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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

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Test Results and Analysis

Characterization Tests

Flexural characterisation tests were performed to all series of FRC following the EN 14651:2007 standard [11]. Figure 6 shows the Load-CMOD curves obtained in these tests. As it can be observed, a wide spectrum of behaviours comprising hardening, flat and softening response was covered.

Table 5 resumes both the compressive strength results for each series and the residual strengths at Limit of Proportionality (LOP) and for CMOD values of 0.5 and 2.5 mm. The coefficient of variation is given as informative of the scatter of results.

Creep Tests

CMOD deformations were registered during flexural creep tests. As reference for both types of concretes, Fig. 7 shows the deferred deformation evolution with time of one specimen of each series. Notice that, for concretes type II, instantaneous deformations are smaller than for concretes type I and ranges from 0.2 to 0.5 mm.

In addition, a number of specimens (40 % of them) developed a sudden increase of crack opening deformations during creep stage. A visual example of these sudden increases can be observed in Fig. 7.

Flexural behaviour of concretes type I (left) and II (right)

Fig. 6 Flexural behaviour of concretes type I (left) and II (right)

Table 5 Characterisation tests results (compressive strength and residual strengths)

Concrete

Comp. strength

Residual flexural strength (MPa) & CoV (%)

fc

fL

fR1

fR3

80/35-40-10

52.7

(10.0)

4.94

(6.5)

5.53

(6.0)

5.66

(6.1)

80/35-70-10

56.1

(4.9)

6.38

(4.9)

10.12

(10.6)

9.78

(9.8)

80/50-40-10

57.1

(4.3)

4.53

(4.9)

6.14

(11.7)

6.79

(5.4)

208-10

58.3

(5.3)

4.80

13.10

18.36

80/50-40-20

39.0

(1.3)

3.93

(2.7)

5.01

(8.6)

6.48

(9.6)

65/40-40-20

29.4

(6.6)

4.03

(2.8)

3.72

(14.0)

3.79

(17.0)

45/50-40-20

38.8

(6.6)

4.27

(4.2)

4.09

(22.9)

4.58

(10.4)

50/30-40-10

41.3

(6.0)

4.68

(3.3)

3.69

(11.6)

1.63

(20.3)

206-20

36.4

(11.2)

3.68

7.03

11.85

CMOD-time curves for concretes type I (left) and II (right)

Fig. 7 CMOD-time curves for concretes type I (left) and II (right)

In case of concretes type I, these sudden increases were produced in some specimens of series reinforced with fibres with slenderness (Я) of 80 and stress level Ic > 90 %. For concretes type II, SFRC with fibres with slenderness (Я) of 45 and 50 developed sudden CMOD deformations when Ic > 70 %. The magnitude of these sudden increases of crack opening during creep tests varied from 0.012 to 0.559 mm, what supposed a percentage of 2-42 % of deferred CMOD deformation at 90 days of the corresponding specimen.

These sudden increases were considered as deferred deformations for the time lapses when they occurred.

 
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