Issue 48

J. Liu et alii, Frattura ed Integrità Strutturale, 48 (2019) 161-173; DOI: 10.3221/IGF-ESIS.48.19 167 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. 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.26 0.28 0.30 0.32 0.34 0.36 0.38 0.40 0.42 a: Curing time 8h Liner fitting Experimental results τ max = 0.509 *σ n + 0.210 ( R 2 =0.977) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 b: Curing time 16h Liner fitting Experimental results τ max = 0.616 *σ n + 0.354 ( R 2 =0.971) 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 0.8 0.9 1.0 1.1 1.2 1.3 1.4 c: Curing time 24h Liner fitting Experimental results τ max = 0.737 *σ n + 0.537 ( R 2 =0.974) 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 d: Curing time 36h Liner fitting Experimental results τ max = 0.837 *σ n + 0.723 ( R 2 =0.998) Peak shear stress, τ max (MPa) 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 1.2 1.4 1.6 1.8 2.0 2.2 2.4 e: Curing time 48h Liner fitting Experimental results τ max = 0.910 *σ n + 0.841 ( R 2 =0.998) 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 f: Curing time 72h Liner fitting Experimental results τ max = 0.956 *σ n + 1.063 ( R 2 =0.981) 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) 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 h: Curing time 168h Liner fitting Experimental results τ max = 1.104 *σ n + 1.181 ( R 2 =0.980) Normal stress, σ n (MPa) 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 i: Curing time 336h Liner fitting Experimental results τ max = 1.069 *σ n + 1.310 ( R 2 =0.997) Figure 11: Relationship between peak shear stress and normal stress of interfaces at different curing time 0 50 100 150 200 250 300 350 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Cohesion of the interface, c (MPa) Curing time, t (h) 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) 4 6 8 10 12 14 16 18 0.4 0.6 0.8 1.0 1.2 1.4 Compressive strength, f c (MPa) Cohesion of the interface, c (MPa) Experimental results c =-2.604 e - 0.239 f c +1.346 ( R 2 =0.916) c =-0.677( f c -4.438) 0.267 ( R 2 =0.922) (a) (b) Figure 12: (a)Time-dependent shear cohesion of interface; (b) Compressive strength vs. shear cohesion of interface