Influence of curing duration on thaumasite formation of Portland-limestone cement pastes

Abstract

Extensive researches have been carried out on the conventional sulfate attack, while it has been found that the thaumasite form of sulfate attack (TSA), sulfate attack at low temperature, has just been discovered and its mechanism is not well understood so far. In this study, the sulfate attack of cement paste incorporating 30% mass of limestone powder was investigated. After 20 °C water cured for 7, 14, and 28 days, respectively, 20 mm cube specimens were exposed in a 5% magnesium sulfate solution at (6 ±1) °C for periods up to 240 days. Their appearance change, compressive strength development were examined at different storage time, and selected paste samples were examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results indicate that all Portland-limstone cement pastes suffer from appearance deterioration to some extent. The compressive strength of cement paste initially increases and after 120 days decreases with increasing exposed period. In addition, the cement paste with short curing time is more susceptible to sulfate attack, which directly leads to the formation of non-binder thaumasite crystal accompanied by the formation of ettringite, gypsum and brucite, and becomes a white, mushy, and incohesive matrix. Additionally, the extent of sulfate attack is greater and the formation of thaumasite is observed earlier for shorter curing time.

Keywords

thaumasite / sulfate attack / limestone / curing / low temperature

References

[1] Collepardi M. Thaumasite Formation and Deteriorarion of Historical Buildings[J]. Cement and Concrete Composites, 1999, 21: 147-154.

[2] Kohler S. Effect of Etringite on Thaumasite Formation[J]. Cement and Concrete Research, 2006, 36: 697-706.

[3] Crammond N J. Thaumasite in Failed Cement Mortars and Renders from Exposed Brickwork[J]. Cement and Concrete Research, 1985, 15: 1039-1050.

[4] Romer M. Steam Locomotive Soot and the Formation of Thaumasite in Shotcrete[J]. Cement and Concrete Composites, 2003, 25: 147-154.

[5] Erlin B, Stark D C. Identification and Occurrence of Thaumasite in Concrete[J]. Highway Research Record, 1965, 113: 108-113.

[6] Crammond N J, Norah C. The Occurrence of Thaumasite in Modern Construction-a Review[J]. Cement and Concrete Composites, 2002, 24: 393-402.

[7] Santhanam M, Cohen M D, Olek J. Mechanism of Sulfate Attack: A Fresh Look Part 1:Summary of Experimental Resuns[J]. Cement and Concrete Research, 2002, 32: 915-921.

[8] Crammond N J. The Thaumasite Form of Sulfateattack in the UK[J]. Cement and Concrete Composites, 2003, 25: 809-818.

[9] Hartshorn S A, Sharp J H, Swamy R N. Thaumasite Formation in Portand-limestone Cement Pastes[J]. Cement and Concrete Research, 1999, 29: 1331-1340.

[10] Hui Y, Bin X X, Liu B W, et al. Effect of Initial Curing Conditions on Thaumasite Form of Sulfate Attack of Cement Based Materials[J]. Applied Mechanics and Materials, 2013, 275-277: _2136-2140

[11] Hansen T C. Physical Structure of Harden Cement Paste[J]. A Classical Approach, Materials and Structures, 1986, 19: 423-436.

[12] Powers T C, Brownyard T L. Studies of the Physical Properties of Hardened Portland Cement Paste[J]. Journal of American Concrete Institute, 2003, 25(8): 59-70.

[13] Edge R A, Tayler H FW. Crystal Structure of Thaumasite, [Ca₃Si(OH)₆· 12H₂O](SO₄)(CO₃) [J]. Acta Crystallographica: Section B, 1971, 27: 594-601.

[14] Bensted J. Some Problems with Ettringite and Thaumasite in the Gypsum Plaster/Cement Contact Area[C]. Proceedings of the International RILEM Symposium on Calcium Sulfates and Derived Materials, France, 1977

[15] Lachowski E E, Barnett S J, Macphee D E. Transmission Electron Optical Study of Ettringite and Thaumasite[J]. Cement and Concrete Composites, 2003, 25: 819-822.

[16] Torres S M, Lynsdale C J, Swamy R N, et al. Microstructure of 5-yearold Mortars Containing Limestone Filler Damaged by Thaumasite[J]. Cement and Concrete Research, 2006, 36: 384-394.

[17] Sahu S, Badger S. Evidence of Thaumasite Formation in Southern California Concrete[J]. Cement and Concrete Composites, 2002, 24: 379-384.

[18] Justnes H. Thaumasite Formed by Sulfate Attack on Mortar with Limestone Filler[J]. Cement and Concrete Composites, 2003, 25: 955-959.