Early-age basic creep of slag-volcanic pozzolan concrete using an improved compliance model based on the solidification theory

Evaluating the thermal cracking risk of early-age Low Carbon Concrete (LCC) requires accurate prediction of its early-age basic creep behaviour. Modern LCC incorporates novel supplementary cementitious materials, which modify hydration kinetics and consequently alters its viscoelastic response compared with Portland Cement Concrete (PCC). Therefore, engineering-oriented compliance models originally developed for PCC may not fully capture the early-age creep behaviour of LCC. In response, this study experimentally investigated and modelled the early-age basic compliance of modern LCC containing Ground Granulated Blast Furnace Slag (GGBFS), Volcanic Pozzolan (VP), Limestone Filler, Super-Plasticizer and Air-Entraining Admixture. The basic creep of six concretes was evaluated at three loading ages, while companion specimens were used to measure autogenous deformation. The performance of six compliance models, including the fib Model Code 2010 and B4 model, was comparatively assessed. Additionally, a novel early-age-focused basic compliance model, based on solidification theory, was proposed. The results showed that LCC containing GGBFS exhibits higher creep at very early ages, whereas lower creep was observed at later ages compared with PCC. The VP exhibited a different influence on the total mechanical strain by increasing the instantaneous compliance while reducing the creep rate. Regarding the models, the current code-recommended parameters provided very inaccurate predictions of the early creep. Moreover, the proposed formulation outstandingly performed (R 2 >0.995), especially for LCC, while maintaining clear contributions of the parameters related to the instantaneous, viscoelastic and viscous flow compliance components.