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Abstract
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
6.1 SUMMARY
An evaluation of the effectiveness and cost effectiveness of pavement preventive maintenance, and an evaluation of using of different types of asphalt materials in pavement maintenance in Egypt are the two main objectives of this study . Preventive maintenance, in this study, means the maintenance which prevent further deterioration of pavement condition. To achieve study objectives, two highways were selected. These highways are kafr Sakr – Abu Kbir and Faqos – El hosnia. A pavement condition survey for the selected highways were provided. Some distresses were considered in this study. These distresses are alligator, block, edge, and longitudinal and transverse cracking. Some pavement sections, on the selected highways, were identified. Three maintenance techniques were carried out on the selected pavement sections. These techniques are no maintenance, technique ( A ), and technique ( B ). These techniques were performed by using asphalt cement (AC 60/70) on the selected pavement sections. An additional asphalt materials were used on Kafr Sakr –Abu Kbir highway. These asphalt materials are cutback asphalt ( RC – 3000 ) and cationic slow setting emulsion asphalt ( CSS – 1h ). The total number of studied test sections are ( 448 ) test sections. A monthly periodic evaluation by pavement condition index method ( PCI ), on the studied pavement sections were provided for a period of 16 months. An evaluation of the maintenance techniques through the progress of distresses quantity, with different levels of severity ( low, medium, and high ), and deduct points were determined. Statistical analysis ( t – distribution and ONE WAY ANOVA (SPSS)), on three periods of the study was presented. These three periods are before and after the application of the maintenance directly, before and after the rainfall period, and before maintenance application ( first survey ) and at the end of the study period (last survey). Also, a comparison among the results of evaluation of using different types of asphalt materials were identified . An effectiveness and cost effectiveness analysis for the used asphalt maintenance techniques and the used asphalt materials were investigated. Also, several regression analysis were made to investigate the relationship between the rate of deterioration of pavement condition and other factors which affect pavement condition such as traffic loads and age of maintenance.
6.2 CONCLUSIONS
Based on the results of this study, the following conclusions were drawn :
1- For all types of selected distresses, for selected highways, the rate of deterioration of no maintenance sections is greater than the rate of deterioration of technique (B) sections then the rate of deterioration of technique (A) sections.
2- For all types of selected distresses, for selected highways, for no maintenance sections, increasing in deduct points, at the end of the study period, ranges between two and four times of the original value of deduct points. But for technique ( B ) sections, this increasing, at the end of the study period, ranges between quarter and two thirds of the original value of deduct points. At the same time, for technique ( A ) sections, the deduct points equal to zero after maintenance applying and until the end of the study period, except for some cracks, the deduct points started to appear in the last few months of the study period with a too small value.
3- For no maintenance sections, for selected highways, the total deduct points doubled at the end of the study period compared with its original value. But for technique ( B ) sections, the value of total deduct points, at the end of the study period, nearly the half of its original value. At the same time, for technique ( A ) sections, the total deduct points equal to zero after maintenance applying, then it started to appear in the last few months of the study period with a too small value.
4- Values of the specified ratios of the three critical phases, ( the ratio of the average second survey to the average first survey, the ratio of the average after rainfall survey to the average before rainfall survey and the ratio of the average last survey to the average first survey ), of no maintenance technique are greater than that of technique ( B ) then that of technique ( A ).
5- For all types of selected distresses, for selected highways, technique ( A ) is more effective and more cost effective than technique ( B ).
6- For selected highways, for asphalt cement ( AC 60/70 ) and cutback asphalt ( RC – 3000 ), the total deduct points equal to zero after maintenance applying until the last four months of the study period, then the total deduct points increase slightly with time, with small values, until the end of the study period. But for emulsion asphalt ( CSS – 1h ), the total deduct points equal to zero for few months, after maintenance applying, then it increases gradually with time, and its value at the end of the study period, decreased to the third of its original value.
7- For all selected distresses, for selected highways, the rate of deterioration of emulsion asphalt sections is greater than the rate of deterioration of cutback asphalt sections then the rate of deterioration of asphalt cement sections.
8- For all types of selected distresses, for selected highways, emulsion asphalt is less effective than asphalt cement and cutback asphalt. For cost effectiveness, for alligator, block and longitudinal and transverse cracks, emulsion asphalt is more cost effective than asphalt cement and cutback asphalt. At the same time, for edge cracks, emulsion asphalt is less cost effective than asphalt cement and cutback asphalt.
9- several models were developed to investigate the effect of traffic loads and maintenance age on the rate of deterioration of pavement condition due to applying different maintenance techniques and due to using different asphalt materials in pavement maintenance.
6.3 RECOMMENDATIONS
In view of the previous analysis and conclusions, the following recommendations are presented :-
1- For highways of conditions similar to the conditions of selected highways in this study, technique ( A ) should be considered to be used in pavement maintenance than technique ( B ) because technique (A) is more effectiveness and more cost effectiveness than technique ( B ) which indicates a good pavement condition for a long period of time. So, technique ( A ) may prolong the pavement life and may decrease the cost of maintenance and construction of highway for a long period of time.
2- For highways of conditions similar to the conditions of selected highways in this study, asphalt cement and cutback asphalt should be used than emulsion asphalt in pavement maintenance in Egypt due to their good performance. Poor performance of emulsion asphalt in pavement maintenance may be due to old mixing method of emulsion asphalt mixture and no presence of slurry seal machine in Egypt. It is recommended to generalize the use of slurry seal machine in highway authority and highway companies.
3- The locations of study sections was determined perfectly, so it is recommended to continue in the evaluation of performance level of these sections in future to gain the following :-
a- To improve the level of the resulted data.
b- To develop the performance curves models concerned with the alternatives considered in this study.
4- Future studies should take into consideration another measurements of pavement evaluation such as roughness and skid resistance of pavement.
5- Future studies should be carried out on the effectiveness of pavement preventive maintenance of urban highways.