The pavement strength is very important for the evaluation of backlog maintenance. The current trend in many developing countries used pavement conditions index-PCI in estimating maintenance costs. The PCI can only ju...The pavement strength is very important for the evaluation of backlog maintenance. The current trend in many developing countries used pavement conditions index-PCI in estimating maintenance costs. The PCI can only justify periodic and routine recurrent maintenance. The condition strength is rarely determined in a flexible pavement creating an opportunity for back long maintenance. This paper reports the study conducted to develop and improve the algorithm for estimating the adjusted structure number to estimate the remaining thickness of the flexible pavement. The analysis of eight ways of computing structure numbers from FWD data ware analyzed and found that the improvement of the HDM 3 - 4 models can influence the usefulness of data collected from road asset management in Tanzania. The algorithm for estimating structural numbers from CBR was improved to compute adjusted structural numbers finally used to estimate the remaining life of the flexible pavement. The analysis of the network of about 6900 km including ST and AM was found that 64.72% were very good, 12% were Good, 10% were fair and 7.84% were poor and 5.4% were very poor.展开更多
Five test sections with different additives and strategies were established to rehabilitate a State-maintained highway more effectively in Rhode Island （RI）： control, calcium chloride, asphalt emulsion, Portland ce...Five test sections with different additives and strategies were established to rehabilitate a State-maintained highway more effectively in Rhode Island （RI）： control, calcium chloride, asphalt emulsion, Portland cement and geogrid. Resilient moduli of subgrade soils and subbase materials before and after full depth rehabilitation were employed as input pa- rameters to predict the performance of pavement structures using AASHTOWare Pave- ment ME Design （Pavement ME） software in terms of rutting, cracking and roughness. It was attempted to use Level i input （which includes traffic full spectrum data, climate data and structural layer properties） for Pavement ME. Traffic data was obtained from a Weigh- in-Motion （WIM} instrument and Providence station was used for collecting climatic data. Volumetric properties, dynamic modulus and creep compliance were used as input pa- rameters for 19 mm （0.75 in.} warm mix asphalt （WMA） base and 12.S mm （0.5 in.） WMA surface layer. The results indicated that all test sections observed AC top-down （longitu- dinal） cracking except Portland cement section which passed for all criteria. The order in terms of performance （best to worst） for all test sections by Pavement ME was Portland cement, calcium chloride, control, geogrid, and asphalt emulsion. It was also observed that all test sections passed for both bottom up and top down fatigue cracking by increasing thickness of either of the two top asphalt layers. Test sections with five different base/ subbase materials were evaluated in last two years through visual condition survey and measurements of deflection and roughness to confirm the prediction, but there was no serious distress and roughness. Thus these experiments allowed selecting the best reha- bilitation/reconstruction techniques for the particular and/or similar highway, and a framework was formulated to select an optimal technique and/or strategy for future rehabilitation/reconstruction projects. Finally, guidelines for long-term evaluation were developed to verify short-term prediction and performance.展开更多
文摘The pavement strength is very important for the evaluation of backlog maintenance. The current trend in many developing countries used pavement conditions index-PCI in estimating maintenance costs. The PCI can only justify periodic and routine recurrent maintenance. The condition strength is rarely determined in a flexible pavement creating an opportunity for back long maintenance. This paper reports the study conducted to develop and improve the algorithm for estimating the adjusted structure number to estimate the remaining thickness of the flexible pavement. The analysis of eight ways of computing structure numbers from FWD data ware analyzed and found that the improvement of the HDM 3 - 4 models can influence the usefulness of data collected from road asset management in Tanzania. The algorithm for estimating structural numbers from CBR was improved to compute adjusted structural numbers finally used to estimate the remaining life of the flexible pavement. The analysis of the network of about 6900 km including ST and AM was found that 64.72% were very good, 12% were Good, 10% were fair and 7.84% were poor and 5.4% were very poor.
文摘Five test sections with different additives and strategies were established to rehabilitate a State-maintained highway more effectively in Rhode Island （RI）： control, calcium chloride, asphalt emulsion, Portland cement and geogrid. Resilient moduli of subgrade soils and subbase materials before and after full depth rehabilitation were employed as input pa- rameters to predict the performance of pavement structures using AASHTOWare Pave- ment ME Design （Pavement ME） software in terms of rutting, cracking and roughness. It was attempted to use Level i input （which includes traffic full spectrum data, climate data and structural layer properties） for Pavement ME. Traffic data was obtained from a Weigh- in-Motion （WIM} instrument and Providence station was used for collecting climatic data. Volumetric properties, dynamic modulus and creep compliance were used as input pa- rameters for 19 mm （0.75 in.} warm mix asphalt （WMA） base and 12.S mm （0.5 in.） WMA surface layer. The results indicated that all test sections observed AC top-down （longitu- dinal） cracking except Portland cement section which passed for all criteria. The order in terms of performance （best to worst） for all test sections by Pavement ME was Portland cement, calcium chloride, control, geogrid, and asphalt emulsion. It was also observed that all test sections passed for both bottom up and top down fatigue cracking by increasing thickness of either of the two top asphalt layers. Test sections with five different base/ subbase materials were evaluated in last two years through visual condition survey and measurements of deflection and roughness to confirm the prediction, but there was no serious distress and roughness. Thus these experiments allowed selecting the best reha- bilitation/reconstruction techniques for the particular and/or similar highway, and a framework was formulated to select an optimal technique and/or strategy for future rehabilitation/reconstruction projects. Finally, guidelines for long-term evaluation were developed to verify short-term prediction and performance.
