Degradation of pore structure and microstructures in hardened cement paste subjected to flexural loading and wet-dry cycles in sea water

Abstract

Hardened cement paste was subjected to the flexural loading and wet-dry cycles in sea water. The degradation of microstructures was obtained using scanning electron microscope (SEM), and the energy dispersive spectrum (EDS) analysis was carried to analyze the local composition. Mercury intrusion porosimetry (Poremaster GT-60) was used to analyze the degradation of pore structures. The experimental results show that the synergistic action of the flexural loading, wet-dry cycles and sea water leads to significant deterioration of hardened cement paste. The degradation of microstructures in the tensile region is more serious than that in the compressive region. The flexural loading and wet-dry cycles accelerate the chemical attack of sea water.

Keywords

hardened cement paste / pore structure / microstructures / flexural loading / wet-dry cycles / sea water

References

[1] Zhang Y. T., Fang Y. H., Zheng B. Recent Advances in Research on Concrete Durability under Simultaneous Action of Load and Other Factors[J]. Materials Review, 2003, 17(9): 48-50.

[2] Maekawa K, Ishida T. Service-life Evaluation of Reinforced Concrete under Coupled Forces and Environmental Actions[C]. In: International Conference on Ion and Mass Transport in Cement-Based Materials. Toronto, Canada, 1999: 219–238

[3] Schneider U., Chen S. W. The Chemomechanical Effect and the Mechano-chemical Effect on HPC Subjected to Stress Corrosion[J]. Cem. Concr. Res., 1998, 28(4): 509-522.

[4] Schneider U., Chen S.W. Behaviour of High-performance Concrete under Ammonium Nitrate Solution and Sustained Load[J]. ACI Mater. J., 1999, 96(1): 47-51.

[5] Piasta W. G., Sawicz Z., Piasta J. Sulphate Durability of Concretes under Constant Sustained Load[J]. Cem. Concr. Res., 1989, 19(2): 216-227.

[6] Zhou Y., Cohen M. D., Dolch L. W. Effect of External Loads on the Frost Resistant Properties of Mortar with and without Silica Fume[J]. ACI Mater. J., 1994, 91(6): 595-601.

[7] Sun W., Zhang Y. M., Yan H. D., Mu R. Damage and Damage Resistance of High Strength Concrete under the Action of Load and Freeze thaw Cycles[J]. Cem. Concr. Res., 1999, 29(9): 1519-1523.

[8] Sun W., Mu R., Luo X., Miao C. W. Affect of Chloride Salt, Freeze Thaw Cycling and Externally Applied Load on the Performance of the Concrete[J]. Cem. Concr. Res., 2002, 32(12): 1859-1864.

[9] Yu H. F., Mu R., Sun W., Miao C. W. Effects of Flexural Loads, Chemical Attack, Carbonation and Their Combination on Freezing Thawing Durability of Concretes[J]. Journal of the Chinese Ceramic Society, 2005, 33(4): 492-499.

[10] Yoon S., Wang K., Weiss W., Shah S. P. Interaction Between Loading, Corrosion, and Serviceability of Reinforced Concrete[J]. ACI Mater. J., 2000, 97(6): 637-644.

[11] Ciach T.D., Gillott J. E., Swenson E. G., Sereda P. J. Microstructure of Hydrated Portland Hardened Cement Pastes[J]. Nature, 1970, 227: 1045-1046.

[12] Mehta P. K., Monteiro P. J. M. Concrete-Microstructure, Properties and Materials[J], 2006 New York McGraw-Hill 72-75.

[13] Diamond S. The Microstructure of Hardened Cement Paste and Concrete-a Visual Primer[J]. Cem. Concr. Comp., 2004, 26(8): 919-933.

[14] Korb J. P. Microstructure and Texture of Cementitious Porous Materials[J]. Magnetic Resonance Imaging, 2007, 25(4): 466-469.

[15] Vroom A. H., Vroom C. H. Banthia N., Gjørv O., Sakai K. Sulfur Concrete for Aggressive Environments[M]. Concrete under Severe Conditions 2: Environment and Loading, 1998 London and New York E & FN Spon 2149-2160.

[16] Haynes H., O’Neill R., Neff M., Mehta P. K. Salt Weathering Distress on Concrete Exposed to Sodium Sulfate Environment[J]. ACI Mater. J., 2008, 105(1): 35-43.

[17] Santhanam M., Cohen M. D., Olek J. Mechanism of Sulfate Attack: A Fresh Look: Part 1: Summary of Experimental Results[J]. Cem. Concr. Res., 2002, 32(6): 915-921.

[18] Lawrence C. D. Sulphate Attack on Concrete[J]. Mag. Concr. Res., 1990, 42(153): 249-264.

[19] Hossain K. M. A. Performance of Volcanic Ash Based Precast and in situ Blended Cement Concretes in Marine Environment[J]. J. Mat. Civ. Engrg., 2005, 17(6): 694-702.