Development of Drilling Type Surface Strength Tester and Estimation Method of Surface Strength of Historic Structures

Effect of Electrical Resistivity of Mortar Surface Layer on Drilling Speed Using Mix Proportion

“…The drilling speed, Vp, at each measured face was taken as the average of 12 drilling speeds obtained from the two samples. Please refer to reference [2] for the extraction criteria of Vp. As the material quality evaluation of the top-most layer was main the objective of this study, the value calculated in the 0-5 mm drilling depth range was used as the drilling speed Vp.…”

“…The bit sharpness decreases roughly linearly with the increase in the number of drilling operations as the diamond particles on the bit tip wear out [2]. However, these particles are heavily worn out in actual practice when drilling high-strength, hard materials for long periods of time; thus, it is difficult to evaluate the extent of decrease in sharpness with just the number of drilling conducted.…”

“…The bit sharpness also varies due to the mounting direction (angle) in addition to variations within the bit itself [2]. Therefore, the drilling speed obtained by procedure 2) was corrected using the drilling speed rVf of the reference mortar drilled before the drilling test for each standard to compare the drilling speed for each standard.…”

“…The small-diameter drilling tester used in this study is similar to the minimally destructive testing device developed by Hasegawa et al [2]. The damage caused by this device on the measured object is extremely small using a drilling diameter of approximately 3 mm.…”