Concrete Additives

MIL-HDBK-1011/1

Coarse Aggregate. The density of aggregates affects concrete

3.3.2.2

strength, cement and water content, workability, and porosity of the concrete,

all of which indirectly influence steel corrosion. Research studies have

shown that satisfactory concrete, which incorporates select coral aggregate,

can be produced, provided a quality control program that is well defined and

closely monitored, is a mandatory requirement. Wash coral aggregate with

fresh water after crushing or dredging to ensure that the cement paste bonds

properly with the aggregate particles. Ensure that the aggregate is devoid of

sodium chloride to the maximum extent possible.

Water. For any reinforced concrete, do not use non-potable water

3.3.3

such as seawater or brackish water either in mixing or curing. Salt crystals

have a very high affinity for moisture. A small amount of residual salt

crystals on a seemingly dry concrete surface results in a damp surface,

especially in a highly humid environment. Such damp surfaces can create

painting problems, mold problems (mildew), and, most importantly, can

accelerate the corrosion of steel embedded in concrete. The total chloride

content of the finished mix shall not exceed 1 pound per cubic yard for any

reinforced concrete.

3.3.4

Concrete Additives

3.3.4.1

Air Entrainment. Air-entraining agents are used to improve

workability of concrete, minimize volume changes, reduce bleeding, and

minimize the porosity of the concrete. The strength of the concrete is

decreased in proportion to the amount of entrainment. The use of an air-

entrainment agent is recommended under the following controlled conditions:

Air-entraining agent contains no chlorides.

a)

b) Air content is within 3.5 and 6.0 percent by volume.

Air-entraining agent is compatible with other admixtures when

c)

specified.

d) Quality control requirements are included in the

specifications.

3.3.4.2

Retardant.

The use of retardant and water-reducing admixtures in

concrete is recommended.

3.3.4.3

Water Reducing Admixtures. High range water reducers are

categorized as a new type of admixture which can either be used to reduce the

water requirement or to be added to the normal amount of water to produce

flowing concrete. Tests and studies by Portland Cement Association have shown

that high range water reducers are capable of lowering the net water content

of concrete mixtures by 12 percent. Since less water is used, drying

shrinkage will be slightly reduced. Another item of particular importance for

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