# Experimental Methods to Evaluate the Carbonation Degree in Concrete--State of the Art Review
## 4 Conclusions
However, its applicability in evaluating CO\({}_{2}\) diffusion capacity is problematic in the case of partial carbonation owing to its potentially limited detection of phase change. * pH indicator could be used widely, but the combination with other techniques needs to be performed. Non-destructive methods by means of embedded fiber optic sensors could offer an adequate and accurate estimation of long-term pH monitoring of reinforced concrete structures in different conditions. * If the problem of high cost could be overlooked, image analysis presented a significant advantage in exploring crystal habit, morphology and size of the core of the sample, with high accuracy in the qualitative carbonation measurement. * Phase analysis seems to be an accurate method when phase measurements are performed by using XRD, TGA, FTIR and ultrasonic phase velocity technique. The margin of error of these measurements has very limited impact on the result and does not need to be familiar for carbonation determination (less than \(\pm\)5%). * A new method, the fiber optic system, has been developed recently to control the change in internal chemistry of a concrete structure. All phase analysis techniques such as XRD, TGA, FTIR and gamma-0 densimetry are carried out in the laboratory with very small-scale specimens and require little destruction to the structure in order to obtain samplings. However, fiber optic systems overcome most these drawbacks and obtain non-destructive, continuous and real-time data in actual time conditions for concrete structures. This method could be considered as a promising application in the field of controlling deterioration in concrete structures. * For the determination of the uptake of CO\({}_{2}\), it is sufficient to measure weight loss at a temperature between 500 and 1000 \({}^{\circ}\)C with regard to TGA method. The CaO content should be considered because it relates to the carbonation of hydrates. The use of CO\({}_{2}\) uptake content to determine the carbonation degree of concrete requires that the carbonation zones are defined in advance. * The gamma-densimetry method should be considered for use at laboratory scale due to the high accuracy in measurement of the CO\({}_{2}\) penetrated. In conclusion, the authors suggest that the spectra data, such as fluorescence, X-ray, FTIR and ultrasonic signals, could be used to measure the carbonation degree quantitatively based on the diffraction intensity, which reflects the amount of CO\({}_{2}\) diffusion. However, further investigation of spectra data treatment should be performed to reveal greater detail in the spectra field. Conceptualization, H.B., D.L. and F.D. ; methodology, H.B. and F.D. ; investigation, H.B. ; writing--original draft preparation, H.B. ; writing--review and editing, H.B., D.L. and F.D. ; supervision, F.D. and D.L. ; project administration, F.D. ; funding acquisition, F.D. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. Informed Consent Statement: Informed consent was obtained from all subjects involved in the study. The data presented in this study are available on request from the corresponding author.