PORTLAND CEMENT CONCRETE' PAVEMENTS. 19 



METHODS, ORGANIZATION, AND EQUIPMENT. 



When it is considered that ordinarily from one-third to one-half 

 of the total cost of constructing a concrete pavement is for the labor 

 employed in doing the work after the materials are delivered, the 

 importance of efficient organization, proper equipment, and eco- 

 nomical methods becomes readily apparent. Failure to give these 

 features proper consideration may easily result in adding from 10 

 to 20 per cent to the cost of a concrete pavement, and has no doubt 

 frequently caused road contractors to sustain a net loss on projects 

 of this kind, where profits might have been made. 



It is not the province of this bulletin to furnish detailed rules for 

 the guidance of contractors in planning and executing their work, 

 but it seems desirable to discuss briefly a few important points which 

 contractors and engineers in charge of force-account work should 

 consider in connection with concrete-pavement construction. The 

 points which are of most importance, and to which the discussion 

 will be confined, are concerned with, first, the proper order and 

 progress of the work; second, the economic handling of materials; 

 and third, the amount of capital necessary to carry on such work 

 economically. 



ORDER AND PROGRESS OF THE WORK. 



In constructing a concrete pavement it is especially desirable that 

 the work of mixing ond placing the concrete be as nearly continuous 

 as practicable after it is once begun. Where the mixer is permitted 

 to stand idle for even a few days the force of laborers employed in 

 operating it will usually become more or less disorganized, and an 

 appreciable amount of loss and unsatisfactory work will generally 

 result when 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, as well as 

 for supplying the mixer with all necessary materials. 



The drainage structures should preferably be completed in ad- 

 vance of the grading in order to obviate the necessity for moving 

 embankment material the second time. Where tlie concrete mate- 

 rials are to be hauled out by means of an industrial railway, how- 

 ever, it is usually impracticable to extend the railway ahead of the 

 grading, and the saving effected in hauling the materials for the 

 drainage structures on the industrial railway may justify permitting 

 the grading to proceed ahead of the drainage structures. 



