Presentation on theme: "1 Barbara Lubelli 1, Rob P.J. van Hees 1,2, Henk P. Huinink 3 Hygric dilation behaviour of NaCl contaminated lime-cement mortar 1 Delft University of Technology,"— Presentation transcript:
1 Barbara Lubelli 1, Rob P.J. van Hees 1,2, Henk P. Huinink 3 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 7 th European Conference SAUVEUR Prague 31 st May -2 nd June 2006
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] In spite of this… The NaCl damage mechanism is not fully understood. therefore it can hardly develop high crystallization pressures.
14 ESEM investigation – NaCl + inh. agglomeration of NaCl crystals NaCl crystals not adhering to the substrate NaCl + inh.: no salt layer
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.