An Evaluation Of Selected Flexible Pavement Roads In Lusaka,Zambia

Flexible pavement deterioration is one of the major challenges faced by transport agencies.Pavement deterioration is mainly caused by traffic load,climate,design deficiencies and human oversight.Most of the premature failures of pavement are caused by design deficiencies and human oversight.Due to uncertainty as a result of climate change,empirical and mechanistic designs need to be enhanced with state-of-the-art design methods such as the laboratory CWTM.Identifying and realizing the root cause of pavement distresses helps engineers to rate the pavement condition and select the most cost-effective treatment.Frequent pavement assessments are required to provide useful pavement condition data.Such information is very essential as raw data for design enhancement,maintenance plan and prediction models.Generally,this study was carried out by employing three(3)proposed methodologies.The first methodology was dedicated to evaluate selected pavement with reference to current pavement condition.Six(6)roads were examined and one(1)road was selected as a candidate for detailed scrutiny using PCI in accordance with ASTM D6433 procedure.After inspecting the six(6)roads,nine(9)distresses were identified.The primary causes of pavement failure were also examined and the M&R needs were recommended.The types of distresses with high occurrences were rutting and cracking at 25.1% and 23.9% respectively.The evaluation results from the PCI survey revealed that the pavement condition was ranging from very poor to very good.The pavement inspected needed variety of repair treatment ranging from overlay,deep patching,crack sealing base repair and repave.The second + and stripping using the CWTM.The results indicated that AC mixtures are sensitive to temperature and air void content but not very sensitive to aggregate grading.The results also demonstrated that using CWTM,the AC sample results can be repeated with less than 20% of the mean value of two individual test samples.The third approach was to develop and validate prediction models.Remaining service life(RSL)estimation and pavement condition prediction are two essential functions of Pavement Management Systems.Survival curves were used to calculate RSL of the pavement by deriving pavement condition rating(PCR)curves.From the PCR curves,it was concluded that RSL increases when the pavement age increases.The average RSL for the road in question was calculated to be 2.9 years based on the PCR for 2018.The models were validated using the R-square and the best-fit-line methods of which the models correlated fairly well with the laboratory results.A relationship was also established between field rut depth,ESAL,laboratory rut results and a good correlation was observed between the model results and field rut development.The results demonstrated that the effect of 1000 CWTM wheel passes on AC sample is equivalent to 0.345 MESAL applied to the field pavement.