Review of Specifications for the Use of Laterite in Road Pavements (Contract: AFCAP/GEN/124) InfraAfrica (Pty) Ltd, Botswana Dr. Frank Netterberg, South Africa Council for Scientific & Industrial Research, South Africa May 2014 TABLE OF CONTENTS Acknowledgements......................................................................................................... iv List of Abbreviations......................................................................................................... v 1. INTRODUCTION 1.1 Background .................................................................................................... 1 1.2 Purpose and Scope of Report ........................................................................ 3 1.3 Approach to Undertaking Literature Review ...................................................................3 1.4 Terminology ....................................................................................................................4 1.5 Structure of Report..........................................................................................................4 2. GENERAL CHARACTERISTICS 2.1 Introduction .................................................................................................. 6 2.2 Formation and Development...........................................................................................6 2.3 Definition, Description and Distribution ..................................................................12 2.4 Classification and Composition ............................................................................. 17 3. GEOTECHNICAL PROPERTIES AND TESTING 3.1 Introduction ................................................................................................ 22 3.2 Properties and Testing............................................................................................. 23 4. SPECIFICATION 4.1 Introduction ...................................................................................................................33 4.2 Review of Existing Specifications .............................................................................33 4.3 Regional Performance-Related studies.....................................................................46 5. CONSTRUCTION AND USE 5.1 Introduction ...................................................................................................................56 5.2 Examples of Use ................................................................................................................56 5.3 Quality Control .........................................................................................................58 6. CONCLUSIONS AND RECOMMENDATIONS 6.1 Summary of Conclusions ..............................................................................................59 6.2 Summary of Recommendations....................................................................................59 REFERENCES .....................................................................................................................................61 i LIST OF TABES Table 2-1: Summary of processes involved in the formation of laterite ..................................... 9 Table 2-2: Possible conditions for development of concretionary laterite ........................ ….11 Table 2-3: Commonly used terms to describe laterite........................................................... 13 Table 2-4: Charman’s recommended classification system for laterites ............................... 18 Table 2-5: Description of nodular laterite containing quartz..................................................... 19 Table 2-6: Typical chemical composition of lateritic material .................................................. 20 Table 2-7: Sesquioxide minerals typically found in lateritic material ..................................... 21 Table 3-1: Differences between traditional and pedogenic materials ................................... 22 Table 3-2: Effects of remoulding on Atterberg Limits of lateritic materials ............................ 25 Table 4-1: Some laterite and lateritic soil base specifications in comparison with the Brazilian general granular base specifications .........................................................35 Table 4-2: Charman’s (1988) recommended material selection criteria for lateritic gravel subbase and road bases under thin bituminous surfacing in the tropics.......36 Table 4-3: Krinitzsky et al’s (1976) recommended criteria for laterite base course materials ... 37 Table 4-4: Krinitzsky et al’s 1978 summary of base course specifications for selected African countries .........................................................................................................38 Table 4-5: Criteria used in Ghana for selecting laterites.......................................................... 39 Table 4-6: Gourley and Greenings (1999) proposed guideline for selection of lateritic gravel base materials for low volume roads with unsealed shoulders...................... 40 Table 4-7: Typical selection criteria for lateritic gravels based on grading and classification tests ................................................................................................ 41 Table 4-8: Typical selection criteria for lateritic gravel based on strength and classification tests ................................................................................................ 42 Table 4-9: Typical selection criteria for crushed lateritic caprock for warm humid and warm sub-humid zones........................................................................................ 43 Table 4-10:Typical selection criteria for lateritic gravels used on heavy duty pavements based on grading and classification tests............................................................44 Table 4-11: Summary of Brazilian specifications for laterite base course (DNIT 098/2007 for laterites base course ....................................................................................... 46 Table 4-12: Comparison of South African material properties from six base courses (20 results) with selected Brazilian specifications...................................................48 Table 4-13: Comparison of Botswana material properties form seven laterite bases courses with selected Brazilian specifications ..................................................... 50 Table 4-14: Comparison of Kenya material properties from seven laterite base courses with selected Brazilian specifications ..........................................51 Table 4-15: Properties of laterites used in low volume roads in Kenya in comparison with Brazilian specifications ......................................................................................... 52 Table 4-16: Properties of laterites used in low volume roads in Zimbabwe in comparison with Brazilian specifications................................................................................... 52 Table 4-17: Properties of laterites used in low volume roads in Malawi in comparison with With Brazilian specifications.................................................................................. 53 Table 4-18: Properties of laterites used in low volume roads in Mozambique in comparison with Brazilian specifications................................................................................... 53 ii Table 4-19: Properties of laterites used in low volume roads in Ethiopia in comparison With Brazilian specifications.................................................................................. 54 Table 4-20 Properties of laterites used in low volume roads in Malawi in comparison with Brazilian specifications ............................................................................................... 54 LIST OF FIGURES Figure 2-1: Schematic representation of tropical weathering profile.......................................... 7 Figure 2-2: Commonly used terms and adopted pedalogical classification .............................8 Figure 2-3: Distribution of lateritic materials and calcrete in South Africa ..............................15 Figure 2-4: Ternary diagram showing composition of lateritic materials .......................... … 15 Figure 2-5: Formation of laterite and ferricrete.......................................................................16 Figure 2-6: Generalized world map showing distribution of laterites......................................17 Figure 3-1: Modification to Particle Size Distribution required with lateritic gravels ..................24 Figure 3-2: Effects of drying on the properties of lateritic soils ............................................... 26 Figure 3-3: Location of common clay minerals on Casagrande’s plasticity chart .................... 27 Figure 4-1: Plot of road condition against PI ..............................................................................48 Figure 4-2: Plot of soaked CBR (Mod AASHO compaction) versus performance of road... ... 49 Figure 4-3: Plot of in situ DCP CBR of base versus performance of road…………….....…. 49 LIST OF PHOTOGRAPHS Photo 2-1: Cutting of laterite brick in quarry ................................................................................. 13 Photo 2-2: Use of laterite bricks for house construction.............................................................13 Photo 2-3: Nodular laterite (in profile) .................................................................................. 19 Photo 2-4: Nodular