48 BULLETIN 1077, U. S. DEPARTMENT OF AGRICULTURE. 



result Tvhen the mixing is resumed. On this account the order and 

 progress of the work should ordinarily be planned with the primary 

 view to keeping the mixer going full time every working day that 

 the weather will permit. This means that ample provision should be 

 made for completing the drainage structures, the grading, and the 

 preparation of the subgrade well ahead of the mixer. Provision 

 should also be made for supplying the mixer with all necessary ma- 

 terials. Where the materials are obtained by rail shipment, and it is 

 expected that these shipments will be rather irregular, sufficient ma- 

 terial for at least ^ to 1 mile of road should be stored on the subgrade 

 or at the unloading yard before the mixing is started. This material 

 can be stored with a comparatively small working force, so that an 

 interruption of their work will not be as costly as a delay to the full 

 hauling and mixing force. 



The small drainage structures should preferably be completed in 

 advance of the grading in order to obviate the necessity of moving 

 embankment material the second time. They should always be com- 

 pleted in advance of the pavement. It is not economical to leave out 

 a section of the pavement over a small culvert, and this practice 

 should not be permitted. The extra expense involved in going back 

 and putting in a section of this kind after the pavement has pro- 

 gressed a considerable distance ahead is usually considerable and is 

 often underestimated. This method of doing the work also involves 

 a delay in opening the road, adds two extra joints, and usually re- 

 sults in securing an improperly cured pavement over the culvert. 



Organizing a force of laborers to operate a paving mixer efficiently 

 requires considerable skill in handling men. The best results are 

 generally obtained when a mixer is fully manned and each laborer 

 is assigned a definite work to perform. 



Diagrams showing organization and plant layout for a number of 

 typical methods employed in concrete pavement construction are 

 given in Figures 11 to 15, inclusive. These organizations and lay- 

 outs have been used in actual construction work and have proved 

 to be very satisfactory. 



EQUIPMENT. 



Any discussion of equipment must necessarily be more or less gen- 

 eral, because the same equipment is not always best suited for each 

 particular piece of work. Each project possesses certain character- 

 istics which determine the kind of equipment best adapted for han- 

 dling it. A contractor may either wait until he has secured a con- 

 tract before he decides on the type of equipment to purchase or he 

 may purchase the equipment which he feels will give him the best 

 satisfaction and only bid on work for which this equipment is suited. 



L..._ 



