NDT.net - May 2001, Vol. 6 No. 5

Ultrasound, Scanning Electron Microscopy and Nuclear Magnetic Resonance Spectroscopy - Comparison of Results Investigating the Hydration Process in Cementitious Materials

Christian U. Grosse, Stephanie U. Köble, Hans W. Reinhardt
Corresponding Author Contact:
Email: reinhardt@iwb.uni-stuttgart.de, Web: http://www.iwb.uni-stuttgart.de

SUMMARY

ZUSAMMENFASSUNG

RESUME

1. INTRODUCTION

2. ULTRASOUND METHOD FOR QUALITY CONTROL

3. TEMPERATURE MEASUREMENT USING A CALORIMETER


Fig 4: Comparison of temperature measurements using a calorimeter and US velocity (smoothed) during the setting and hardening of different mortar mixtures, different w/c ratios.


Fig 5: Comparison of temperature measurements using a calorimeter and US velocity (smoothed) during the setting and hardening of different mortar mixtures, cement type variation and influence of admixtures.

4. SCANNING ELECTRON MICROSCOPY (SEM)

         Enlargement 200:1

Probes after
a) 2 h          b) 5 h          c) 8 h

Enlargement
a) 1500:1           b) 200:1
Fig 6: CEM I 42.5; PFA = 25 %; w/c ratio = 0.6. Fig 7: CEM I 42.5; w/c ratio = 0.55.
Probes after 24 h.

Fig 8: Hexagonal crystals of calcium hydroxide. Enlargement 1500:1.
Fig 9: CEM I 42.5; AEA w/c ratio = 0.5. Probes after a) 2 h, b) 8 h. Enlargement 200:1.
Fig 10: Mixtures with 25 % of PFA (left hand with detail) and 10 % (right hand).

5. NUCLEAR MAGNETIC RESONANCE (NMR) SPECTROSCOPY


Fig 11: Principle of nuclear magnetic resonance spectroscopy measurements. Explanation

Explanation
1. Probe to be measured is outside the magnetic field. The momenti of the atomic nuclei are in random positions.
2. The momentum of the atomic nuclei is aligned due to their angular momentum when the probe is given into a strong magnetic field B. The stronger the applied magnetic field the lower the energy of the parallel and the higher the energy of the anti-parallel phase.
3. Stimulation: Supply of energy using a short electromagnetic wave (pulse).
4.There is a dynamic equilibrium caused by the absorption of emitted electro-magnetic energy until parallel and anti-parallel momentum is equally represented in the atomic nuclei.
5. 6. Relaxation: After turning off the pulse the old distribution of the momenti ( 2. ) is re-established while the adsorbed energy is emitted by an electro-magnetic radio wave (FID – free induction decay). The NMR spectrum of this wave is analysed with a Fourier transform using the FT-NMR method.

6. CONCLUSIONS AND OUTLOOK

7. ACKNOWLEDGEMENT

REFERENCES

  1. ABRAHAM, R. J.; FISHER, J.: NMR Spectroscopy. New York: J. Wiley (1988).
  2. BARBIC, L.; KOCUVAN, I.: The determination of surface development in cement pastes by nuclear magnetic resonance. American Ceramic Society 1 (1982), no 1, pp 25-31.
  3. GROSSE, C. U., WEILER, B., HERB, A., SCHMIDT, G., HÖFLER, K.: Advances in ultrasonic testing of cementitious materials. In: "Werkstoffe und Werkstoffprüfung im Bauwesen - Festschrift zum 60. Geburtstag von Prof. Reinhardt" (Ed. Chr. Grosse), Hamburg: Libri-BOD (1999), pp 106-116.
  4. GROSSE, C. U., REINHARDT, H. W.: Ultrasound technique for quality control of cementitious materials. International Committee for Non-destructive Testing ICNDT. Proceedings of the 15 th World Conf. on NDT, Rome (2000), on CD-ROM.
  5. KOCUVAN, I.; URSIC, J.; BARBIC, G.: Nuclear Magnetic Resonance Measurements of the Influence of Some Concrete Admixtures on the Hydration of Cement. Silikattechnik, Bulletin no 30 (1979), pp 22-25.
  6. KÖBLE, S.: Physikalisch-chemischer Hintergrund des Hydratationsvorgangs von Frischmörtel im Hinblick auf Ultraschallmessungen. Diploma thesis, Institute of Construction Materials, University of Stuttgart, (1999), 84 p.
  7. HERZOG, W.-D.; MESSERSCHMIDT, M.: NMR-Spektroskopie für Anwender. Weinheim: VCH (1995).
  8. REINHARDT, H. W., GROSSE, C. U.: Setting and hardening of concrete continuously monitored by elastic waves. Bartos, P. J. M. et al. (Ed.). Proc. of the Int. RILEM Conference "Production methods and workability of concrete", Paisley/Scotland (1996), no 32, pp 415-425.
  9. REINHARDT, H. W., GROSSE, C. U., HERB, A. T.: Kontinuierliche Ultraschal-lmessung während des Erstarrens und Erhärtens von Beton als Werkzeug des Qualitätsmanagements. Deutscher Ausschuss für Stahlbeton, Bulletin no. 490, Berlin: Beuth (1999), pp 21 - 64.
  10. SCHMIDT, P.: Praxis der Elektronenmikroskopie und Mikrobereichsanalyse. Kontakt&Studium Bd. 444, Renningen/Malmsheim: Expert-Verlag (1994).

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