﻿406 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  tion. 
  As 
  stated 
  above 
  limestone 
  is 
  sometimes 
  used 
  but 
  in 
  other 
  

   cases 
  marl 
  is 
  employed, 
  specially 
  in 
  the 
  United 
  States: 
  With 
  

   marl 
  the 
  expense 
  of 
  crushing 
  and 
  grinding 
  the 
  material 
  is 
  saved, 
  

   but 
  both 
  have 
  their 
  advantages 
  as 
  well 
  as 
  their 
  disadvantages. 
  

   The 
  chemistry 
  of 
  portland 
  cement 
  has 
  been 
  most 
  carefully 
  studied 
  

   by 
  S. 
  B. 
  and 
  W. 
  B. 
  Newberry 
  a 
  who 
  come 
  to 
  the 
  following 
  conclu- 
  

   sions: 
  

  

  1 
  The 
  essential 
  constituents 
  of 
  portland 
  cement 
  are 
  tricalcis 
  

   silicate 
  with 
  varying 
  amounts 
  of 
  dicalcic 
  aluminate. 
  The 
  com- 
  

   position 
  is 
  therefore 
  expressed 
  by 
  the 
  following 
  formula: 
  

  

  X 
  (3CaOSI0 
  2 
  ) 
  +Y 
  (2CaOAl 
  2 
  3 
  ) 
  

  

  From 
  this 
  the 
  proportion 
  calculated, 
  i. 
  e. 
  

  

  Lime 
  by 
  weight 
  = 
  2.8 
  Si0 
  2 
  1.1 
  A1 
  2 
  3 
  

  

  2 
  Fe 
  2 
  3 
  combines 
  with 
  lime 
  at 
  a 
  high 
  heat 
  and 
  acts 
  like 
  the 
  

   alumina 
  in 
  promoting 
  the 
  combination 
  of 
  the 
  silica 
  and 
  calcium. 
  

   For 
  practical 
  purposes 
  the 
  presence 
  of 
  ferric 
  oxid 
  in 
  clay 
  is 
  not 
  

   to 
  be 
  considered. 
  

  

  3 
  Alkalies, 
  judging 
  from 
  the 
  behavior 
  of 
  soda, 
  are 
  of 
  no 
  value- 
  

   in 
  promoting 
  the 
  combination 
  of 
  calcium 
  and 
  silica 
  and 
  probably 
  

   play 
  no 
  part 
  in 
  the 
  formation 
  of 
  cement. 
  

  

  4 
  Magnesia 
  possesses 
  strong 
  hydraulic 
  properties 
  when 
  ignited 
  

   alone 
  but 
  has 
  none 
  when 
  heated 
  with 
  silica, 
  alumina 
  and 
  clay, 
  

   and 
  probably 
  plays 
  no 
  part 
  in 
  the 
  formation 
  of 
  cement. 
  It 
  will 
  

   not 
  replace 
  lime 
  in 
  mixtures 
  the 
  composition 
  of 
  which 
  should 
  

   be 
  calculated 
  on 
  the 
  basis 
  of 
  lime 
  only 
  without 
  regard 
  to 
  the 
  

   magnesia 
  present. 
  

  

  Using 
  the 
  formula 
  previously 
  given 
  they 
  made 
  up 
  and 
  tested 
  

   cements 
  as 
  shown 
  below. 
  6 
  

  

  

  

  

  

  

  

  

  Tens. 
  str. 
  *4sq. 
  

  

  

  

  

  

  

  

  

  in. 
  section 
  

  

  

  R. 
  Ca 
  to 
  

  

  

  

  

  

  

  

  

  

  Si 
  A 
  

  

  CaO 
  

  

  Si0 
  2 
  

  

  A1 
  2 
  3 
  

  

  Pat. 
  test 
  

  

  Hot 
  test 
  

  

  7 
  da. 
  

  

  28 
  da. 
  

  

  Silicate 
  95.8 
  ^ 
  

   Aluminate 
  4.2 
  S 
  

  

  2.67 
  

  

  72.79 
  

  

  25.21 
  

  

  2.00 
  

  

  Set 
  hard, 
  sound, 
  

   on 
  glass 
  

  

  Sound, 
  off 
  glass, 
  

   hard 
  

  

  154 
  

  

  173 
  

  

  Silicate 
  91.6 
  ) 
  

   Aluminate 
  .4 
  $ 
  

  

  2.57 
  

  

  71.90 
  

  

  24.10 
  

  

  4.00 
  

  

  Set 
  hard, 
  sound, 
  

   on 
  glass 
  

  

  Sound, 
  off 
  glass, 
  

   hard 
  

  

  148 
  

  

  2*7 
  

  

  Silicate 
  85.3) 
  

   Aluminate 
  14.7 
  $ 
  

  

  2.39 
  

  

  70.55 
  

  

  22.45 
  

  

  7.00 
  

  

  Set 
  hard, 
  sound, 
  

   off 
  glass 
  

  

  Sound, 
  on 
  glass, 
  

  

  180 
  

  

  205 
  

  

  Silicate 
  74.8) 
  

   Aluminate 
  25.2 
  J 
  

  

  2.15 
  

  

  68.31 
  

  

  19.69 
  

  

  12.00 
  

  

  Set 
  quick, 
  sound, 
  

   off 
  glass 
  

  

  Sound, 
  on 
  glass 
  

  

  105 
  

  

  84 
  

  

  a 
  Cement 
  and 
  engineering 
  news, 
  1898. 
  4:5. 
  

   b 
  Cement 
  and 
  eng. 
  news, 
  1897, 
  3, 
  no. 
  6, 
  p. 
  85 
  

  

  