Abstract
Early‐age cracking due to restrained shrinkage affects the performance and service life of concrete structures. Recent studies are successfully making use of the free ring shrinkage test in conjunction with restrained shrinkage measurements for the evaluation of the cracking potential of cementitious materials. This study provides information to improve the interpretation of cracking in ring specimens and a theoretical approach for predicting the stress rate of thick ring specimens. Results show that the rate of strain development and the age‐at‐cracking vary with specimen drying direction and the exchange surface‐to‐volume ratio. The results further revealed that early‐age shrinkage cracking depends more on the shrinkage rate than the magnitude of the shrinkage itself. Also, it was found that although the restrained ring specimens attained approximately similar strain levels, the cracking age varies significantly, suggesting that elastic stress‐strength analysis alone may be inadequate for predicting early‐age cracking due to the contribution of creep‐relaxation phenomena.
Highlights
Shrinkage of cementitious materials is inevitable when the material is exposed to an environment with lower relative humidity (R.H.) and undergoes drying
Many concrete structures worldwide require repair and rehabilitation, sometimes repeatedly, due to problems triggered by restrained shrinkage cracking
Many studies relating to shrinkage cracking have focused on the free shrinkage deformations
Summary
Shrinkage of cementitious materials is inevitable when the material is exposed to an environment with lower relative humidity (R.H.) and undergoes drying. The AASHTO T 334-08 [6] ring procedure was used to appraise the influence of the boundary conditions (i.e., drying direction) and the exchange surface to-volume-ratio (Se/V) on shrinkage and the associated cracking of thick AASHTO ring specimens. E data analysis methods presented here will help to better interpret the data obtained from the ring test procedure recently developed for sprayed concrete [15]. The present study is part of the ongoing research on the durability of concrete and shotcrete mixtures and is aimed at better characterizing the drying shrinkage cracking potential of shotcrete, through improved interpretation of the ring test results. E paper provides useful information on the influence of drying direction (boundary conditions) upon stress development and age at cracking in the restrained ring specimen. The influence of the water-to-cement ratio (w/cm) and exchange surface-to-volume ratio is discussed. is study is of interest to engineers and material specifiers in view of better assessing and/or predicting the drying shrinkage sensitivity of concrete
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