Effects of shrinkage reducing admixture and internal curing agent on shrinkage and creep of high performance concrete

The shrinkage and creep behavior of track beam concrete have the significant influence on the stability and safety of train operation. While superabsorbent polymer (SAP) and shrinkage reducing agent (SRA) are two commonly used admixtures in such high-performance concrete. So, the shrinkage and creep behavior of concrete with SRA or SAP were studied in this paper. Moreover, The microstructure of the interfacial transition zone (ITZ) observed by the scanning electron microscope (SEM) was discussed for the improvement of the mechanical properties of the concrete after the creep test. The experimental results indicate that SRA has a positive effect on reducing the shrinkage and creep deformation of concrete, and it is beneficial to the improvement of long-term strength and elastic modulus with little influence on creep recovery. In contrast, SAP reduces shrinkage, but increases the creep of concrete with less creep recovery and higher re-sidual stress. Meanwhile, the fib 2010 model was revised to improve the ability to predict the creep of concrete containing SAP and other admixtures. Besides, it was found concrete after creep test has better mechanical properties, and the improvement of sample with SAP is the most obvious. The analyses of SEM also conformed that the concrete after creep test has a higher degree of hydration, and the denser ITZ microstructure.