Research On The Influence Factors Of Pumping Concrete Rebound Characteristics

The rebound method is one of the most commonly used non-destructive testing for concrete quality testing.The compressive strength of the concrete is estimated by the rebound value and the depth of concrete carbonization.The error precision of the estimated strength is kept within allowable range.In the process of rebound,there are many factors influencing the characteristics and error of rebound of pumping concrete,for example the energy of the rebound instrument,the concrete pouring face and the age of the concrete.The study of these three aspects can effectively improve the accuracy of on-site inspection,and it is of great practical significance to popularize the rebound method in pumping concrete slab and long-term pumping concrete.The experiment received the pumping concrete directly from the concrete station and made in model,and the experiment simulated the actual working condition by natural conservation.This paper through doing rebound test,compression test and carbonization test on different strength grade and the long-term pumped concrete.According to analyzing the measured data,this paper studied the rebound characteristics of different energy hammer,and gave the correction of the rebound value of different pouring faces,and put forward several methods for improving detecting precision of pumping concrete in Long – age.The results show that:(1)With the increase of energy,the strength of the pumped concrete applied by the rebound instrument is increasing.The range of the 2.207 J rebound apparatus is 30 ~ 60 MPa,and the range of the 4.5J rebound apparatus is 40 ~ 70 MPa,the range of the 5.5J rebound apparatus is 40 ~ 87.4 MPa.In low age,the growth strength of is the major factor influenced the increase of rebound value.With the increase of age,the effect of carbonization increases gradually.(2)The increase of the compressive strength of the pumping concrete has the greatest influence on the rebound value of the casting roof.With the decrease of the water-cement ratio and the increase of the age,the difference in the surface hardness of the three pouring surfaces is gradually reduced.The back surface spring value and the pouring side of the spring value is well correlated,we can adjust the rebound value to enhance the estimated accuracy.(3)The increase of the rebound value of the pumped concrete in the long age is mainly caused by the carbonization,the carbonation effect on the growth of rebound value is greater than the compressive strength;Long age pumped concrete can be modified by the coefficient and re-fit to improve the detection accuracy of the rebound method.