Bituminous Sandstone Mixtures

In certain sections of the state of Indiana sources of recognized ag­ gregates for use in bituminous construction are very few, and the trans­ portation of aggregates to the job site from remote locations becomes necessary. Often the distance over which the aggregate must be moved is considerable, and the importation involves the expenditure of a size­ able sum of money, which it would be desirable to reduce or eliminate. In some of these sections of the state, notably the south-central and southwestern portions, there are local deposits of sandstone which, if they could be used, would obviate the necessity of hauling in aggregates from outside sources. It was in recognition of this problem that the study was initiated. The purpose of the study was to provide a basis for the reasonable utilization of sandstone in bituminous mixes which are to serve as the surface courses of highways. Realizing that sand­ stones as a class fail to meet Indiana specifications, it is not proposed to use sandstone in wide general practice. Rather, its use is under con­ sideration where it can serve as an economic alternate in lieu of other aggregates. The approach to the problem has been divided into two sec­ tions. The first of these is a study of the properties of representative Indiana sandstones. The second is a study of the properties of asphaltsandstone mixtures in reference to sandstone characteristics. The initial phase of the work consisted of an investigation of the locations of sandstone in Indiana. The outline map of Figure 1 shows the general extremities of the Mississippian and Pennsylvanian geologic formations which contain the most extensive and prominent sandstones. Extending eastward from the western boundary of Indiana are the form­ ations of the Pennsylvanian period. The Post-Alleghanian age of this period outcrops adjacent to the Wabash River and is represented by the weakly-cemented Merom sandstone, which is the only major sandstone member of this age. East of the Post-Alleghanian formation is the Alleghanian formation, where the coal measures of Indiana are located. Little or no sandstone is to be found in this age. At the base of the Pottsvillian formation, which follows next, is found the Mansfield sand-