138 



The mixing shall be continued for a minimum time of one minute after all ingredients 

 are assembled in the mixer before any concrete is drawn off, during which time the 

 mixer shall rotate at a peripheral speed of 200 feet per minute. The consistenc\- of the 

 mix will be controlled by the Engineer in proportioning the water. In general, the 

 consistency shall be as dry as can be used with the tamping hereinafter specified. 

 Excessively wet concrete shall be wasted and the cement contained charged to the 

 Contractor. Any excess of concrete which has been standing long enough to take an 

 initial set shall not be retempered and used in the work. 



2. Transportinn. Unless otherwise authorizetl l)y the Engineer, concrete shall be 

 transported from mixer to forms in appro\-ed containers such as buckets, buggies, or 

 barrows. Spouts, troughs or de\-ices which may affect the consistency or limit dry 

 consistencies shall not be used unless expressly permitted by the Engineer. In case 

 separation or other deleterious changes occur during transportation, the concrete 

 shall be dumped into a hopper and remixed by sho\elling before being deposited in 

 the forms. 



3. Tamping. After depositing in the forms, the concrete shall be thoroughly 

 worked with tools of an approved type. For the purpose of insuring thorough compact- 

 ing, the contractor shall furnish in addition to wheelers, dumpers and finishers, one 

 tamper for every two yards of concrete and fraction thereof placed per hour, who shall 

 do nothing other than spread and work the concrete as directed by the Engineer. 

 When the area of deposit is sufficient, concrete shall be spread in six-inch layers and 

 each layer thoroughly rammed to a plastic mass before the succeeding layer is placed. 

 When the area between forms does not permit of spreading, the concrete shall be 

 compacted both by rodding from the surface and by xibrating the forms with mallets 

 and hammers. 



4. Joints. All joints shall be made at locations designated by the Engineer. 

 When work is begun on any section it shall be carried on continuously to the line or 

 joint previously determined. Unless otherwise directed, joints shall be framed with 

 offsets, keys or reinforcing dowels approved by the Engineer. When concrete is de- 

 posited against a hardened layer or joint, the entire surface shall be cleaned, roughened 

 with a pick, made thoroughly wet, and slushed with neat cement paste. 



5. Forms. Forms shall be constructed of steel or of surfaced lumber of sufficient 

 strength to hold the concrete in position, and tight enough to prevent any leakage or 

 washing out of mortar. They shall be correct in shape and dimension and shall be 

 properly braced or tied together so as to maintain shape and position. I'nless otherwise 

 specified all right-angled corners shall be chamfered by means of mouldings or beveled 

 strips. 



Before any concrete is deposited, all dirt and foreign substances shall be removed 

 and the forms thoroughly hosed out and wet down. 



Forms shall remain in place until in the judgment of the Engineer the concrete 

 has hardened sufficiently to sustain its own weight and to resist loads or impacts which 

 are likely to occur during construction. 



6. Curing. The surfaces of newly placed concrete shall be carefully protected 

 from rapid drying by covering them with sand or burlap which shall be kept wet for a 

 period of two weeks after depositing concrete. Xo formed surfaces shall be exposed 

 either in air or under sea water until 48 hours after depositing concrete. 



Pre-cast members shall not be handled until 28 da\'s after depositing concrete. 

 Pre-cast piles or other members subject to impact shall not lie dri\en until 40 days 



