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Title:Early age creep and shrinkage of emerging concrete materials
Author(s):D'Ambrosia, Matthew
Director of Research:Lange, David A.
Doctoral Committee Member(s):Struble, Leslie J.; Roesler, Jeffery R.; Popovics, John S.; Gamble, William L.
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):concrete volume change
tensile creep
autogenous shrinkage
restrained cracking
self-consolidating concrete (SCC)
shrinkage reducing admixtures (SRA)
high-performance concrete (HPC)
Abstract:Concrete pavements and structures are especially vulnerable to cracking at early age. The volumetric instability of concrete at early age is a frequent cause of cracking. The primary components of volume change are external drying shrinkage, autogenous shrinkage, and thermal dilation. When concrete is restrained, tensile stress develops due to shrinkage and increases the probability of cracking. Early age properties, such as tensile creep, are not well understood and the availability of literature on the subject is limited. The goal of this research is to improve the understanding of early age behavior in emerging materials in order to improve long term durability. The early age volume changes of self-consolidating concrete (SCC), high-performance concrete (HPC), and concrete with shrinkage reducing admixture (SRA), or shrinkage-reduced concrete (SRC) were studied in order to understand mechanical behavior and develop guidelines for practice. A restrained uniaxial testing frame was previously developed for the purposes of understanding of early age mechanical properties and it was used to explore the role of tensile creep for relaxation of shrinkage stress in materials that are outside the scope of many current prediction models and design guidelines. Tensile creep was compared to compressive creep and up to a tenfold increase was observed, indicating an urgent need for updating models. Other observations, such as non-linearity of creep at early age and under restrained conditions, led to new insights regarding the use of superposition for long term deformations. Experimental characterization of early age behavior aided the development of a new modeling approach based on the utilization of relative humidity (RH) as the driving force for shrinkage. This approach was validated using new experiments developed to characterize tensile creep and autogenous shrinkage, and results demonstrate that RH is a powerful parameter for modeling shrinkage stress development and drying gradients. Based on the experimental work and modeling efforts, practical guidelines were developed for specifications, mixture proportioning, and acceptance testing, and mitigation strategies were suggested to minimize the potential for shrinkage cracking. Improvements were also suggested for existing prediction models to account for early age behavior. These research contributions enable practitioners to implement new concrete materials technology and realize the benefits of innovative concrete materials without sacrificing long term durability.
Issue Date:2012-02-01
Genre:Dissertation / Thesis
Rights Information:© 2011 Matthew D. D'Ambrosia
Date Available in IDEALS:2014-02-01
Date Deposited:2011-12

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