REPORT ON EXPERIMENTAL PROJECT IN MINNESOTA

IN 1940, THE MINNESOTA DEPARTMENT OF HIGHWAYS CONSTRUCTED AN INVESTIGATIONAL CONCRETE PAVEMENT UNDER REGULAR CONTRACT AND CONSTRUCTION PROCEDURES. THE PURPOSE OF THIS EXPERIMENTAL PROJECT WAS TO STUDY AND EVALUATE VARIOUS FUNDAMENTAL PRINCIPLES OF CONCRETE PAVEMENT DESIGN AND THE RELATIVE PERFORMANCE OF SUCH PAVEMENTS OVER A PERIOD OF YEARS. THE MINNESOTA PROJECT, CONSISTING OF 8.1 MILES OF 22- FOOT CONCRETE PAVEMENT, WAS CONSTRUCTED ON STATE HIGHWAY 60 BETWEEN WORTHINGTON AND BREWSTER DURING THE PERIOD FROM AUGUST 6 TO SEPTEMBER 20, 1940. CLIMATOLOGICAL AND TRAFFIC DATA WERE RECORDED AS WELL AS DAILY, SEASONAL, AND PERMANENT CHANGES IN WIDTH AND ELEVATION. CONDITION SURVEYS FOR FAULTING, CRACKING, PUMPING, AND BLOW-UPS WERE REPORTED. THE FOLLOWING GENERAL CONCLUSIONS SEEM TO BE INDICATED BY THE DATA OBTAINED DURING THE FIRST TEN YEARS OF THE LIFE OF THIS PAVEMENT: (1) EXPANSION JOINTS ARE NOT NECESSARY IN RURAL PAVEMENTS, EXCEPT AT FIXED OBJECTS. THEY MAY BE CONSIDERED DETRIMENTAL, IF PLACED AT CLOSE INTERVALS BECAUSE THEY PERMIT EXCESSIVE SLAB MOVEMENT OVER A LONG PERIOD OF TIME. THE ELIMINATION OF EXPANSION JOINTS WILL NOT CAUSE EXCESSIVE LONGITUDINAL STRESSES BECAUSE OF THE COMPENSATORY EFFECT OF INITIAL AND SUBSEQUENT SHRINKAGE OF THE CONCRETE. (2) CONTRACTION JOINTS SHOULD BE PLACED AT INTERVALS OF 15 FEET IN ORDER TO OBTAIN THE BEST OVER-ALL PERFORMANCE OF THE PAVEMENT SLAB FROM THE STANDPOINT OF JOINT MOVEMENT, CRACKING, WARPING, FAULTING AND ROUGHNESS. (3) THE 7-INCH UNIFORM PAVING SECTION APPEARS TO BE SUPERIOR TO THE 9-6-9 SECTION BUT NEITHER IS ENTIRELY ADEQUATE. THE 9-6-9 SECTION WAS NOT THICK ENOUGH THROUGH THE CENTER TO COPE WITH THE SUBGRADE AND LOAD STRESSES AS INDICATED BY LONGITUDINAL CRACKING. THE 7-INCH UNIFORM SECTION DID NOT HAVE ADEQUATE STRENGTH AT THE OUTER CORNERS AS COMPARED TO THE INNER CORNERS AS EVIDENCED BY THE ADDITIONAL EXTERNAL CORNER BREAKS. IT APPEARS THAT A TAPERED 7-INCH SECTION, SUCH AS A 9-7-9, IS INDICATED AS BEING DESIRABLE. (4) MESH REINFORCEMENT WILL NOT PREVENT CRACKING IN SLABS 30 FEET OR MORE IN LENGTH. (5) DOWELS ARE EFFECTIVE IN REDUCING FAULTING AT JOINTS. AGGREGATE INTERLOCK MAY ALSO BE EFFECTIVE WHEN EXPANSION JOINTS ARE ELIMINATED AND SHORT PANELS, ON THE ORDER OF 15 FEET IN LENGTH, ARE USED. (6) METAL SEALS, COOPER BEING USED ON THIS PROJECT, ARE NOT SIGNIFICANTLY EFFECTIVE IN PREVENTING VERTICAL JOINT DEFORMATIONS. (7) THE JOINT SEALING MATERIAL OF THE TYPE MANUFACTURED BY THE RUBBER ASSOCIATES COMPANY IN 1940 PROVED TO BE MORE EFFECTIVE THAN THE ASPHALT OR LATEX-OIL MATERIALS. HOWEVER, THIS PROJECT HAS INDICATED THAT EXTENDED POSTPONEMENT OF JOINT MAINTENANCE IS DETRIMENTAL TO THE PAVEMENT AND EVEN THE BETTER MATERIAL DID NOT ADEQUATELY SEAL THE JOINTS AFTER 10 YEARS. (8) EXPANSION JOINT FILLERS, WHERE USED, SHOULD BE NON-EXTRUSIVE IN SERVICE AND SHOULD PREVENT THE LEAKAGE OF WATER DOWNWARD TO THE SUBGRADE SOIL. (9) CONCRETE PAVEMENTS TEND TO BECOME GRADUALLY ROUGHER WITH AGE. IT IS BELIEVED THAT THIS IS DUE TO THE EFFECTS OF LOADING, CLIMATE AND SUBGRADE RATHER THAN TO PAVEMENT DESIGN FEATURES. OF THESE, THE SUBGRADE OFFERS THE GREATEST OPPORTUNITY FOR IMPROVING THE STABILITY, PERFORMANCE AND SERVICE LIFE OF THE ENTIRE ROAD STRUCTURE.

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 89-141
  • Monograph Title: Joint spacing in concrete pavements: 10 year reports on six experimental projects
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00207418
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: May 22 1972 12:00AM