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Concrete In Australia : December 2013
32 Concrete in Australia Vol 39 No 4 FEATURE: RHEOLOGY obtained excellent finishability as shown in Figures 4 to 6 – even on some sites with congested reinforcement. Application example 2 Work summary: • Construction name: Dam construction work • Construction location: Setup part of checking up tunnel in dam • Design strength of concrete: 40 N/mm2. Originally, powder-type SCC containing limestone powder was used. However, limestone powder could not be used due to the limitation of the production facility of RMC plant. Accordingly, LF-SCC was applied to achieve a better self- compacting property even in the case of a simple substance. Total placing volume was 1200 m3. Tables 4 and 5 show materials used for of LF-SCC and mix proportion respectively. The water to cement ratio was 0.40 to satisfy the design strength. Unit water content was 170 kg/m3. In order to improve compaction, the volume of coarse aggregate was determined to be 300 L. The target slump flow and air content were determined to be 63 cm and 4.6% by adjusting the dosage of the unique viscosity-type superplasticiser for LF-SCC and the AE agent. Fresh property Table 6 shows the fresh property of LF-SCC. The slump flow of 63 cm and time of reaching 500 mm flow of 4.5s were obtained respectively when using the unique viscosity-type superplasticiser for LF-SCC of Cx1.4%. Low viscosity self- compacting concrete was obtained while it showed better segregation resistance by visual judgment in this construction condition as well. Summary of work LF-SCC was used for the set up part of the checking tunnel in the dam. It showed very good workability and obtained excellent finishability as shown in Figures 7 to 9. Singapore The BCA (Building and Construction Authority) in Singapore has been championing the cause for a higher productivity drive in the construction industry (Productivity Improvement Program) since 2010. To support this with concrete Material Property Ordinary portland cement Density: 3.16 g/cm3 Blended sand (mountain, river and crushed) Density (Saturated surface-dry condition): 2.62 g/cm3 Andesite crushed stone Density (Saturated surface-dry condition): 2.81 g/cm3 Table 4: Materials used. Table 5: Mix proportion of LF-SCC . W/C s/a Unit content (kg/m3) Water Cement Fine aggregate Coarse aggregate 0.378 0.522 170 450 858 842 Table 6: Fresh property of LF-SCC . Superplasticiser AE agent Slump flow Air content Time of 500mm SF Time of stop of SF Concrete temp. Cx1.4% Cx0.001% 63.0 cm 4.6% 4.5s 37.4s 21.3 °C Figure 4: Placing LF-SCC by pumping. Figure 5: Placing (cover shot). Figure 6: Finishing (cover shot). 29-35 Kar.indd 32 29-35 Kar.indd 32 25/11/13 2:56 PM 25/11/13 2:56 PM