compatibility of ultra high performance concrete as repair material

4.2 Slant-shear testThe slant-shear test is the most broadly recognized method to assess the bond strengthbetween two different materials and has been implemented by different internationalcodes, such as, ASTM C 882 and BS EN 12615:1999 (British Standard 1999). Aninterface angle of 60° from horizontal is usually used by standard codes or researchers,however, in this research, besides this inclination, another two joint angles were utilizedto yield a better understanding of the bond performance under shear and compressionstresses. The main aim of the experimental program was to study the bond strength at 8days with four different degrees of roughness of the concrete substrate (brushed,sandblasted, grooved and high aggregate exposure, called, rough surface) and twodifferent interface angles (60° and 70°). Afterwards, with spare samples, it was possibleto assess some specimens at earlier age (2-3 days) with three different interface angles(55°, 60° and 70°) to assess the evolution of the failure envelop with respect to time.4.2.1 ResultsTable 4.8 shows the results of the slant-shear test at 8 days and Table 4.9 presents theresults obtained at 2 and 3 days. The bond capacity is estimated by using Equation 2.2and Equation 2.3. The real angle and cross area were measured from each sample andused to calculate compressive and shear stresses. The compressive strength of NSC andUHPC at the age of testing was estimated by the compressive strength test of at least 2cylinders of each material. Some slant-shear specimens did not have a perfect flat surfaceat the NSC corner. A small portion (0.1-0.3 in) was cut from these corners in order toobtain a regular surface. The failure mode was visually examined. Figure 4.11 exhibitsthe different failure modes considered in this test. Pictures of all slant-shear specimensafter testing can be found in the Appendixes.83