Internal relative humidity and creep of concrete with modified admixtures

The creep characteristics and internal relative humidity (IRH) of concrete with shrinkage reducing admixtures (SRA), poly vinyl alcohol fiber (PVAF) and a mixture of fly ash and slag (MFS) were investigated by the self-made loading device. The pore structure was tested, and the relationship of creep and IRH of concrete was discussed. The results indicate that MFS and SRA reduce the total creep and delay the change of IRH. However, the effect of PVAF is contrary, relative to MFS and SRA. The total creep depends largely on drying creep. The basic creep of concrete is similar, which is significantly influenced by volume fraction of pores whose diameter is between 3.5 nm and 50 nm to the total pore (VP), and IRH of concrete is connected with porosity. It is easy to obtain a good linear relationship predicting the creep of concrete according to the change of IRH.