Concrete shall be cured by protecting it against loss of moisture, rapid temperature change, from rain, flowing water and mechanical injury for a period of not less than five days from the beginning of the curing operation. Moist curing, waterproof paper, white pigmented liquid membrane compound or a combination thereof may be used for curing. Immediately after finishing operations have been completed, the entire surface of the newly laid concrete shall be covered by the curing medium which is applicable to local conditions and approved by the Planning Commission, or its duly authorized representative.
The edge of concrete slabs exposed by the removal of forms shall be protected immediately to provide these surfaces with continuous curing treatment equal to the method selected for curing a slab surface and to prevent injury to concrete edges.
The covering material shall be kept free of any substances which may be detrimental to the surface of the concrete. The initial curing medium shall be effective and shall be applied so as to prevent checking, cracking and the appearance of dry spots in the surface of the concrete. The contractor shall have the equipment needed for adequate curing at hand and ready to install before actual concrete placement begins. In all cases in which the curing medium requires the use of water, the curing shall have prior right to all water supply. Failure to provide sufficient cover material of the type selected, failure to maintain saturation for the entire curing period in the moist-curing methods, lack of water to adequately care for both curing and other requirements or other failures to comply with curing requirements shall be cause for immediate suspension of concreting operations.
9.1 MOIST CURING: Moist curing shall be accomplished by covering of burlap, cotton mats, or other approved fabric mat used singly or in combination.
Curing mats shall be thoroughly wet when applied and kept continuously wet and in intimate contact with the pavement surface for the duration of the moist curing period. Other fabric mats shall conform in design and shall provide a curing medium at least equal to cotton mats. Cotton mats, other fabric mats, burlap mats, and burlap strips shall be furnished in the widths or lengths, after shrinkage, required to cover the entire width and edges of the pavement lane. Mats or burlap shall be lapped at joints between adjacent sheets to prevent drying of this location. Moist curing, when used as initial curing, shall be continued for not less than 24 hours. Type and weight of cotton mats for curing concrete shall conform to ASTM C-440 or AASHO M-73. Burlap strips shall conform to AASHO M-182.
9.2 WATERPROOF PAPER AND POLYETHYLENE SHEETING CURING: The surface of the concrete shall be wetted with a fine spray of water and then covered with the waterproof paper or sheeting. The paper or sheeting shall be in pieces large enough to cover the entire width and edges of the slab and shall be lapped not less than 12 inches. Paper or sheeting shall be adequately weighted to prevent displacement or billowing due to wind. Paper or sheeting folded down over the side of the pavement widths shall be secured by a continuous bank of earth. Tears or holes appearing in the paper or sheeting during the curing period shall be immediately repaired.
9.3 LIQUID MEMBRANE CURING COMPOUND: Pigmented liquid membrane during compound shall meet the specifications under ASTM C-309. The curing compound must be applied to cover the surface completely and uniformly at a rate which will achieve the performance requirement specified in AASHO specifications M-148 or ASTM Designation C-309. This method of curing shall be applied immediately behind the final finishing operation or after the initial curing when a combination of methods are used. Failure to provide complete and uniform coverage at the required rate will be cause for discontinuance of this method of curing and the substitution of one of the other approved methods. The compound shall be kept agitated to prevent the pigment from settling. Special care shall be taken to apply the curing compound to the pavement edges immediately after the forms have been removed.
(Ord. 1971-2, passed 4-6-71)