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f. Vibration shall not be applied directly or indirectly to sections • <br />or layers of concrete which have hardened to the degree <br />that the concrete ceases to be plastic under vibration. It <br />shall not be used to make concrete flow in the forms over <br />distances so great as to cause segregation, and vibrators <br />shall not be used to transport concrete in the forms. <br />g. Vibration shall be supplemented by such spading as is necessar;,+ <br />to insure smooth surfaces and dense concrete along form <br />surfaces and in corners and locations inaccessible to the vibrators. <br />h. These provisions shall apply to precast paling, concrete cribbing <br />and other precast members except that, if approved by the <br />Engineer, the manufacturer's methods of vibration may be <br />used. <br />b. In any given layer the separate batches shall follow each <br />other so closely that each one shall be placed and consolidated <br />before the preceding one has taken initial seL in order that <br />the fresh concrete shall not be injured and there shall be <br />no lines of separation between the batches. <br />3. When vibrating is not practical, concrete shall be consolidated and <br />all faces well spaded by continuous working with a suitable tool <br />in a manner acceptable to the Engineer. <br />4. Concrete shall be placed in continuous horizontal layers, the thickne;s <br />of which generally shall not exceed 10 to 12 inches; however, slabs <br />shall be placed in a single layer. <br />a. When it is necessary in an emergency to place less than a <br />complete horizontal layer in one operation, such layer shall <br />terminate in a vertical bulkhead. <br /> <br />c. Each layer of concrete shall generally be left somewhat rough. <br />to secure efficient bonding with the next layer above. <br />d. A succeeding layer placed before the underlying layer has <br />become set shall be consolidated in a manner that will entirely <br />break up and obliterate the tendency to produce a construction <br />joint between the layers. <br />H. <br />5. Layers completing a day's work or placed prior to temporarily dis- <br />continuing operations shall be cleaned of all laitance and other ob- <br />jectionable material as soon as the surface has become sufficiently <br />firm to retain its form. To avoid visible joints as far as possible <br />upon exposed faces, the top surface of the concrete adjacent to <br />the forms shell be finished by being smoothed with a trowel. <br />Finishing <br /> <br />03300-10 <br />