EFFECT OF HIGH EVAPORATION DURING AND SHORTLY AFTER CASTING ON THE CREEP BEHAVIOR OF HARDENED CONCRETE /IN ENGLISH/

PRISMATIC SPECIMENS OF DIFFERENT CONCRETE MIXES WERE SUBJECTED SHORTLY AFTER CASTING TO HIGH EVAPORATION IN A WIND TUNNEL UNDER CONTROLLED CLIMATES. EXPOSURE TIME RANGED FROM ZERO TO TWENTY-TWO HOURS, AND EVAPORATION AND SHRINKAGE OF THE FRESH MATERIAL WERE CONTINUOUSLY MEASURED. AFTER REMOVAL FROM THE TUNNEL, ALL SPECIMENS UNDERWENT IDENTICAL CURING-28 DAY' IMMERSION AND SUBSEQUENT STORAGE AT 20 DEGREES C AND 50% R.H. AT 60 DAYS ALL SPECIMENS WERE LOADED FOR COMPRESSIVE CREEP AND THE FOLLOWING EFFECTS WERE OBSERVED AT REGULAR TIME INTERVALS UP TO 425 DAYS: 1. CREEP. 2. SHRINKAGE OF CONTROL SPECIMENS. 3. WEIGHT LOSS. THE ABOVE RESULTS, AS WELL AS STRENGTH VALUES, WERE ANALYZED AS AFFECTED BY EXPOSURE TIME. THE MAIN CONCLUSIONS ARE THAT SHORT EXPOSURES IMPPROVE ALL PROPERTIES, WHILE BEYOND A CERTAIN OPTIMUM TIME EXPOSURE IS DETRIMENTAL TO CREEP AND STRENGTH BUT NOT TO SHRINKAGE. THE PROPOSED THEORY, ACCOUNTING FOR THESE PHENOMENA, IS BASED ON THE MUTUALLY- COUNTERACTIVE ACTION OF TWO MECHANISMS, BOTH RESULTING FROM EVAPORATION: DENSIFICATION AND INTERNAL CRACKING. /LCPC(A) /RRL/