Establishment Of The Curve To Detect Concrete Strength By Using The Ultrasonic Rebound Combined Method In Liaoning Province

The evaluation of concrete strength in highway engineering requires the use of rebound method or ultrasonic-rebound method based on the Quality Evaluation Method for Highway Engineering(2010 Edition)which was published by the Ministry of Transport.According to the field applications of these methods in Liaoning Province,it was found that many factors,including the aggregate properties,cement types,admixtures,mix ratio,construction technology and moisture content etc.can influence the test results of concrete strength.In addition,the current unified test curves on strength,which were recommended in the Technical Specification for Detecting Strength of Concrete by Ultrasonic-rebound Combined Method(CECS 02:2005)are always deviated in the practical application in Liaoning province and failed to meet the accuracy requirements of testing concrete strength in Liaoning province.In this paper,the characteristics of ultrasonic resilience of concrete in transportation construction engineering of Liaoning province were studied.According to the raw materials used in different regions,nine kinds of factors were tested to determine the main factors that influencing the ultrasonic rebound value of concrete in Liaoning,which include the coarse aggregate size,cement types and fly ash content.Concrete samples with different strength levels were made with representative materials chosen from fourteen regions of Liaoning province.When the specimen reached the prescribed age,the detection of ultrasonic-rebound properties and concrete compression strength were made.The test curves of strength in Liaoning area were then established.And the curves of strength for each city and expressway were separately established based on the data obtained from the experiment.Through the verifications of test samples and field coring specimens,the average relative error of strength curves for Liaoning province was 13.96% and 6.47%,while the error for national strength curve was 28.0% and 15.37%.This indicated that the strength prediction using the strength curve obtained by this thesis is much more accurate than the curve recommended by(CECS02:2005).