Investigation on water absorption of concrete under the coupling action of uniaxial compressive load and freeze-thaw cycles

In service life, the premature destruction mechanism and durability of reinforced concrete (RC) structures are mainly governed either by mechanical or environmental loads or by combined ones. These damages can strongly affect the water transport in concrete which may lead to more serious deterioration. This paper presented an experimental investigation on the coupling action of different uniaxial compressive stress levels (lambda(c)= 0, 0.6, 0.7, 0.8) and freeze-thaw cycles (0, 50, 100, 150, 200, 250 and 300 cycles), following by capillary water absorption tests. The residual strain was measured by strain gauges to evaluate the damage evolution of concrete. Moreover, the cumulative water content and sorptivity of specimens under the coupling action were recorded at a given time of exposure through an improved water absorption test set-up. The results show that concrete specimens with fly ash (15% by cement) exhibit better frost and water penetration resistance than ordinary concrete. The frozen samples with applying 60% ultimate load (0.6f(c)) have the best water penetration resistance in comparison with that samples are applied 0, 0.7 and 0.8, which is consistent with the result that under uniaxial compressive load only. Residual strain derived from strain-temperature curves indicates the deterioration of concrete is a continued accumulated and irreversible damage process. The distribution of water content and wetting front of penetration depth are remarkably influenced by the stress levels and freeze-thaw cycles (FTCs). The test data of cumulative water content confirms that FTCs play a relatively important role in the water absorption of concrete under the coupling action. In addition, an effectively theoretical method for predicting water absorption of concrete damaged under the coupling action of uniaxial compressive load and FTCs was developed in terms of the sorptivity. These conclusions presented in this paper will be helpful to better understand the degradation mechanism of frost resistance for RC structures after subjected to uniaxial compressive loading in coastal regions.