Title: Comprehensive Database for Concrete Creep and Shrinkage: Analysis and Recommendations for Testing and Recording

Author(s): Mija H. Hubler, Roman Wendner, and Zdenek P. Bažant

Publication: Materials Journal

Volume: 112

Issue: 4

Appears on pages(s): 547-558

Keywords: admixtures; aggregate type; composition; compressive strength; correlation; database; shrinkage; statistics; testing.

DOI: 10.14359/51687453

Date: 7/1/2015

Abstract:
The first large worldwide database of creep and shrinkage tests was assembled at Northwestern University (NU) in 1978. It was expanded as the RILEM database in 1992 and further in 2008. A major expansion, completely restructured and verified, named the NU Database, is now presented. The number of the test curves of creep and drying shrinkage is more than doubled and over 400 test curves of autogenous shrinkage are added. The database covers longer measurement periods and encompasses the effects of admixtures in modern concrete mixtures. The database contains roughly 1400 creep and 1800 shrinkage curves, of which approximately 800 creep and 1050 shrinkage curves contain admixtures. Their analysis shows significant influence of admixtures on the creep and shrinkage behavior. The mixture proportions, testing conditions, and specimen geometries are documented in greater detail, and information on the admixture contents and aggregate types is included. The new database makes it possible to calibrate and verify improved creep and shrinkage prediction models. Additionally, the statistics of the mixture parameters, strength distributions, and scatter of the compliance curves have been extracted for applications in reliability engineering and probabilistic performance assessment. Data analysis brings to light various recommendations for testing and recording, and suggests corrections of various oversights distorting the reported data. These recommendations would make future test data more useful, consistent, complete, and reliable. The NU database is now available for free download at www. civil.northwestern.edu/people/bazant/ as well as at www.baunat.boku.ac.at/creep.html.