Issue 48

J. Liu et alii, Frattura ed Integrità Strutturale, 48 (2019) 161-173; DOI: 10.3221/IGF-ESIS.48.19

Time-dependent shear strength of bond interface The relationships between peak shear stress and normal stress from the experimental results for different curing time were illustrated in Fig. 11 through linear fitting. The shear cohesion and friction angle of the interfaces of different ages were obtained, when the Mohr-Coulomb failure criterion was applied. To regress the time-dependent behaviors of the interfacial shear properties, different equations were attempted for curve fitting as presented in Fig. 12 and Fig. 13.

0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85

1.4

c: Curing time 24h

b: Curing time 16h

0.26 0.28 0.30 0.32 0.34 0.36 0.38 0.40 0.42

a: Curing time 8h

1.3

1.2

1.1

1.0

Liner fitting Experimental results

Liner fitting Experimental results

Liner fitting Experimental results

0.9

+ 0.210 ( R 2 =0.977)

+ 0.354 ( R 2 =0.971)

+ 0.537 ( R 2 =0.974)

τ

= 0.509 *σ n

τ

= 0.616 *σ n

τ

= 0.737 *σ n

0.8

max

max

max

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45

2.4

e: Curing time 48h

d: Curing time 36h

f: Curing time 72h

2.8

2.4

2.2

2.6

2.2

1.0 Peak shear stress, τ max (MPa) 1.2 1.4 1.6 1.8 2.0

2.4

2.0

2.2

1.8

2.0

1.6

1.8

Liner fitting Experimental results

Liner fitting Experimental results

Liner fitting Experimental results

1.4

1.6

+ 1.063 ( R 2 =0.981)

+ 0.723 ( R 2 =0.998)

+ 0.841 ( R 2 =0.998)

τ

= 0.956 *σ n

τ

= 0.837 *σ n

τ

= 0.910 *σ n

1.2

1.4

max

max

max

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

h: Curing time 168h

i: Curing time 336h

1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 g: Curing time 120h Liner fitting Experimental results τ max = 0.901 *σ n + 1.325 ( R 2 =0.969)

1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2

Liner fitting Experimental results

Liner fitting Experimental results

+ 1.181 ( R 2 =0.980)

τ

= 1.104 *σ n

+ 1.310 ( R 2 =0.997)

τ

= 1.069 *σ n

max

max

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Normal stress, σ n

(MPa)

Figure 11: Relationship between peak shear stress and normal stress of interfaces at different curing time

1.6

1.4

1.4

1.2

0.2 Cohesion of the interface, c (MPa) 0.4 0.6 0.8 1.0 1.2

4 Cohesion of the interface, c (MPa) 6 8 0.4 0.6 0.8 1.0

Experimental results c =1.308(1- e -0.022 t ) ( R 2 =0.983) c =-0.327+0.304ln( t -2.928) ( R 2 =0.936) c =-1.300 e - 0.024 t +1.346 ( R 2 =0.984)

Experimental results c =-2.604 e - 0.239 f c

+1.346 ( R 2 =0.916) -4.438) 0.267 ( R 2 =0.922)

c =-0.677( f c

10 12 14 16 18

0 50 100 150 200 250 300 350

Compressive strength, f c

(MPa)

Curing time, t (h)

(a)

(b)

Figure 12: (a)Time-dependent shear cohesion of interface; (b) Compressive strength vs. shear cohesion of interface

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