Vibratory hammer compaction of bitumin stabilized materials

[摘要] There are currently well established compaction methods being used in laboratories globallyto prepare specimens for material testing. None of these methods provides the repeatabilityand reproducibility, ease of execution or simulation and correlation to field compaction desiredby engineers. The research presented in this report was aimed at the development of a newor adapted compaction method for bituminous stabilized materials (BSM) that would addressthe aforementioned factors, by making use of a vibratory hammer. Along with this, a newprotocol was to be established.The initial vibratory hammer that was tested was the Kango 637®. This specific vibratoryhammer suffered irreparable damage to the gearbox during the research. A replacementKango hammer could not be purchased, therefore a substitute hammer was purchased i.e. aBosch GSH 11E®, for which back-up service and replacement parts are readily availablethroughout South Africa.Significant progress had been made with the development of a laboratory compactionprotocol for BSM using the Kango Hammer. The specifications of the Bosch® hammer showedit was superior in terms of power, weight and other technical features. Comparative testingwas therefore carried out. This allowed for the adaptation of the results achieved to thatpoint.Extensive experimentation was then carried out using two types of BSM i.e. foamed bitumen(80/100 bitumen) and bitumen emulsion (60/40 Anionic Stable Grade) stabilized material. Theinitial material used for the experimentation was a G2 quality graded crushed stone.Additional material was also obtained from a recycling project taking place along the N7 nearCape Town. The N7 material was used to perform correlation experiments so as to determinehow representative the laboratory compacted specimens were to field compacted material.Results showed that the vibratory hammer is capable of producing specimens for testing inthe laboratory as well as providing a possible benchmark method for accurately controlling thequality of work on site i.e. field density control. This was done by identifying the time to andlevel of refusal density compaction. The level of refusal density compaction was expressed asa percentage of Mod AASHTO compaction and using current specifications, a potentially newsite compaction level specification was determined.In order to asses the material applicability of the vibratory hammer compaction method, testsregarding moisture sensitivity analysis were carried out on a G5 material. The vibratorycompaction protocol includes a specification for the type of hammer, guide-frame, surchargeweight, compaction moisture and number of layers. Vibratory compaction can be used toprepare two types of specimens:• Specimens for triaxial testing with a diameter of 150mm and a height of 300mm• Specimens for laboratory testing with a diameter of 150mm and a height of 125mm. Tests showed that the material properties prove to have an influence on the compactabilityof the material. Material from the N7 recycling project had been milled out thus altering thegrading and including some RAP. This in turn influenced compaction. The vibratory hammermoisture curve was found to shift slightly to the left when compared to the Mod AASHTOmoisture curve. The variability of the vibratory hammer was found to be well below thespecified variability of 15%. Repeatability experiments on G5 material indicate that vibratoryhammer compaction may be used on lesser quality granular materials.A recommended procedure for the compaction of BSM was developed following theexperimentation results.

[发布机构] Stellenbosch University