CTB-50 vertical vibration compaction method for cement stabilized macadam
In order to evaluate the physical and mechanical properties of ultra-large particle size cement stabilized macadam with a maximum particle size of 53 mm accurately(CTB-50),the influence of specimen size on the mechanical strength test values of CTB-50 was investigated using theoretical analysis and laboratory tests.Then the effect of vibration parameters of the vertical vibration compaction testing equipment(VVTE)on the dry density and gradation of CTB-50 was investigated,and the vertical vibration compression testing method(VVTM)of CTB-50 was developed.The reliability of VVTM was verified by comparing the mechanical properties with the field core samples.The results show that with the increase of specimen size,the interfacial effect of the loose area of the specimen becomes weakened and the effective compression area increases,which shows that the test value of CTB-50's strength increase,and increasing the specimen size has no significant effect on the strength when the specimen size reaches Φ200 mm(diameter)Xh200 mm(tall).With the increase of working frequency,the dry density of CTB-50 increases significantly,while the dry density does not change significantly when the working frequency exceeds 32 Hz.With the increase of loading weight of working system,the dry density of CTB-50 varies as parabolic approximately,and the dry density reaches the maximum when the working mass is 302 kg.Then the vibration is less destructive to the gradation when the loading weight of upper-system and lower-system is 122 and 180 kg,respectively.With the extension of vibration time,the dry density of CTB-50 increases significantly,while the dry density does not change significantly when the vibration time exceeds 165 s.Therefore,it is recommended that the size of CTB-50 cylindrical specimen is Φ200 mm× h200 mm,the working frequency of VVTE is 32 Hz,while the working mass is 302 kg(loading weight of upper-system of 122 kg,loading weight of lower-system of 180 kg),and the nominal amplitude is 1.2 mm.To determine the maximum dry density and optimum moisture content,the vibration time is 165 s,and the vibration time for preparing the cylindrical specimen is 120 s.The correlation between the mechanical strength of VVTM specimens and field core samples of CTB-50 is 91％.It is reasonable and feasible to form CTB-50 specimens by VVTM.8 tabs,6 figs,30 refs.
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