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Laboratory testing
The laboratory testing generally followed the Standard Methods for Testing Materials (TMH 1; NITRR, 1979). The tests included Atterberg Limits, particle size distribution (sieve and hydrometer), compac~ion characteristics and soaked and unsoaked California Bearing Ratio (CBR). The only modifications to the test methods were for the compaction and CBR tests where the crushed oversize material (larger than 19,0 mm) was not added to the sample. The addition of this material resulted in a very coarse grading which would not compact properly. This problem, as well as the problems caused by substituting the oversized fraction with finer material is well known (Beaven et al, 1987). The laboratory strength should therefore only be taken as a guide to the actual strength. As the field and laboratory gradings, compaction and moisture content are so different the applicability of the test is questionable. In the absence of nothing better the results must be used. As the normal specified compaction for wearing course materials is about 95 % Modified AASHO density, Proctor compaction was used in the laboratory in order to save time. Other tests carried out were the aggregate pliers value (APV) and aggregate fingers value (AFV) (Netterberg, 1967), the cone liquia limit (Sampson, 1986), field moisture equivalent (AASHTO, 1982), and a modified British Standard linear shrinkage. This test was modified to be used as a possible quick, simple field indicator test and consisted of material passing the 40 mesh sieve being mixed at the field moisture equivalent and then oven dried in a British Standard shrinkage trough.
EXPERIMENT TO DEFINE ACCEPTABILITY CRITERIA
Acceptability criteria for paved roads are well defined and have been summarised by Visser (198la). Acceptability criteria for unpaved roads, however, have generally consisted of various criteria such as those affecting the profitability of haulage routes in the forestry industries of the USA and Canada (Paterson et al, 1975; Visser, l98la). These criteria are suitable for this type of service but are unsuitable even for developing countries where the all weather trafficability of important routes is necessary. African situation where together with the all weather the road roughness, passenger comfort and safety In the southern trafficability, are considered equally important, acceptability criteria for these parameters needed to be defined. Visser (198la), instead of considering a set of subjectively determined standards proposed a set of limiting conditions, mainly related to maintenance philosophies. For this study, it was necessary to quantify acceptability criteria for road roughness, passenger comfort and safety in order to relate the material properties to these parameters.
1 INTRODUCTION
1.1 Background
1.2 Justification of the project
1.3 Objectives of the project
1.4 Structure of the dissertation
2 EXISTING INFORMATION
2.1 Introduction
2.2 Historical research
2.3 Previous studies – other countries
2.4 Previous studies – local
2.5 Ideal wearing course requirements
2.6 Specifications
2.7 Discussion
2.8 Statistical methods
2.9 Conclusions
3 EXPERIMENTAL DESIGN, TESTING AND MONITORING
3.1 Introduction
3.2 Experimental design of the study
3.3 York programme
3.4 Testing and monitoring techniques
3.5 s~~ary of results
3.6 Climatic effects
3.7 Conclusions
4 GENERAL PERFORMANCE
4.1 Introduction
4.2 Dust
4.3 Stoniness
4.4 Potholes
4.5 Cracks
4.6 Loose material
4.7 Drainage and erosion
4.8 Slipperiness
4.9 Trafficability (Passability)
4.10 Corrugations
4.11 Ruts
4.12 Conclusions
5 ROUGHNESS PREDICTION
5.1 Introduction
5.2 Results
5.3 Analysis
5.4 Discussion
5.5 Conclusions
6 GRAVEL LOSS PREDICTION
6.1 Introduction
6.2 Results
6.3 Analysis
6.4 Discussion
6.5 Comparison with other models
6.6 Conclusions
7 SPECIFICATION DEVELOPMENT
7.1 Introduction
7.2 Requirements of good specifications
7.3 Experiment to define acceptability criteria
7.4 Acceptability limits for specification development
7.5 Applicability of existing specifications
7.6 Analysis of results
7.7 Development of specifications
7.8 Discussion
7.9 Conclusions
8 PRACTICAL IMPLICATIONS OF FINDINGS
8.1 Introduction
8.2 Material location and selection
8.3 Material preparation
8.4 Pavement design
8.5 Construction considerations
8.6 Maintenance
8.7 Road user costs
8.8 National economy
8.9 Shoulders for sealed roads
8.10 Other roads
8.11 Other implications
8.12 Conclusions
9 SUMMARY OF CONCLUSIONS AND RECOMMENDATIONS
9.1 Summary of conclusions
9.2 Recommendations
9.3 Summary of findings
10 REFERENCES
