Sika WT-100P IN
A pore-blocking integral admixture that builds waterproofing into the concrete itself, so watertightness no longer depends on a membrane installed correctly on site.
What is it?
An integral waterproofing admixture from Sika’s WT-100 series that blocks the capillary pores inside concrete, reducing its permeability across the full cross-section rather than treating only the surface.
Where is it used?
Below-ground and water-retaining concrete: basement rafts and retaining walls, water tanks and reservoirs, tunnel linings, podium and car-park decks, and other structures that must stay watertight under hydrostatic pressure.
Why use it?
It makes the concrete itself the waterproofing barrier, so performance does not hinge on the quality of a surface membrane that can be punctured, poorly lapped, or damaged during backfilling.
How is it applied?
Dosed into the concrete during batching at roughly 1-3% by weight of cement, dispersed uniformly through the mix, and placed and cured as normal watertight concrete.
About Sika WT-100P IN
Sika WT-100P IN belongs to the water-resisting, pore-blocking family within Sika’s watertight concrete range, and it approaches waterproofing from a different direction to the surface membranes most site teams are used to. Instead of wrapping a finished structure in a sheet or a coating, the admixture is added to the concrete while it is still in the mixer, so the finished element is inherently more resistant to water. That distinction matters on Indian sites, where basement rafts, water tanks and retaining walls often fail not because the specified membrane was wrong, but because it was lapped badly, tore during backfilling, or was compromised at a construction joint no one could reach afterwards. Building the resistance into the concrete removes that single point of failure.
For engineers and contractors, the practical appeal is control and durability. Because the active chemistry is distributed evenly through the pour, the whole cross-section carries the same reduced permeability rather than relying on a skin a few millimetres thick. That is particularly useful for thick, heavily reinforced sections and for structures that will be permanently buried or submerged, where re-access for repair is expensive or effectively impossible. Space Arc Engineering supplies WT-100P IN as an authorised Sika distributor and applicator across Delhi NCR and pan-India, and we would always recommend confirming the exact grade, dosage and the current Sika Product Data Sheet against your specific mix design before you commit a large pour.
The technical insight
The mechanism is pore-blocking rather than crystal-growing. Concrete is not solid; as cement hydrates it leaves behind an interconnected network of fine capillary pores and micro-voids, and it is this network that lets water track through a wall under pressure. The active components in WT-100P IN react with the calcium hydroxide and other products of cement hydration to precipitate insoluble compounds inside those capillaries. Those deposits physically narrow and block the pathways, so the concrete’s permeability drops substantially compared with an untreated control mix. Because the reaction feeds on the concrete’s own chemistry and moisture, the pore structure stays sealed over the life of the element rather than degrading like a sacrificial surface layer. It is worth being clear about what it is and is not: this is a water-resisting, pore-blocking admixture, distinct from Sika’s crystalline WT-200 range, which additionally regrows crystals to re-seal fine cracks. For hairline-crack self-sealing as a headline requirement, the crystalline grade is the more direct answer.
Where it is used
- Basement rafts, retaining walls and below-ground boxes that must resist standing groundwater
- Water-retaining structures such as tanks, reservoirs and treatment plant compartments
- Tunnel linings and other underground infrastructure with limited re-access
- Podium slabs and car-park decks over occupied or sensitive spaces
- Sewage and effluent containment and industrial process tanks
- Foundation and substructure concrete where an external membrane is hard to protect during backfilling
- Thick, heavily reinforced sections where full-depth low permeability is preferred over a thin surface layer
- Watertight concrete specified as a primary or secondary barrier within a designed waterproofing system
Key advantages
- Waterproofing is integral to the concrete, so it is not dependent on membrane workmanship or on-site protection
- The full cross-section carries reduced permeability, not just a thin treated skin
- No sheet laps, terminations or penetrations to detail, chase and seal
- Cannot be punctured or torn during subsequent trades, backfilling or steel fixing
- Protects concrete that is permanently buried or submerged and effectively impossible to re-access for repair
- Added at the batching stage, so it fits the normal ready-mix or site-mix workflow
- Suited to thick and congested sections where membranes are awkward to apply cleanly
- Supplied with distributor and applicator support from Space Arc across Delhi NCR and pan-India
Limitations & considerations
- It is a water-resisting, pore-blocking admixture, not a crystalline self-healing product; wide or moving cracks still need dedicated crack treatment
- It reduces permeability but does not make concrete waterproof on its own; good mix design, low water-cement ratio, proper compaction and curing remain essential
- Construction joints, tie-holes, penetrations and movement joints must still be waterstopped and detailed separately
- Performance depends on accurate, consistent dosing through the mix; a fresh trial mix with the actual cement and design is strongly advised
- For potable-water contact the specific grade and any certification must be confirmed with Sika before use
- Dosage and workability can interact with other admixtures in the mix, so compatibility should be checked
Selection & best practice
Treat WT-100P IN as one component of a designed watertight-concrete system, not a standalone cure. Start from a sound mix: a low water-cement ratio, well-graded aggregate, and a cement content that supports durable, low-permeability concrete. Run a trial batch with your actual cement, supplementary materials and other admixtures to confirm dosage, workability and setting before any structural pour. Dose within the recommended band, add and disperse it thoroughly during batching so the chemistry is uniform through every part of the pour, and avoid topping up water on site, which undoes much of the benefit. Compaction and curing still decide the outcome, so vibrate to remove voids and cure the concrete properly. Crucially, keep waterstopping and joint detailing in the design; the admixture densifies the body of the concrete, but construction joints, movement joints and penetrations remain the routes water will exploit if they are left untreated.
Specifications
| Product type | Pore-blocking integral waterproofing (water-resisting) admixture |
| Series | Sika WT-100 watertight concrete range |
| Mechanism | Reacts with cement hydration products to precipitate insoluble compounds that block capillary pores |
| Typical dosage | Approximately 1-3% by weight of cement (confirm on current PDS and by trial mix) |
| Effect on permeability | Substantial reduction versus an untreated control mix |
| Point of addition | Added during concrete batching / mixing |
| Cement compatibility | Suitable with Portland cement and SCM-blended mixes |
| Distinction from WT-200 | Water-resisting/pore-blocking, not the crystalline self-sealing grade |
Industry use cases
Commercial & residential basements
Rafts, retaining walls and lift pits below the water table where an external membrane would be vulnerable during backfilling and impossible to repair later.
Water & wastewater
Tanks, reservoirs, sumps and treatment-plant compartments that must stay watertight under continuous hydrostatic head.
Infrastructure & tunnelling
Underground boxes, tunnel linings and utility structures where full-depth low permeability protects concrete that cannot be re-accessed.
Podiums & parking decks
Podium and car-park slabs over occupied space, where integral watertightness backs up the deck waterproofing system.
Industrial containment
Process tanks, bunds and effluent structures needing durable resistance to water and moisture ingress across thick sections.
Frequently asked questions
Is Sika WT-100P IN a crystalline waterproofing admixture?
Does adding this admixture mean I can skip the waterproofing membrane and waterstops?
What is the dosage and how is it added?
Will it affect the strength or workability of my concrete?
Can it be used for potable water tanks?
Does Space Arc supply and support this product in Delhi NCR and elsewhere in India?
How we position Sika WT-100P IN
Position WT-100P IN as the entry point to Sika’s watertight concrete range: it is the water-resisting, pore-blocking grade. When a project’s headline need is self-sealing of fine cracks, step up within the same family to Sika’s crystalline SikaControl WT-200 P (IN). For liquid integral waterproofing of concrete, mortar and plaster, the SikaCim range and Sika Plastocrete Plus/Super sit alongside it, and Sika Noleek covers powder-based needs. From our other brands, Fosroc’s Conplast integral admixtures are the natural Indian-standard alternatives, and Dr. Fixit offers comparable integral solutions where a client is standardised on that brand. Whichever admixture is chosen, remember it densifies the concrete body only, so pair it with the right waterstops, joint sealants and, where the design calls for it, a surface membrane to complete the watertight system.
Fosroc Conplast X421IC — A specifier working to IS:2645 or already standardised on Fosroc may prefer this integral liquid admixture, which lowers permeability by reducing water demand and densifying the matrix rather than by pore-blocking chemistry.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.