CAPILLARY WATER ABSORPTION CHARACTERISTICS OF CONCRETE AND ITS RELATIONSHIP WITH PORE STRUCTURE

In order to better understand the capillary water absorption characteristics of concrete, the influence of different types of concrete, steel fiber content, and curing conditions on the solution absorption amount were studied in the paper. The capillary water absorption coefficients were also obtained. Moreover, the relationship between pore structure and capillary water absorption coefficient was analyzed. The results showed that the two stages, 15~180 min and 180~480 min, of solution absorption amount of different types of concrete (damage and undamaged) were linear with t^1/2. The capillary water absorption coefficient of ultra-high performance concrete (UHPC) was much smaller than that of high-performance concrete (HPC). With the increase of the steel fiber content, the solution absorption amount of the first stage and the capillary water absorption coefficients of UHPC both increased. Under the influence of rehydration, the solution absorption amount of UHPC specimens cured in water was slightly larger than that cured in the room condition at the age of 720 d. The capillary water absorption coefficient was mainly affected by the pore content in the range of 100~3 nm, and the capillary water absorption coefficient in the first stage increased with the increase of its content. Considering the influence of porosity, the cumulative capillary water absorption height was calculated, and the calculation results were in accordance with the actual situation.