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. 2020 May 9;13(9):2183.
doi: 10.3390/ma13092183.

Bond Strength Tests under Pure Shear and Tension between Masonry and Sprayed Mortar

Dawei Huang  1 , Oriol Pons  1 , Albert Albareda  1
Affiliations

Bond Strength Tests under Pure Shear and Tension between Masonry and Sprayed Mortar

Dawei Huang et al. Materials (Basel). .

Abstract

Sprayed mortar or shotcrete is a construction technology that could enhance existing masonry buildings' resilience by reinforcing low-safety load-bearing walls. Many factors affect the resistance of shotcrete-reinforced structures. One of the most important is the bond strength at the interface between the shotcrete and the reinforced wall. According to previous technical literature, bond strength usually has two evaluation criteria: shear and tensile strength. The experimental campaign described in this article focused on the bond strength between sprayed mortar and three masonry materials without the influence of normal force or constraint, as well as the roughness of these materials. The analysis of these tests focused on determining the relation between bond strength, roughness, and material strength. The analyses revealed that material strength has a more significant effect on bond strength than roughness, and bond strength is related to shrinkage of the materials. On the basis of previous theories, these researchers found that when there is no obvious influence due to normal force and constraint, the shear strength and tensile strength are different, and the shear strength is likely to be the cohesion force of the two materials. Finally, this article concludes with a novel logarithmic relationship between these strengths.

Keywords: JRC-JCS; adhesion strength; roughness; shear strength; shotcrete; structure reinforcement.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Arrangement of the specimens in the two troughs; (b) Wooden troughs placed at a 30-degree angle on the ground to be sprayed with mortar.
Figure 2
Figure 2
Roughness tests: (a) surface profile gage; (b) measurement process followed to define surfaces roughness.
Figure 3
Figure 3
Roughness definition method to define roughness curves: (a) roughness parameters Ln and L0 measured in the roughness curves and (b) zx dx and L from the roughness curves.
Figure 4
Figure 4
Location of the specimens to carry out the pull-out tests on each masonry piece. (a) Manual jack, (b) tensile and (c) direct shear types.
Figure 5
Figure 5
Typical failure modes in pull-out tests: (a) disconnection of the bond, (b) photo of case (a) magnified, (c) the specimen broke in its own section (d) photo of case (c) magnified, (e) fracture of the bond material itself, (f) photo of case (e) magnified.
Figure 5
Figure 5
Typical failure modes in pull-out tests: (a) disconnection of the bond, (b) photo of case (a) magnified, (c) the specimen broke in its own section (d) photo of case (c) magnified, (e) fracture of the bond material itself, (f) photo of case (e) magnified.
Figure 6
Figure 6
Results of tensile and shear bond strength of the interface depending on the masonry compressive strength (fb).
Figure 7
Figure 7
Calculated values of JCS depending on the compressive strength of tested masonry specimens (fb).
Figure 8
Figure 8
Calculated values of tensile bond strengths depending on bricks (fb) at different ages of mortar drying.
Figure 9
Figure 9
Calculated values of shear bond strengths depending on bricks (fb) at different ages of mortar drying.
Figure 10
Figure 10
Tensile bond strengths depending on the roughness factor JRC.
Figure 11
Figure 11
Comparison between cohesion at different bond strengths and JRC.
See this image and copyright information in PMC

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