Study On Ji'an Area Ready-mixed Concrete Rebound Strength Curve

The spread and application of ready-mixed concrete is a new green enterprise and system engineering. Rebound method is the most widely used nondestructive examination method in application of field strength test on concrete construction. In view of strength curve for rebound method built by ready-mixed concrete in Ji'an, this paper studies the effects of differentiating factor on accuracy of rebound test caused by different materials, different constructions and molding process, and has the modification of coring experiment and the engineering test considering the differences caused by the strength of test block and construction entity. The following conclusions:(1) By analysis of mixed regression and error comparing on the rebound test data of concrete test block at local area, this paper points out that major differences in the strength test accuracy of molding process and different material compositions are caused by the mixed regression curve, proposes to set up the strength test curve at local area, and puts forward the measures to improve the accuracy of strength test curve aiming at minimizing relative error, with consideration of different situations caused by pebbles, rubbles, pumping or non-pumping.(2) Considering different situations caused by pebbles, rubbles, pumping or non-pumping influencing classified regression and error comparing on the rebound test data of concrete test block, this paper points out that there exists minor relative errors between the regression curve of test block examination in the pumping and non-pumping of pebbles in local area and the strength of homological curve prescribed by "Technical Specification for Inspection of Concrete Compressive Strength by Rebound Method" (JGJ/T23-2001) in our country; major relative errors exists between the regression curve of test block examination in the pumping and non-pumping of rubbles in local area and the strength of homological curve in our country; and the strength test accuracy of regression curve on test block examination is significantly superior than homological curve prescribed by " Technical Specification for Inspection of Concrete Compressive Strength by Rebound Method " (JGJ/T23-2001)(3) Considering the differences of the strength of test blocks and construction entities, this paper has the modification of coring experiment and the engineering test on the curve of rebound strength test set by test block examination, and gets such conclusions:1)The strength of homological curve prescribed by《Technical Specification for inspection of Concrete Compressive Strength by Rebound Method》in our country adopts modified coefficient K value 1.034 and1.065 respectively, which applies to the test strength of the C20-C60 pumping and non-pumping rubble concrete in the local area.2) The post-modified strength curve of non-pumping rubble concrete in the local area (ft4= 0.05371×R1.8682×10-0.03980d) applies to the rebound strength of the C20-C60 non-pumping rubble concrete in the local area. And the post-modified strength curve of pumping rubble concrete (ft5= 0.30588×R1.41204×10-0.03163d) applies to the rebound strength of the C20-C60 pumping rubble concrete in the local area.The results of this study can be the important basis on researching the strength curve of ready-mixed concrete in Ji'an of Jiangxi province and homological strength curve in the country.