Research For The Main Factors And Testing Curve Of Detecting The Concrete Compressive Strength By Rebound Method

Rebound method is one of the basic methods of nondestructive testing technology of concrete strength, because it’s low cost, convenient, simple, fast and efficient, so it has been widely used in engineering testing. This method is the use of the relationship exists between concrete compressive strength value and rebound value to presume the results. This relationship can be used to represent the "- " strength test curve. Because of the rebound method is an indirect testing method, so it depends on the concrete surface hardness to presume its strength, and the applicability of the national unified strength test curve is different all over the country. Accordingly, the reliability and accuracy of the testing results appear deviation.The main purpose of this thesis is to improve the reliability of the rebound method, So as to spread the application of rebound method in the field of concrete strength testing. The thesis starts from two aspects: One is to analysis the main factors affecting test results of rebound method; the other one is research of analysis and application on the rebound strength test curve. Analyzing the main factors gives the ideas to establish the strength test curve. Then the special strength curve and regional strength curve of Guangzhou area have been established. The research findings have a certain reference value for the formulation of concrete compressive strength detection rules by rebound method of Guangzhou area. The specific content and findings of this thesis are as follows:(1) By collecting the research findings of the main factors affecting the rebound method testing from predecessors, this topic compares the strength test curve of different areas, and explores the main influence factors of the rebound method from three aspects: material, construction technology, test procedure;(2) Fitting strength curve is based on the principle of least square method, to minimize the relative error values, considering the influence of multiple factors and then drawing the curve. This thesis also gives several effective methods to improve the accuracy of fitting;(3) By analyzing a large number of engineering test data of Guangzhou area, the author uses mathematical statistics to study the applicability of the unified strength test curve in Guangzhou area. The results show that there is necessity to establish the regional strength curve;(4) In the light of the rebound and core drilling data from one engineering testing project in Guangzhou area, the thesis establishes C40 special strength test curve, The curve well for testing results of rebound method of this project can meet the accuracy requirements;(5) Raw materials widely used in Guangzhou area are used to make molded a number of concrete specimens, using the rebound method and core drilling method for a large number of tests and testing data collection, the thesis establishes a C40 preliminary strength test curve. The results show that there are practical and applicability to establish the regional test curve for using in the engineering testing project in the Guangzhou area. The research result of this paper is a good reference to test other level concrete strength.