STP ShaliPlast IW
IS 2645-compliant liquid admixture from STP Limited that waterproofs concrete, mortar and plaster from within — added to the gauging water at just 0.2–0.4% by weight of cement.
What is it?
A brownish liquid integral waterproofing compound from STP Limited, formulated on surface-active agents, plasticisers and polymer, conforming to IS 2645:2003 and IS 9103:2000.
Where is it used?
RCC and PCC elements, screeds, mortars and plasters — basements, roof slabs, terraces, water tanks, sunken slabs, sumps, drains and external renders across new construction.
Why use it?
Cuts water permeability to under half that of an untreated control mix while keeping compressive strength equal to control, with chloride content below 0.02%.
How is it applied?
Dispersed into the final portion of gauging water at 0.2–0.4% by weight of cement — roughly 100–200 ml per 50 kg bag — during normal batching, then mixed and placed as usual.
About STP ShaliPlast IW
ShaliPlast IW is STP Limited’s integral waterproofing compound for concrete, mortar and plaster — a brownish liquid that goes into the mix itself rather than onto the finished surface. Built on a blend of surface-active agents, plasticisers, polymer and performance additives, it works by tightening the capillary network that water would otherwise travel through. The product carries dual conformity to IS 2645:2003 (integral waterproofing compounds) and IS 9103:2000 (concrete admixtures), which lets consultants specify it for both waterproofing performance and admixture behaviour in RCC without a separate approval trail.
For site engineers, the appeal is operational as much as technical. There is no surface preparation, no separate applicator gang and no waiting for a coating to cure — waterproofing happens in the mixer, at a dosage small enough to measure with a graduated jug. Space Arc Engineering stocks ShaliPlast IW in 1 L, 5 L, 20 L and 200 L packs for supply across Delhi NCR and pan-India, from single-bungalow plaster jobs to RMC-batched pours.
The technical insight
Concrete leaks primarily through its capillary pore network — fine channels left behind as excess mixing water evaporates. ShaliPlast IW attacks this on two fronts. Its plasticising fraction improves workability at a given water content, so the mix needs less free water and forms fewer capillaries in the first place. Its surface-active agents and polymer then line and block the capillaries that do form, making them hydrophobic so water cannot wick through. The lab numbers reflect this mechanism: water permeability drops below 50% of the control mix while compressive strength stays equal to control — you are removing pathways, not paste. Because the film is pore-level rather than surface-level, the concrete keeps breathing, and with chlorides held under 0.02% the admixture adds nothing that threatens rebar passivation.
Where it is used
- Basement rafts, retaining walls and roof slabs in RCC
- Floor screeds and PCC levelling or blinding courses
- Overhead and underground water tanks, sumps and reservoirs
- Terraces, balconies and sunken slabs in bathrooms and toilets
- Storm and sanitary drains and minor water-retaining works
- External and internal cement plaster on masonry
- Site-mixed waterproof mortars for bedding and rendering
Key advantages
- Water permeability below 50% of the untreated control mix, tested per IS 2645:2003
- No strength penalty — compressive strength equal to the control mix
- Chloride content under 0.02%, safe for use around reinforcement
- Improves workability and cohesion of the fresh mix, helping full compaction
- Reduces shrinkage crack development in RCC, PCC and plaster
- Retains the breathability of concrete — no vapour-sealing surface film
- Dosed through the gauging water with no extra plant, gang or downtime
- Economical per cubic metre versus surface-applied systems, in packs from 1 L to 200 L drums
Limitations & considerations
- Works only in new concrete, mortar or plaster — it cannot remediate leakage in an existing structure
- Not a substitute for membrane or crystalline systems on basements under sustained hydrostatic head or other critical wet areas; treat it as the first line of defence, not the only one
- Overdosing beyond 0.4% by weight of cement can retard setting — the setting-time window spans 40 to 550 minutes across the dosage band, so dose control matters
- It cannot compensate for poor workmanship: honeycombing, cold joints and inadequate curing will leak regardless of admixture
- Must be dispersed in the gauging water; pouring it neat onto dry aggregates gives uneven distribution and patchy performance
Selection & best practice
Run a trial mix first to fix the dosage within the 0.2–0.4% band for your cement content and target workability — dosage is always calculated on the weight of cement, not total mix. Follow the TDS batching sequence: charge cement, sand and aggregate per the mix design and dry-mix for 2 minutes; add 75–80% of the mixing water and mix for 3 minutes; dispense ShaliPlast IW into the remaining water, add it, and wet-mix for 2 minutes; give a final 2-minute mix before placing. Never exceed the recommended dosage — the main penalty is retarded setting. Compact thoroughly and cure per good practice; an integral compound performs only as well as the concrete around it. Store sealed packs cool and shaded; shelf life is 12 months unopened.
Specifications
| Form / colour | Brownish liquid |
| Specific gravity (27°C) | 1.06 ± 0.01 |
| Non-volatile content | 14 ± 1% |
| Chloride content | < 0.02% |
| Water permeability | < 50% of control mix |
| Compressive strength | Equal to control mix |
| Dosage | 0.2–0.4% by weight of cement (approx. 100–200 ml per 50 kg bag) |
| Standards | IS 2645:2003; IS 9103:2000 |
| Packing | 1 L, 5 L, 20 L and 200 L |
Industry use cases
Residential & Group Housing
Dosed into sunken-slab fills, terrace screeds and bathroom plaster in apartment projects, cutting the seepage callbacks that dominate post-handover complaints.
Commercial Basements
Added to basement rafts and retaining walls as integral back-up beneath the membrane system, so a local membrane defect does not become a wet basement.
Water Infrastructure
Specified in overhead tanks, underground reservoirs, sumps and drains where IS 2645 conformity and low chloride content satisfy departmental approval requirements.
Industrial Sheds & Flooring
Mixed into PCC sub-bases and floor screeds in warehouses and light industrial units to limit rising dampness through ground-supported slabs.
Facade & Renovation Plastering
Gauged into external render on wind-driven-rain-exposed elevations, reducing water absorption and shrinkage cracking in the plaster coat.
Frequently asked questions
What is the dosage per 50 kg bag of cement?
Will ShaliPlast IW reduce concrete strength?
Can it replace a basement waterproofing membrane?
Is it safe for reinforced concrete?
How is it added — to the water or the dry mix?
What pack sizes are available and how long does it keep?
How we position STP ShaliPlast IW
Within the STP range, ShaliPlast IW is the everyday integral waterproofer; step up to ShaliPlast IW CI where chloride exposure calls for built-in corrosion inhibition, pair it with ShaliCem EWP elastomeric cementitious coating for wet-area surfaces, or move to ShaliCrystal 100 where a crystalline self-healing system is specified. Among the other brands Space Arc distributes, Fosroc Conplast WL is the closest like-for-like liquid and Conplast WP90 Powder suits sites that prefer bag-dosed powder admixtures. Talk to our team to match the system to your spec and water table.
Fosroc Conplast WL — Specifiers already standardised on Fosroc, or preferring a lignosulphonate-based liquid with the same IS 2645:2003 conformity and a long institutional track record, typically choose Conplast WL.
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