Similar articles

Abstract: A preloading frame is firstly designed to accurately apply external flexural stress to concrete specimens. Then a method is developed to measure one and two dimensional (1D and 2D) chloride ion concentrations at different distances from the surface of concrete under flexural stress. Using this method and the preloading frame, 1D and 2D stress-diffusion is systematically investigated for fly ash concretes made with different fly ash contents (0%, 10%, 20%, 40%, and 60%), and water to binder ratios (0.3, 0.35, and 0.4). The stress accelerating effect on 1D and 2D chloride ion diffusion is also quantitatively analyzed through a comparison between stress-diffusion and nonstress-diffusion. A diffusion accelerating effect caused by external flexural stress can clearly be observed through the comparison. In order to quantify the stress accelerating effect, a stress accelerating factor is proposed in this paper. The relationship between stress accelerating factor and external stress-to-ultimate stress ratio is given as an exponential function. Finally, the process of the initiation, prorogation, and distribution of microcracks on the tensile face of specimen is observed in-situ by using a small-sized loading frame and scanning electron microscope (SEM). The above research provides an insight into chloride attack on the edge reinforcing bars of concrete structures under flexural stress, such as large-span beam and board in the field of civil engineering.

[1]ASTM C1152, 2004. Standard Test Method for Acid-Soluble Chloride in Mortar and Concrete. ASTM International, West Conshohocken, PA, USA.

[2]ASTM C1218, 2008. Standard Test Method for Water-Soluble Chloride in Mortar and Concrete. ASTM International, West Conshohocken, PA, USA.

[3]ASTM C150, 2005. Standard Specification for Portland Cement. ASTM International, West Conshohocken, PA, USA.

[4]ASTM C593, 2006. Standard Specification for Fly Ash and Other Pozzolans for Use with Lime for Soil Stabilization. ASTM International, West Conshohocken, PA, USA.

[5]Chalee, W., Teekavanit, M., Kiattikomol, K., Siripanichgorn, A., Jaturapitakkul, C., 2007. Effect of W/C ratio on covering depth of fly ash concrete in marine environment. Construction and Building Materials, 21(5):965-971.

[6]Chindaprasirt, P., Chotithanorm, C., Cao, H.T., Sirivivatn, V., 2007. Influence of fly ash fineness on the chloride penetration of concrete. Construction and Building Materials, 21(2):356-361.

[7]Choi, Y.S., Kim, J.G., Lee, K.M., 2006. Corrosion behavior of steel bar embedded in fly ash concrete. Corrosion Science, 48(7):1733-1745.

[8]Darmawan, M.S., 2010. Pitting corrosion model for reinforced concrete structures in a chloride environment. Magazine of Concrete Research, 62(2):91-101.

[9]Dhir, R.K., Jones, M.R., 1999. Development of chloride-resisting concrete using fly ash. Fuel, 78(2):137-142.

[10]Friedmann, H., Amiri, O., Ait-Mokhtar, A., Dumargue, P., 2004. A direct method for determining chloride diffusion coefficient by using migration test. Cement and Concrete Research, 34(11):1967-1973.

[11]Friedmann, H., Amiri, O., Ait-Mokhtar, A., 2008. Physical modeling of the electrical double layer effects on multispecies ions transport in cement-based materials. Cement and Concrete Research, 38(12):1394-1400.

[12]GB175, 2007. Common Portland Cement. State General Administration of the People’s Republic of China for Quality Supervision and Inspection and Quarantine, Beijing, China (in Chinese).

[13]GB/T1596, 2005. Fly Ash Used for Cement and Concrete. State General Administration of the People’s Republic of China for Quality Supervision and Inspection and Quarantine, Beijing, China (in Chinese).

[14]JTJ270-98, 1998. Testing Code of Concrete for Port and Waterwog Engineering. Ministry of Communications of China, Beijing, China (in Chinese).

[15]Khatri, R.P., Sirivivatnanon, V., 2004. Characteristic service life for concrete exposed to marine environments. Cement and Concrete Research, 34(5):745-752.

[16]Liang, M.T., Wang, K.L., Liang, C.H., 1999. Service life prediction of reinforced concrete structures. Cement and Concrete Research, 29(9):1411-1418.

[17]Liang, M.T., Huang, R., Feng, S.A., 2009. Service life prediction of pier for the existing reinforced concete bridges in chloride-laden environment. Journal of Marine Science and Technology-TAIWAN, 17(4):312-319.

[18]Maage, M., Helland, S., Poulsen, E., 1996. Service life prediction of existing concrete structures exposed to marine environment. ACI Materials Journal, 93(6):602-608.

[19]Mehta, P.K., 1997. Durability—critical issues for the future. Concrete International, 19(7):27-33.

[20]Mien, T.V., Stitmannaithum, B., Nawa, T., 2009. Simulation of chloride penetration into concrete structures subjected to both cyclic flexural loads and tidal effects. Computers and Concrete, 6(5):421-435.

[21]Montemor, M.F., Cunha, M.P., Ferreira, M.G., Simões, A.M., 2002. Corrosion behavior of rebars in fly ash mortar exposed to carbon dioxide and chlorides. Cement and Concrete Composites, 24(1):45-53.

[22]NT Build 208, 1996. Concrete, Hardened: Chloride Content by Volhard Titration. Nordtest, Tekniikantie, Espoo, Finland.

[23]Rukzon, S., Chindaprasirt, P., 2008. Mathematical model of strength and porosity of ternary blend Portland rice husk ash and fly ash cement mortar. Computers and Concrete, 5(1):75-88.

[24]Rukzon, S., Chindaprasirt, P., 2009. Strength and chloride penetration of Portland cement mortar containing palm oil fuel ash and ground river sand. Computers and Concrete, 6(5):391-401.

[25]Suwito, C., Xi, Y., 2008. The effect of chloride-induced steel corrosion on service life of reinforced concrete structures. Structure and Infrastructure Engineering, 4(3):177-192.

[26]Tang, L.P., Nilsson, L.O., 1993. Rapid determination of the chloride diffusivity in concrete by applying an electrical field. ACI Materials Journal, 89(1):49-53.

[27]Thomas, M.D.A., Bamforth, P.B., 1999. Modelling chloride diffusion in concrete effect of fly ash and slag. Cement and Concrete Research, 29(4):487-495.

[28]Weyers, R.E., 1998. Service life model for concrete structures in chloride laden environments. ACI Materials Journal, 95(4):445-453.

[29]Zhang, Y.S., Sun, W., Chen, S.D., Guo, F., Zhao, Q.X., 2007. 1D and 2D carbonation of fly ash concrete under flexural stress. Journal of Southeast University (Natural Science Edition), 37(1):118-122 (in Chinese).

[30]Zhang, Y.S., Sun, W., Chen, S.D., Li, Z.J., 2011. Two and three dimensional chloride ingress into fly ash concrete. Journal of Wuhan University of Technology-Materials Science Edition, in Press.