excess of the rated capacity, nor be operated in excess of the rated speed. Excessive mixing, requiring the addition of water to preserve the required consistency, will not be permitted. charging. The entire batch shall be discharged before re- 2. MixingTime: Mixing time shall be measured from the instant when the water is introduced into the drum containing all solids. All mixing water shall be introducec before 1 of the mixing time has elapsed. Mixing time for mixer of 1 cubic yard or less Shall be 1-1/4 minutes; for mixers larger than 1 cubic yard, the mixing time shall be increased 15 seconds for each additional half cubic yard or fraction thereof. If an air-entraining agent is used, mixing time shall be such as will provide the specified air content, 5-12, READY MIXED CONCRETE: Ready-mixed concrete in con- formity with A.S.T.M. Designation C 94-48 may be used, sub- ject to approval by the Engineer. Ready-mixed concrete shall be plant-mixed or truck-mixed as specified below. Concrete delivered in an atmospheric temperature lower than 40 degrees F, shall have a temperature of not less than 60 degrees F, The storing, weighing, batching and mixing at the site, except as hereinafter modified, shall apply to ready-mixed concrete. The Engineer shall have free access to the mixing plant at all times. a. Plant Mixed Concrete: The plant shall be equipps« for the accurate proportioning, mixing, and delivery of the concrete and have sufficient capacity and transportation facilities to deliver the concrete at the rate required. Concrete shall have an initial mixing at the plant of not less than one minute after all materials are in the mixer. The time elapsing between the discharge of the concrete fro! the mixer to its final position shall not exceed one (1) hour unless otherwise approved by the Contracting Officer. Transportation of concrete from the plant to the job shall be in clean watertight receptacles equipped with an agitation device which shall operate until the concrete is discharged. Maximum size of batch carried shall not be more than 70 per cent of the rated capacity of the container (for agitation) and the agitating speed shall not be less than 2 revolutions per minute or more than 8 revolutions per minute of the drum or revolving agitating device. b. Transit-Mixed Concrete: Material shall be batched and discharged into the truck-mixer and agitator which shall be capable of transporting and mixing the separate ingredients into a thoroughly mixed and uniform mass 5-9