Self consolidating concrtete

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Improved consolidation around reinforcement and bond with reinforcement Improved pumpability.Improved uniformity of in-place concrete by eliminating variable operator-related effort of consolidation.Control of aggregate moisture content is also critical to producing a good mixture.SCC mixtures typically have a higher paste volume, less coarse aggregate and higher sand-coarse aggregate ratio than typical concrete mixtures.Modern structural elements are often designed with congested networks of reinforcing steel, requiring the high-flow characteristics of Self-Consolidating Concrete (SCC) to prevent voids and honeycombing.The ASTM C1621 J-Ring test, together with the C1611 Slump-Flow test, determine the passing ability of SCC, defined as the ability of the concrete to flow under its own weight to completely fill all spaces within the formwork.Job site water addition to SCC may not always yield the expected increase in flowability and could cause stability problems Full capacity mixer truck loads may not be feasible with SCCs of very high flowability due to potential spillage.

The viscosity, as visually observed by the rate at which concrete spreads, is an important characteristic of plastic SCC and can be controlled when designing the mix to suit the type of application being constructed.The slump flow test (see Figure 1), using the traditional slump cone, is the most common field test and is in the process of being standardized by ASTM.The slump cone is completely filled without consolidation, the cone lifted and the spread of the concrete is measured.The high flowability of SCC is generally attained by using high-range-water-reducing (HRWR) admixtures and not by adding extra mixing water.The stability or resistance to segregation of the plastic concrete mixture is attained by increasing the total quantity of fines in the concrete and/or by using admixtures that modify the viscosity of the mixture.

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