UltraTech Microkrete HS3
A pour-only, non-shrink micro-concrete that fills the tightest, most congested rebar cages without a single pass of a vibrator.
What is it?
A single-bag, polymer-modified cementitious micro-concrete engineered to flow into narrow, densely reinforced sections without segregating.
Where is it used?
Column and beam jacketing, spalled RC repair, foundation and pile-cap encasement — anywhere a vibrator can’t physically reach.
Why use it?
It self-compacts under its own flow, resists shrinkage as it cures, and reaches a designed 40 MPa — enough for most repair and strengthening specs.
How is it applied?
Mixed with 11-13% water by weight to a lump-free slurry, then poured or pumped through a header box into shuttered formwork — no vibration.
About UltraTech Microkrete HS3
UltraTech Microkrete HS3 is the entry-strength member of UltraTech’s Microkrete range — a single-bag, polymer-modified micro-concrete built for situations where ready-mix or hand-packed mortar simply can’t get where it needs to go. Congested column cages, thin jacketing sections, pockets behind old formwork, the underside of a beam under encasement — anywhere a vibrator can’t be worked in, or where segregation would ruin a conventional pour, is the gap this product is built to fill. It arrives as one factory-blended powder — cement, polymers and graded fillers already proportioned — so there’s no second component to measure on site.
What makes it usable on an actual repair site, not just on a data sheet, is how forgiving the pour itself is. Mixed to the specified water ratio, it turns into a flowable slurry that finds its own way into a rebar cage — poured through a funnel or header box, or pumped where access is tight. HS3 is designed for 40 MPa, which covers the bulk of jacketing, spalled-section repair and RC restoration work Space Arc handles across Delhi NCR; UltraTech’s HS2 and HS1 variants step up to 60 and 80 MPa where the structural design specifically calls for it.
The technical insight
The mechanism is straightforward once you see it. Ordinary concrete relies on vibration to work out entrapped air and let the mix settle around rebar; ordinary repair mortar relies on hand-packing to fill a cavity — both fail once a section gets too narrow or too congested to reach. Microkrete HS3 solves this in the mix design rather than the application. Polymer modification lowers internal friction and raises flowability at a controlled water content, so the mix moves under gravity or light pump pressure and wraps around reinforcement and blockouts without external energy input. The same polymer chemistry that gives it flow also restrains shrinkage as it cures — plain cementitious mixes lose volume while drying and pull away from the substrate they’re meant to be bonding to, which is exactly where repairs fail years later. Controlling that shrinkage is what keeps the encasement in full contact with old concrete and rebar long after the pour has set, instead of curing into a shell with hidden voids behind it.
Where it is used
- Column and beam jacketing to restore or increase load capacity
- Repair of spalled, corrosion-damaged RCC sections
- Micro-concreting of slabs and structural members during RC restoration
- Filling congested reinforcement pockets a vibrator can’t reach
- Grouting and encasement behind existing formwork
- Reinstating cover concrete after corrosion-repair work
- Pile-cap and foundation repair in congested layouts
- Flowable, non-shrink infill for precast connections
Key advantages
- Self-compacting — no vibration needed, so it reaches spaces a poker vibrator physically can’t
- Non-shrink formulation keeps repairs in full contact with substrate and rebar
- Single-bag system — nothing to proportion or mismeasure on site
- Designed 40 MPa strength covers most jacketing and repair specifications
- Pours or pumps, depending on site access conditions
- Extendable with up to 8 mm aggregate for larger-volume pours
- Factory-controlled quality, consistent batch to batch
- Backed by UltraTech’s nationwide manufacturing and stock availability
Limitations & considerations
- Rated to 40 MPa only — specify HS2 or HS1 where the design calls for 60 or 80 MPa
- Water ratio is unforgiving — a slightly wet mix sharply cuts strength and bond
- Not a substitute for ordinary RMC on large, unrestricted structural pours
- Six-month shelf life; damp or aged stock shouldn’t go into structural work
- Needs sound surface prep and proper shuttering — it fills space, it doesn’t fix poor formwork
Selection & best practice
Treat the water ratio as non-negotiable — measure by weight, not by eye, and stay within 11-13% for the neat mix (6-8% once aggregate is added). Mix mechanically to a thick, lump-free consistency, let it stand for about two minutes to mature, then give it a short remix before pouring — skipping that maturation step is a common reason site batches underperform. Pour continuously through a funnel or header box rather than in stages, and keep formwork properly sealed and braced, since the mix is fluid enough to find any gap. Once it’s placed, resist the instinct to vibrate it; an unfilled pocket is a formwork or pour-rate problem to fix on the next lift, not something to chase with a poker vibrator. Store bags off the ground, away from moisture, and use within the shelf life — ageing stock is a common, avoidable cause of underperformance.
Specifications
| Product Type | Single-component, polymer-modified cementitious micro-concrete |
| Designed Compressive Strength (HS3) | Up to 40 MPa |
| Water Demand (neat mix) | 11-13% by weight of powder |
| Water Demand (with aggregate extension) | 6-8% by weight of powder |
| Aggregate Extension | Up to 8 mm graded aggregate, blended up to 1:1 by weight |
| Approx. Yield | 14-15 litres per 25 kg bag at 13% water/powder ratio |
| Bulk Density (dry powder) | 1500-1650 kg/m3 |
| Wet Density (mixed) | 2250-2350 kg/m3 |
| Standards Referenced | ASTM D109, ASTM C580, IS 5816:1999, IS 1237:2012 |
| Pack Sizes | 25 kg and 40 kg bags |
| Shelf Life | 6 months from manufacture, stored cool and dry |
| Vibration Requirement | None — self-compacting; pour or pump only |
Industry use cases
Bridges & Flyovers
Pier and column jacketing to restore section after corrosion loss, without shutting down traffic for extended vibration work.
Industrial & Process Plants
Encasing corroded RCC columns near live equipment, where vibration and noise restrictions rule out conventional repair mortar.
Residential & Commercial Towers
Jacketing columns flagged in structural audits ahead of re-occupancy or change of use.
Marine & Coastal Structures
Repairing chloride-damaged jetty and seawall columns where dense rebar leaves no room for hand-packed mortar.
Frequently asked questions
Does Microkrete HS3 need to be pumped, or can it be poured?
Should I vibrate it after pouring, like normal concrete?
What’s the actual difference between HS1, HS2 and HS3?
Can I stretch the yield by adding aggregate?
How soon can formwork be struck?
How we position UltraTech Microkrete HS3
Within the UltraTech range, HS3 sits alongside Microkrete HS1 (80 MPa) and HS2 (60 MPa) — same working method, different design strength, so it’s usually a matter of specifying up rather than switching products if a job calls for more. For the surface prep and bonding work that typically accompanies a jacketing job — rebar priming, bonding coats between old and new concrete, corrosion inhibitors — Space Arc also stocks Fosroc’s Renderoc repair range and Sika’s MonoTop system, so a full repair sequence can be sourced from one supplier instead of mixing brands mid-project.
Fosroc Fosroc Renderoc RG — Renderoc RG is Fosroc’s equivalent single-component, shrinkage-compensated microconcrete for the same congested-rebar, pour-only repair work, rated to a comparable 50 N/mm2 — a direct swap on jobs where the specification names Fosroc rather than UltraTech.
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