12 BULLETIN 249, U. S. DEPAKTMENT OF AGKICULTUEE. 
Before any concrete is placed the subgrade should be thoroughly"! 
sprinkled with water or a part of the water contained in the concrete 
will be absorbed by the subgrade, which may interfere with the 
process of setting. 
For one-course work the concrete should be deposited between the 
forms in such quantity that when it is struck off and compacted it 
will present a uniform surface and have the depth required for the 
finished pavement. Each batch of concrete should be dumped as 
nearly in place as is practicable and should preferably be spread by 
means of mortar hoes. The men who do the spreading should avoid 
walking in the concrete, because each time the foot sinks into it the 
coarse aggregate is shoved down, and when the foot is withdrawn the 
space thus left tends to fill with mortar, which causes a lack of uni- 
formity in the concrete. 
After the concrete has been spread approximately to the required 
cross section it should be struck off with a strike board having slightly 
more crown than the cross section of the road. This allows for a 
slight amount of settlement when the concrete is compacted. The 
compacting should be done with a tamper shaped to conform with 
the cross section of the road and operated by two men, one standing 
on each side of the pavement. Suitable designs for strike boards are 
shown in Plate X, figures 2 and 3. The heavier design (PL X, fig. 3) , 
on account of its durability, is especially adapted for use where a 
considerable amount of work is to be done. It is also in general 
somewhat more satisfactory than the light design on account of its 
greater rigidity. Plate X, figure 4 shows a design for a tamper 
made of steel which has been used very satisfactorily for compacting 
concrete after it has been struck off, and which is very rigid and 
durable. 
Sometimes the tamping and striking off are done with the same 
template, but this is not altogether satisfactory, because when this is 
done it is impracticable for the template to have a greater crown than 
is required for the finished pavement, and it is difficult to strike off 
the concrete with such a template and at the same time make pro- 
vision for compacting. 
In the case of two-course pavements it is important that the top 
course be placed before the concrete in the bottom course has taken 
its initial set. The bottom course should be well compacted and 
struck off, but the striking off need not be as carefully done as in the 
case of the top course. The top course should be constructed in a 
manner similar to that described for one-course pavements. 
FINISHING THE SURFACE. 
The surface of a concrete pavement may be given either a rough or 
a smooth finish. A slightly roughened surface has the advantage of 
