جستجوی مقالات مرتبط با کلیدواژه « : unsaturated concrete » در نشریات گروه « عمران »

The durability-based design of reinforced concrete structures especially in hot marine environment of Bandar-Abbas became extensively important during the last few years. It has been known that the durability of concrete mainly depends on how easily seawater containing chloride ions can ingress into an unsaturated concrete (Sabir et al., 1998; Hubert et al., 2003; Prabakar et al., 2010; Yoo et al., 2011). Chloride-induced corrosion of embedded reinforcement is more severe in tidal condition because of more ingress of chloride due to moisture convection phenomena. (Broomfield, 1997; Olajumok et al., 2009; Akindahunsi et al., 2010). In is necessary to approximate the moisture distribution in concrete due to wetting and drying cycles for determination of the moisture convection zone. The moisture transfer coefficient (MTC) is one of the most important parameters for prediction of moisture distribution. The moisture distribution is often influenced by environmental conditions such as temperature. The changes of the depth of convection zone can be assessed if MTC is available in various temperatures. In this research, six concrete mixtures were prepared in which four plain concrete mixtures were proportioned with water to cementitious materials (w/cm) ratios of 0.40, 0.45, 0.50, and 0.55. In addition to the plain concretes, one silica fume and one natural zeolite blended concrete mixtures with cement replacement levels of 7.5, and 10% and a w/cm ratio of 0.45 were considered. The moisture loss or water absorption of specimens exposed to wetting and drying were measured using the gravimetric method at temperatures of 23, 43, and 63 ºC. A finite element analysis was performed afterward to fit the experimental data to the governing equations of moisture transfer to determine the MTC. The moisture distribution of concrete exposed to wetting and drying and then the depth of convection zone (DCZ) are determined using approximated MTC and finite element-based model. The amount of water entered (AWE) to concrete surface subjected to tidal condition is also calculated.

The chloride ingress into concrete and corrosion of steel reinforcement due to wetting/drying (WD) cycles is a main issue caused to decline the service life of reinforced concrete structures. In this paper, the effects of WD cycles on chloride penetration in concrete were studied using a finite element based numerical model. The results showed that the chloride ingress into concrete increased with increasing in daily WD cycles. The chloride concentration after 10 years at depth of 50 mm and the maximum chloride concentration of the submerged specimen were 2.4 and 2.0 times lower than the specimen exposed to 2 and 24 WD cycles, respectively. These ratios increased up to 4.2 and 3.7 when the WD cycle increased to 24 cycles. The numerical model outputs also indicated that the chloride concentration at depth of 50 mm and the maximum chloride closely tended up to a constant amount by increasing the number of WD cycle up to 100 cycles (similar to splash condition).