Creep and Shrinkage Behavior of Concrete in Segmental Bridge Applications

Abstract

The objective of this study is to accurately predict creep and shrinkage behavior of concrete in the I-59/I-20 segmental bridge located in downtown Birmingham, Alabama. In order to quantify creep and shrinkage, four different sample dates distributed throughout the segment casting schedule were selected to collect concrete specimens for testing. Concrete specimens were loaded at 7 days, 28 days, 91 days, and 182 days for creep testing. Shrinkage testing began for concrete specimens as soon as specimens were exposed to drying after initial curing. All concrete specimens were cured using increased temperatures for the first 24 hours after casting. Creep and shrinkage measurements were collected at set time intervals for the duration of the project from April 10, 2018 to September 30, 2020. In order to accurately predict creep and shrinkage, six commonly used models were evaluated in this project: ACI 209, AASHTO LRFD 2017, GL 2000, B3, CEB MC 1990, and CEB MC 2010. Measured and predicted values were compared using statistical analyses to determine which model most accurately predicted the test data. It was determined that the April 10, 2018 specimens exhibited the largest amount creep and shrinkage; however the percentage of total segments cast with similar concretes is very small. Likewise it was shown that concrete used for casting the April 16, 2019 specimens produced the smallest amount of creep and shrinkage, where a much larger percentage of total segments were cast with similar concretes. A similar trend was found for each sample date across all loading ages for creep; however, creep significantly decreased as the loading age increased. Statistical analyses determined that the GL 2000 Model most accurately predicted creep and shrinkage combined for all specimens tested during the project. Several empirical parameters were adjusted in the calibration of the GL 2000 Model to improve the creep and shrinkage prediction accuracy of the concrete cast in segments of the Birmingham I-59/I-20 segmental bridge. After calibration, the Modified GL 2000 significantly improved the creep and shrinkage predictions. In addition the CEB MC 1990 Model was calibrated, which allows for improved estimates of creep and shrinkage in some commonly used bridge analysis software.