On Modified Pull-off Method Assessing Strength at Arbitrary Distance from Concrete Surface

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(1) Establishment of test method1) Variations of pull-off tensile strength at each different distance from concrete surface were analyzed in the relation between maximum size of coarse aggregate and the size of core.2) Relations of the pull-off tensile strength versus the compressive strength, splitting tensile strength, pulse velocity, rebound number and pin penetration depth were examined.3) The accuracy of prediction of compressive strength by the pull-off tensile strength was made clear and compared to those by above non-destructive testing methods.(2) Application for evaluating strength in various kinds of concrete1) Characteristics of pull-off tensile strength at each different distance were investigated using specimens with a variety of mix proportion, age of test, cement type and moisture content.2) Pull-off tensile strength was available to evaluate the interface behavior such as bond strength between concrete and finishing materials.3) Pull-off tensile strength in the surface layr of concrete increased with the lowering of water cement ratio by using permeable form.(3) Application for assessing the deterioration1) Pull-off tensile strength was available to evaluate the degree of damage at each different distance due to freeze-thaw action.(4) Application for repair construction method1) Pull-off tensile strength was available to evaluate the required chipping depth of weakend portion, and the interface behavior such as bond strength after repairing.