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The influence of curing conditions on mechanical strength and porosity of geopolymers

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37th International Conference and Expo on Advanced Ceramics and Composites

The  influence  of  curing  conditions  on  mechanical  strength  and  porosity  of  geopolymers  

Håkan  Engqvist

1

,  Bing  Cai

1

,  Torbjörn  Mellgren

1

,  Susanne  Bredenberg

2

 

1. Division  for  Applied  Materials  Science,  Department  of  Engineering  Sciences,  The   Ångström  Laboratory,  Uppsala  University,  Box  534,  SE-­‐751  21  Uppsala,  Sweden;  

2. Orexo  AB,  Box  303,  SE-­‐751  05  Uppsala,  Sweden   Email:  hakan.engqvist@angstrom.uu.se,  bing.cai@angstrom.uu.se,   torbjorn.mellgren@angstrom.uu.se,  susanne.bredenberg@orexo.com    

Geopolymers  have  been  suggested  to  be  used  as  construction,  waste  treatment  and  even  drug   delivery  material  due  to  its  excellent  mechanical  strength,  acid  resistance  and  biocompatibility.  

The  aim  of  this  study  is  to  investigate  the  influence  of  temperature,  time  and  humidity  during   curing  on  mechanical  strength  and  porosity  of  geopolymers.    

The  geopolymer  was  synthesized  by  mixing  metakaolin,  waterglass  and  de-­‐ionized  water  until  a   homogenous  paste  was  obtained.  The  following  molar  oxide  ratio  was  used:  Al

2

O

3

/SiO

2

=0.353,   Na

2

O/SiO

2

=0.202,  H

2

O/SiO

2

=2.977. The  paste  was  molded  into  cylindrical  rubber  moulds  (6     12   mm)   and   cured   under   different   temperatures   (ambient   temperature,   37°C   and   90°C),   humidity   and   time   (24,   48   and   96   hours).   The   compressive   strength   was   determined   using   a   universal   testing   machine.   Helium   pycnometer   was   used   to   measure   the   porosity.   Via   x-­‐ray   diffraction  the  phase  composition  of  the  cured  samples  was  determined.    

Higher  curing  temperature  increased  the  compressive  strength  after  24  hour  but  did  not  affect  

the   strength   for   longer   curing   times.   In   general,   the   samples   cured   in   moisture   had   higher  

mechanical  strength  than  those  cured  in  air.  More  metakaolin  remained  in  samples  cured  under  

high   temperature,   while   for   samples   cured   under   low   temperature   for   longer   time   showed   a  

higher  conversion  to  geopolymer.  Curing  time  did  not  show  much  influence  on  the  total  porosity.  

References

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