Effect of internal curing on shrinkage and creep of self-compacting lightweight concrete under different curing conditions

Self-compacting concrete (SCC) utilized in precast concrete often experiences significant shrinkage and creep deformations due to its high paste content. This study explored the effectiveness of internal curing using coal bottom ash aggregates in mitigating these time-dependent deformations of SCC under ambient as well as heat curing conditions. Additionally, the incorporation of 0.75 vol% hooked-end steel fibers into mixtures was evaluated as a supplementary method for restraining deformations. The desorption behavior analysis confirmed that the used coal bottom ash is a suitable internal curing agent, facilitating continuous hydration and enhancing both the pore structure and the microstructure of the interfacial transition zone (ITZ) across all curing conditions. This internal curing resulted in a reduction of up to 47.1 % in autogenous shrinkage and a 6.9 % decrease in total specific creep, with heat curing further mitigating drying shrinkage by up to 52.9 %. The addition of steel fibers provided further deformation restraint, reducing autogenous shrinkage by up to 14.4 % and creep by 6.8 %, irrespective of the curing conditions. The experimentally observed shrinkage and creep behaviors of concrete were also simulated and compared with several classical models. These findings provide quantitative insights into the effectiveness of internal curing and fiber reinforcement in mitigating the time-dependent deformations of SCC under both ambient and heat curing conditions.