Experimental Study On Ultrasonic Testing Of Strength Of Foam Concrete

Foam concrete has the advantages of light weight,good thermal insulation,adjustable density,self-reliance and high mobility.Now it is widely used in building insulation,roadbed widening,roadbed filling and so on.It is of great practical significance to carry out the research on the detection technology of foam concrete strength.The traditional drawing method,rebound method and core drilling method are not suitable for the strength testing of foam concrete.Therefore,this paper attempts to use ultrasonic nondestructive testing method to detect the strength of foam concrete,and establish the ultrasonic strength curve of foam concrete,so as to provide some reference for its application in practical engineering.In this paper,two sets of 324 foam concrete specimens are produced.The first group is 264 specimens of 100 mm×100 mm×100 mm size,which are divided into four density grades(A03,A04,A05,A06),70 for each density class.120 specimens were used to study the relationship curve between ultrasonic velocity and compressive strength.120 specimens were used to study the influence factors of ultrasonic testing of the strength of foam concrete,and the 24 specimens was used to verify the applicability of the strength curve.The second group consisted of 20 specimens with 150 mm×150 mm×150 mm sizes,20 specimens with 100 mm×100 mm×200 mm sizes and 20 specimens with 100mm×100 mm×300 mm sizes.They were divided into four density classes(A03,A04,A05,A06)and each density level of 5,used to study the effect of ranging on ultrasonic velocity.The research contents and results are as follows:(1)Four kinds of foam concretes with different densities and different ages(3d,7d,14 d,21d,28d)were tested by ultrasonic test and compressive strength test.According to the experimental data,regression analysis was carried out by using four models of linear function,quadratic function,exponential function and Gauss function,Gaussian function and exponential function curve have higher fitness,which can be used as the single parameter strength curve of the ultrasonic method..(2)Based on the wave equation,a two-parameter ultrasonic strength measurement model with ultrasonic speed and amplitude-dependent attenuation coefficient is established.According to the experimental data,the two-parameter strength curve isobtained.The fitting degree is higher than that of single-parameter strength curve.The two-parameter strength curve can improve the detection accuracy.(3)The main influencing factors of ultrasonic testing of foam concrete strength were studied,including raw materials,external conditions,water content and testing methods.Correct the ultrasonic speed to improve the detection accuracy.(4)Verify the ultrasonic detection strength curve with the foam concrete pieces prepared under the same conditions.The results show that the established two-parameter strength curve and one-parameter strength curve meets the standard requirements,two-parameter strength curve has high detection accuracy.It is suitable for foam concrete prepared under the same condition.