ACI 544.2R-17 Report on the Measurement of Fresh State Properties and Fiber Dispersion of Fiber- Reinforced Concrete.
To perform the test, the same equipment used for the lump test is required. Once tilled, the cone is lifted, and, after the free flow of the concrete has finished, the total horizontal spread. or slump-flow diameter, is measured Acceptable ranges for the slump-flow diameter as well as recommended values for specific applications can be found in EN 206-9, ACt 237R, and EFNARC 2002.
Information on the flow rate of SCC—a measure of its viscosity—can be inferred from slump flow tests by measuring the time required for the concrete to spread to a diameter of 20 in. (500 mm), generally denoted as 7 or T. Limit values of’ T for defining viscosity classes of’ SCC and related classification can be found in ACt 237R and EN 206-9. Concrete mixwres featuring higher Tc, values will also exhibit thixotropic effects that may be good for limiting fonnwork pressure (Lomboy et aL 2014: Tichko Ct aL 2015) and improving segregation resistance, but may also lead to surface-finish issues (such as bugholes)(da Silva and tembek 2013) and sensitivity to stoppages or delays between successive lifts. Concretes with lower T, values will also exhibit good filling ability, even with congested reinforcement, and improved self-leveling ability and best surlce finish, but they will be more likely to suffer from bleeding and segregation.
Tregger et al. (2012) states that the time required for the spread flow to stop (T) is likely to correlate better with the viscosity of the fluid concrete than T. As shown in Fig., investigation focuses on two families of SCC mixtures. characterized by two values of slump-flow diameters, and, for each value of the slump-flow diameter. by different contents of viscosity-modifying admixwres (VMAs), resulting in different values of the viscosity. A visual stability index has been proposed as a standard means of determining segregation stability ot’a mixture (Khayat et al. 2000: Ferrara ci al. 2007). A numerical score on a scale of 0 (no evidence of segregation or bleeding) to 3 (clear evidence of’ a segregating mortar halo greater than 38 in. 10 mmj. large aggregate pile and fiber clumps in the center of the concrete mass, or both) is assigned bused on a visual evaluation of the segregation and bleeding in the sample. The subjectivity of’ this score limits its usefulness.
Studies have been perl’ormed to identify parameters. measurable l’rom the slump flow test. that correlate with the resistance of the fluid mixture to dynamic segregation of solid particles, including coarse aggregates and fIbers, The time required for the spread flow to stop has been correlated to the resistance of the fluid mixture to dynamic segregation of coarse aggregates and fibers (Tregger et al. 2012: Fenara et al 2012a). In this respect, threshold values of TFrnUJ to be used for quality control of SCC batches can be calibrated and selected depending on the level of resistance to dynamic segregation that is acceptable for the intended application. The selected casting procedure (pouring system and height. and maximum flow distance) can influence the selected threshold values.ACI 544.2R pdf download.