704.2(b) 704.2(c) samples taken approximately at the beginning, the midpoint, and the end of the batch. If the air content varies by more than 1.5%, discontinue the use of the mixer or agitator until the condition is corrected. If mixing in truck mixers at the plant, use inclined- axis, revolving- drum type mixers or horiz ontal -axis, revolving -drum high- discharge type mixers.
concrete, and between 50F and 80F for bridge deck concrete. Do not ship concrete exceeding these temperatur e ranges. Maintain adequate two- way communications between the concrete plant and the work site to provide both uniformity and control of the concrete mixture. For each truck, transmit a delivery ticket to the Representative at the time of each delivery (according to AASHTO M 157) with the following information:
• Contract number, complete state project number or purchase order number.
• The concrete plant supplier code.
• Method of concrete mixing (i.e., central or truck).
• Class of concrete, JMF number, and trial mix number (i.e., trial #1, 2, etc.).
• Number of cubic yards.
• Time of completion of mixing.
• Unique Truck ID.
• Number of mixing revolutions, if applicable.
• Total amount of batch water used in each truck (pounds).
• The total weight in pounds of the total cementitious materials.
• The types of additives used in each truck (i.e., water reducer, AEA, retarder, etc.). Transmit the information on the batcher -mixer slip Form CS -4220 to the Representative. Do not use any concrete until it is approved for use by the Representative. Co nform to AASHTO M 157, except as follows:
• If mixing in a plant, mix for not less than 50 seconds or more than 90 seconds for normal strength concrete, and not less than 70 seconds for HES concrete.
• If mixing in the truck drum at the plant, mix for not less than 70 or more than 125 truck -drum revolutions, at a mixing speed of not less than 6 truck -drum revolutions per minute ( rpm) nor more than 18 truck -drum rpm. Upon completion of the designated number of mixing revolutions, reduce the truck -drum speed to not less than 2 rpm or more than 6 rpm. Do not exceed a total of 300 truck -drum revolutions.
Deliver the mixed concrete to the work site and discharge within 1 1/2 hours after completion of mixing . As an alternative, use a set retarding admixture or a workability retention admixture or both, listed in Bulletin 15 and according to manufacturer's dosage recommendations, to extend the initial set time and time for discharge to 2 hours after the completion of mixing. Agitate, but do not mix the concrete enroute to the work site.
• In hot weather, under conditions