Change in Flowability of Self-Compacting Concrete due to Pumping

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Rm 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 5 min 5 min 3 min 3 min 1 min 0.0 2.0 4.0 6.0 8.0 Gm External force 1 minute still A-1 A-2 The relationship between the duration of applying the external force and the rate of change in the deformability is shown in (Fig. 8). The deformability was reduced due to the external force. When the water to cement ratio or the dosage of SP was high, the reduction in the deformability was small. It was found from the result that when Gm was large, the influence of external force was small. If the viscosity before applying external force was low, the change in Gm was also small. Rm Rm Fig. 5 Change in flowability due to external force: difference in SP dosage 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 5 min 5 min 3 min 1 min 0.0 2.0 4.0 6.0 8.0 5 min 1 min 3 and 5 min 3 min Gm 1 min 3 min 1 min still 0.0 2.0 4.0 6.0 8.0 Gm still A-1 B-1 Fig. 6 Change in flowability due to external force: difference in water to cement ratio still A-1 C-1 Fig. 7 Change in flowability due to external force: difference in water to cement ratio The rate of change of Rm is shown in Fig. 9. Rm of C-1 was reduced remarkably after one minute as well as Gm. . Rate of change of Gm (%) Rate of change of Rm (%) 20 0 -20 -40 -60 -80 -100 60 50 40 30 20 10 0 -10 -20 -30 -40 A-1 A-2 B-1 C-1 0 1 2 3 4 5 6 Action time of external force (min) Fig. 8 Rate of change in deformability due to external force A-1 A-2 B-1 C-1 0 1 2 3 4 5 6 Action time of external force (min) Fig. 9 Rate of change in viscosity due to external force
3.2 Influence on compressive strength The relationship between the duration of applying the external force and the compressive strength is shown (Fig. 10). The compressive strength was increased with the increase of the duration of applying the external force despite of the type of the mix-proportioning. It is assumed that the external force dispersed the coagulated cement particles and it promoted the hydarion of the cement particles, which resulted in the higher compressive strength 4) . SP adsorbed amount (mg/g) 6.5 A-1 A-2 6.0 B-1 5.5 5.0 4.5 0 1 2 3 4 5 6 Action time of external force (min) Fig. 11 External force increased adsorption of superplasticizer to cement Also, the specific surface area of cement particle Compressive strength (N/mm 2 ) 75 73 71 69 67 65 63 61 59 57 55 A-1 A-2 B-1 C-1 0 1 2 3 4 5 6 Action time of external force (min) Fig. 10 External force increased compressive strength 3.3 Specific surface area of a cement particle due to action of external force The external force increased the amount of superplasticizer adsorbed to cement (Fig. 11). However, the deformability was reduced although the deformability was reduced. was measured for A-1 and A-2 (Fig 12) by BET method. The specific surface were increased greatly due to the external force. It was found from the result that the cement particles were dispersed due to the external force. That is, it is possible that the dispersion of cement particles influenced the change in the flowability. 2.0 Specific surface area (m 2 /g) 1.8 1.6 1.4 1.2 A-1 A-2 1.0 0 1 2 3 4 5 6 Action time of external force (min) Fig. 12 External force increased surface area of cement particles The relationship between the amount of superplasticizer adsorped to the cement particles and the specific surface area was examined (Fig. 13). Increased total surface area of the cement particles
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Change in Flowability of Self-Compacting Concrete due to Pumping

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