Title:
Sulfate Resistance of Portland and Slag Cement Concretes Exposed to Sodium Sulfate for 38 Years
Author(s):
Fatemeh Alapour and R. Douglas Hooton
Publication:
Materials Journal
Volume:
114
Issue:
3
Appears on pages(s):
477-490
Keywords:
concrete durability; ettringite; slag; sulfate attack
DOI:
10.14359/51689678
Date:
5/1/2017
Abstract:
In 1976, production of separately ground, pelletized blast-furnace slag started near Hamilton, ON, Canada, and a research program began in 1977 to study the effects of this slag cement on sulfate resistance of concrete. For this purpose, concrete cylinders were cast from eight batches using normal, moderate sulfateresistant and highly sulfate-resistant portland cement types as well as mixtures of high-C3A portland cement plus slag at a watercementitious materials ratio (w/cm) of 0.45 or 0.50. In the present study, samples were cut from concrete cylinders after 38 years of exposure to sodium sulfate solutions and thin sections were prepared for analysis using scanning electron microscopy. Microstructural details were investigated from the exposed surface to the center of each cylinder, and different phases were determined. Ettringite, thaumasite, gypsum, and layers of calcium carbonate were found to have formed in the samples. A 65% slag substitution of high-C3A portland cement was very effective in improving the performance of concrete exposed to sodium sulfate.
Related References:
Brown, P., and Hooton, R. D., 2002, “Ettringite and Thaumasite Formation in Laboratory Concretes Prepared Using Sulfate-Resisting Cements,” Cement and Concrete Composites, V. 24, No. 3-4, pp. 361-370. doi: 10.1016/S0958-9465(01)00088-9
Brown, P. W.; Hooton, R. D.; and Clark, B., 2003, “The Co-Existence of Thaumasite and Ettringite in Concrete Exposed to Magnesium Sulfate at Room Temperature and the Influence of Blast-Furnace Slag Substitution on Sulfate Resistance,” Cement and Concrete Composites, V. 25, No. 8, pp. 939-945. doi: 10.1016/S0958-9465(03)00152-5
Brown, P.; Hooton, R. D.; and Clark, B., 2004, “Microstructural Changes in Concretes with Sulfate Exposure,” Cement and Concrete Composites, V. 26, No. 8, pp. 993-999. doi: 10.1016/j.cemconcomp.2004.02.033
Chabrelie, A., 2010, “Mechanisms of Degradation of Concrete by External Sulfate Ions under Laboratory and Field Conditions,” PhD thesis, EPFL, Switzerland.
Famy, C.; Scrivener, K. L.; and Crumbie, K., 2002, “What Causes Differences of C-S-H Gel Grey Levels in Backscattered Electron Images?” Cement and Concrete Research, V. 32, No. 9, pp. 1465-1471. doi: 10.1016/S0008-8846(02)00808-6
Higgins, D. D., and Crammond, N. J., 2003, “Resistance of Concrete Containing GGBS to the Thaumasite Form of Sulfate Attack,” Cement and Concrete Composites, V. 25, No. 8, pp. 921-929. doi: 10.1016/S0958-9465(03)00149-5
Hooton, R. D., and Emery, J., 1990, “Sulfate Resistance of a Canadian Slag Cement,” ACI Materials Journal, V. 87, No. 6, Nov.-Dec., pp. 547-555.
Mehta, P. K., 1981, “Studies on Blended Portland Cments Containing Santorn Earth,” Cement and Concrete Research, V. 11, No. 4, pp. 507-518. doi: 10.1016/0008-8846(81)90080-6
Ramezanianpour, A. M., 2012, “Sulfate Resistance and Properties of Portland-Limestone Cements,” PhD thesis, University of Toronto, Toronto, ON, Canada.
Santhanam, M.; Cohen, M. D.; and Olek, J., 2002, “Mechanism of Sulfate Attack: A Fresh Look—Part 1: Summary of Experimental Results,” Cement and Concrete Research, V. 32, No. 6, pp. 915-921. doi: 10.1016/S0008-8846(02)00724-X
Santhanam, M.; Cohen, M. D.; and Olek, J., 2003, “Mechanism of Sulfate Attack : A Fresh Look—Part 2: Proposed Mechanisms,” Cement and Concrete Research, V. 33, No. 3, pp. 341-346. doi: 10.1016/S0008-8846(02)00958-4
Scrivener, K. L., 2004, “Backscattered Electron Imaging of Cementitious Microstructures: Understanding and Quantification,” Cement and Concrete Composites, V. 26, No. 8, pp. 935-945. doi: 10.1016/j.cemconcomp.2004.02.029
Yang, R., and Buenfeld, N. R., 2000, “Microstructural Identification of Thaumasite in Concrete by Backscattered Electron Imaging at Low Vacuum,” Cement and Concrete Research, V. 30, No. 5, pp. 775-779. doi: 10.1016/S0008-8846(00)00244-1