Flexible base thickening can be used to improve the structural capacity of low to moderate volume highways. This technique can be used where there are low levels of existing structural damage, the existing base is uniform, and the subgrade offers good (> 15 ksi) support. The new base material should be of equal or higher quality than the existing base; where this is not the case, it is essential that the new material be thoroughly blended with the existing base. When the materials are blended, cutting into the subgrade must be avoided. This subject was explored as a part of research project 0-4182. Field performances were evaluated in “Field Performance and Design Recommendations for Full Depth Recycling in Texas.”