The chloride permeability of persulphated phosphogypsum-slag cement concrete

Abstract

The chloride permeability and microstructure of persulphated phosphogypsum-slag cement concrete (PPSCC), the Portland slag cement concrete (PSCC) and ordinary Portland cement concrete (OPCC) were investigated comparatively. Some test methods were used to evaluate the chloride permeability and explain the relationship between the permeability and microstructure of concrete. The results show that the resistance to chloride penetration in PPSCC is significantly better than that in OPCC, the reasons are as follows: 1) the slag in PPSCC is activated by clinker (alkali activation) and phosphogypsum (sulfate activation), forming more low Ca/Si C-S-H gel and gel pores below 10 nm than OPCC, improving the resistance to chloride penetration; 2) the hydration products of PPSCC have a much stronger binding capacity for chloride ions; and 3) in the same mix proportion, PPSCC has a better workability without large crystals calcium hydroxide in the hydration products, the interfacial transition zone (ITZ) is smoother and denser, which can cut off the communicating pores between the pastes and aggregates.

Keywords

PPSCC / chloride permeability / pore structure / ITZ

References

[1] Ismail I. Influence of Fly Ash on the Water and Chloride Permeability of Alkali-activated Slag Mortars and Concretes[J]. Construction and Building Materials, 2013, 48(11): 1187-1201.

[2] Phair J W. Green Chemistry for Sustainable Cement Production and Use[J]. Green Chemistry, 2006, 9: 763-780.

[3] Boga A R, Topçu I B. Influence of Fly Ash on Corrosion Resistance and Chloride ion Permeability of Concrete[J]. Construction and Building Materials, 2012, 31(6): 258-264.

[4] Xie Y J. Influence of Mineral Admixture on Chloride Ion Permeability of Concrete[J]. J. Chin. Ceram. Soc., 2006, 34(11): 1345-1350.

[5] Guo L. Research of Influence of Mineral Admixtures on Permeability of Concrete, 2010 Harbin: Harbin Institute of Technology.

[6] Hu H M, Ma B G. The Influence of Mineral Functional Material on Chloride Permeability of Conerete[J]. Journal Wuhan University of Technology, 2004, 26(3): 19-22.

[7] Huang Y, Lin Z S. Investigation on Phosphogypsum-steel Slaggranulated Blast-furnace Slag-limestone Cement[J]. Construction and Building Materials, 2010, 24(7): 1296-1301.

[8] Reijnders L. Cleaner Phosphogypsum, Coal Combustion Ashes and Waste Incineration Ashes for Application in Building Materials: A Review[J]. Building and Environment, 2007, 42(2): 1036-1042.

[9] Shen W G, Zhou M K, Zhao Q L. Study on Lime-Fly ash-Phosphogypsum Binder[J]. Construction and Building Materials, 2007, 21(7): 1480-1485.

[10] Yi Y L, Gu L Y, Liu S Y. Microstructural and Mechanical Properties of Marine Soft Clay Stabilized by Lime-activated Ground Granulated Blastfurnace Slag[J]. Applied Clay Science, 2015, 103(1): 71-76.

[11] Wu Z W, Lian H Z. High Performance Concrete[M], 1999 Beijing: China Railway Publication House.

[12] Mindess S, Young J F, Darwin D. Translation by WU Keru et al. Concrete[M], 2005 Beijing: Chemical Industry Press.

[13] Chen Y Z, Pu X C. Hydration Characteristics of Sodium Sulfate Slag Cement System[J]. Journal of Wuhan University of Technology-Materials Science Edition, 2001, 04: 45-47.

[14] Li L Y, Shi Z L, Ai Y P. Alkaline Activation of Gypsum-Granulated Blast Furnace Slag Cementing Materials[J]. J. Chin. Ceram. Soc., 2008, 36(3): 408-410.

[15] Kwan S, Thompson J, Grutzk M W. Structures and Phase Relations of Aluminum-Substituted Calcium Silicate Hydrate[J]. Journal of the American Ceramic Society, 1996, 79(4): 967-971.

[16] Lv L N, Hao X G, He Y J, et al. Effect of C/S Ratio on Morphology and Structure of Calcium Silicate Hydrate. 1st Academic Conference Symposium of Cement Branch of Chinese Ceramic Society, 2009

[17] Wei F Y. Formation of Low Ca/Si |Ratio^C-S-H Gel and Its Mechanism in Controlling ASR in High Performance Cement, 2005 Nanjing: Nanjing Industrial University.

[18] Wang S D, Huang Y B, Wang Z. Concrete Resistance to Chloride Ingress: Effect of Cement Compositon[J]. J. Chin. Ceram. Soc., 2000, 28(6): 570-574.

[19] Cao Q, Tan K F, Yuan W. Study on Mineral Admixture on Binding of Chloride Ions into Cementitous Material[J]. Sichuan Build Sci., 2009, 35(3): 189-192.

[20] Zhao J, Cai G C, Gao D Y. Analysis of Mechanism of Resistance to Chloride Ion Erosion of Sulphoaluminate Cement Concrete[J]. J. Build. Mater., 2011, 14(3): 357-361.