Sika SikaRep Microcrete-3 UW
Sika’s anti-washout, pumpable micro concrete that restores submerged and tidal-zone concrete in place, without pumping the water out first.
What is it?
A factory-blended, non-shrink cementitious micro concrete carrying an anti-washout admixture, so it can be poured or pumped straight into water without the cement paste dispersing.
Where is it used?
Submerged and tidal-zone repairs — bridge piers, piles, pile caps, quay walls, cofferdams and marine or river structures below the waterline.
Why use it?
It lets crews rebuild damaged concrete under water without dewatering, saving the cost and delay of cofferdams or pumping, while still reaching structural strength above 45 N/mm2.
How is it applied?
Add clean water at 0.18-0.19 by weight, mix to a flowable consistency, then place by tremie pipe or pump within about 20 minutes into the prepared, reinforcement-exposed section.
About Sika SikaRep Microcrete-3 UW
SikaRep Microcrete-3 UW is Sika India’s answer to one of the most awkward problems in concrete rehabilitation: how do you rebuild a pier, pile or pile cap that sits permanently under water? Conventional repair mortars simply wash apart the moment they touch flowing water, leaving a weak, honeycombed mess and cement bleeding downstream. This product is a single-component, factory-designed micro concrete supplied as a grey powder that needs only clean water added on site. Its formulation blends selected cement, graded aggregate and an anti-washout admixture, so the fresh mix holds together as a cohesive mass even as it falls through water and consolidates around congested reinforcement.
For engineers and contractors working on India’s ageing river bridges, ports and irrigation assets, the practical appeal is straightforward. Because the material resists wash-out, there is no need to build a cofferdam or run continuous dewatering pumps just to keep the repair zone dry. That removes a large, expensive and schedule-critical part of the job. The mix is also shrinkage-compensated and chloride-free, so the hardened repair stays dimensionally stable and does not introduce chlorides that would attack the embedded steel. Space Arc Engineering supplies and applies SikaRep Microcrete-3 UW across Delhi NCR and Pan-India, and the notes here follow Sika’s published data rather than field guesswork.
The technical insight
The whole product turns on the anti-washout admixture, which is typically a high-molecular-weight water-soluble polymer that dramatically raises the cohesion and viscosity of the wet mix. In plain terms, the polymer grabs the mixing water and binds the cement and aggregate into a sticky, self-supporting body, so the paste cannot be scoured away when the material passes through or sits in water. That cohesion is why the mix must be discharged low and continuously through a tremie pipe kept below the rising concrete surface, minimising free fall and turbulence. A second useful effect is thermal: under water the surrounding mass acts as a heat sink, drawing off the heat of hydration, which is why Microcrete-3 UW can be placed up to 150 mm thick in a single pour under water against a limit of roughly 80 mm above water, where that heat has nowhere to go. Shrinkage compensation from a controlled expansive component keeps the repair in intimate contact with the parent concrete and the reinforcement as it sets, protecting the bond line and helping the section reach its full design strength despite the demanding placement conditions.
Where it is used
- Repair of submerged bridge piers, pile caps and pile shafts in rivers and estuaries
- Reinstatement of quay walls, jetties and harbour structures below the waterline
- Marine and tidal-zone concrete repair where cyclic wetting and salt exposure occur
- Cofferdam and dam-face patch repairs without full dewatering
- Reinstatement of spalled or eroded canal and irrigation structures under water
- Filling of large voids and honeycombing in permanently submerged sections
- Structural repair of intake and outfall structures in water-treatment and power plants
- Encasement and section rebuilding around exposed reinforcement in wet conditions
Key advantages
- Anti-washout action lets the mix be placed directly under water without the cement paste dispersing
- Eliminates the need for cofferdams or continuous dewatering, cutting cost and programme time
- Reaches structural compressive strength above 45 N/mm2, suitable for load-bearing repairs
- Shrinkage-compensated, so the repair stays in tight contact with the parent concrete
- Chloride-free formulation avoids introducing chlorides that would corrode embedded steel
- Pourable and pumpable, so it flows around congested reinforcement without heavy vibration
- Allows thick single-pour placement up to 150 mm under water thanks to the heat-sink effect
- Single-component bagged product needing only site addition of clean water, simplifying logistics
Limitations & considerations
- Anti-washout performance depends on correct tremie technique; free-falling the mix through water or excessive turbulence still causes some loss
- Not intended for dry above-ground repairs where a standard micro concrete would be more economical
- Working time is short — placement must be completed within about 20 minutes of mixing to capture the expansion benefit
- Water dosage must be held tightly at 0.18-0.19 by weight; over-watering weakens the mix and can compromise wash-out resistance
- Sound surface preparation and exposed, clean reinforcement are still required; the product does not compensate for poor cutting-out of unsound concrete
- Six-month shelf life and moisture-sensitive packaging demand disciplined dry storage between +5 C and +40 C
Selection & best practice
Break out all unsound and delaminated concrete back to a sound substrate and expose the reinforcement fully, cleaning steel of loose rust and marine growth before placement. Set formwork tightly with a discharge point that lets a tremie pipe or pump line stay embedded below the concrete surface throughout the pour. Mix each 30 kg bag with clean water at 0.18-0.19 by weight — around 5.4 to 5.7 litres — using a forced-action or slow-speed drill mixer to a uniform, flowable consistency, and never re-temper with extra water. Place continuously and steadily within about 20 minutes so the fresh mix displaces water upward rather than falling through it, keeping turbulence to a minimum. Plan pour thickness to the placement conditions: up to roughly 80 mm per lift above water and up to 150 mm under water. For skin repairs or where extra bond assurance is wanted above water, a scrub coat of a compatible Sika bonding agent can be used on the prepared substrate.
Specifications
| Product type | Anti-washout, non-shrink cementitious micro concrete (single-component powder) |
| Compressive strength (1 day) | 20 N/mm2 |
| Compressive strength (28 days) | 55 N/mm2 (site-verified above 45 N/mm2) |
| Flexural tensile strength (28 days) | 8 N/mm2 |
| Water : powder ratio | 0.18 to 0.19 by weight |
| Water per bag | Approx. 5.4 to 5.7 litres per 30 kg bag |
| Placement thickness | Up to 80 mm per lift above water; up to 150 mm under water |
| Working time | Place within approx. 20 minutes of mixing |
| Pack size / shelf life | 30 kg bags; 6 months in sealed, dry storage at +5 C to +40 C |
Industry use cases
Bridges and Highways
Rebuilding scoured and spalled river-bridge piers and pile caps in flowing water, keeping the structure in service without a cofferdam.
Ports and Marine
Restoring quay walls, jetty piles and harbour structures in the tidal and submerged zones where salt attack and wave action have eroded the concrete.
Dams and Irrigation
Patching eroded canal linings, dam faces and intake structures under water, avoiding the cost and delay of draining the reservoir or channel.
Power and Water Utilities
Repairing submerged intake, outfall and cooling-water structures at power stations and treatment plants without shutting down and dewatering the asset.
Frequently asked questions
Can SikaRep Microcrete-3 UW really be placed without dewatering?
How much water do I add per bag?
How thick can I place it in one pour?
What strength does it reach?
Is it safe for reinforced concrete?
How long do I have to place it after mixing?
How we position Sika SikaRep Microcrete-3 UW
SikaRep Microcrete-3 UW sits at the specialist end of Sika’s concrete-repair range, alongside the broader SikaRep and Sikacrete families — for dry above-water structural repairs a standard flowable micro concrete such as Sikacrete-155 UW IN or a SikaRep patch mortar is usually the more economical choice, with a compatible SikaLatex bonding agent for skin repairs. Where the client or specifier prefers the Fosroc system, the direct equivalent is Renderoc UW, and for dry rapid-gain repairs Renderoc RG is the natural counterpart. Space Arc also supplies allied waterproofing and protective coatings from Dr. Fixit and MC-Bauchemie for the splash-zone protection that often follows a submerged repair. The honest rule of thumb: reach for Microcrete-3 UW only when the repair is genuinely under water or in the tidal zone — for anything you can keep dry, a conventional micro concrete will do the job at lower cost.
Fosroc Renderoc UW — A specifier standardised on the Fosroc concrete-repair system, or matching an existing Renderoc specification on the project, would choose Renderoc UW as the equivalent anti-washout underwater micro concrete.
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