SikaRapid®-330 R is a calcium nitride-based corrosion-inhibiting admixture for steel reinforced concrete. SikaRapid®-330 R contains minimum 30% active ingredients by mass and meets ASTM C494 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 moisture resulting in corrosion of steel.
SikaRapid®-330 R delays corrosion by re-passivating defects on the oxide / steel surface. These defects are ferrous oxide ions attack the ferrous ions, they combine to create a ferrous chloride complex (rust) and initiate pitting corrosion on the reinforcing steel. If un-treated, chloride ions continue to attack newly exposed ferrous ions and form additional expansive corrosion products leading to staining, cracking and spalling of the concrete.
Nitride ions contained in SikaRapid®-330 R are effective in preventing ferrous chloride complex formation by reacting with defective ferrous oxide ions prior to chloride attack and reforming the passive layer. Nitride 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 re-passivate the reinforcing steel and re-establish the barrier between the steel and chlorides that initiate corrosion.
SikaRapid®-330 R may also be used to offset the potentially corrosive effects of the chloride-bearing concrete-making ingredients, and in applications where the initial chloride ion content of the concrete may exceed code requirements or other specified chloride limits.
SikaRapid®-330 R provides plastic and hardened concrete properties consistent with an ASTM C494 Class C admixture. The extension in service life due to the product is a function of the product dosage, the chloride exposure level, structure design factors and the transport properties of the concrete. The following tables illustrate the effect of SikaRapid®-330 R dosage and chloride exposure level per chloride protection limit:
Dosage (liter/m3) With chloride bearing materials (kg/m3) All other applications (kg/m3) 51.2-102.4 3.6153.65.9204.87.7256.08.9 30 7.2 9.5
SikaRapid®-330 R is identical in composition and mechanism to other commercially available 30% calcium nitride corrosion-inhibiting admixtures; and at equal dosage rates, provides similar performance and corrosion protection. The water content of SikaRapid®-330 R 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 SikaRapid®-330 R should be used in calculation of the water per cementitious material ratio of the concrete.
SikaRapid®-330 R will not initiate or promote corrosion of reinforcing steel embedded in concrete, pre-stressed concrete or concrete placed on galvanized steel floor and roof systems. Neither calcium chloride nor any chloride-based ingredients are used in the manufacture of SikaRapid®-330 R. Concrete setting times may be accelerated with the use of SikaRapid®-330 R.
If desired, a retarding or hydration control admixture may be added to the concrete mixture to offset the acceleration effects of SikaRapid®-330 R. SikaRapid®-330 R is recommended for steel reinforced concrete where longer service lives are desired and it is expected that the concrete will be exposed to environmental chlorides from deicing salts or marine exposure.
