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SUMMARY:Neutron research\, Contr. talk 4 - Detection of water in cement mo
 rtar at room temperature and during freezing
DTSTART;VALUE=DATE-TIME:20210510T130000Z
DTEND;VALUE=DATE-TIME:20210510T132000Z
DTSTAMP;VALUE=DATE-TIME:20260528T085823Z
UID:indico-contribution-1070@lindico453.srv.lu.se
DESCRIPTION:Speakers: Katja Frid (Malmö University)\nWater is present in 
 most of the degradation mechanisms that concrete is exposed to. When these
  mechanisms are studied experimentally to build models\, it is very import
 ant that the moisture content in the material is controlled and correct. T
 he aim for the experiment was to study the water and pore distribution in 
 air-entrained cement mortar with varying moisture preconditioning using du
 al-modality neutron and x-ray tomography. Furthermore\, in-situ freeze-tha
 w cycling of cement mortar was performed to visualize the evolution of the
  water distribution in the pores.\nThe test was divided into two parts. In
  the first part different moisture pre- conditionings was studied in four 
 samples : (1) Dried at 40C\, (2) Capillary saturated\,\n(3) cured moist
 ure sealed (4) Vacuum saturated. The samples had a diameter of 10 mm and a
  height of 10 mm and were moisture sealed during the measurements. A voxel
  size of 7 μm was used for the neutron imaging and 19.5 μm for the x-ray
  imaging. Analysis found that it was possible to detect water in the large
 r pores. It was also found that even after vacuum saturation not all pores
  were filled.\n\nIn part two\, an in-house built freezing device was used 
 to study the evolving water distribution during freeze-thaw cycling. The d
 evice was based upon a Peltier element and circulation of a cooling fluid 
 to reach temperatures well below 0C. A vacuum saturated cement mortar s
 ample (outer diameter 10 mm\, height 10 mm) with water on the top surface 
 was subjected to three freeze-thaw cycles. The sample was imaged at each f
 rozen/thawed state but due to time limitations\, a full dual-modality data
 set was only acquired before and at the first freezing as well as at and a
 fter the third freezing (in total four complete data sets). During the fre
 ezing\, the temperature was lowered to approximately -13C measured in t
 he sample and held constant during the imaging. A voxel size of 7 μm was 
 used for the neutron imaging and 19.5 μm for the x-ray imaging.\n\nThe pr
 eliminary analysis of the sample during freeze-thaw cycling shows some sma
 ll changes in greyscale value in the cement matrix during temperature cycl
 ing which can be used to understand the filling of the pore structure due 
 to freezing/thawing. We also found and small changes in relative water con
 tent of partially filled air voids. This can be used to understand the pro
 tective role of air voids.\nThis technique is very promising for further v
 erification of different parts of the mechanism of frost deterioration in 
 concrete. Something that the frost community has longed for!\n\nhttps://li
 ndico453.srv.lu.se/event/214/contributions/1070/
LOCATION:
URL:https://lindico453.srv.lu.se/event/214/contributions/1070/
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