Grouted Macadam: Material Characterisation for Pavement Design

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Chapter 2 Review of “Traditional” Road Pavement Types and Design The major factors influencing fretting are the bitumen content of the mixture and the degree of compaction. Loss of aggregate can be due to either loss of adhesion between the aggregate and the bitumen or brittle fracture of the bitumen film connecting particles of aggregate (Read and Whiteoak, 2003). Ravelling differs from the above in that it involves the plucking out of surface aggregate by traffic without any loss of cohesion of internal fines. It occurs when individual aggregate particles move under the action of traffic. If the tensile stress (induced in the bitumen as a result of the movement) exceeds the breaking strength of the bitumen, cohesive fracture of the bitumen will occur and the aggregate particle will be detached from the road surface. Thus, ravelling is most likely to occur at low temperatures and at short loading times when the stiffness of the bitumen is high (Read and Whiteoak, 2003). Another type of degradation visible at the surface of pavements is the fatting-up of bitumen. This occurs in over-rich bituminous mixtures, i.e., with too high a binder content, or with too low a voids content. An eventual consolidation of the aggregates in the mixture may force the bitumen to move to the surface. In this case, it would result in a smooth, shiny surface that has poor skidding resistance in wet weather. 2.2.2 Rigid Pavements Rigid pavements (or concrete pavements) normally consist of two structural layers, the concrete slab and the sub-base. The slab may be laid in composite form using different aggregates in the upper and lower layers. Upper and lower sub-base layers and a capping layer may also be used (Croney and Croney, 1991). Capping is used to improve and protect weak subgrades, by using a relatively cheap material between the subgrade and the sub-base. The aim is to increase the stiffness modulus and strength of the formation, on which the sub-base will be placed (Highways Agency, 1994a). In a rigid pavement, the concrete slab should be strong enough to support the traffic loads and to protect the subgrade and the sub-base. Thus, a separate base layer is not 16
Chapter 2 Review of “Traditional” Road Pavement Types and Design necessary to reduce the stresses in the pavement. The sub-base is used as a drainage layer and also to protect the subgrade during the construction of the concrete slab and to protect it from the action of frost. The pavement structure may vary, depending upon the type of concrete slab used, but the main composition of the pavement is similar in all cases (Figure 2.5). The concrete slab can be reinforced or unreinforced and it can be constructed with or without joints. Figure 2.5 – Components of concrete pavements (Adapted from Croney and Croney, 1991) An unreinforced concrete pavement (UCP), often referred to as jointed plain concrete pavement (JPCP), has no reinforcement and is normally constructed with induced joints (spaced at 5 m or less) to reduce the probability of thermal cracking. It is designed to be thick enough to resist traffic induced cracking. If a crack occurs, it tends to widen rapidly and granular interlock is lost (Figure 2.6). Detritus entering the crack tends to cause spalling and water entering the crack results in loss of strength in the sub-base and sometimes pumping of fines. The commonest cause of such cracking may be low-strength concrete (Croney and Croney, 1991). The transverse joints are usually induced by saw cutting the concrete slab over at least one third of the thickness of the slab. Expansion joints are used only in particular locations such as on approaching bridges or other structures and sometimes in winter construction. If the width of the surface is greater than 4.50 m, a longitudinal joint is always placed between lanes of traffic, to prevent the appearance of a longitudinal crack along the road axis. Except on roads with light traffic, the 17
Page 1 and 2: GROUTED MACADAM - MATERIAL CHARACTE
Page 3 and 4: ACKNOWLEDGEMENTS The present projec
Page 5 and 6: LIST OF CONTENTS Abstract i Acknowl
Page 7 and 8: List of Contents 6 Grouted Macadams
Page 9 and 10: LIST OF FIGURES List of Contents Fi
Page 11 and 12: List of Contents Figure 4.2 - Grout
Page 13 and 14: List of Contents Figure 6.32 - Crac
Page 15 and 16: List of Contents Figure 8.12 - Infl
Page 17 and 18: LIST OF TABLES List of Contents Tab
Page 19 and 20: 1 INTRODUCTION 1.1 Background Road
Page 21 and 22: Chapter 1 Introduction These facts
Page 23 and 24: Chapter 1 Introduction is discussed
Page 25 and 26: Chapter 2 Review of “Traditional
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Page 57 and 58: 3 REVIEW OF GROUTED MACADAMS 3.1 In
Page 59 and 60: Chapter 3 Review of Grouted Macadam
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Chapter 3 Review of Grouted Macadam
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4 DEVELOPMENT OF FOUR-POINT BENDING
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Chapter 4 Development of Four-Point
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5 BASIC CHARACTERISATION OF THE MAT
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Chapter 5 Basic Characterisation of
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6 GROUTED MACADAMS MIX DESIGN STUDY
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Chapter 6 Grouted Macadams Mix Desi
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7 DETERIORATION OF HALF-SCALE PAVEM
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Chapter 7 Deterioration of Half-Sca
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8 DEVELOPMENT OF DESIGN METHOD FOR
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Chapter 8 Development of Design Met
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9 CONCLUSIONS AND RECOMMENDATIONS I
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Chapter 9 Conclusions and Recommend
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References Brown, S. F. and Brodric
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References Di Benedetto, H., De La
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References Osman, S. A., (2004). Th
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References van de Ven, M. F. C. and
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APPENDICES Appendix A: Engineering
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Stiffness (MPa) 25000 20000 15000 1
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Stiffness (MPa) 12000 11000 10000 9
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Stiffness (MPa) 10000 9500 9000 850
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Stiffness (MPa) 8500 8000 7500 7000
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Stiffness (MPa) 10000 9000 8000 700
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Fatigue life of the studied mixture
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Mixture Specimen Slab 05-0296 PTF -
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Stiffness Modulus of DBM 50 and sta
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Grouted Macadam: Material Characterisation for Pavement Design

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