WASHING AND GRADING SAND FOR CONCRETE. XVII. 
sandstone, as compared with standard sand, the following 
figures were obtained :— 
Standard. Unwashed. 
7 days ie 220) ea 212 
2a re we 329 e 316 
or the unwashed samples proved only about 4% inferior 
in strength to the standard sand, bothat 7 and at 28 days. 
It may be mentioned that drift sand, from Bourke 
Street, Surry Hills, and from Double Bay is far inferior 
to crushed sandstone, either washed or unwashed, and 
therefore to standard sand, as the following table shows : 
Neutral Double Surry 
Nepean. Nepean. George’s Bay. Bay. Hills. 
Standard. Fine. Coarse. River. Sandstone. Drift. Drift. 
@@ayse foo: 162) 200.) 1672) 180), 16205) 158 
eoistiy 55 may Joo mal Ole a2468 1 96a ZI 2h are 
6 months... 353 . 263 320 232 341 208 214 
12 oe eee ood 200) = S00) 230) 7 a228 19S 22T 
The mixtures for the above were all made with the same 
cement on the same day. It will be seen that Neutral 
Bay crushed sandstone proved only slightly inferior to 
the standard, while two samples of drift sand were much 
weaker. 
To test the strength of briquettes made with coarse and 
fine samples of sand, and obtained from same place, six 
tests were made in all from three different places. In 
every case, both at 7 and 28 days, the coarse samples gave 
the better results, the averages being— 
Coarse. Fine. 
7 days ose 213lbs. sic 174 lbs. 
Zo. 5, ae 271 lbs. as 248Ibs. 
so that, other things being equal, the word ‘“‘ coarse’’ 
should be included in the specification for sand for con- 
crete, unless “ carefully graded ”’ are the words used. 
These results were strictly in accordance with what 
might have been anticipated, from the fact that if all the 
2—June 20, 1906. 
