Progress Report on Calcium Chloride Maintained Traffic Bound Roads

The object of this study is to evaluate the effectiveness of calcium chloride in maintaining traffic-bound roads. Various theses propose that the use of calcium chloride will minimize the loss of granular material from the base by reducing attrition and dusting; thereby aiding in stabilization. Such theses further suggest that when the proper amount of binder or soil mortar is present, calcium chloride will preserve a more uniform moisture condition within the soil-mortar and thus hold the aggregate in place and in a more stable condition. The primary purpose of the study is not to test these theses, but rather to evaluate the practice with respect to currently routine maintenance procedures and their comparative costs. A maximum of fifty miles of traffic-bound roads were to be programmed for the study. Projects were selected by each maintenance district in cooperation with the Research Division. The initial application of calcium chloride was to be made at the rate of l.6 lbs. per sq. yd. of the anhydrous material or 2.0 tbs. per sq. yd. of the hydrated material. Thereafter, calcium chloride was to be added twice annually: in the spring, at the rate of 0.8 lbs. per sq. yd, based upon anhydrous material; and in the fall, at the rate of 0.4 lbs. per sq. yd., based upon anhydrous material. Prior to applying the calcium chloride, the surfaces were to be re-shaped and any necessary aggregate and binder added. It was desirable, of course, that this operation be made while the surface was in a moist condition. Since economic considerations were of primary importance in the study, all surface maintenance cost records on these projects were to be closely evaluated and, insofar as possible, compared with costs of maintaining roads of this type without the use of calcium chloride