Experimental Study Of The Impact-echo Method On-site Detection Of Structural Concrete Strength And Elastic Modulus

With the accelerating process of urbanization, a large number of new building is growingup. As the most widely used materials, the quality of concrete is paid more and more attention.Concrete strength is the foundation of the building, if the strength is not up to the designrequirements; it will seriously affect the bearing capacity of structure and service life. Thequality testing of concrete is of great significance, not only to play a regulatory role in theenterprise, can also master the law of the development of concrete strength as soon as possible,providing the necessary guidance for the conduct of construction.The concrete strength detection is divided into destructive and nondestructive testing.Destructive testing needs to be sampled at the detection site, destroying the structure,especially some important parts of the structure d are not allowed to be destructed. In ourcountry the nondestructive detection method mainly used is rebound method.The concretesurface quality directly determines the strength of concrete. There is a lot of controversy aboutthe examination results of rebound method, and the detection results are questionable.When the water cement ratio is0.3, the formula to calculate the wave and strength is：f_c=-252V_p~2+2081V_p-4214; water binder ratio is0.4:f_c=186V_p~2+1487V_p-2908water binder ratio is0.5: f_c=-28V_p~2+278V_p-599;water binder ratio is0.6:f_c=-161V_p+1244V_p-2348. When the ratio of different water to binder, calculationformula of velocity and elastic modulus, as water binder ratio is0.3: E_d=33V_p-92;waterbinder ratiois0.4:E_d=27V_p-60; water binder ratio is0.5: E_d=30V_p-78;water binderratio is0.6: E_d=28V_p-58. Calculation of static modulus of elasticity, the formula ofcoefficient is multiplied by0.8.Through the application of detection of highway T type box beam and foundation, usingthe established formula to calculate strength of concrete, and the drilling core sample in thecorresponding position, compressive test, were compared with the calculation formula, errorsare within the scope of15%.