Modified nigeria cbr procedure for design of cement stabilized lateritic base low volume asphalt pavement in Nigeria

Excessive fatigue and rutting strains due to traffic loading contribute significantly to the failure of asphalt pavement. In the design of asphalt pavement, it is necessary to investigate these critical strains and design against them. In Nigeria, the only developed design method for asphalt pavement is the California Bearing Ratio (CBR) method. Most of the roads designed using the CBR method failed soon after construction by fatigue cracking and rutting deformation. This study was conducted to develop a modified Nigeria CBR procedure for low volume asphalt pavement adopting the layered elastic analysis procedure which involves selection of materials and layer thickness for specific traffic conditions such that fatigue cracking and rutting deformations are minimized. Analysis were performed for hypothetical asphalt pavement sections using the layered elastic analysis program EVERSTRESS. Regression equations were developed for predicting pavement thickness in cement-stabilized base, low-volume asphalt pavement. The result was validated by comparing calculated maximum fatigue and rutting strains developed using the modified procedure and measured strain data from the Kansa Accelerated Testing Laboratory (K-ATL). The calculated and measured fatigue and rutting strain were calibrated and compared using linear regression analysis. The calibration of calculated and measured fatigue and rutting strains resulted in R2 of 0.999 and 0.994 respectively for subgrade modulus of 31MPa, 0.997 and 0.997 respectively for subgrade modulus of 41MPa, 0.996 and 0.999 respectively for subgrade modulus of 62MPa, 0.992 and 0.995 respectively for subgrade modulus of 72MPa, 0.999 and 0.998 respectively for subgrade modulus of 93MPa, and 0.999 and 0.999 respectively for subgrade modulus of 103MPa. The results indicate that the coefficients of determination were very good.