Establishment And Validation Of The Hefei Arca Ultrasonic Rebound Strength Crrve

In view of the Hefei region being on large-scale infrastructure, the concrete strength testing of building structures becomes very important.Ultrasonic and rebound method has been most widely used in nondestructive testing of concrete detection methods, this method does not damage the concrete structural strength, and it is more convenient to use, the error relative smaller than the single assay. Since ultrasonic and rebound method was introduced in, our country have promulgatd the norms and standards and established the National ultrasonic rebound strength curve. Hefei area has been using National ultrasonic and rebound strength curve on the structural concrete strength testing, whether it is applicable in Hefei, in particular in the high strength concrete testing on the project has not been in depth study.This thesis is based on the Hefei area engineering practice. Choosing the common materials of Hefei and the surrounding areas, using the optimum mixture ratio and common concrete molding process, we produce strength class of C15, C20, C25, C30, C35, C40, C45, C50, C55and C60at the size of150mm×150mm×150mm concrete test blocks, each strength grade has six groups, being in laboratory nature conservation, test each intensity levela set of data at the curing period of seven days, fouteen days, tweenty-eight days, sixty days, ninety days, one hunderd and eighty days.This set of data includes rebound values, ultrasonic speed value, compressive strength values. The measured experimental data is substituted into National ultrasonic and rebound strength curve of strength curve for authentication. After the verification of the curve, we draw the conclusion that the error is quite large (the average relative error is48.64%and the relative standard deviation is57.66%), National ultrasonic and rebound strength curve has little applicability in Hefei, which should not promote the use of in Hefei region. In accordance with the relevant specifications, where the conditional region,based on the representation of material in the region, produces a certain number of test block, and take ultrasound,rebound test and compression test, to establish a regional curve, required adaptability and strength of the presumption of error better than the national benchmark curve.After a comparative analysis, selecting best equation form, we obtain fitting parameters and Hefei area ultrasonic rebound strength curve equation by binary linear regression of the experimental data.We take the experimental data into the equation of the established curve again for the comparative validation, and give specific evaluation of the applicability of the ultrasonic and rebound of the Hefei area measured in the region. After the verification of the curve, Hefei ultrasonic rebound strength curve is better than the national ultrasonic rebound strength curve in the applicability of the region (the average relative error is10.60%relative standard deviation is13.88%), meeting the regional ultrasonic rebound strength curve the required precision.Through the analysis and evaluation, we draw a conclusion that Hefei area ultrasonic rebound strength curve have the applicability for the common strength grade C25and C30concrete strength testing; have some applicability for high-strength concrete. The paper also predicts compressive strength of concrete at early age,in order to identify the concrete compressive strength with time variation and regression coefficient.Takeing early age concrete strength prediction for early detection,we can find the construction problems as soon as possible, which has important significance in the practical application of engineering.After this experimental study, we obtain that it is necessary to establish in the region of ultrasonic rebound strength curve in Hefei area,in order to meet the region’s concrete ultrasonic and rebound strength testing requirements.After the verification and analysis of the curve, ultrasonic rebound strength curve obtained by this experiment can be used for the detection of ultrasonic and rebound of the region’s strength. For strength detection of high-strength concrete, this curve can be used for some reference.