RHEOCRETE CNI is a calcium nitrite based corrosion-inhibiting
admixture for steel reinforced concrete.
RHEOCRETE CNI contains minimum 30% active
ingredients by mass and meets ASTM C494 interim
requirements for Type C, accelerating admixtures.
In the alkaline environment of concrete, a natural
passive ferric oxide layer naturally forms on the surface
of embedded reinforcing steel and protects the steel
from corrosion. This passive oxide layer may break
down in the presence of chlorides, oxygen and moixture
resulting in corrosion of the steel.
RHEOCRETE CNI delays corrosion by repassivating
defects on the oxide/steel surface. These defects are
ferrous oxide ions that are susceptible to chloride
attack. When chloride ions attack the ferrous ions, they
combine to create a ferrous chloride complex (rust) and
initiate pitting corrosion on the reinforcing steel. If
untreated, chloride ions continue to attack newly
exposed ferrous ions and form additional expansive
corrosion products leading to staining, cracking and
spalling of the concrete.
Nitrite ions contained in RHEOCRETE CNI are effective
in preventing ferrous chloride complex formation by
reacting with defective ferrous oxide ions prior to
chloride attack and reforming the passive layer. Nitrite
ions surround the defective ferrous oxide ion and
convert it to a more stable ferric ion species less
susceptible to corrosion. This oxidation reaction serves
to repassivate the reinforcing steel and re-establish the
barrier between the steel and chlorides that initiate
corrosion.
RHEOCRETE CNI contains a minimum of 30% calcium
nitrite by mass as an active ingredient. RHEOCRETE
CNI is identical in composition and mechanism to other
commercially available 30% calcium nitrite corrosioninhibiting
admixture, and at equal dosage rates,
provides similar performance and corrosion protection.
The water content of RHEOCRETE CNI is
approximately 0.875 kg/L. This water contributes to the
consistency of the concrete mixture and the hydration of
the cementitious materials. The water contributed by
RHEOCRETE CNI should be used in the calculation of
the water-cementitious material ratio of the concrete.
RHEOCRETE CNI will not initiate or promote corrosion
of reinforcing steel embedded in concrete, prestressed
concrete or concrete placed in galvanised steel floor
and roof systems. Neither calcium chloride nor any
chloride-based ingredients are used in the manufac ture
of RHEOCRETE CNI.
RHEOCRETE CNI may be used with Portland cements
and mineral admixtures approved under recognised
international standards. It is compatible with other
chemical admixtures, including water reducers,
superplasticisers, retarders and air entrainers.
Chemical admixtures should be added separately to the
concrete to ensure desired results.