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Concrete In Australia : December 2013
Concrete in Australia Vol 39 No 4 31 The reason why LF-SCC was applied for this work was its construction speed and secured compaction. Total placing volume was 1000 m3. Tables 1 and 2 show materials used for LF-SCC and mix proportion respectively. High early strength portland cement was used for the purpose of shortening work periods by enhancement of early strength. Mountain sand and gravel were applied because of existing use of the materials in the ready- mixed concrete plants as aggregate. The water to cement ratio was 0.40 to satisfy the design strength and unit water content was 170 kg/m3. In order to improve compaction, the volume of coarse aggregate was determined to be 310 L. The target slump flow and air content were determined to be 60 cm and 4.5% by adjusting the dosage of the unique viscosity-type superplasticiser for LF-SCC and the AE agent. Fresh property Table 3 shows the fresh property of LF-SCC. The slump flow of 63.0 cm was obtained when using the unique viscosity-type superplasticiser for LF-SCC of Cx1.5%. Time of reaching 500 mm flow is 3s in that case. It is faster than that of existing self-compacting concrete in Japan, around 10s, and showed very low viscosity. Additionally, the concrete has better segregation resistance by visual judgment as shown in Figure 2. Height of U-shaped test (R2) was over 300 mm as shown in Figure 3. Summary of work LF-SCC was used for the main-girder in the superstructure work. Previously ordinary concrete of 12 or 15 cm slump were cast. Since LF-SCC has excellent fluidity and compaction, it Table 1: Materials used. Material Property High-early-strength portland cement Density: 3.14 g/cm3 Mountain sand Density (Saturated surface-dry condition): 2.52 g/cm3 Gravel Density (Saturated surface-dry condition): 2.61 g/cm3 Table 2: Mix proportion of LF-SCC . W/C s/a Unit content (kg/m3) Water Cement Fine aggregate Coarse aggregate 0.40 0.522 170 425 855 810 Table 3: Fresh property of LF-SCC . Superplasticiser AE agent Slump flow Air content Time of 500mm SF Time of stop of SF Concrete temp. Height of U shape (R2) Cx1.5% Cx0.002% 62.0 cm 4.6% 3.0 s 24.5 s 16.0 °C 340 mm Figure 2: Visual judgment of fresh property of LF-SCC. Figure 3: Result of U-shaped test (R2). 29-35 Kar.indd 31 29-35 Kar.indd 31 25/11/13 2:56 PM 25/11/13 2:56 PM