Concrete engineers and the concrete industry must continue to face the challenge of building still heavier duty pavements needed for greater fleets of commercial, industrial, and military vehicles running at higher speeds and causing more serious dynamic effects. Generally, it is more economical to design the slab for the existing subgrade bearing capacity than to raise the subgrade support by using an extra-thick subbase. If, however, a subbase is used, minimum requirement are: that the material passing the no. 200 sieve must be not over 10 percent; that low plasticity, optimum gradation, and high density should be achieved consistent with permissive economy; and that cement-treated subbases may be considered if the available granular material is of substandard quality. Concrete for heavy-duty pavements should be of the driest consistency possible to work with a sawing motion of the strike-off board. The lowest water content compatible with thorough compaction can be achieved by selecting a water/cement ration that will insure the required compressive strength; selecting aggregate that is graded in such a way that it will give the densest concrete; and selecting an aggregate/cement ratio that will permit a workable mix to be full compacted. Application or air entrainment increases the durability of concrete pavements subjected to weathering, enhances the resistance of concrete to freezing and thawing and to the action of sodium and calcium chlorides, eliminates the development of D-cracks that are usually attributed to accelerated weathering, and adds to the concrete's sulfate resistance.