Title:
Creep and Shrinkage Revisited
Author(s):
N. J. Gardner and J.-W. Zhao
Publication:
Materials Journal
Volume:
90
Issue:
3
Appears on pages(s):
236-246
Keywords:
concretes; creep properties; deformation; modulus of elasticity; shrinkage; Materials Research
DOI:
10.14359/3875
Date:
5/1/1993
Abstract:
Modern construction techniques enable reinforced concrete structures to be constructed rapidly. The loads occurring due to the construction process can be as large as the design service load. These construction loads can cause significant immediate deflections due to concrete cracking and its low early-age modulus of elasticity. Because of the high applied stress-developed strength ratio and shrinkage, the time-dependent deflections may be unacceptably large. These changes in the construction process, together with the increasing use of finite element programs, warrant a review of the validity of current creep and shrinkage provisions. Based on a survey of published experimental data, equations were developed to calculate modulus of elasticity, shrinkage, and creep coefficient in terms of developed strength. The time function used was the product of a Ross-type relationship for size effects and logarithmic time. The proposed equations, together with those recommended by ACI 209-82 and the CEB 1990 Model Code, are compared to the published data.