a 
| 
STATE GEOLOGIST. 215 
SPECIFICATIONS FOR CONCRETE ROAD FOUNDATIONS, 
In order to give opportunity for comparison, the specifications for 
concrete foundations under streets and roads for three cities are given. 
The specifications in use in Columbus, Ohio, are as follows: 
Sec. 28.—CONCRETE ROAD FOUNDATION. 
American Portland Cement.—Upon the sub-grade a foundation of Amer- 
ican Portland cement concrete shall be laid to a uniform depth of six (6) 
inches, prepared and applied as hereinafter specified. 
Sand, —-The sand used in the mortar shall be clean, coarse, screened river 
or lake sand of approved quality. 
Crushed Stone.—The material for the body of the concrete shall be com- 
posed of limestone, crushed limestone boulders, or other material, equally 
hard and approved by the Engineer, broken so as to pass through a two-inch 
ring in its largest dimensions. The material shall be free frem all dust or 
dirt; no gravel will be used. 
Cement, —The cement used will be of the best quality American Portland 
cement, delivered in original packages, with the brand stamped or printed 
upon the same. 
Fineness, —It must be finely ground, so that at least 90 per cent. will pass 
through a sieve with 10,000 meshes per square inch. 
When mixed with water and worked up into a cake it must not attain its 
initial set until one hour after mixing, nor its final set until after three hours. 
Tensile Strength, —When mixed neat and worked up into briquettes. and 
exposed one day in air and six days in water, it must develop a tensile strength 
of 400 pounds per square inch. 
When mixed with three parts by weight of standard sand to one of 
cement, it must develop a tensile strength of 150 pounds per square inch 
in seven days. 
Unsoundness and Color. —T'wo cakes with thin edges will be made of 
neat cement, one will be kept under water to note changes of color; the other 
will be placed in boiling water, after its final set, and kept there for 12 hours; 
if the color changes in irregular spots during a period of ten days, or if 
the boiled cake shows any cracks or softness, it shall be rejected as unsound. 
Packages to be Marked by Engineer,—All packages of cement must be marked 
by the Engineer or superintendent before being used. 
Mixing.—One part by measure of cement and three parts of sand will be 
thoroughly mixed dry and then made into mortar with a minimum quantity 
of water; six parts by measure of crushed boulder, limestone or other equally 
hard material, having been previously saturated with water, will then be 
incorporated immediately with the mortar. 
Size of Crushed Stone, —Each batch of concrete will be thoroughly mixed, 
the mixing to be continued on the board until each piece of stone is com- 
pletely coated with mortar. It will then be spread and at once thoroughly 
compacted by ramming until free mortar appears upon the surface. The 
whole operation of mixing and laying each batch will be performed as 
expeditiously as possible and with the use of a sufficient number of skilled 
men. The upper surface will be made exactly parallel with the surface of 
