Properties of supersulphated phosphogysumslag cement (SSC) concrete

Abstract

Supersulphated phosphogysum-slag cement (SSC) is a newly developed non-burned cementitious material mainly composed of phosphogysum (PG) and ground granulated blast furnace slag (GGBFS), with small amount of steel slag (SS) and clinker (CL). SSC is a kind of environmentally-friendly cementitious material due to its energy-saving, low-carbon emission, and waste-utilization. We prepared concretes with supersulphated phosphogysum-slag cement, and studied the mechanical properties, microproperties and resistance to chloride penetration of concrete in comparison with those of portland slag cement (PSC) and ordinary portland cement (OPC) concrete. The test results show that the compressive strength of SSC concrete can reach 38.6 MPa after 28 d, close to PSC concrete and OPC concrete. Microanalyses indicate that large quantities of ettringite and C-S-H, and little amount of Ca(OH)₂ are generated during the hydration of SSC. The dense cement paste structure of SSC is formed by ettringite and C-S-H, surrounded unreacted phosphogysum. The property of resistance to chloride penetration of SSC concrete is better than PSC and OPC concrete due to the fact that SSC can form much more ettringite to solidify more Cl⁻.

Keywords

supersulphated phosphogysum-slag cement / chloride penetration / ettringite

References

[1] Huang Y, Lin Z Investigation on Phosphogypsum-Steel Slag-Granulated Blast-Furnace Slag-Limestone Cement[J]. Construction and Building Materials, 2010, 24(7): 1 296-1 301.

[2] 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): 1 036-1 042.

[3] Shen W, Zhou M, Zhao Q Study on Lime-Fly Ash-Phosphogypsum Binder[J]. Construction and Building Materials, 2007, 21(7): 1 480-1 485.

[4] Matschei T, Bellmann F, Stark J Hydration Behaviour of Sulphate-Activated Slag Cements[J]. Advances in Cement Research, 2005, 17(4): 167-178.

[5] Gruskovnjak A, Lothenbach B, Winnefeld F, . Hydration Mechanisms of Super Sulphated Slag Cement[J]. Cement and Concrete Research, 2008, 38(7): 983-992.

[6] Erdem E, Ölmez H The Mechanical Properties of Supersulphated Cement Containing Phosphogypsum[J]. Cement and Concrete Research, 1993, 23(1): 115-121.

[7] Grounds T, Nowell D V, Wilburn F W The Influence of Temperature and Different Storage Conditions on the Stability of Supersulphated Cement[J]. Journal of Thermal Analysis, 1994, 41(2): 687-699.

[8] Bijen J, Niël E Supersulphated Cement from Blastfurnace Slag and Chemical Gypsum Available in the Netherlands and Neighbouring Countries[J]. Cement and Concrete Research, 1981, 11(3): 307-322.

[9] Gao Y X, Yu B Y, Xu F L Effect of Modified Phosphogypsum on the Mechanical Properties of Supersulphate Cement[J]. Applied Mechanics and Materials, 2012, 161: 264-268.

[10] Martinez-Aguilar O A, Castro-Borges P, Escalante-Garcia J I Hydraulic Binders of Fluorgypsum-Portland Cement and Blast Furnace Slag, Stability and Mechanical Properties[J]. Construction and Building Materials, 2010, 24(5): 631-639.

[11] Mun K J, Hyoung W K, Lee C W, . Basic Properties of Non-Sintering Cement Using Phosphogypsum and Waste Lime as Activator[J]. Construction and Building Materials, 2007, 21(6): 1 342-1 350.

[12] Shi X, Xie N, Fortune K, . Durability of Steel Reinforced Concrete in Chloride Environments: An Overview[J]. Construction and Building Materials, 2012, 30: 125-138.

[13] Ekolu S O, Thomas M D A, Hooton R D Pessimum Effect of Externally Applied Chlorides on Expansion Due to Delayed Ettringite Formation Proposed Mechanism[J]. Cement and Concrete Research, 2006, 36(4): 688-696.