§ 6-126. Hot weather concreting specifications.

(a)

Concrete placing and finishing operation during hot weather shall be done as quickly as possible. Ample personnel shall be available to handle and place the concrete immediately after its mixing or delivery at the site of the work. Concrete shall be placed in layers thin enough, and over areas small enough, to ensure complete bond and union of adjacent layers and thus, prevent "cold joints."

(b)

At air temperatures of eighty (80) degrees Fahrenheit or above, the following precautions shall be taken:

(1)

In no case shall the temperature of the concrete exceed eighty (80) degrees Fahrenheit when placed in the work.

(2)

Every effort shall be made to obtain cool mixing water and to keep it cool by adequate protection of pipes and storage tanks. Water supply lines shall be shaded, insulated or buried.

(3)

Stockpiled aggregates shall be saturated and kept surface moist by continuous fog spray or by intermittent sprinkling.

(4)

Forms, reinforcements and subgrade surfaces shall be wet down immediately before concrete is placed in contact therewith. Wetting down of areas around the work, to cool the surrounding air and increase the humidity, is recommended.

(5)

In extremely hot, windy weather (temperatures over ninety (90) degrees Fahrenheit) sunshades, wind breakers and/or fog nozzles may be required during flat slab finishing operations. If in the engineer's or administrative authority representative's opinion adequate hot weather precautions are not being observed, concreting operations shall be suspended.

(6)

Concrete shall be kept cool during the specified curing period by the following methods: Top surfaces of slabs shall be coated with white pigmented membrane curing compound (as hereinafter specified under curing) within twenty (20) minutes after final finishing has been completed at any point. When ambient air temperatures exceed ninety (90) degrees Fahrenheit, and as soon as practicable without damage to the surface finish, all exposed concrete shall be kept continuously moist by means of fog sprays, wet burlap or cotton mats, or other effective method. Such water cooling to be in addition to initial surface sealing by membrane curing compound.

(7)

The cement factor used in the approved concrete design mix shall be increased when and as necessary to maintain the specified maximum water-cement ratio in all cases where additional water is added to compensate for loss of slump during transportation, handling or placing.

(8)

Retarding admixtures may be used only when necessary and only under strict supervision and with written approval of the city engineer or authorized representative.

(9)

Additives at no time shall be used for the purpose of reducing specified quantity of cement.

(10)

Slump limits shall remain the same with or without additives.

(Code 1974, § 5-15)