Experimental Study And Theoretical Analysis Of Small Core Sampling Method To Test Concrete Strength

Core drilling method is generally acknowledged as an accurate one among various kindsof concrete compressive strength tests. It is widely applied to both the quality identificationand reinforcement of the buildings or building structures. With the present building structuresextending in breadth and depth, the reinforcement of concrete components becomes more andmore dense, the diameter of chosen concretes longer, the difficulty of drilling150mmdiametric cores more and more bigger. Besides, the drill to concrete core samples will bringnumerous topical damages to components that are obvious to small, thin-walled components,particularly beam-column joints, etc. So the engineering have increasingly strong desire thattest with the small diameter core samples instead of a large diameter core sample.Due to the small diameter of drilled core samples, the relatively flexible distribution ofcore sampling points and the minimal damage to the test structure or component, this methodwhich is very promising makes up for the insufficiency of core method in engineering appliedscope. But so far, the compressive strength of core samples has not yet formed unifiedconversion relation with the standard cube compressive strength, especially for the34.5mmdiameter core samples. This is because the scope the test refers to is broad and it is affected bymany factors, such as the flatness, perpendicularity of core samples and the error of its heightand diameter, etc. All these result in a big discreteness of compressive strength. In addition, indrilling, processing core specimens, mechanical damages also have great influence on the testaccuracy. Therefore in the course of core specimens making, this thesis adopted a stricteracquisition and processing system compared with the standard core specimens to narrowdown the impacts of these factors on the test.In practical engineering, it is necessary to optimize the experimental scheme to reduce the negative impacts of the above factors on the core samples and increase the stability of thetesting data. Based on the thought of breaking up the whole into parts, the thesis puts forwarda method that sticks three34.5mm diameter core samples together by adhesive to resist theforce jointly. This amounts to increase the equivalent diameter of core samples by which itsolves the mismatch between the maximum aggregate diameter and its core sample diameter.Meanwhile, when the experiment is loaded, rubber gaskets are added on end face of the coresamples. Thus, by doing so, internal stress is more even and the influence of the ferrule effecton concrete face is less. Moreover, under the control of strength of specimen, once one of thespecimens is broken and does not work, the other two specimens also soon achieve theirultimate compressive strength and then damage. This can greatly lowers the discreteness ofcompressive strength of core samples.This thesis makes a large number of specimens and elaborates the whole test process.Besides, it also has the measured data of core samples under the different experimentalmethods analyzed and contrasted. And then draws a conclusion that the improved test methodto reduce the detecting data discreteness is remarkably effective. And the regression equationof the small diameter core sample and standard cube specimen in compressive strength isdetermined. It preliminarily established the unified inspection procedures and strengthcriterion.