SAND-LIME  BEICKMAKING   NEAR  BIRMINO 
HAM.  ALA. 
By  Charles   Bi  its. 
The  manufacture  of  sand-lime  brick  is  rapidly  approaching  the  pro-i 
portions  of  an  important  industry  in  the  United  States,  as  it  lias  been 
in  Germany  for  the  last  ten  or  fifteen  years.  In  the  following  brief 
discussion  of  the  subject  no  effort  is  made  to  go  into  detail. 
A  sand-lime  brick  is  essent  hilly  a  mass  of  sand  cemented  by  hydrous 
lime  silicates.  The  -and  may  be  either  loose  sand  or  pulverized 
sandstone.  Sand  and  quicklime  are  thoroughly  mixed  in  the  pro- 
portion of  5  to  l'>  pounds  of  lime  to  100  pounds  of  sand.  The  lime 
may  be  slaked  to  a  putty  or  to  a  powder;  or  it  may  be  ground  dry 
and  mixed  with  the  sand,  enough  water  being  added  to  slake  the 
lime.  In  any  case  the  mixture  should  contain  enough  water  to  he 
plastic.  The  brick  are  molded  and  placed  in  a  steam  drying  cylinden 
where  they  remain  from  seven  to  ten  hours  under  a  pressure  of  lb") 
to  1  Co  pounds  to  t  he  square  inch,  at  a  temperat  lire  of  1 70°  to  185°  C. 
It  is  believed  by  the  advocates  of  sand-lime  brick  that  this  treat-! 
inent  results  in  the  formation  of  lime  silicates  or  lime  hydrosilicate, 
by  which  the  -and  grains  are  firmly  cemented  together,  making  a 
brick  of  great  strength.  These  brick  can  easily  be  made  with  a 
crushing  strength  of  over  1,000  pounds  per  square  inch  and  a  tensile 
strength  of  over  200  pound-  per  square  inch.  The  crushing  strength 
and  elasticity  exceed  that  of  -nine  sandstones.  The  brick  with- 
stand severe  freezing  and  thawing  tests,  as  well  as  fire  tests.  With 
pure  sand  the  color  is  white,  but  by  the  addition  of  various  pro- 
portions of  manganese  or  graphite,  pink  or  gray  brick  can  be  made. 
It  is  claimed  that  these  brick  will  make  v(>vy  rigid  structures  and 
that  they  are  in  vvwy  way  safe  and  satisfactory  building  material. 
Both  common  and  front  brick  are  made.  Their  chief  merits  seem 
to  be  their  white  color  and  their  somewhat  lower  cost  of  manufacture 
than  that  of  clay  or  shale  brick  used  for  building  fronts  and  for 
ornamental  purposes. 
The  sand  used  for  brick  should  be  comparatively  free  from  clay 
and  feldspar,  neither  of  which  probably  should  exceed  1  0  per  cent  and 
even  a  smaller  amount  maybe  desirable.  The  best  results  appear  to 
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