The B4 Model for Multi-decade Creep and Shrinkage Prediction

Presented is a new model, labeled B4, which can overcome some of the shortcomings of the CEB-fib, ACI, JSCE and GL prediction models for concrete creep and shrinkage. The B4 model represents an extension and systematic recalibration of the theoretically founded model B3, a 1995 RILEM recommendation. In addition to introducing the so far missing separation of autogenous and drying shrinkage, model B4 takes into account the cement type and admixture parameters, as well as the effects of various types of aggregate. The new predictors for the creep compliance function more accurately, capture the composition information, and are recalibrated to match the multi-decade behavior. This behavior has recently been documented by observed deflection records of many bridges, which is evidence that has so far been systematically underestimated. The improved model was calibrated through a joint optimization of a new, significantly enlarged database of laboratory creep and shrinkage tests and a new database of bridge deflection records.