Evaluation of Cracking Tendency and Unrestrained Shrinkage of High-Performance Concrete Mixes in Cast-in-Place and Precast Bridge Applications

ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

  


Title: Evaluation of Cracking Tendency and Unrestrained Shrinkage of High-Performance Concrete Mixes in Cast-in-Place and Precast Bridge Applications

Author(s): B. Czarnecki and J. Kroman

Publication: Special Publication

Volume: 228

Issue:

Appears on pages(s): 1315-1328

Keywords: admixtures; autogenous shrinkage; concrete durability; curing conditions; restrained shrinkage; unrestrained shrinkage

Date: 6/1/2005

Abstract:
Concrete bridge structures in Canada experience exposure to extreme environmental conditions, such as prolonged low temperatures, frequent freezing and thawing cycles, and, in urban maintenance conditions, extensive use of deicing salts. In addition, windy conditions combined with a very low relative humidity increase the potential for concrete cracking. The intensity of shrinkage of high performance concrete (HPC) is affected not only by the type and duration of the fresh concrete curing but also by high cement content, low water/cementitious materials ratio (w/cm), and the use of silica fume. The amount of unrestrained shrinkage, as identified by laboratory tests, does not always properly characterize the performance of HPC mixes. The restrained shrinkage test in accordance with the provisional AASHTO standard may provide better prediction of early age shrinkage (tendency to crack). In the study described in this paper, the effect of mix parameters and curing regime was researched extensively. The impact of shrinkage reducing admixtures in comparison with moist curing was assessed for cast-in-place concrete and precast concrete. Based on the results of this study, optimum mix design parameters, curing conditions, and w/cm ranges were determined to satisfy both durability and structural performance of HPC.