1925 (#1403-1607) - Laserfiche WebLink

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The coarse aggregate shill consist of a class "A' mixture of either crushed stone or gravel as hereinbefore specified. The voids in the concrete shall be completely fiiled with mortar. If voids appear, this condition shall be remedied by reducing the proportion of coarse aggregate and not by increasing the amount of fine aggregate. A cubic yard of concrete in place shall contain not less than six (6) bags of Portland Cement. SECTION 3. MIXING CONCRETE. A mechanical batch mixer shall be used, in which the material, including the water, can be precisely and regularly proportioned and thoroughly mixed. The Contractor shall mix, without slopping or spilling, such quantity of aggregates, as will be within the capacity of the mixer and in no case shall the quantity be such as to require the splitting of a sack ot cement. The mixing shall continue /or a minimum time of one (1) minute within the drum after all of the ingredients, including the water, are assembled therein, during which time the drum shall revolve at the speed for which it was designed, but shall not make less than fourteen (14) revolutions nor more than eighteen (18) revolutions per minute. The entire contents of the drum shalt be discharged before any materials are placed therein for the succeeding batch. Leaking water valves, pipe, or hose conections either within the mixer drum or else- where, will not be permitted, and will be considered sufficient grounds for susimnding the work. until the same is repaired. No concrete shall be used that shows evidence of having become set or that has become unfit for use from any cause, and no remixing of concrete will be permitted. 8BCTION 4. CONSISTENCY. The concrete shall be mixed with only sufficient water to produce a mass which will hold its shape when struck off with a templet, and in no case shall it be such as to permit a separation of the coarse aggregate from thc fine a~regatc, in handling. The consistency of the concrete shall he determined by the [ollowing test: A truncated cone, eight ($) inches at the base, four (4) inches it the top and twelve (12) inches high, shall be filled with the freshly mixed concrete and worked wRh I pointed three-eighths (~) inch round rod as the concrete is placed in the mold. It shall then be struck off level with the top, and the mold gently removed by a continuous upward pull. The difference between the height of the concrete after the mold is removed and the height of the mold will be considered the slump. For all concrete finished with a mechanical tamping and figishing machine, the slump shall not exceed one and one-fourth (1~) inches and for all hand tamped and finished concrete, the slump shall not exceed two (2) inches. SBCTION 5, PLACING CONCRETE. Immediately prior to placing the concrete, thc subgrlde shall be brought to an even surface and all loose earth removed or thoronghly compacted. The surface shall then be thoroughly sprinkled, but no pools of water shall exist when the concrete is placed. After mixing, the coucrcte shall be deposited rapidly upon the subgrade to a depth of three-eiihths (~) of an inch ~eater than the required thickness of the pavement unless i construction joint is to be used along the center line~ Where a construction joint is to be used alon~ the center llne, the concrete shall be placed to the full width of one-half (~) the pavement and in ill cases in a continuous operation of successive batches between