﻿TESTS 
  OF 
  ROAD 
  MATERIAL 
  X07 
  

  

  Stone 
  used 
  in 
  the 
  construction 
  and 
  maintenance 
  of 
  the 
  national 
  highways 
  

   of 
  France. 
  These 
  results 
  are 
  said 
  to 
  agree 
  well 
  with 
  those 
  obtained 
  in 
  

   actual 
  practice. 
  

  

  The 
  apparatus 
  used 
  in 
  the 
  tests 
  consists 
  of 
  a 
  cast-iron 
  cylinder 
  8 
  in. 
  

   in 
  diameter 
  and 
  13.6 
  in. 
  in 
  depth. 
  At 
  one 
  end 
  is 
  an 
  opening 
  which 
  can 
  

   be 
  closed 
  with 
  a 
  tightly 
  fitting 
  iron 
  cover. 
  This 
  cylinder 
  is 
  mounted 
  on 
  

   an 
  axle 
  at 
  an 
  angle 
  of 
  30° 
  with 
  the 
  axis 
  of 
  the 
  cylinder, 
  and 
  is 
  supported 
  

   on 
  an 
  iron 
  frame. 
  At 
  one 
  end 
  of 
  the 
  axle 
  is 
  a 
  pulley 
  wheel 
  by 
  which 
  the 
  

   cylinder 
  is 
  revolved 
  ; 
  at 
  the 
  other 
  is 
  an 
  instrument 
  which 
  records 
  its 
  

   revolution. 
  

  

  The 
  stone 
  to 
  be 
  tested 
  is 
  first 
  broken 
  into 
  pieces, 
  between 
  2^ 
  in. 
  

   and 
  i^in. 
  in 
  diameter, 
  which 
  are 
  carefully 
  washed, 
  to 
  remove 
  any 
  foreign 
  

   matter. 
  In 
  the 
  cyhnder 
  are 
  placed 
  5 
  kilograms 
  (i3^lbs.) 
  of 
  this 
  stone. 
  

   The 
  top 
  is 
  then 
  bolted 
  on, 
  and 
  the 
  cylinder 
  is 
  made 
  to 
  revolve 
  for 
  5 
  

   hours 
  at 
  the 
  rate 
  of 
  2,000 
  revolutions 
  an 
  hour, 
  making 
  in 
  all 
  10,000 
  revo- 
  

   lutions. 
  By 
  this 
  process 
  the 
  stones 
  are 
  thrown 
  from 
  one 
  end 
  of 
  the 
  

   cylinder 
  to 
  the 
  other, 
  and 
  at 
  the 
  same 
  time 
  are 
  roiled 
  against 
  the 
  sides 
  

   of 
  the 
  vessel 
  and 
  against 
  one 
  another. 
  When 
  10,000 
  revolutions 
  are 
  com- 
  

   pleted, 
  the 
  cover 
  is 
  removed, 
  and 
  the 
  contents 
  emptied 
  into 
  a 
  tray. 
  The 
  

   cylinder 
  is 
  then 
  thoroughly 
  washed, 
  to 
  remove 
  the 
  dust 
  that 
  adheres 
  to 
  

   its 
  sides. 
  Each 
  stone 
  above 
  i^ 
  in. 
  in 
  diameter 
  is 
  then 
  washed 
  under 
  

   the 
  same 
  water. 
  This 
  water 
  is 
  then 
  filtered, 
  and 
  the 
  filtrate 
  when 
  dry 
  is 
  

   mixed 
  with 
  the 
  detritus 
  taken 
  from 
  the 
  cylinder. 
  The 
  detritus 
  is 
  then 
  

   put 
  into 
  a 
  sieve, 
  by 
  which 
  it 
  is 
  separated 
  automatically 
  into 
  seven 
  sizes. 
  

   These 
  seven 
  sizes, 
  together 
  with 
  the 
  stones 
  that 
  have 
  not 
  been 
  worn 
  

   below 
  3.18 
  cm. 
  ia 
  diameter, 
  are 
  each 
  carefully 
  weighed, 
  and 
  their 
  

   weights 
  recorded. 
  

  

  The 
  amount 
  of 
  detrition 
  under 
  1-16 
  im. 
  is 
  rarely 
  less 
  than 
  20 
  grams 
  per 
  

   kilogram 
  of 
  stone 
  used 
  2 
  %, 
  therefore 
  20 
  has 
  been 
  adopted 
  as 
  the 
  standard, 
  

   and 
  the 
  coefficient 
  of 
  quality 
  is 
  obtained 
  by 
  the 
  following 
  formula: 
  

  

  20 
  400 
  

  

  u 
  u 
  

  

  u 
  = 
  per 
  cent 
  

  

  in 
  which 
  u 
  represents 
  the 
  weight 
  in 
  grams 
  15.43 
  grs. 
  of 
  detritus 
  per 
  

   kilogram 
  (2 
  2-3 
  lbs) 
  of 
  stone. 
  

  

  It 
  seemed 
  well, 
  in 
  beginning 
  this 
  work, 
  to 
  be 
  guided 
  as 
  far 
  as 
  possible 
  

   by 
  the 
  experience 
  of 
  others, 
  and 
  for 
  this 
  reason 
  the 
  Deval 
  test 
  was 
  

   adopted, 
  for 
  it 
  appeared 
  to 
  be 
  the 
  only 
  practical 
  method 
  of 
  testing 
  road 
  

   metals 
  yet 
  devised. 
  After 
  a 
  number 
  of 
  trials 
  were 
  completed 
  with 
  the 
  

   Deval 
  apparatus, 
  and 
  their 
  results 
  studied, 
  it 
  was 
  recognized 
  that 
  all 
  the 
  

   valuable 
  properties 
  possessed 
  by 
  a 
  good 
  road 
  metal 
  were 
  not 
  embraced 
  

   in 
  this 
  test. 
  The 
  value 
  of 
  any 
  good 
  stone 
  as 
  a 
  road 
  metal 
  is 
  due 
  to 
  cer- 
  

   tain 
  properties 
  possessed 
  by 
  it. 
  Among 
  these 
  there 
  are 
  three 
  which 
  

   stand 
  prominent 
  — 
  cementing 
  value, 
  toughness 
  and 
  hardness. 
  It 
  is 
  evi- 
  

   dent 
  that 
  the 
  Deval 
  apparatus 
  does 
  not 
  test 
  the 
  very 
  important 
  property 
  

   of 
  cementing 
  value 
  in 
  the 
  different 
  road 
  metals. 
  The 
  commission, 
  recog- 
  

   nizing 
  this 
  deficiency, 
  accordingly 
  directed 
  its 
  attention 
  to 
  devising 
  some 
  

   means 
  of 
  supplying 
  it. 
  As 
  no 
  previous 
  attempt 
  has 
  been 
  made 
  in 
  this 
  

   direction, 
  the 
  commission 
  had 
  to 
  invent 
  its 
  own 
  method, 
  which 
  is 
  as 
  

   follows 
  : 
  

  

  The 
  stone 
  to 
  be 
  tested 
  is 
  ground 
  to 
  a 
  powder, 
  and 
  passed 
  through 
  a 
  

   sieve 
  of 
  100 
  meshes 
  to 
  i 
  m. 
  The 
  powder 
  is 
  then 
  put 
  in 
  a 
  slightly 
  tap- 
  

  

  