For high/traditional strength concrete, is the carbonation an advantageous on mechanical properties of concrete?
What are its positive/negative effects ?
For normal strenght concrete and especially high strength concrete made with Portland cement, the penetration of the carbonation front is rather limited and you would not see any appreciable effect on the mechanical properties in the short term (see for example here Chi, J. M., Huang, R., & Yang, C. C. (2002). Effects of carbonation on mechanical properties and durability of concrete using accelerated testing method. Journal of marine science and technology, 10(1), 14-20.).
The effect of carbonation on the pore structure is a porosity reduction but a coarsening of the porosity in Portland cement mortars (measured by mercury intrusion porosimetry). In mortars with blast furnace slag, a porosity increase and a coarsening are observed. This is based on unpublished data (actually, a submitted journal paper) of our research group, lead author Dr Andreas Leemann.
Whether the carbonation process results in positive/negative effect will depend on how the carbonation process is conducted (natural conditions, accelerated or supercritical) and on the constituents of your concrete samples (chemical phases of the binder, aggregates, etc.).
- A. Hidalgo, C. Domingo, C. Garcia, S. Petit, C. Andrade, C. Alonso. “Microstructural changes induced in Portland cement-based materials due to natural and supercritical carbonation,” Journal of Materials Science, 43, 3101-3111 (2008).
- V.G. Papadakis, C.G. Vayenas, M.N. Fardis. “Fundamental Modeling and Experimental Investigation of Concrete Carbonation,” ACI Materials Journal, 88-M43, 363-373 (1991).
- A.M. Neville. “Properties of Concrete,” 3rd Edition Longman Scientific and Technical (1981), Chapter 6: “Elasticity, Shrinkage and Creep”.
- E. Zornoza, P. Garcés, J. Monzó, M.V. Borrachero, J. Payá. “Accelerated carbonation of cement pastes partially substituted with fluid catalytic cracking residue (FC3R),” Cement and Concrete Composites 31, 134-138 (2009)
- V. Rostami, Y. Shao, A.J. Boyd. “Carbonation Curing versus Steam Curing for Precast Concrete Production,” Journal of Materials in Civil Engineering, 24, 1221-1229 (2012).
I agree with Prof. Lura that for low extent of carbonation (low penetration depth) will not cause a significant modification of the mechanical properties. But normally, carbonation results in a physicochemical transformation of the material that results in an increase of the solid phase, a reduction of the total porosity, and an increase of the mechanical properties (elastic modulus and strength), if strength-giving phases such as CSH are not severely carbonated.
- J.N Eiras, T. Kundu, J.S. Popovics, J. Monzó, M.V. Borrachero, J. Payá, “Monitoring accelerated carbonation on standard Portland cement mortar by nonlinear resonance acoustic test,” in Proc. SPIE, 9438D (2015) [doi: 10.1117/12.2084124].
- C-F. Chang and J-W. Chen, “Strength and Elastic Modulus of Carbonated Concrete,” ACI Mat J. 102, 315-321 (2005) [doi: 10.14359/14710].
- B. Johannesson, P. Utgenannt, “Microstructural changes caused by carbonation of cement mortar,” Cem. Concr. Res. 31, 925-931 (2001) [doi: 10.1016/S0008-8846(01)00498-7].
- S.T. Pham, “Effects of Carbonation on the Microporosity and Macro Properties of Portland Cement Mortar CEM I,” J. Mater. Sci. Chem. Eng. 2, 40-52 (2014) [doi: 10.4236/msce.2014.27005].
Dear All, Things are happening, whether they are advantageous or not is questioned.
The surface of ordinary concrete will become harder, due to this reason carbonation is to be taken into consideration during rebound hammer testing. A question is that if the concrete is old, thin, the total cross section is carbonated and it is unreinforced, will it become more brittle???
In case if high alumina cement (bauxite concrete) was used for the construction, than following the relatively rapid decrease in strength a slight regain was observed (literature from '80-es). This is absolutely advantageous.
In the mean time one should not forget about the corrosion of reinforcement as a side effect of carbonation, what is definitely disadvantageous.
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