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.