STP ShaliBond 41
A two-component, non-sag structural epoxy that works as both a high-strength adhesive and a fast-setting repair mortar on vertical and overhead concrete.
What is it?
A solvent-free, two-part thixotropic epoxy that mixes 2:1 by weight into a concrete-grey paste, doubling as a structural bonding adhesive and a fast-setting repair mortar.
Where is it used?
Concrete spall repair, crack and rigid-joint filling, and structural bonding of stone, masonry, steel and timber, especially on vertical faces and soffits where ordinary mortars slump.
Why use it?
It builds over 45 MPa in 24 hours and above 70 MPa at 7 days, needs no primer, tolerates damp substrates, and stays put on overhead work thanks to its non-sag body.
How is it applied?
Blend Component A into B at 2:1 by weight for three minutes with a slow-speed drill, then trowel or hand-apply 2 to 30 mm thick; as an adhesive, butter both faces and support heavy pieces until cured.
About STP ShaliBond 41
STP ShaliBond 41 is a two-component, solvent-free thixotropic epoxy that earns its place on site by doing two jobs at once. Straight out of the pack it behaves as a structural bonding adhesive, and with the same mix you can trowel it in as a fast-setting repair mortar. The white base (Component A) and black hardener (Component B) combine at a 2:1 ratio by weight into a homogeneous concrete-grey paste with a mix density of 1.92 kg per litre. Because the material is thixotropic and non-sag up to 10 mm, it holds its shape on vertical faces and overhead soffits, which is where most cement-based patch repairs simply slump off the wall.
For engineers and applicators across Delhi NCR and pan-India, the appeal is the strength-to-effort ratio. ShaliBond 41 meets ASTM C 881, Type I and II, Grade 3, Class B and C, and develops a compressive strength above 45 MPa within 24 hours and beyond 70 MPa at seven days when tested to ASTM C 579. Tensile adhesion exceeds 10 N/mm² to ASTM C 882, tensile strength is at least 8 N/mm² to ISO 527, and flexural strength reaches 20 N/mm² or more at seven days. It bonds to dry or damp concrete, needs no separate primer, and cures without shrinkage, so it suits both quick defect repairs and load-path-critical bonding where a single, reliable epoxy is preferred over juggling several products.
The technical insight
The behaviour that defines ShaliBond 41 is thixotropy paired with a cold-cure epoxy chemistry. A thixotropic paste has high viscosity at rest but flows under the shear of a trowel, so the material spreads cleanly during application yet firms up the moment you stop working it. That is why it stays non-sag up to a 10 mm layer on vertical and overhead surfaces without primers, formwork, or thickeners added on site. The two-part epoxy cures by chemical reaction between the resin base and the amine hardener rather than by drying, which is why humidity does not stall the reaction and why a damp but sound substrate is acceptable. Curing without solvent evaporation also means there is no shrinkage as it hardens, so the repair does not pull away from the parent concrete or open micro-cracks at the bond line. The result is an interface where the cured epoxy is typically stronger than the surrounding concrete, letting the repair genuinely share load rather than merely fill a void.
Where it is used
- Sealing and filling structural cracks and rigid joints in concrete members
- Reinstating spalled or honeycombed concrete on columns, beams and soffits
- Structural bonding of precast or repair sections to hardened concrete
- Bonding natural stone, brick, block masonry, steel, iron, aluminium and timber
- Fast-setting mortar repairs on vertical and overhead surfaces
- Fixing anchors, dowels and inserts into prepared concrete
- Patching damp but sound concrete where cementitious mortars would fail to bond
- Localised repairs on beams, columns, water-retaining structures and industrial floors
Key advantages
- Adhesive and repair mortar in a single product, cutting the number of items on site
- High early strength, above 45 MPa at 24 hours and over 70 MPa at 7 days
- Non-sag body allows clean vertical and overhead application up to a 10 mm layer
- Moisture-tolerant, bonding to both dry and damp concrete surfaces
- Cure is unaffected by humidity, useful in Indian monsoon and coastal conditions
- No primer required, saving a coat and a wait on the programme
- Hardens without shrinkage, protecting the bond line from cracking
- Solvent-free and impermeable to liquid and water vapour once cured
Limitations & considerations
- Formulated for hand or trowel application, not for pressure crack injection
- Substrate must be cured at least 28 days with minimum 25 N/mm² compressive strength and 1.5 N/mm² pull-off
- Pot life is only 30 to 40 minutes at 30 degrees C, so mix in workable batches
- Maximum layer thickness is 25 to 30 mm per pass; deeper repairs need building up
- Cured material can only be removed mechanically, so tools must be cleaned immediately
- Heavy components bonded vertically or overhead need temporary support until cured
Selection & best practice
Start with substrate discipline. The concrete should be at least 28 days old, sound, and open-textured, with laitance and all loose or friable particles removed and a minimum compressive strength of 25 N/mm² and pull-off of 1.5 N/mm². Add Component A to Component B at 2:1 by weight and mix for a full three minutes with a slow-speed drill at 500 to 600 rpm on a suitable paddle until the colour is uniform grey with no streaks. Work only what you can place inside the 30 to 40 minute pot life at 30 degrees C, and remember pot life shortens as temperature rises. Apply with a spatula, trowel, notched trowel or gloved hand in layers of 2 mm minimum to 25 to 30 mm maximum. When bonding, butter both mating faces and provide temporary support for any heavy piece placed vertically or overhead until the adhesive has hardened. Clean tools with STP Epoxy Thinner immediately, because once cured it can only be removed mechanically.
Specifications
| Composition | Two-component, solvent-free thixotropic epoxy adhesive and mortar |
| Standard compliance | ASTM C 881, Type I & II, Grade 3, Class B & C |
| Mixing ratio (A:B by weight) | 2 : 1 |
| Compressive strength (ASTM C 579) | > 45 MPa at 24 hours, > 70 MPa at 7 days |
| Tensile adhesion strength (ASTM C 882) | greater than or equal to 10 N/mm2 |
| Consumption | 2.0 to 2.1 kg/m2 per mm thickness |
| Pot life at 30 C (100 g mass) | 30 to 40 minutes |
| Layer thickness | 2 mm minimum to 25 to 30 mm maximum |
| Pack size / shelf life | 12 kg pack (6 kg x 2); 12 months unopened |
Industry use cases
Structural repair and rehabilitation
Reinstating spalled cover and sealing cracks on columns, beams and soffits where the non-sag body allows overhead work without formwork.
Precast and construction bonding
Structurally bonding precast segments, repair sections and dowels to hardened concrete with a bond typically stronger than the parent substrate.
Industrial and process facilities
Localised epoxy repairs on floors, plinths and equipment bases where solvent-free, chemical-resistant, high-early-strength patching keeps downtime short.
Water-retaining and coastal structures
Patching damp but sound concrete in tanks, sumps and marine-exposed elements, using the material’s moisture tolerance and vapour impermeability.
Mixed-material fixing
Bonding stone, masonry, steel, aluminium and timber to concrete in restoration and fit-out work where one versatile structural adhesive is preferred.
Frequently asked questions
Can ShaliBond 41 be used for overhead and vertical repairs?
Is it an adhesive or a repair mortar?
Can I use it on damp concrete?
What is the coverage and pot life?
Does it need a primer?
Can it be injected into cracks under pressure?
How we position STP ShaliBond 41
ShaliBond 41 sits in STP’s ShaliBond structural adhesive family, alongside ShaliBond S and ShaliBond TPE, and pairs naturally with STP’s ShaliFix repair mortars and epoxy primers on a full repair package. Where the job needs low-viscosity pressure injection of fine cracks rather than trowel-applied filling, move to an injection-grade epoxy resin, and for large-volume horizontal reinstatement a graded-aggregate epoxy mortar is more economical than buttering by hand. Across our other brands, teams often specify Sika, Dr. Fixit or MC-Bauchemie equivalents where a project already standardises on that supplier; we stock parallel options so the specification, not the label, drives the choice.
Fosroc Nitomortar S — A specifier working to a Fosroc-approved schedule may prefer Nitomortar S, a factory-batched three-part epoxy mortar with pre-graded silica, for larger horizontal structural reinstatement where ShaliBond 41’s non-sag vertical behaviour is not the priority.
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