heating causes, or would cause, less than 0.1 percent additional  loss  in  weight. 3. Weigh and record the weight of the oven-dried sample. 4₀ Calculate the total moisture content following   formula: using the Where: P = total  moisture  content  (percent) W  =   weight of original sample (in grams) D   = weight of oven-dried sample (in grams) The  surface  moisture  is  equal  to  the  difference between  the  total  moisture  content  and  the  absorption. An  alternate  determination  of  surface  moisture  in fine aggregate is obtained by displacement as follows: 1.  Select  a  representative  sample  of  the  fine aggregate weighing not less than 200 grams. 2.  Weigh  a  pycnometer  filled  to  the  calibration mark with water. 3. Place the sample in the pycnometer half filled with water. Add additional water to the calibration mark and  remove  all  entrapped  air.  Weigh  the  pycnometer, water, and sample. 4. Calculate the weight of the water displaced by the sample using the following formula: Where: V_s  =  weight  of  displaced  water  (in  grams) W_c   = weight of water-filled pycnometer (in grams) W_s =   weight of sample (in grams) W  =   weight of pycnometer, water, and sample (in grams) 5.  Calculate  the  percent  of  surface  moisture  using the  following  formula: Where: P =   percent of surface moisture V_s =    weight of displaced water (in grams) W_s =    Weight of sample (in grams) V_d    =  weight of sample in grams divided by the bulk specific gravity of the sample ADMIXTURES Several   chemical   agents,   or   admixtures,   are available  to  improve  workability,  increase  resistance  to freezing  and  thawing,  and  compensate  for  inadequate curing time and conditions. Accelerators Sometimes it is desirable to accelerate the hydration reactions. The result is a high-early strength and a higher rate of heat production. This combination can be useful in  winter  operations.  The  addition  of  a  chemical accelerator (generally calcium chloride) to the mix will produce  the  desired  conditions.  The  amount  specified  is usually 2 percent of the weight of cement and rarely more  than  3  percent.  The  main  reaction  with  calcium chloride occurs within the first 3 days. The ultimate strength of concrete is not affected by the use of this chemical. Retarders Retarders  are  used  when  excessively  high  heat  and too   rapid   setting   of   concrete   would   prevent   full hydration.  Many  materials  retard  setting  of  concrete. Basically,  these  materials  are  types  of  fatty  acids, starches, or sugars. Workability Agents or Plasticizers The  workability  of  concrete  is  governed  by  the amount of aggregate in the mix. Where reduction of aggregate  (or  increase  in  cement)  is  impractical, workability  is  increased  by  adding  a  plasticizer. Air-entraining agents, when used, are plasticizers. Other substances include calcium chloride, lime, fly ash, and other pozzolans. Calcium chloride is also an accelerator. Lime increases the cementing properties of cement, as do  pozzolans  combined  with  lime.  Fly  ash  is inexpensive compared to cement and is used as a partial replacement (up to as much as 50 percent) of the cement. It changes both the plastic and the hardened properties of  concrete.  Fly  ash  improves  workability  and  reduces segregation,  bleeding,  and  the  heat  of  hydration.  The 13-27