Effect of modulus of elasticity on creep prediction of high strength concrete containing pozzolans

The use of pozzolanic material, such as fly ash and silica fume, is becoming more popular in producing high performance/high strength concrete (HP/HSC) for various structural applications. Many studies have addressed the mechanical properties as well as durability of HP/HSC, however, the effect of pozzolans on the shrinkage and creep behaviors are not clearly addressed. There is a need to understand and identify how changes in the composition and porosity of HP/HSC, and consequently the elastic modulus, would affect its early age as well its long term performance. The main objective of this paper is to examine the effect of using various models for modulus of elasticity on the prediction of creep of high strength concrete (HSC) containing pozzolans. The study included an experimental program and a comparison of available analytical models for predicting the compressive creep and modulus of elasticity of HSC. Results from creep tests performed on different mixes (with compressive strength up to 90 MPa) were compared with those from prediction models available in the literature. Three creep models, ACI 209, CEB 90, and GL 2000, were used. In addition, various values of modulus of elasticity obtained from experimental calculation, ACI 318, ACI 363, CEB 90, Gardner, and from an equation proposed by the authors were evaluated. Results show that the modulus of elasticity has high impact on the accuracy of predicted creep and that available modulus of elasticity models needs to be revised to reflect HSC containing pozzolans.