In thick continuously reinforced concrete pavement (CRCP), thicknesses greater than 356 mm, the Texas Department of Transportation (TxDOT) places longitudinal steel in two mats, with equal amount of steel in both top and bottom mats. These longitudinal steel layouts may not be optimal for restraining concrete volume changes from temperature and moisture variations (environmental loading), which are most severe near the surface. This study mechanistically evaluated and optimized two-mat reinforcement layouts by placing more steel in the top layer while reducing the amount in the bottom layer. A total of 2160 three-dimensional finite-element models were developed in ANSYS to examine how variations in steel depth and spacing influence steel stress, concrete stress, and crack width under different environmental loading conditions. The results indicated that top-focused configurations with reduced bottom reinforcement satisfied all performance thresholds for steel and concrete stresses as well as crack width, reducing concrete stress by about 4% and 11% for 356 mm slabs and about 13% for 381 mm slabs, and reducing crack width by about 2% for 356 mm slabs and about 5% for 381 mm slabs. These optimized designs achieved performance better than the existing TxDOT two-mat design standards while requiring less steel amount. The findings in this study will be validated in the field experiment in the second phase of the study.