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Home arrow Engineering arrow Creep Behaviour in Cracked Sections of Fibre Reinforced Concrete: Proceedings of the International RILEM Workshop FRC-CREEP 2016

Statically Indeterminate Plate Test

The centrally loaded plate tests confirm the observations of the flexural tests, as PFRC specimens consistently show higher 5creep m up to 4 times higher than SFRC specimens in identical test programs (Table 6). In test program B1, all PFRC specimens failed as well and the actual time to failure shows a large scatter with failure occurring at 13, 225 and 666 days (Fig. 6). The 3D 80/60BG steel fibre was tested in the same setup at dosage rates of 25 and 40 kg/m3. With this increasing amount of steel fibres, the scatter of 5creep results reduces from 40 % to about 15 % while the 5creepm slightly increases.

The latter could be an effect from creep in the compression zone, because the absolute Fcreep is higher for the higher fibre dosages. Thus deformations originating from creep in the compression zone are expected to be higher. When comparing the

EN14488-5

Fig. 7 EN14488-5: Effect of load level and pre-cracking deflection on Screep (B2; B3)

Table T Fcreep,m and 5СЮер,ш at 250 days (B2, B3)

Fiber type

Dosage

F

creep,m

^creep,m

kg/m3

-

kN

mm x 10-2

3D 65/35BG

25

40 % Fr

20

33

PF-73/65

7

Spc = 2 mm

18

43

3D 65/35BG

25

60 % Fr

32

42

PF-73/65

7

Spc = 3 mm

30

81

Program B2

Fig. 8 Program B2: EN14488-5 on 600 mm x 600 mm x 100 mm at 40-60-80 %

Fr (SpC = 2 mm)

results of 40 kg/m3 3D 80/60BG and 3D 65/35BG, 5creep and its variation are of the same order. When comparing programs B2 and B3 (Table 7), there is an actual increase of the average sustained load per series (Fcreep,m) by 50 % while increasing the 5pc from 2 to 3 mm.

As can be seen in Fig. 7, the effect is more important in the case of PFRC, with an increase of 90 % compared to 30 % for SFRC. Test program B2 shows similar results, where the impact of the load intensity on the creep rate seems to be of major importance for PFRC, but less for SFRC. Program B2 is, as mentioned before, still running. In this program, as shown in Fig. 8 the observed 5creep of PFRC at 40 % of Fr 5pc = 2 mm was shown to be 30 % higher than that of SFRC specimens. However once the load was increased to 60 % Fr 5pc = 2 mm and higher, the rate of creep of the specimens with 7 kg/m3 PF—73/65 quickly rose to more than two times of that of the SFRC specimens. The influence of the pre-cracking and testing at early age can’t be compared due to the fact that different fibres and concrete were applied in the older setup B1.

 
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