PSI - Issue 28

Chbani Hamza et al. / Procedia Structural Integrity 28 (2020) 430–439 Author name / StructuralIntegrity Procedia 00 (2019) 000–000

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steel cylinder 600 mm ± 10 mm deep and 160 mm ± 2 inside diameter, attached and secured to a table by a base and an attachment system (Fig. 2. (a)). This test is carried out in accordance with standard NF EN 932-2 (2009). We start by putting a seven kilogram granular sample in an oven at 110°C until it reaches a constant weight. Then we place this sample in three fractions in the mould under the stress of a piston. We apply a set of mechanical shakes (twenty shakes for each fraction of the sample at a rate of 2 per second), which causes a rearrangement and compaction of the aggregates. The measurement is then the bulk density of the sample, which is used to calculate the compactness of the sample. This density is determined firstly by measuring the distance between the wedges and the plunger in an empty mould and then measuring the same distance again in a second step, but with the filled mould (Fig.2. (b)). Three compaction tests have been carried out, each test is repeated twice, the result of the test is then the mean value of the compactness obtained on the three samples. The expression of the apparent density, the apparent volume and the compactness are given respectively by the relations (4), (5) and (6) according to NF EN 1097-6 (2014).

V M 

a 

(4)

2

( 2 D H H   

)

 

V

v

c

(5)

4

real a    

(6)

(a)

(b)

Fig. 2. (a) Compactness testing apparatus; (b) Principle of depth gauge measurements for concrete compactness determination.

Table 2 summarizes the results of the compactness tests. For the same test, the two measurements give practically the same values. However, there was a slight discrepancy around 3% in for the coefficient of compactness between the three tests. The average value of the coefficient of compactness is γ =0.801. Table 2. Summary of test compactness results

Average compactness value

Sample weight (kg) ρ real (gm/cm 3 )

Standard deviation

Test

Hv (cm)

Hc (cm)

V (cm 3 )

γ

1 2 3

7 7 7

2,72 2,72 2,72

46,9 46,9 46,9

31,46 30,81 30,43

3102,822 3233,446 3309,811

0,829 0,796 0,778

0,801

0,026