No description available.

Thesis (MScIng)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

In this report a relationship is established between the variables of compaction temperature, compaction effort, mixture gradation and, density, air void content and stability of asphalt mixtures. The Marshall method of mix design was used, and Vibratory Kneading Compactor was utilized for compaction. Results include Marshall Stability and density-air void analysis for 4 and 6-inch specimens. It was found that the densities generally increased with increase of compaction temperatures and compaction efforts. From selected sets of 6-inch specimens, 4-inch cores were obtained. Density and stability studies were carried out on these cores and the results obtained were found to have the same trends. The air void content and voids in the mineral aggregates decreased with the increase of compaction effort. Stability increased with the increase in density. All the results found, indicate strong effects of compaction temperature and compactive effort on the amount of air voids, VMA, density, and stability of the mixes used.

M.Tech. / There is a general lack of understanding of the laboratory compaction test based on the vibrating hammer method. The impact method of testing soil in the laboratory is conservatively used by engineers for design and construction control purposes even when the specified mode of compaction on site is vibratory. Furthermore, the effects of vibratory compaction are not fully understood, and hence this mode of compaction in the field has not always been effectively utilized. The objective of this research project was to determine whether the vibrating hammer method could be used in the laboratory for design and control purposes, through an investigation of its operating characteristics, and a comparison of its effectiveness against that of the impact method, following a study of the compaction properties of a range of different soils used in road and embankment construction. The results of the study showed that the vibrating hammer can be used in place of impact in the laboratory for non-cohesive soils and gravels. In one instance, vibratory compaction produced maximum dry densities for a decomposed granite which were almost 5 % higher than that for impact compaction. Cohesive soils reached maximum compaction at moisture contents which were 7 % wetter under the vibratory mode as opposed to those for impact, but at lower densities. This showed that field densities under vibratory compaction would be difficult to achieve when the laboratory control method was based on impact. The research showed that electrical power input to the vibrating hammer must be carefully regulated in order to maintain specified standards which are based on a fixed frequency. Further study based on operation at different frequencies would be required to determine whether the vibrating hammer would be suitable for cohesive soils having natural frequencies lower than the current standard specified.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.283-292).

Includes bibliography. / The thesis consists of a literature review and a limited experimental investigation in a soils laboratory. The objective of the literature review is to determine what standard laboratory test methods based on vibration exist for the control of compaction, to what soil types these tests are applicable and what the factors are which affect laboratory vibratory compaction. The study revealed that extensive research has been carried out in the USA and Europe, where standard laboratory compaction tests exist for the determination of the maximum dry density of cohesionless, free-draining soil. The US methods are based on the use of a vibratory table, while the European practice is based on the use of a vibratory tamper. No standard tests appear to exist for soil exhibiting cohesion, though limited research has been carried out in the USA into the behaviour of such soils under laboratory vibratory compaction. The factors; frequency, amplitude, mould size and shape surcharge intensity and manner of application, soil type, time of vibration, number of layers and moisture content are all reported to have an effect on the maximum dry density achievable. It has been recognised that significant interaction occurs between the factors affecting vibratory compaction, but the extent of the interaction appears to be only partly understood. The objective of the limited experimental program was to determine whether a specific graded crushed stone could be compacted to Modified AASHTO maximum dry density with a laboratory vibratory compaction technique using a vibratory table, and how this could best be achieved. The effects on dry density of changing the frequency, the time of vibration, mould size, surcharge pressure, grading and moisture content were investigated. It is concluded that the graded crushed stone in question can be compacted to Mod. AASHTO maximum dry density but that before reliable reproducible results can be achieved with this type of test further work is necessary. Such research should be aimed at investigating the interaction effect between the amplitude of vibration, the soil type and the type and intensity of the applied surcharge pressure.

This study models the compaction of soil by a vibratory roller compactor and examines changes to current designs that may provide more efficient compaction. The modeling of the soil differs from previous analyses of the compaction process in its use of a distributed-parameter characterization of the soil mass and in the application of nonlinear constitutive relations that predict the continuous evolution of residual stresses in the soil. The model was used to determine whether compactor performance might be improved by changes in the forward speed of the compactor or by redistribution of the weight of the frame. No improvement was found to occur. The model was also used to estimate the effects of varying the frequency of vibration to match the evolutionary changes in soil properties during compaction. Hardly any improvement over operation at constant frequency was indicated, but this finding may reflect the tendency of the model to underestimate the rate of stiffening in the soil. / Master of Science

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / There are currently well established compaction methods being used in laboratories globally to prepare specimens for material testing. None of these methods provides the repeatability and reproducibility, ease of execution or simulation and correlation to field compaction desired by engineers. The research presented in this report was aimed at the development of a new or adapted compaction method for bituminous stabilized materials (BSM) that would address the aforementioned factors, by making use of a vibratory hammer. Along with this, a new protocol was to be established. The initial vibratory hammer that was tested was the Kango 637®. This specific vibratory hammer suffered irreparable damage to the gearbox during the research. A replacement Kango hammer could not be purchased, therefore a substitute hammer was purchased i.e. a Bosch GSH 11E®, for which back-up service and replacement parts are readily available throughout South Africa. Significant progress had been made with the development of a laboratory compaction protocol for BSM using the Kango Hammer. The specifications of the Bosch® hammer showed it was superior in terms of power, weight and other technical features. Comparative testing was therefore carried out. This allowed for the adaptation of the results achieved to that point. 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. The initial 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 near Cape Town. The N7 material was used to perform correlation experiments so as to determine how representative the laboratory compacted specimens were to field compacted material. Results showed that the vibratory hammer is capable of producing specimens for testing in the laboratory as well as providing a possible benchmark method for accurately controlling the quality of work on site i.e. field density control. This was done by identifying the time to and level of refusal density compaction. The level of refusal density compaction was expressed as a percentage of Mod AASHTO compaction and using current specifications, a potentially new site compaction level specification was determined. In order to asses the material applicability of the vibratory hammer compaction method, tests regarding moisture sensitivity analysis were carried out on a G5 material. The vibratory compaction protocol includes a specification for the type of hammer, guide-frame, surcharge weight, compaction moisture and number of layers. Vibratory compaction can be used to prepare 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 compactability of the material. Material from the N7 recycling project had been milled out thus altering the grading and including some RAP. This in turn influenced compaction. The vibratory hammer moisture curve was found to shift slightly to the left when compared to the Mod AASHTO moisture curve. The variability of the vibratory hammer was found to be well below the specified variability of 15%. Repeatability experiments on G5 material indicate that vibratory hammer compaction may be used on lesser quality granular materials. A recommended procedure for the compaction of BSM was developed following the experimentation results.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Compaction is one of the key processes in the construction of road pavement layers. Not only is it significant in ensuring the structural integrity of the material in the road layers, but it also has an influence on the engineering properties and performance of the soil material. A poorly compacted material is characterised by low density, high porosity and below standard shear strength. This, as a result causes rutting, moisture susceptibility, potholing, corrugations and passability problems on the road. Therefore, it is vitally important that field compaction is done correctly. For this reason, laboratory compaction methods have been developed to simulate the field compaction process in the laboratory. The Mod AASHTO test has long been used as the laboratory compaction method of choice by virtue of its simplicity and the lack of bulky equipment required. However, previous studies have established that the Modified AASHTO method does not adequately simulate field compaction criteria especially for cohesionless materials. Two reasons have been advanced; The Mod AASHTO compaction method does not adequately simulate the compaction done in the field when the granular mix is laid; The compaction method may cause disintegration of the material. Alternative tests have been considered and much research has focused upon the use of a modified demolition hammer (vibratory hammer) for laboratory compaction of granular materials. This study undertook to evaluate the influence of test factors pertinent to the vibratory hammer compaction method. The influence of these test factors on compaction time and obtainable material density was assessed with the objective of developing a compaction method for granular materials. Vibratory hammer compaction tests were conducted on G3 hornfels, G4 hornfels and G7 sandstone material types and to a lesser extent, reclaimed asphalt (RA). Densities obtained were referenced to Mod AASHTO compaction density. Findings of the study showed that, the mass of the tamping foot has a significant influence on the obtainable compaction density. Other factors such as, moisture content, frequency and frame rigidity were also found to affect compaction with the vibratory hammer. In addition, it is shown that the surcharge load does not significantly influence the obtainable compaction density but does contribute to the confinement of the material and restricts the upward bounce of the hammer. On the basis of the results and findings, a compaction method was proposed, incorporating test parameters and factors that would provide ideal results for a set compaction time. Repeatability tests showed that, the developed vibratory hammer compaction method was effective in compacting graded crushed stone material types (i.e. G3 and G4) and probably RA. The test was not as effective on the G7 material. Further studies on this material (G7) are required. In addition to the previous testing regime, a comparative assessment of the developed vibratory hammer compaction method in relation to the vibratory table method was done. The results show that the vibratory hammer is capable of producing specimens of densities comparable to those of the vibratory table. A sieve analysis undertaken before and after compaction showed that compaction with the developed vibratory hammer compaction method does not result in any significant material disintegration. Based on the results of this study, a specification for the determination of maximum dry density and optimum moisture content of granular material using the vibratory hammer is recommended. / AFRIKAANSE OPSOMMING: Kompaksie is een van die belangrikste prosesse in die konstruksie van die padplaveisel. Dit is nie net waardevol vir die versekering van strukturele integriteit van die materiaal, maar dit het ook 'n invloed op die ingenieurseienskappe en vermoë van die grond materiaal. 'n Swak gekompakteerde materiaal word gekenmerk deur 'n laë digtheid, hoë porositeit, on onvoldoende skuifweerstand. Die kenmerke maak die material vatbaar vir vogen. Lei tot spoorvorming, slaggate, golwe en deurgangs probleme op die pad. Dit is dus uiters noodsaaklik dat veld kompaksie korrek gedoen word. Om hierdie rede, is kompaksie metodes in die laboratorium ontwikkel om sodaend veldkompaksie te simuleer. Die “Mod AASHTO” laboratorium kompaksie toets is die gekose laboratorium kompaksie metode op grond van sy eenvoudigheid en gebruik van minimale toerusting. Vorige studies het egter bevestig dat die “Mod AASHTO”-metode nie veldkompaksie akkuraat kan simuleer nie, veral vir kohesielose materiaal. As gevolg van twee hoofredes; Die Mod AASHTO kompaksiemetode is nie ‘n realistiese en vergelykende simmulering van kompaksie soos dit in die veld gedoen word nie; Die kompaksie metode mag verbrokkeling van die materiaal veroorsaak. Alternatiewe toetse was oorweeg en baie navorsing het gefokus op die gebruik van 'n aangepaste vibrerende hamer. Hierdie studie het onderneem om verskeie relevante toetsfaktore van die vibrerende hamer en hul invloed op die kompaksie en verkrygbare digtheid te bestudeer. Die invloed van hierdie toetsfaktore op kompaksietyd en verkrygbare materiaal digtheid was geassesseer met die doel om 'n kompaksiemetode vir granulêre materiaal te ontwikkel. Vibrerende hammer kompaksietoetse was uitgevoer op G3 hornfels, G4 hornfels en G7 sandsteen materiaal en tot 'n mindere mate herwinde asfalt. Digthede verkry was verwys na die Mod AASHTO kompaksie digtheid. Resultate van die studie het getoon dat die gewig van die stamp voet ‘n merkwaardige invloed het op die verkrygbare kompaksie digtheid. Ander faktore soos voginhoud, frekwensie en raam styfheid het ook getoon om kompaksiedigtheid te beïnvloed met die vibrerende hammer. Benewens was ook getoon dat die toeslaglading geen beduidende invloed het op die verkrygbare kompaksie digtheid nie, maar wel bydrae tot die inperking van die materiaal en verhoed die vertikale terugslag van die hammer. Gebaseer op die resultate en bevindinge was ‘n kompaksiemetode voorgestel wat toets parameters integreer met toetsfaktore en tot volg ideale resultate vir ‘n gegewe kompaksietyd voorsien. Herhaalde kalibrasie toetse het getoon dat die ontwikkelde kompaksiemetode effektief is in die kompaktering van gegradeerde gebreekte klip materiaaltipes (G3 en G4) en moontlik herwanne asfalt. Die toets was nie so doeltreffend op die G7 materiaal nie. Verdere studies op hierdie materiaal (G7) is dus nodig. Addisioneel tot die vorige toets, is bevind dat ‘n vergelykende assesering van die ontwikkelde vibrerende hammer kompaksiemetode in verhouding tot die vibrerende tafel. Die resultate wys dat die vibrerende hammer die vermoë het om toetsmonsters met digthede vergelykbaar met die vibrerende tafel te produseer. Sifanalise voor en na kompaksie het getoon dat verdigting met die ontwikkelde vibrerende hamer kompaksie metode nie lei tot die disintegrasie van die materiaal nie. Gebasseer op die resultate van dié studie was ‘n spesifikasie vir die bepaling van maksimum droé digtheid en optimale voginhoud van granulêre material aangeraai.