SHRINKAGE OF CONCRETE-COMPARISON OF LABORATORY AND FIELD PERFORMANCE

IN GENERAL, PORTLAND CEMENT CONCRETE, ON DRYING, DOES NOT DEVELOP AN AMOUNT OF SHRINKAGE DETRIMENTAL TO ADEQUATE SERVICE. HOWEVER, THERE ARE CASES WHERE SERVICEABILITY IS KNOWN TO HAVE SUFFERED DUE TO AN ADNORMAL SHRINKAGE AMOUNT OF THE HARDENED CONCRETE. SUCH DISTRESS HAS OCCURRED IN BOTH STRUCTURES AND PAVEMENTS. ONE REASON FOR THE POOR PERFORMANCE WAS THAT THE ACCEPTABILITY OF THE WORK IN PROGRESS WAS BASED LARGELY ON STRENGTH TESTS THAT BORE LITTLE RELATIONSHIP TO SHRINKAGE. IN THIS PAPER, FACTORS PRODUCING SHRINKAGE OF LABORATORY SPECIMENS ARE REVIEWED FROM THE LITERATURE AND SUPPLEMENTED BY ORIGINAL TEST DATA. OF THE MANY FACTORS CONTRIBUTING TO SHRINKAGE, THOSE THAT ARE CONTROLLABLE ON THE WORK UNDER TYPICAL SPECIFICATIONS ARE OF LESS IMPORTANCE THAN THE CHARACTERISTICS OF THE CONSTITUENT MATERIALS FOR WHICH THE USUAL SPECIFICATION REQUIREMENTS PROVIDE INADEQUATE PROTECTION. A COMBINATION OF UNFAVORABLE CONDITIONS AND MATERIALS CAN INCREASE SHRINKAGE FOURFOLD, AN AMOUNT CONDUCIVE TO POOR PERFORMANCE. THE RESULTS OF LABORATORY SPECIMENS DRIED UNDER STANDARD CONDITIONS ARE COMPARED TO THOSE OF FIELD EXPOSURE OF FULL-SIZE OR NEAR FULL-SIZE STRUCTURES AND PAVEMENTS. IT IS SHOWN THAT BY PROPER DESIGN OF LABORATORY TESTS, THE PERFORMANCE OF JOB CONCRETE CAN BE PREDICTED WITH ASSURANCE. THE NEED OF SPECIFICATION REQUIREMENTS AGAINST HIGH SHRINKAGE PRODUCED BY CEMENTS AND AGGREGATES AND MORE RESTRICTIVE REQUIREMENTS FOR ADMIXTURES IS DEMONSTRATED. /AUTHOR/