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Keep underwater concrete mixes cohesive during placement. Sika® UCS Pak is a powdered anti-washout admixture designed to reduce cement paste washout, segregation and bleeding in specialised concrete mixes. Water-soluble bags support measured batching on civil and marine projects.
Key benefits
- Better cohesion: helps concrete resist segregation during underwater placement.
- Reduced washout: helps retain cementitious material when concrete is placed in water.
- Controlled batching: pre-measured water-soluble bags simplify dosing.
- Mix design flexibility: used with a compatible water reducer to achieve the required workability.
Typical applications
Designed for underwater civil works, marine construction and suitable piling concrete. Dose and mixing procedures must be confirmed for the project's water conditions and concrete mix design.
Important to know
Add the water-soluble bags at batching as specified in the current technical data sheet, not directly to gauging water. Use project mix trials to verify performance, setting time and strength. This is a concrete admixture, not a standalone waterproofing product.
Improves cohesion in specified underwater concrete mixes.
Reduces washout and segregation during underwater placement.
Water-soluble bags support controlled batching.
Add water-soluble bags with aggregate or cement at the batching plant, not to gauging water. Use with an appropriate Sika high-range water reducer or superplasticiser and mix wet for at least 120 seconds, subject to mixer effectiveness. If dosed into a truck, rotate at maximum revolutions for at least one minute per cubic metre and at least five minutes overall. Develop and verify a high-workability underwater mix through laboratory trials before pumping, skip or tremie placement.
Do not add to gauging water. Overdosing may increase air entrainment, reduce compressive strength, reduce workability and extend set time; even normal use can increase set time. Underwater concrete may show modest strength reduction. Mix designs and admixture compatibility require trials; avoid free fall through water-filled pump or tremie lines because it may cause segregation.
Sika® UCS Pak Physical Properties
| Property | Value |
|---|---|
| Product Type | Underwater anti-washout concrete admixture |
| Composition | Powder blend of plasticisers and viscosity modifiers |
| Appearance | Pale buff powder |
| Unit | 0.4 kg water-soluble bag |
| Sealed tub | 24 bags (9.6 kg total) |
| Indicative dosage—static segregation control | 1–2 bags/m³ |
| Indicative dosage—moderate underwater conditions | 2–3 bags/m³ |
| Indicative dosage—severe flowing water | 4–5 bags/m³ |
| Recommended wet mixing time | At least 120 s under suitable mixer conditions |
| Indicative minimum cementitious content | 400 kg/m³ |
| Indicative maximum water/cement ratio | 0.45 |
| Technical conformity | BS 8443 requirements |
| Shelf Life | 12 months unopened |
| Storage | Dry, 5°C to 35°C; protect from sun and frost |