Concrete Mix Design and Experimental Program

Concrete Mix Design

Based on industry practice, standard mix designs for 40 and 25 MPa concrete were used in this study (as shown in Table 4.3). Two types of PP fibres used in this study were: 100% virgin PP fibres and 100% recycled PP fibres. For the 40 MPa concrete mix design, 6 kg/m3 of PP fibres were mixed with concrete. This mix design is normally used for precast panels. For the 25 MPa target strength concrete, 4 kg/m3 of PP fibres were mixed. This design is commonly used for construction of concrete footpaths.

In this study, concrete was delivered from the batch plant (Holcim Australia Pty. Ltd.) in a standard concrete truck without plastic fibres. The average slump of 40 MPa concrete was 60 mm, while the 25 MPa concrete was 100 mm, based on AS 1012.3.1-2014 (AS 2014a). Recycled and virgin PP fibres were then mixed separately with concrete in a drum mixer. Good dispersion of fibres could be achieved using this method as fibres were sprinkled into concrete to avoid clumping. After casting, based on AS 1012.8.1:2014 (AS 2014b), all the concrete

Table 4.3 Concrete mix proportions

Material

40 MPa concrete

25 MPa concrete

0.6-4.75 mm coarse sand (kg/m3)

350

410

6.7-9.5 mm concrete aggregate (kg/m3)

950

260

0.3-5 mm crusher dust (kg/m3)

220

200

0.075-0.3 mm fine sand (kg/m3)

290

350

9.5-19 mm concrete aggregate (kg/m3)

-

690

Fly ash (kg/m3)

130

134

Cement (kg/m3)

256

186

Polyheed 8190 admixture (ml/100 kg cementitious materials)

337

281

Air entrapment admixture (ml/100 kg cementitious materials)

22

Water (l/m3)

105

116

PP fibre (kg/m3) (virgin or 100% recycled)

6

4

cylinders, beams and round panels were allowed to stand for 24 h in laboratory before demoulding. The specimens were cured in water at 23 ± 2 °C for 28 days.

 
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