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Hygric dilation behaviour of NaCl contaminated lime-cement mortar

Barbara Lubelli 1 , Rob P.J. van Hees 1,2 , Henk P. Huinink 3. 7 th European Conference SAUVEUR Prague 31 st May -2 nd June 2006. Hygric dilation behaviour of NaCl contaminated lime-cement mortar. 1 Delft University of Technology, The Netherlands 2 TNO BenO, Delft, The Netherlands

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Hygric dilation behaviour of NaCl contaminated lime-cement mortar

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  1. Barbara Lubelli1, Rob P.J. van Hees1,2, Henk P. Huinink3 7th European Conference SAUVEUR Prague 31st May -2nd June 2006 Hygric dilation behaviour of NaCl contaminated lime-cement mortar 1 Delft University of Technology, The Netherlands 2 TNO BenO, Delft, The Netherlands 3 Eindhoven University of Technology, The Netherlands

  2. COMPASS Project Compatibility of plasters and renders with salt loaded substrates in historic buildings (2002-2005) Main partners: TNO BenO – NL (coordinator) LRMH – F TUE – NL TUD – NL CSIC IET – ES LNEC - P Main aims: Model of transport & degradation mechanism Requirements for plasters and renders Accelerated crystallisation test Experts system www.compass-salt.org

  3. NaCl damage mechanism Sodium chloride does not reach high super-saturation “However, as it is not possible to obtain higher supersaturation than m/m0=2.2 of NaCl in levitated droplets, the occurrence of even higher supersaturation in pore solution is unlikely” [Steiger M., J. Cryst. Growth, 282,(3-4) 2005] “During this experiments with NaCl no supersaturation is found…” [Pel L. et al., Applied Physics letters, 81 (15) 2002] The NaCl damage mechanism is not fully understood. therefore it can hardly develop high crystallization pressures. In spite of this…

  4. La Rochelle (F) Venice (I) Brouwershaven (NL) …damage occurs

  5. No expansive reaction No crypto-florescences Damage due to NaCl

  6. High salt conc. Low salt conc. Hypothesis: differential dilation shear stresses at the interface

  7. LVDT support evaporation surface lateral sides sealed with epoxy resin salt contamination by capillary rise from the bottom surface Experimental set-up

  8. Hygric dilation Dilation occurs during crystallization

  9. Hygric dilation If the RHequ is not crossed, no irreversible dilation occurs

  10. Damage mechanism The dilation is irreversible and leads to damage

  11. NaNO3 and KCl

  12. ESEM investigation - NaCl NaCl: salt layer Salt layer Pores >0.5m empty Pores >0.5m empty Salt layer

  13. ESEM investigation – NaNO3 and KCl

  14. ESEM investigation – NaCl + inh. NaCl + inh.: no salt layer agglomeration of NaCl crystals NaCl crystals not adhering to the substrate

  15. Hygric behaviour NaCl + inh. No dilation occurs in presence of the inhibitor

  16. Hygric behaviour – NaCl + inh. No dilation and no damage occurs in presence of a crystallization inhibitor

  17. Conclusions NaCl modifies the hygric dilation behaviour of a material. Damage may result from the differential dilation between zones having different salt loads A damage mechanism based on the mechanical interaction between salt and pore wall is proposed. NaCl crystallizing as a layer on the pore walls causes irreversible dilation and damage during crystallization. No dilation and no damage is observed when the same salt crystallizes without adhering to the pore wall.

  18. Thanks for your attention

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