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

随着高强度混凝土在现浇混凝土结构中的应用越来越多，在每一个关键的施工操作中，可靠的现浇混凝土强度预测变得越来越重要。本课题的第一个目标是发展混凝土就地强度评定的拉拔方法。第二个目的是提出一种用于保证现浇混凝土质量的拉拔试验的应用方法。本课题的主要成果总结如下：1。在前人对拉拔法研究的基础上，从可靠性、简便性、性价比和时效性的角度出发，开发适合建筑结构试验的尺寸和试验设备。可以开发用于检测沿垂直于表面的轴方向的强度分布的试验方法。将所开发的拉拔方法应用于某36层建筑结构的施工现场，该结构采用高强混凝土。所采用的强度保证方法可以可靠地记录结构的现浇混凝土强度。拉拔法可成功地应用于蒸汽固化预制板8小时强度的评定。室内试验结果表明，筒体试验的变异系数平均值约为3%，岩心试验的变异系数平均值约为6%，拔出试验的变异系数平均值约为10%。从非线性有限元分析出发，阐明了拉拔法的失效机理。提出了一种以抽拔法为核心的现浇混凝土质量保证体系。

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.