﻿416 
  

  

  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  this 
  material 
  in 
  American 
  is 
  about 
  4$, 
  while 
  in 
  the 
  European 
  ones 
  

   it 
  is 
  2.5$. 
  Magnesia 
  was 
  formerly 
  considered 
  very 
  objectionable 
  

   but 
  opinion 
  is 
  now 
  receding 
  on 
  this 
  point. 
  Those 
  American 
  brands 
  

   containing 
  4$ 
  of 
  magnesia 
  are 
  not 
  shown 
  to 
  be 
  at 
  all 
  detrimental. 
  

  

  In 
  the 
  various 
  numbers 
  of 
  the 
  Thonindustrie 
  Zeitung 
  for 
  1897 
  

   and 
  1898, 
  i. 
  e. 
  vol. 
  21 
  and 
  22, 
  will 
  be 
  found 
  a 
  number 
  of 
  articles 
  and 
  

   discussions 
  concerning 
  the 
  effect 
  of 
  magnesia 
  in 
  portland 
  cement. 
  

  

  Elaborate 
  experiments 
  of 
  K. 
  Dyckerhoff 
  abroad 
  have 
  not 
  shown 
  

   any 
  injurious 
  effects 
  to 
  come 
  from 
  4$ 
  of 
  magnesia. 
  

  

  Many 
  American 
  manufacturers- 
  adulterate 
  cement 
  by 
  adding 
  

   calcium 
  sulfate. 
  This 
  generally 
  acts 
  as 
  a 
  dilutant 
  and 
  it 
  should 
  

   always 
  be 
  stated 
  when 
  done. 
  The 
  German 
  association 
  has 
  declared 
  

   against 
  any 
  addition 
  except 
  up 
  to 
  2$ 
  to 
  regulate 
  setting 
  time. 
  

  

  It 
  is 
  the 
  general 
  practice 
  in 
  the 
  United 
  States 
  now 
  to 
  put 
  in 
  

   2$ 
  calcium 
  sulfate 
  to 
  produce 
  slow 
  set. 
  

  

  Tables 
  showing 
  the 
  increase 
  in 
  strength 
  which 
  results 
  from 
  an 
  

   increase 
  in 
  time 
  occupied 
  in 
  setting. 
  

  

  Pounds 
  to 
  a 
  square 
  inch 
  

   Kesults 
  reported 
  by 
  Dyckerhoff 
  prior 
  to 
  1880. 
  a 
  

  

  No. 
  

  

  One 
  sort 
  of 
  cement 
  

  

  Setting 
  

   time 
  

  

  Neat-cement 
  Briquette 
  

  

  Briq. 
  1 
  cement, 
  3 
  sand 
  

  

  d. 
  

  

  28 
  

   d. 
  

  

  12 
  

  

  wk 
  

  

  25 
  

   wk 
  

  

  1 
  . 
  

  

  yr 
  

  

  d 
  

  

  28 
  

   d. 
  

  

  12 
  

   wk 
  

  

  25 
  

   wk 
  

  

  1 
  

  

  ' 
  l 
  

  

  

  0° 
  20' 
  

   3° 
  30' 
  

   10° 
  0' 
  

   14° 
  0' 
  

  

  10° 
  30' 
  

  

  323 
  

   315 
  

   3T5 
  

   423 
  

  

  318 
  

  

  405 
  

   456 
  

   50S 
  

   543 
  

  

  450 
  

  

  518 
  

   572 
  

   568 
  

   688 
  

  

  550 
  

  

  620 
  

   623 
  

   695 
  

  

  718 
  

  

  592 
  

  

  700 
  

   650 
  

   780 
  

   805 
  

  

  618 
  

  

  115 
  

   142 
  

   159 
  

  

  180 
  

  

  168 
  

  

  168 
  

   212 
  

   238 
  

   263 
  

  

  21S 
  

  

  238 
  

   339 
  

   311 
  

   305 
  

  

  318 
  

  

  302 
  

   353 
  

   368 
  

   375 
  

  

  360 
  

  

  360 
  

  

  2 
  

   3 
  

   4 
  

   5 
  

  

  Same 
  w. 
  .5% 
  gypsum 
  .. 
  

  

  " 
  .1% 
  " 
  •• 
  

  

  2% 
  " 
  

  

  No 
  gyp. 
  but 
  kept 
  in 
  store 
  

  

  for 
  some 
  mos 
  

  

  390 
  

  

  384 
  

   410 
  

  

  431 
  

  

  Eesults 
  reported 
  by 
  John 
  Grant 
  in 
  1880. 
  

  

  7 
  d. 
  31 
  d. 
  60 
  d. 
  90 
  d. 
  

  

  1-1 
  briq. 
  ; 
  average 
  of 
  5 
  '. 
  . 
  107 
  159 
  188 
  26T 
  

  

  1-1 
  " 
  w. 
  . 
  H 
  2 
  S0 
  4 
  added 
  to 
  water 
  ; 
  aver- 
  

   age 
  of 
  5 
  129 
  227 
  260 
  255 
  

  

  oPro. 
  Inst. 
  civ. 
  eng. 
  62:92 
  

   fclbid, 
  p. 
  89, 
  90. 
  

  

  