﻿

  R.Ca 
  to 
  

  

  

  Formula 
  

  

  Si 
  A 
  

  

  CaO 
  

  

  2 
  Ca 
  SiO 
  

  

  1.85 
  

  

  65.11 
  

  

  2^ 
  CaO! 
  SiO 
  2 
  

  

  2.33 
  

  

  70.00 
  

  

  3 
  CaO 
  Si0 
  2 
  

  

  2.80 
  

  

  73.68 
  

  

  3^ 
  CaO 
  SiO, 
  

  

  3.21 
  

  

  76.56 
  

  

  LIMESTONES 
  OP 
  NEW 
  YORK 
  AND 
  THEIR 
  ECONOMIC 
  VALUE 
  407 
  

  

  The 
  actual 
  composition 
  of 
  some 
  leading 
  cements 
  on 
  the 
  market 
  is 
  

  

  given 
  below. 
  

  

  Calcium 
  silicates 
  

  

  Si 
  O 
  a 
  Pat. 
  test 
  Hot 
  test 
  

  

  34.89 
  Set 
  hard, 
  hard 
  7 
  da. 
  hard 
  6 
  wk. 
  Sound, 
  on 
  glass 
  hard 
  

  

  30.00 
  Set 
  soft, 
  fairly 
  hard 
  7 
  da, 
  hard 
  6 
  wk. 
  " 
  

  

  26 
  . 
  32 
  Set 
  soft, 
  fairly 
  hard 
  7 
  da 
  . 
  hard 
  6 
  wk. 
  ' 
  ' 
  

  

  23.44 
  Cracked 
  soft, 
  1 
  da. 
  hard 
  6 
  wk. 
  " 
  

  

  In 
  good 
  portland 
  cement 
  Dr 
  Michaelis 
  considers 
  that 
  the 
  ratio 
  

  

  of 
  the 
  total 
  silicates 
  to 
  the 
  lime 
  should 
  be 
  about 
  as 
  1 
  to 
  2 
  

   and 
  that 
  the 
  variation 
  from 
  this 
  ratio 
  should 
  only 
  be 
  within 
  nar- 
  

   row 
  limits. 
  Cements 
  rich 
  in 
  lime 
  set 
  more 
  slowly, 
  but 
  harden 
  

   better 
  than 
  those 
  poor 
  in 
  lime. 
  Cements 
  rich 
  in 
  silica 
  generally 
  

   set 
  slower 
  that 
  those 
  rich 
  in 
  alumina 
  but 
  the 
  former 
  harden 
  very 
  

   energetically 
  in 
  the 
  beginning 
  and 
  are 
  better 
  for 
  use 
  under 
  salt 
  

   water. 
  

  

  According 
  to 
  Dr 
  Michaelis 
  (Schoch, 
  Mortel-materialien, 
  p. 
  85) 
  

   the 
  celebrated 
  German 
  portland 
  cement 
  manufactured 
  at 
  Stettin 
  

   in 
  Germany 
  has 
  a 
  silica 
  percentage 
  of 
  nearly 
  25^ 
  with 
  5.7 
  of 
  

   alumina 
  and 
  2.5 
  of 
  ferric 
  oxid. 
  

  

  A 
  material 
  like 
  the 
  chalk 
  of 
  Theil 
  is 
  for 
  instance 
  admirably 
  

   suited 
  for 
  the 
  manufacture 
  of 
  portland 
  cement 
  to 
  be 
  used 
  in 
  

   marine 
  work, 
  its 
  composition 
  is: 
  

  

  silica 
  2i 
  

  

  alumina 
  2.80 
  

  

  ferric 
  oxid 
  .90 
  

  

  lime 
  70 
  

  

  Schoch 
  expresses 
  the 
  opposite 
  opinion 
  from 
  Newberry 
  and 
  con- 
  

   siders 
  that 
  alkalies 
  act 
  as 
  a 
  flux, 
  and 
  they 
  can 
  be 
  replaced 
  by 
  

   calcined 
  soda. 
  He 
  also 
  states 
  that 
  they 
  are 
  of 
  great 
  benefit 
  in 
  

   connection 
  with 
  the 
  hardening 
  process 
  of 
  cement, 
  as 
  they 
  con- 
  

   vert 
  the 
  silica 
  into 
  a 
  soluble 
  condition 
  so 
  that 
  it 
  combines 
  with 
  

   the 
  lime 
  when 
  wet. 
  

  

  An 
  addition 
  of 
  \$ 
  to 
  f^ 
  of 
  fluorspar 
  is 
  very 
  beneficial 
  for 
  bring- 
  

   ing 
  about 
  an 
  easy 
  clinkering 
  of 
  the 
  materials. 
  Nearly 
  all 
  cements 
  

   contain 
  some 
  magnesia 
  and 
  sulfur, 
  which 
  come 
  originally 
  either 
  

   from 
  the 
  clay 
  or 
  from 
  the 
  fuel 
  used. 
  Redgraves's 
  Calcareous 
  

   cements 
  states 
  that 
  all 
  mixtures 
  containing 
  77^ 
  of 
  carbonate 
  of 
  

   lime 
  will 
  when 
  sufficiently 
  calcined 
  give 
  portland 
  cement 
  of 
  fair 
  

  

  