregate content between top and bottom sections gives a static segregation index.

A measure of a fresh SCC mixture's resistance to flow, controlling how quickly it spreads and how well it carries coarse aggregate without separation.

The minimum shear stress needed to start a fresh concrete mixture flowing; in SCC it is low enough that the material deforms and spreads under its own weight.

The study of flow and deformation of fresh mixtures, often described for concrete with yield stress and plastic viscosity parameters that govern SCC performance.

A chemical admixture, also called a superplasticizer, that greatly increases flow at low water content by dispersing cement particles; it is central to producing SCC.

An admixture that increases the cohesiveness and viscosity of fresh SCC, improving segregation resistance and stability while limiting bleeding and settlement.

A material such as fly ash, slag cement, or silica fume used with portland cement to improve workability, reduce heat, or increase strength and durability in SCC mixtures.

The mass ratio of water to total cementitious binder in a mixture; it strongly influences strength, durability, and the balance between flow and stability in SCC.

The proportion of a concrete mixture occupied by cementitious materials, water, and admixtures; SCC typically uses a high paste volume to lubricate aggregate and enable flow.

The mass or volume of gravel or crushed stone per unit volume of concrete; limiting it helps SCC pass through reinforcement without blocking.

The mixture of cementitious materials, water, admixtures, and fine aggregate; its flow properties largely control the filling ability of SCC.

A laboratory test that measures the spread of mortar on a flow table after a set number of drops, used to assess the flow and stability of the mortar fraction of SCC.

The upward migration of mixing water to the surface of freshly placed concrete; excessive bleeding in SCC can reduce bond and indicate poor stability.

Downward movement of solid particles in fresh SCC as it rests, which can cause bleeding, surface laitance, or reduced uniformity around embedded reinforcement.

The lateral pressure exerted by fresh SCC on formwork; because SCC flows and consolidates under its own weight, pressure can approach full hydrostatic values and requires stronger form design.

The speed at which SCC is placed into forms; it influences form pressure development and must be coordinated with formwork capacity and mixture setting characteristics.

Separation of the constituents of fresh concrete, such as coarse aggregate settling from mortar or paste separating from aggregate, leading to non-uniform hardened properties.

The ability of fresh SCC to remain uniform and cohesive, resisting segregation, bleeding, and settlement from mixing through hardening.

The standard metal mold, open at both ends, used to form fresh concrete for slump flow and related tests before it is lifted vertically.

A mechanical table that imparts repeated vertical drops to a mortar sample, used in laboratory flow testing of the mortar fraction of SCC.

Standardized handling of a fresh SCC sample before testing, including mixing, temperature, and elapsed time, so results are representative and repeatable.

The required number of field tests per volume of concrete or per placement, set by specification to verify that SCC consistently meets slump flow and stability requirements.

The specified limits on test results, such as slump flow range, T50 time, or VSI, that a delivered SCC mixture must meet to be accepted for placement.

The process of verifying and adjusting test equipment, such as scales, timers, or flow tables, against known references so measurements are accurate and traceable.

The closeness of agreement among test results obtained by the same operator with the same equipment on identical material under the same conditions.

Laboratory testing of hardened SCC specimens, such as compressive strength or density, to confirm that field-placed material meets specified performance requirements.