Creep and Shrinkage of High-Performance Concrete

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Title: Creep and Shrinkage of High-Performance Concrete

Author(s): W. H. Dilger and C. Wang

Publication: Special Publication

Volume: 194

Issue:

Appears on pages(s): 361-380

Keywords: admixtures; creep; high-performance concrete; prediction model; shrinkage

Date: 5/1/2000

Abstract:
Creep and shrinkage of concrete are important factors in the design and analysis of concrete structures, particularly for the long-term serviceability and durability and for the construction stage of long span, prestressed con-crete structures. Because of very low water-cementitious ratio (w/cm), chemical admixtures and sometimes mineral admixtures, the evolutions of moisture state and rate of cement hydration in high-performance concrete (HPC) are significantly different from those in normal concrete. For example, the cement hydration in HPC terminates earlier due to the lack of water, resulti ng in faster development of relative strength at early ages and little long-term strength gain. At the same time, self-desiccation in the form of a rapid decrease in internal relative humidity starts in HPC at very early ages. Consequently, base (autogenous) shrinkage of HPC is very high compared with normal concrete. The moisture permeability, which affects the development of creep and shrinkage of concrete, is at least one order smaller for HPC than for normal concrete. As a result well as creep and the development shrinkage property of strength and modulus of elasticity as es of HPC are remarkably different from those of normal concrete. The current prediction models for time-dependent properties, particularly creep and shrinkage, which have been derived from experimental data on normal concrete, are not applicable to HPC. This paper will discuss the main parameters affecting the time-dependent properties and the differences between HPC and normal concrete, based on the results of an extensive experimental program at the University of Calgary and data from the literature. A recently developed model to estimate creep and shrinkage of HPC is also presented and examined.