The validation of elastic modulus models: Code models and their modified versions

Elastic modulus (E) estimation forms an important element in the methods used to predict concrete creep deformation, which is an important structural design consideration. A variety of different E estimation models for concrete exist but there is uncertainty as to which of the models is the most accurate. This research study assesses the performance of models namely, the ACI 318, ACI 318 Simplified, Mendis et al., Rüsch et al., Carrasquillo et al., ACI 363, AS 3600, Omar et al., AS 3600, BS 8110, Alexander and Davis, SANS 10100, CEB-FIP, and the EC 2. The included list of models is taken from national codes and includes their superseded and modified versions. The E values of 108 specimens, whose properties differed (in aggregate type, cement type, concrete strength, and curing age), were measured. The actual E value was compared to each model's estimations to determine which were most accurate statistically using the coefficient of variation (ω_j). The ACI 363 model was the most accurate out of the 16 models assessed, yielding an overall ω_j of 16%. The CEB-FIP model was found to be the least accurate showing an overall ω_j of 31.8%. From the 16 models considered, it was recommended that the ACI 363 model be utilized by creep prediction models. In addition, it was found that not all modified estimate models produced better estimates.