140 



The Philippine Journal of Science 



1914 



conclusively that such fine grinding is very beneficial because 

 it increases the sand-carrying capacity, permits better seasoning, 

 and increases the constancy in volume after induration. As 

 stated in a previous publication, we believe "that the influence 

 of fineness on the rate of set introduces no new^ or insurmount- 

 able factors into the problem of the control of the set." How- 

 ever, as our conclusions in this respect have not been generally 

 accepted, we reground all of the cements except No. 5, and then 

 subjected them to physical tests, the results of which are re- 

 corded in Tables IX and X. 



Table IX. — Characteristics of the reground cements^ 











Results 









Test. 

















No. 1. 



No. 2. 



No. 3. 



No. 4. 



No. la. 



No. 2a. 



No. 3a. 



Fineness in per cent: 

















Through the 100-mesh sieve 



98.6 



99.4 



99.6 



99.6 



99.3 



99.6 



99.6 



Through the 200-mesh sieve 



86 



&4.6 



85 



85.4 



85 



85.6 



85.4 



Soundness: 

















5-hour steam test.- --- - - 



sound 



sound 



sound 



sound 



sound 



sound 



sound 



Normal consistency: 

















Per cent water required 



21 



21 



20 



21 



21 



f28 



21 



Setting properties: 









, 









Initial set in hours 



3 



2.60 



0.25 



1.75 



3.20 



6 flash 



1.75 



Final set in hours- - . .- 



4.25 



4.35 



1.45 



2.46 



4.15 



t> flash 



4 



Tensile strength in pounds per square 



inch: 

















7-day, 1:3, Ottawa-sand mortar 



303 



317 



<:250 



307 



320 



•200 



343 



28-day, 1:3, Ottawa-sand mortar-,. 



366 



360 



=283 



335 



350 



c226 



369 



3-month, 1 : 3, Ottawa-sand mortar . 



447 



421 



c392 



440 



385 



'=330 



380 



■' Content of plaster = 2 per cent, except for cement 2a which contained 3 per cent. 



••See footnote (a) to Table III. 



■" Very erratic development of strength on account of quick-setting properties. 



Table X. — Setting properties of cement 3, reground.'' 



Seasoning. 



Per cent 

 plaster 

 added. 



Per cent 

 water 

 required 

 for nor- 

 mal con- 

 sistency. 



Sound- 

 ness 



(steam 

 test). 



Time of setting, in 

 hours. 



Initial 



set. 



Final 

 set. 



None 



0.5 



1.0 



none 



21 

 21 

 20 



sound 1 1.60 



3.00 

 3.75 

 5.00 



Do 



Aerated 4 hours - 



sound 

 sound 



1.75 

 1.00 



content of plaster = 2 per cent. 



Regrinding caused no undesirable characteristics to develop in 



