Calcium-Silicate-Hydrate (C-S-H) – xCaO.ySiO2.zH2O – is essentially the glue of a cement matrix which consists roughly 50% of C-S-H. Although cement-based materials are complex multiphase materials, C-S-H is the dominant phase controlling its performance. Knowledge of the exact nature of C-S-H, its nano/microstructure and degradation mechanisms is essential to improve significantly the ability to predict and control the performance of cementitious materials, more particularly those used for the encapsulation of radioactive wastes.
This PhD project aims at performing a comprehensive experimental study to assess the nano level of C-S-H to fundamentally understand the changes in structure and chemical composition of C-S-H under chemical degradation by carbonation, leaching and recalcification. Various types of C-S-H (real and synthetic) with different Ca/Si ratios will be subjected to a number of degradation conditions to understand the C-S-H degradation mechanism. A variety of characterization techniques will be used to quantify the change in chemistry and structure of C-S-H, which is combined with a conceptual model in order to explore the effect of different degradation mechanisms, this may lead to engineering of cementitious materials with highly durable C-S-H.
Fundamental knowledge obtained from this study would help to better explain the chemical degradation processes and as such could also enable the possibility to prevent or repair the degraded concrete structures. It could help to engineer the C-S-H growth for better performance, in terms of durability and/or higher capacity for radionuclide sorption.
- Auroy M, Poyet S, Le Bescop P, Torrenti J-M, Charpentier T, Moskura M, Bourbon X (2018) Comparison between natural and accelerated carbonation (3% CO2): Impact on mineralogy, microstructure, water retention and cracking Cement and Concrete Research 109:64-80 doi:https://doi.org/10.1016/j.cemconres.2018.04.012
- Black L, Garbev K, Stemmermann P, Hallam KR, Allen GC (2003) Characterisation of crystalline C-S-H phases by X-ray photoelectron spectroscopy Cement and Concrete Research 33:899-911 doi:http://dx.doi.org/10.1016/S0008-8846(02)01089-X
- Borges PHR, Costa JO, Milestone NB, Lynsdale CJ, Streatfield RE (2010) Carbonation of CH and C–S–H in composite cement pastes containing high amounts of BFS Cement and Concrete Research 40:284-292 doi:https://doi.org/10.1016/j.cemconres.2009.10.020
- Carde C, François R, Torrenti J-M (1996) Leaching of both calcium hydroxide and C-S-H from cement paste: Modeling the mechanical behavior Cement and Concrete Research 26:1257-1268 doi:https://doi.org/10.1016/0008-8846(96)00095-6
- Chen JJ, Thomas JJ, Taylor HFW, Jennings HM (2004) Solubility and structure of calcium silicate hydrate Cement and Concrete Research 34:1499-1519 doi:https://doi.org/10.1016/j.cemconres.2004.04.034
- Harris AW, Manning MC, Tearle WM, Tweed CJ (2002) Testing of models of the dissolution of cements—leaching of synthetic CSH gels Cement and Concrete Research 32:731-746 doi:https://doi.org/10.1016/S0008-8846(01)00748-7
- Hunnicutt W, Struble L, Mondal P (2017) Effect of synthesis procedure on carbonation of calcium‐silicate‐hydrate J Am Ceram Soc 100:3736-3745
- Patel RA et al. (2016) Diffusivity of saturated ordinary Portland cement-based materials: A critical review of experimental and analytical modelling approaches Cement and Concrete Research 90:52-72 doi:http://dx.doi.org/10.1016/j.cemconres.2016.09.015
- Phung QT (2015) Effects of Carbonation and Calcium Leaching on Microstructure and Transport Properties of Cement Pastes. PhD thesis, Ghent University
- Phung QT, Maes N, De Schutter G, Jacques D, Ye G (2013) Determination of water permeability of cementitious materials using a controlled constant flow method Constr Build Mater 47:1488-1496 doi:http://dx.doi.org/10.1016/j.conbuildmat.2013.06.074
- Phung QT, Maes N, Jacques D (2018) Current concerns on durability of concrete used in nuclear power plants and radioactive waste repositories. In: Tran-Nguyen H-H, Wong H, Ragueneau F, Ha-Minh C (eds) Proceedings of the 4th Congrès International de Géotechnique - Ouvrages -Structures, Lecture Notes in Civil Engineering 8. Springer Nature Singapore, Singapore, pp 1108-1121
- Phung QT, Maes N, Jacques D, Bruneel E, Van Driessche I, Ye G, De Schutter G (2015a) Effect of limestone fillers on microstructure and permeability due to carbonation of cement pastes under controlled CO2 pressure conditions Constr Build Mater 82:376-390 doi:http://dx.doi.org/10.1016/j.conbuildmat.2015.02.093
- Phung QT, Maes N, Jacques D, De Schutter G, Ye G (2015b) Investigation of the changes in microstructure and transport properties of leached cement pastes accounting for mix composition Cement and Concrete Research 79:217-234 doi:http://dx.doi.org/10.1016/j.cemconres.2015.09.017
- Phung QT, Maes N, Jacques D, De Schutter G, Ye G, Perko J (2016a) Modelling the carbonation of cement pastes under a CO2 pressure gradient considering both diffusive and convective transport Constr Build Mater 114:333-351 doi:http://dx.doi.org/10.1016/j.conbuildmat.2016.03.191
- Phung QT, Maes N, Jacques D, Jacop E, Grade A, Schutter GD, Ye G (2015c) Determination of diffusivities of dissolved gases in saturated cement-based materials Paper presented at the International Conference on Concrete Repair, Rehabilitation and Retrofitting IV, Leipzig, Germany,
- Phung QT, Maes N, Jacques D, Perko J, Schutter GD, Ye G Modeling the decalcification of cement paste in ammonium nitrate solution. In: 3rd internatinal conference on Service Life design for Infrastructure: Keynote speech, Zhuhai, China, 2014 -a. pp 27-40
- Phung QT, Maes N, Jacques D, Schutter GD, Ye G Decalcification of cement paste in NH4NO3 solution: Microstructural alterations and its influence on the transport properties. In: Bastien J, Rouleau N, M. Fiset, Thomassin M (eds) 10th fib International PhD Symposium in Civil Engineering, Québec, Canada., 2014 -b. pp 179 - 187
- Phung QT, Yu L, Rogiers B, Maes N, Jacques D (2016b) Experimental methodology to study accelerated carbonation in cracked concrete. Deliverable 1 in the CARBOCRACK project – Extent of accelerated carbonation in reinforced concrete due to microcracks. Studiecentrum voor Kernenergie