EVALUATING SUBGRADE FRICTION-REDUCING MEDIUMS FOR RIGID PAVEMENTS

AS EARLY AS 1924 THE U. S. BUREAU OF PUBLIC ROADS CONDUCTED STUDIES TO DETERMINE THE MAGNITUDE OF THE RESISTANCE OFFERED BY THE SUBGRADE TO THE HORIZONTAL MOVEMENT OF CONCRETE PAVEMENT SLABS. THESE EARLY STUDIES CLEARLY SHOWED THAT THIS RESISTANCE VARIED CONSIDERABLY WITH THE TYPE OF MATERIAL ON WHICH THE PAVEMENT RESTS. IN RECENT YEARS INCREASED INTEREST IN PRESTRESSED CONCRETE PAVEMENTS INDICATES A NEED FOR MEDIUMS THAT OFFER A LOW RESISTANCE TO SLAB MOVEMENT. THIS PAPER PRESENTS THE RESULTS OF A STUDY OF SEVERAL FRICTION-REDUCING MEDIUMS THAT HAVE BEEN PROPOSED BY DESIGNERS OF PRESTRESSED PAVEMENTS. THE DATA ON THESE MEDIUMS WERE DEVELOPED BY MOVING 6-FT SQ SLABS HORIZONTALLY, ALTERNATELY FORWARD AND BACKWARD SEVERAL TIMES. THE THRUST NECESSARY TO CAUSE HORIZONTAL MOVEMENT OF THE SLAB AND THE MAGNITUDE OF DISPLACEMENT CAUSED BY THE THRUST WERE MEASURED FROM THE TIME THAT THE FIRST DETECTABLE MOVEMENT TOOK PLACE UNTIL FREE SLIDING BEGAN. /AUTHOR/