Study on grading envelope of AC-16 asphalt mixture based on rutting resistance performance
In this paper, the coarse aggregate packing density tests are studied on different proportion the various particle sizes over 4.75mm, and the demarcation point between coarse and fine aggregate of AC-16 asphalt mixture is 4.75mm, the optimum grading of coarse aggregate is determined by the minimum voids in mineral aggregate. Freeze-Thaw Split and Rutting are tested on 9 kinds of grading AC-16 asphalt mixture with different size and proportion fine aggregate. The results show that the percent passing 4.75mm sieve has affected significantly on the high-temperature rutting resistance and water stability of the asphalt mixture. Based on laboratory test results and grading application experience, it is proposed that the engineering design grading envelope of AC-16 asphalt mixture adapted to the summer hot climates characteristics, which improved the rutting resistance capability of asphalt pavement in hot areas during summer.
Study of Molding Control on Wheel Tracking Specimens for Asphalt Mixtures
The difference in terms of control index and standard of typical wheel tracking test specimen was reviewed.Test results of California HVS were also analyzed.Through analysis,it is found that field air void under track is no less than 4% after long-term vehicle loading.When asphalt pavements vary from field initial air voids to the air voids of the end of life,creep defor-(mation) mainly contributes the rut depth,while dense deformation contributes little.So the maximum expected field initial air voids are suggested as the specimen molding control index.At last,through tests and analysis,(7.0±1.0)% air void is suggested for dense-graded hot-mix asphalts as the molding control standard,and (5.5±0.5)% for stone matrix asphalts(SMA).
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.