DRAINAGE METHODS FOR COUNTY ROADS. 71 



in the foimdation, struck off and shaped, it is not at all likely to be 

 seriously defective in streng'th on account of the mixture Kaving 

 been too wet. The consistency necessary to meet this requirement 

 frequently is described in specifications as " jellylike." 



, The amount of water required to produce a jelly like consistency 

 varies with the condition of the aggregates as well as with the 

 amount of mixing a batch of concrete receives. In general, the better 

 the concrete is mixed the less water is required, and the amount of 

 water used for each batch should be just sufficient to produce the 

 desired consistency when the batch has been mixed thoroughly. This 

 amount can be best ascertained by trial, and frequently must be modi- 

 fied from time to time as the work progresses. 



CONSTRUCTION. 



The different steps involved in constructing a concrete foundation 

 should proceed in the following order: (1) The subgrade should be 

 prepared in accordance with the method already described. (2) The 

 materials should be hauled out and deposited on the subgrade. (3) 

 The concrete should be mixed, placed, and properly finished. (4) 

 The foundation should be kept closed to all traffic for about 10 days, 

 and protected from too rapid drying out by a covering of earth or 

 other suitable material. (5) The earth covering is removed and the 

 foundation is ready to receive the pavement. 



Curbs are not mentioned above, because the order in which they 

 are constructed depends on the type employed. If the curbs are sepa- 

 rate from the foundation they should be constructed while the sub- 

 grade is being prepared and before the foundation materials are 

 hauled out. If constructed as flanges on the foundation, the outside 

 forms should be set as the subgrade is prepared and then side forms 

 while the concrete is being placed. Forms may consist of either 2^- 

 inch wooden boards or of steel channels, though the steel is to be pre- 

 ferred. The forms should, of course, be set true to line and grade 

 and should be well braced so as to resist springing out of shape 

 when concrete is placed against them. 



The materials may be hauled out in any one of several different 

 ways. From the standpoint of economy alone, teams ordinarily 

 would be used for small quantities of work and moderately short 

 hauls, tractors or motor trucks for good roads and long hauls, and 

 industrial railways where the roads are poor and the quantity of 

 work to be done is sufficient to warrant the purchase of the necessary 

 equipment. From a standpoint of excellence, the industrial railway 

 is preferable to the other methods, because hauling over an industrial 

 railway would not disturb the prepared subgrade in any way, while 

 with the other methods it usually is impracticable to prevent the sub- 



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