Ultrasonic Rebound Method For Testing The Strength Of Recycled Concrete

With the recycling of construction waste,recycled concrete is widely used in civil engineering.At present,comprehensive domestic and international situation,it is found that there is little research on the nondestructive testing of recycled aggregate concrete strength,and the actual strength of recycled aggregate concrete cannot be accurately predicted,thus reducing the quality assurance of recycled aggregate concrete engineering applications.In view of the above problems,this paper conducts a comprehensive experimental study on ultrasonic rebound of two kinds of recycled aggregate concrete,and establishes a comprehensive method of ultrasonic rebound rebound strength regression curve of recycled aggregate concrete,which provides an effective reference for the non-destructive testing technology of recycled concrete strength.In this paper,waste concrete blocks and waste fired bricks are selected as raw materials for recycled aggregates to make recycled aggregates for research.The substitution rates of recycled concrete aggregates and recycled brick aggregates are 50% and 30%,respectively,and 100 sets of different ages are adopted.In the standard cube test block of reclaimed aggregate concrete during the period of testing to analyze the changing rules of each data,and to study the “rebound value-compressive strength value” and “ultrasonics” of the recycled aggregate concrete by the two factors of recycled aggregate type and strength grade.The influence of the relationship between the sound speed value and the compressive strength value was established,and the corresponding rebound method special intensity regression curve,ultrasonic special strength regression curve and ultrasonic rebound comprehensive method special strength regression curve were established,and error analysis was performed.The results show that with the increase of age,the rebound value,ultrasonic sound velocity value and compressive strength value of the two recycled aggregates all show an upward trend.Among them,the compressive strength value has the fastest growth rate,and the rebound value has the second highest value.Ultrasonic speed of sound is minimal;the type of recycled aggregate has a great influence on the relationship between "rebound value-compressive strength" and "ultrasonic velocity of sound-compressive strength" of recycled aggregate concrete;and the application of ordinary concrete(crushed stone)to the national unified test The strong curve predicts the compressive strength of the recycled concrete in this test.The resulting error is large and does not meet the specification requirements.Therefore,the recycled aggregate concrete cannot be directly applied to the general national strength curve of ordinary concrete(crushed stone)to determine the compressive strength,and it must be established separately.Dedicated curves;analysis of the power function model and polynomial function model fitting results of the three methods used to establish the strength regression curve,the error is within the scope of the specification requirements,but the power function model fitting effect is better;three regression curves The errors all meet the specification requirements.By comparison we can see that the regression formula of the recycled aggregate concrete application method of ultrasonic rebound synthesis,precision Higher,better correlation.