Test And Engineering Application Studies On The Material And Structure Performance For Typical Asphalt Pavement Base

As the aorta of the national economy, the highway attracts much attention, its performances such as drive comfort, service life and anti-heavy-duty capacity, especially the maintenance of riding quality. And all these performances are closely linked with the roadbase, which is the main stress layer and structural conversion layer. Base layer with excellent performance will improve the operating quality and extend the service life of highway.In order to study the impact from flexible base, semi-rigid base and rigid base on the performances of asphalt pavement, and propose the reasonable structure fits the climate condition and transportation condition, Test road with usual and rational base structures at home and abroad was paved in Datong-Xin guangwu expressway in Shanxi Province. The test road includes four pavement structure combinations, four gradation types, four types of modified asphalt, seven base layer structure combinations and two kinds of composite pavement structures, has 22 pavement structure types and a total length of 7km. Both pavement structure types and total length are the firth time in china,Relying on real engineering, according to test indoor and test road outdoor, the material design and performance of three main base tapes:flexible base, semi-rigid base and rigid base were studied. Using the orthogonal sensitive analysis method and the BISAR procedure, the design parameter of roadbase courses were analyzed in detail; Combined with the construction of test road, the construction technology of three roadbase courses were compared; with the continuous examination on deflection and cracks, the cause was analyzed and effective treatments were proposed; using the life-cycle-cost-analytic method, the influence on the constructing cost of asphalt pavement about the design of roadbase was analyzed.The conclusions as follows:(1) With the large-scale Marshall method, Flexible base materials ATB-30 has the excellent anti-distortion capacity under high temperature, crack resistance performance under low temperature and fatigue-tolerance;using physical-mechanical method, ATB-25 has excellent low temperature crack resistance performance, the fatigue-tolerance and anti-distortion capacity under high temperature are also good; using physical-mechanical method, AC-30Ⅱalso has good fatigue-tolerance, anti-distortion capacity under high temperature and crack resistance performance under low temperature; AM-30 with traditional Marshall method has excellent crack resistance performance. Flexible base materials ATB-30 has the more superior anti-distortion capacity under high temperature, anti-crack capacity under low temperature and fatigue-tolerance.(2) Comparison the proportioning design, strength and rigidity of lean concrete and high fly ash content concrete:along with the addition of the flying ash and the reduction of cement, the compressive strength and rupture strength all reduce and the reduce trend became weaker. The fly ash plays micro-aggregate effect, pozzolanic effect and ball grinding effect. The proportion and age of fly ash, cement and aggregate affect the mechanical performance.(3) Compressive strength>flexural strength, compressive elastic modulus> flexural elastic modulus. With the increase of age, both the strength and modulus of cement-stabilized macadam are increasing. From linear equation:compressive strength Rc=0.0549T(age)+3.5782,R2= 0.999, the variation of compressive strength has little difference between pre-ratio and later.(4)Critical factors orthogonal sensitive analysis in pavement structure design show that the sensitivity sequence is thickness of base> subbase modulus> rigid base >base modulus, the calculation result of the bearing capacity of pavement show that the bearing capacity sequence is:rigid base>semi-rigid base> flexible base.(5) In the construction of flexible base, the thickness, temperature and prevent separation are key technologies, the construction thickness could be more than 5 times of grain diameter, control of compaction temperature should be determine by viscosity-temperature curve, and the roller compaction should complete before the temperature drops to 80℃.(6) The distribution density sequence of The cracks on asphalt pavement construction entity is:flexible base< semi-rigid base< rigid base, the width density sequence of crack is flexible base< semi-rigid base< rigid base, the maximum width sequence of crack is flexible base< semi-rigid base< rigid base. The result of the core-drilling at crack show that the main crack pattern is basement reflect crack. the too fast temperature drop speed and the low temperature is the main reason of the base course crack and the generation of reflect crack, which produce the crack on test road.(7) Evaluation different basement asphalt pavement with method of life cycle cost analysis. The results show that flexible base have a long service life than semi-rigid base; hold its service ability in a longer time; reduce the travel time, vehicles running costs and accident cost.(8) There are several essential points should be considered in basement pattern selection. The characteristics of rigid base, semi-rigid base and flexible base should be deeply analyzed combined with the local traffic volume, climate condition and hydrogeology condition. Consider the main performance requirements first and make a compromise on the subordinate performance requirements on the premise of guarantee the principle base performance requirements, and select the maximum economic efficiency base.