Development of Pullout Test Method and Proposal for Quality Assurance System of In-place Concrete Strength

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With the increasing use of high-strength concrete for cast in-situ concrete structures, the prediction of reliable in-place concrete strength becomes more important at every critical construction operation. The first objective of this project is to develope the pullout method of in-place strength evaluation of concrete. The second objective is to propose an application method of the pullout test for the quality assurance of in-place concrete. Summary of the main results of this project are as follows:1. On the basis of the studies by earlier researchers on the pullout method, the appropriate size and the test equipment for testing building structures could be developed from the viewpoints of reliablity, simplicity, cost performance and time effectiveness.2. The test method for examining the strength distribuition alog the axis perpendicular to a surface could be developed.3. The developed pullout method was applied to the construction site of a thirty six story building structure, to which high strength concrete was used. The strength assurance method applied could give reliable records of in-place concrete strength of the structure.4. The pullout method could be successfully applied for the evaluation of eight hour strength of steam cured precast pannels.5. It was shown from laboratory tests that the average value of the coefficients of variation were about 3% for cylinder test, 6% for core tests and 10% for pullout tests.6. From the non-linear finite element analysis, the mechanism of failure of the pullout method was clarified.7. A quality assurance system of in-place concrete was proposed in which the pullout method played an important role.