Self consolidating concrete spread test vs slump, research decorative concrete

Note how there is almost no segregation, bleeding or variation. In other words, the mix should require minimal force to initiate flow, yet have adequate cohesion to resist aggregate segregation and excess bleeding.

A well graded aggregate distribution minimizes cement paste content as well as minimizes admixture dosage.

Understanding Self-Consolidating Concrete | Concrete Countertops Blog

A T20 between 2 and 5 seconds is taken as a low viscosity concrete. Typical SCC mixes have slump flows ranging from 18 to 30 inches. The spread can range from 18 to 32 inches to mm. ASTM A slump flow test is often performed with the slum cone upside down.

The slump flow is measured as the diameter of the pancake.

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When the cone is lifted, the SCC spreads out like pancake batter. A higher T20 T50 value indicates a more viscous mix which is more appropriate for concrete in applications with congested reinforcement or in deep sections.

The resistance to segregation is observed through a visual stability index VSI. The technician observes the concrete as it spreads out in the slump flow test.

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Recently, pads with a printed inch circle have been developed to make this test easier. J-ring—The J-Ring is a measure of the concrete's passing ability—how easily it flows through obstructions and reinforcing.

Self-Consolidating Concrete Testing - The Concrete Network

Here is a brief description tinder dating sites photos of girls each—more information can be found in the appropriate ASTM test self consolidating concrete spread test vs slump. Thanks to Euclid Chemical for this video segment.

Other considerations Excess moisture in the ingredients, especially the fine aggregates, can have a profound influence on the consistency of the mix. The flowability of SCC is measured in terms of spread instead of slump, because the material flows so readily. This new generation of synthetic admixture has been specially designed to increase the dispersion of the cement particles, which aids in plasticity, strength and can also help with pigment dispersion.

Understanding Self-Consolidating Concrete

SCC diagram The preferred admixture for reducing yield stress in self-consolidating concrete is a polycarboxylate-based admixture due to its superior water-reduction capabilities and high early-strength gains at low dosing rates. And variations in the aggregate gradation from batch to batch can also cause consistency problems.

Segregation probe—Not yet standardized, this test measures segregation by placing a thin wire ring atop the SCC and measuring how far it sinks into the concrete in two minutes. T20 or T50 test-This is a measure of the concrete's viscosity and is measured as the amount of time it takes for concrete in the slump flow test to reach a diameter of 20 inches or 50 centimeters.

Bill Palmer The T20 test measures viscosity by timing how many seconds it takes for the concrete to spread to 20 inches in diameter. This test promises to provide a quantitative value for segregation potential. The J-ring test is a variation to the slump flow, where a simulated rebar cage is placed around the slump cone and the ability of the SCC mix to spread past the cage without segregation is evaluated.

Another test being standardized is a column test, which measures the coarse aggregate content of concrete at different heights in a placed columnar specimen as an indication of stability or resistance to segregation.

Testing Self-Consolidating Concrete

A VSI of 0 or 1 indicates a stable mix, while a 2 or 3 is unstable. Avoiding segregation through aggregate gradation and by increasing the amount of fines is possible, but it must be done carefully to preserve the SCC properties.

In the decorative concrete arena it has been used to produce castings with a high surface quality, often with few or no pinholes.

The primary test used in the field for SCC is slump flow, although there are other fields tests currently in use.

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A lower T20 T50 value may be appropriate for concrete that has to travel long horizontal distances without much obstruction. The slump flow test is run both with and without the J-Ring in place and the passing ability is the difference in slump flow.

The U-Box and L-Box tests are used for product development or prequalification and involve filling concrete on one side of the box and then opening a gate to allow the concrete to flow through the opening containing rebar.

The U- box, L-box and J-ring tests measure the passing ability of concrete in congested reinforcement. A difference greater than 2 inches indicates poor passing ability.

A more robust mix is ultimately created with an enhanced capacity to absorb fluctuations in aggregate gradations and moisture contents. The slump cone is completely filled without consolidation, the cone lifted, and the spread of the concrete measured.

A number from 0 to 3 is assigned—0 for no segregation to 3 for obvious segregation and paste separation cement, water, and fines from the concrete matrix. The slump flow test, using the traditional slump cone, is the most common field test and is in the process of being standardized by ASTM.

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Thanks to our Website Sponsors Testing Several test procedures have been successfully employed to measure the plastic properties of Self-Consolidating Concrete.

The yield stress is reduced by using an advanced synthetic high-range water-reducing admixture HRWRwhile the viscosity of the paste is increased by using a viscosity-modifying admixture VMA or by increasing the percentage of fines incorporated into the SCC mix design.

The VSI is established based on whether bleed water is observed at the leading edge of the spreading concrete, or if aggregates pile at the center. Less labor, quicker casting times, better surface finish and increased concrete densities are common reasons for choosing SCC.

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During the slump flow test, the viscosity of the SCC mixture can be estimated by measuring the time taken for the concrete to reach a spread diameter of 20 inches mm from the moment the slump cone is lifted up.