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CCEER-03-6: Creep and Shrinkage Losses in Highly Variable Climates
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This study had several objectives, including studying the effects of aggregate type and climate on creep and shrinltage losses, determining and quantifying tile effects of moist-c~rring concrete (after prestressing), and proposing necessary revisions to the current AASHTO equations for creep and shrinkage loss prediction. 111 Reno and Las Vegas, twelve post-tensioiled concrete beams made with local aggregates were monitored for creep and shrinkage losses along with a niunber of cylinder specilnens that were monitored for creep and shrinkage strains independently. At each location, hvo box girders were left indoors exposed to a more stable environment, and tvo box girders and two solid beams were left outdoors exposed to precipitation and a wider varying enviromlient. Of each pair of beams, one beam was kept moist for two weeks after presu-essing (moist-curing) and one beam was not. Tesring 2nd analysis found that moisn:re ca:: increase the stiffness of ap- ed concrete by 20%, possibly reducing creep and shrinkage losses. Aggregate type was fo~indto influence concrete susceptibility to creep and slxinlcage losses cmd the effects of moisture. Testing and analysis also found that in some cases the liferime creep and shrinkage losses calculated from measured extrapolated surface strains exceeded the losses predicted by current prestress loss prediction metl-iods fi-on1 AASHTO: Naaman, and Nawy. Based on these findings: necessary revisions to the AASHTO equations for creep and sixinkage losses were proposed.
Report No. CCEER-03-6