Experimental Study On Performance Test Of Asphalt Mixture With Ultrasonic Method

After decades of construction, the national highway mileages reached astaggering scale, look back at our country highway development process, and thencompared with the trending of other national highway development, the asphaltpavement design, construction and maintenance of our country are still in theinitial stage compared with foreign countries, and there are many problems to bestudied. However, the performance of asphalt mixture testing are generallyaccording to the standard method which use standard test machine in the laboratory,the testing process is complex, and has long test cycle. In this paper we put forwardthe rapid test of asphalt mixtures by ultrasonic method, verify the feasibility of thismethod, which paves the way for the future application.The basic principle of ultrasonic testing method is through ultrasonictransducer generate elastic wave with certain frequency in specimen, this elasticwave propagation in various waveform in the interior of materials or structures,and by another transducer acceptance to the machine, the machine can analyze thefluctuation characteristic parameters of elastic wave in intra-body propagation,wave velocity of sound, amplitude, waveform analysis, according to themeasurement of these parameters and build the relationship with somecharacteristics such as modulus, strength, porosity,to directly test results.The first is the use of ultrasonic testing instrument to test the modulus of thespecimen, ultrasonic test the high frequency （30KHZ） state of Asphalt MixtureSpecimens with the sound and the velocity, according to the formulav=（（E（1-μ））/（ρ（1+μ）（1-2μ）））^1/2 to derive dynamic modulus at high frequency. Using theexperimental standard material machine （MTS） test the dynamic modulus of lowerfrequencies （the10HZ） of specimens after the ultrasonic test. According to theexisting research verified the high correlation of test dynamic modulus with low frequency of machine testing and high frequency of ultrasonic testing. This paperpresents the correction factor, directly use the dynamic modulus with ultrasonictest to predict the dynamic modulus with MTS, the range of correction factor for0.38⁰.43.Followed by the use of ultrasonic to test the splitting strength of the asphaltmixture, through the ultrasonic testing of four kinds of asphalt mixture of differentkinds of material specimens which carried out at room temperature and splittingstrength test, after the curve fitting and found the higher correlation between theultrasonic velocity and the splitting strength of the asphalt mixture, and the fittingformula isf=0.0065e^0.0016v, on the other test parts for the error of validationuse this formula, the error within±7%, so using ultrasonic directly estimatingtensile strength of asphalt mixture can still be accepted, which verify the possibilityof the estimation of sample splitting strength using ultrasonic.The third aspect is the application test of ultrasonic wave in the air voids ofasphalt mixture, as an attempt, the ultrasonic method is applied to control andevaluation of porosity of asphalt mixture, using ultrasonic method for selfcalibration method to overcome the influence of other factors on ultrasonic testing.Through the specimen porosity and void test code density was generally consistentto the ultrasonic method, density method test result is slightly larger than theultrasonic testing results, the relative error of the two basically within5%, theultrasonic method for asphalt mixture void ratio test is feasible. Knowing thechange of void ratio, we can further infer the changes of the degree of compaction,laying the groundwork for future evaluation of degree of compaction on the road.The ultrasonic method research on the asphalt mixture freezing-thawingdamage test, the variation of wave velocity reflecting the freeze-thaw damagedegree, the freeze-thaw cycle test damage degree has a certain relationship with thefreeze-thaw cycle and wave velocity decrease, therefore we can use reducedvelocity ultrasonic test before and after the injury, to reflect the freeze-thawdamage variable, achieve non-destructive testing effect. Through the research of this thesis, we verify the feasibility of ultrasonicmethod on asphalt mixture testing, provides a simple and feasible method forasphalt mixture specimen or asphalt pavement test.