Basic tensile creep of concrete with and without superabsorbent polymers at early ages

Internal curing with superabsorbent polymers (SAP) significantly affects both deformational and mechanical properties of cement-based composites at early ages. Despite substantial previous research, the impact of SAP on the basic tensile creep of early-age concrete is hardly investigated. In this paper, through direct tensile testing, the basic tensile creep of concrete with a water-to-binder ratio of 0.35 and containing 0.3% SAP (by mass of binder) loaded at early ages was studied. Concrete with SAP exhibited higher basic tensile creep than the reference concrete without SAP when first being loaded at 1 day, 6 days, and 14 days. The higher basic tensile creep of early-age concrete with SAP may be due mainly to the formation of large air voids, delayed cement hydration, and also higher internal relative humidity. The applicability of using the B3 model and the MC2010 model to predict the basic tensile creep of early-age concrete was examined. A modified MC2010 model was then proposed to more realistically reflect short-term tensile creep characteristics of early-age concrete with and without SAP. The model parameters were first determined through best-fitting with the measured creep data for reference specimens loaded at 1 day. Subsequently, the model, with parameters so determined, was used to predict the specific basic tensile creep for specimens loaded at 6 days and 14 days. The good agreement between the model predictions and test results suggests an acceptable predictive capability of the modified model. Besides, the autogenous shrinkage, compressive strength, and elastic modulus of the two types of concrete, with and without SAP, were also investigated and highlighted.