EFFECT OF EXPERIMENTAL SUBGRADE TREATMENTS ON PAVEMENT FAULTING AND PUMPING

THE EFFECTS OF VARIOUS SUBGRADE TREATMENTS ON THE PERFORMANCE OF A HEAVILY TRAVELED, CONCRETE PAVEMENT CONSTRUCTED ON PLASTIC, SILTY-CLAY SOILS WERE STUDIED. ONE OF THE MANY PROBLEMS IN THE DESIGN OF CONCRETE PAVEMENTS IS THE SELECTION OF THE PROPER BASE OR SUBGRADE TO AID THE PAVEMENT IN WITHSTANDING THE VOLUME AND WEIGHT OF MODERN TRAFFIC. WITH THIS IN MIND, THE STATE HIGHWAY COMMISSION OF INDIANA, DURING THE CONSTRUCTION OF U.S. HIGHWAY NO. 30 IN 1937, INSTALLED SEVEN TEST SECTIONS WITH DIFFERENTLY TREATED SUBGRADES. MANY STRUCTURAL FAILURES HAVE DEVELOPED ON THIS HIGHWAY. A STUDY OF THESE FAILURES OFFERS A MEANS OF EVALUATING THE EFFECTS OF THE VARIOUS SUBGRADE TREATMENTS ON THE PAVEMENT PERFORMANCE BY COMPARISON WITH THE UNTREATED PORTIONS. AERIAL STRIP MAPS WERE USED AS ONE MEANS OF EVALUATING PAVEMENT PERFORMANCE. THE PERFORMANCE DATA INDICATE THAT SIX OF THE SUBGRADE TREATMENTS IMPROVED THE CONCRETE PAVEMENT PERFORMANCE. GRANULAR BASE COURSES CONTRIBUTED THE MOST, THE RESULT OF THEIR USE BEING A PAVEMENT OF NEARLY AS GOOD A RIDING QUALITY TODAY AS AT THE TIME OF CONSTRUCTION NINE YEARS AGO. THE MIXING OF BITUMINOUS MATERIALS WITH THE FINE-GRAINED SUBGRADE SOIL IMPROVED THE PAVEMENT PERFORMANCE BUT NOT AS EFFECTIVELY AS DID THE GRANULAR BASE COURSES. NO SIGNIFICANT DIFFERENCE WAS READILY APPARENT IN THE PAVEMENT PERFORMANCE ON THE BITUMINOUS TREATED SECTIONS, ALTHOUGH ALL THREE TREATMENTS IMPROVED THE PERFORMANCE IN COMPARISON WITH UNTREATED SECTIONS. /AUTHOR/