99
OF ENGINEERING FORMULÆ.
Portland Cement Concrete.
(Sandeman, ‘ Trans. Inst. Civ. Eng.,’ vol. liv.)
Proportions to 1 of Cement.
Sand.
Volume
of
Mortar
per cent,
of
Concrete.
Strength compared
with Mortar, 1 Sand to
1 Cement.
Tensile. ’ Compressive.
2
2
3
3
Total.
Aggregates.
3'16 4-16 42-4
2-16 4-16 61-73
4-Ü 6-74 42-4
3’74 6-74 55-4
6’32 9-32 42-4
5-32 9’32 1 52-19
•655
•655
•458
•458
•316
•655
•655
•438
•438
•315
Volume of Interstices in Concrete.
Per cent,
of Total.
Welsh limestone broken in a stone crusher
into flat oblong pieces, which, when gauged
the narrowest way, would pass through
3" ring....................................51
Gravel free from sand gauged through .
2J'' ring............................ .. 34
Welsh limestone and gravel as above, in
equal proportions.................__ ■■ ..34
Limestone (masons’ chips) varying in size
from small to pieces gauged by 4" ring .. 48
Red sandstone, hand broken, gauged from 4"
to 8" ring ................................50
Ditto, from sand to pieces gauged by 4" ring 34
Ditto, two previous materials mixed in equal
proportions................................36
Reduction of bulk of dry cement mixed with
water ....................................10|
Ditto of saud ............................«20
Ditto of sand and cement in equal proportions 19|
h 2