PSI - Issue 55

Afif Rahma et al. / Procedia Structural Integrity 55 (2024) 206 – 213 Afif Rahma/ Structural Integrity Procedia 00 (2019) 000 – 000

209

4

step, the fibres were added to the concrete during mixing in 2 sizes (4 and 8 cm) and 2 amounts of weight (2.5 and 5 kg/m3). The first control mix (M(0)) without fibre was designed to define the resistance value of an eligible batch for a fibre of 8 cm. The addition of Polypropylene fibre showed the impossibility of providing a batch of W/C =0.7 for a suitable slump. Thus, the M(0) batch was modified to M(0/0) by increasing the amount of water to reach a value of W/C=1.55 which allowed the production of a concrete capable of accepting the fibres in the mixer and ensuring easy mixing and a valuable consistency. The main information on the concrete batches and the average output after the compression test are detailed in Table (2), where the values of Slump and Compression Strength are reported as the average value of 5 samples for each batch

Table 2: Coding samples and input and output information

Fresh concrete density Kg/m 3

Number of fibres per cube

Fibre length (cm)

Average load (P) (kN)

Fibre ratio

Strain  %

W/C

Slump

Strength

 H

Batch

M(0)

1840 1702 1717 1717 1737 1737

0 0

0.70 1.55 1.55 1.55 1.55 1.55

- -

- -

8.0

108.00

4.800 0.911 2.763 3.053 3.653 3.524

0.4 0.2

0.27 0.13 6.00 6.67 8.00 8.67

M(0/0)

18

20.50 62.17 68.70 82.20 79.30

M(4/2.5) M(8/2.5) M(4/5.0) M(8/5.0)

3297.4 1648.7 6594.8 3297.4

4 8 4 8

2.5 2.5 5.0 5.0

6.7 6.1 5.9 5.1

9

10 12 13

2.4. Sampling To investigate the role of fibre on the concrete behaviour 5 cubic samples of 15 cm were taken for each batch. The total number of trial tests was of 25 samples coded as in Table 3. According to ASTM-192 recommendation, 15 samples were cured for 24 hours, and conserved in water with a temperature of 22 ± 2C o . 3. Experimental results and discussion 3.1. The consistency Analysis of the effect of fibre length and weight on the slump of fibred concrete, in both cases either for 2.5 and 5 kg of fibres either for 4 and 8 cm length, shows that the fibres decrease the consistency and significantly reduce the slump of the fibered concrete (Figure 3).

Figure 3: slump test

The conception of concrete mix for W/C=1.55 gives the concrete high fluidity; however, the addition of fibre significantly reduces the workability (figures 4, 5). This phenomenon could be explained by the special structure of the fibres which act as an interstitial textile that behaves according to the intensity of the interlocking of the fibre itself and their amount of number in the concrete batch (Table 2).