STP ShaliPlast CI
Bipolar migratory corrosion-inhibiting admixture from STP Limited that shields embedded reinforcement from chloride attack in marine, bridge and parking-structure concrete.
What is it?
A brownish liquid, chloride-free corrosion-inhibiting admixture from STP Limited. Its migratory inhibitor travels through the concrete pore network and forms a bipolar protective layer on embedded steel.
Where is it used?
Marine and coastal RCC, bridge decks and piers, multi-level car parks, structures exposed to de-icing salts, and any reinforced concrete facing chloride-laden service conditions.
Why use it?
It suppresses both the anodic and cathodic halves of the corrosion cell, delaying chloride-induced rebar corrosion and extending structure service life without changing normal concreting practice.
How is it applied?
Dosed at 0.4–2% by weight of cement into the gauging water or the mixer — never onto dry cement. Dosage is fixed by site trials; it can also be added in the transit mixer at discharge.
About STP ShaliPlast CI
Chloride-induced corrosion of reinforcement is the single biggest durability threat to Indian coastal and highway infrastructure — and it usually starts years before the first visible crack. ShaliPlast CI from STP Limited attacks the problem at the mixing stage. Added to fresh concrete at 0.4–2% by weight of cement, its migratory inhibitor moves through the pore structure and deposits a protective layer directly on the embedded steel. Because the action is bipolar, both the anodic and cathodic reactions of the corrosion cell are restricted — not just one.
STP Limited has manufactured construction chemicals in India for more than eight decades, and ShaliPlast CI sits within its wider ShaliPlast admixture family. The product carries nil chloride content, is evaluated against ASTM G109, G3, G1 and C1582 along with JIS Z 1535, and works with all Portland cements including sulphate-resisting cement. Space Arc Engineering supplies it in 20 L and 200 L drums with pan-India delivery and application guidance.
The technical insight
Corrosion in RCC is an electrochemical cell: chlorides breach the passive oxide film at anodic sites where iron dissolves, while oxygen reduction proceeds at cathodic sites nearby. Conventional nitrite-type inhibitors act mainly on the anode. ShaliPlast CI works differently — its molecules migrate through pore moisture and adsorb onto the steel surface as a film that interferes with both half-reactions at once, which is why STP describes it as bipolar. The migratory behaviour matters on real sites: protection reaches the rebar even where mixing dispersion is imperfect, and performance against chloride ingress is reflected in RCPT values of 500–700 coulombs on treated concrete, grade-dependent. The trade-off of this surface-active chemistry is set retardation at high doses, which is exactly why the dosage window and trial mixes are non-negotiable.
Where it is used
- Jetties, wharves, seawater intakes and other marine RCC in the splash and tidal zones
- Bridge decks, piers and crash barriers exposed to chlorides or de-icing salts
- Multi-level car parking structures where vehicle-borne salts attack slabs
- Coastal building substructures — basements, rafts and piles in saline groundwater
- Precast elements destined for aggressive chloride-exposure service
- Industrial RCC near cooling towers and chemical plants with chloride-laden atmospheres
- Long-design-life infrastructure where the durability spec calls for a corrosion-inhibiting admixture
Key advantages
- Bipolar action restricts both anodic and cathodic corrosion reactions on steel
- Migratory inhibitor reaches reinforcement through the pore network, not just at points of contact
- Nil chloride content — safe for reinforced concrete by design
- Compatible with other site admixtures when each is dosed separately
- Works with all Portland cements, including sulphate-resisting cement (SRC)
- Wide 5–45°C application temperature band suits Indian site conditions year-round
- Extends service life of structures in marine and de-icing salt environments without changing placing practice
Limitations & considerations
- Overdosing severely extends setting time — trial mixes to fix the optimal dose are essential, not optional
- Not compatible with high alumina cement
- It is an admixture for fresh concrete only; it cannot arrest corrosion already underway in an existing structure — surface-applied migratory inhibitors or repair systems are needed there
- It boosts the efficiency of air-entraining agents, so AEA dosage must be cut and air content re-verified
- Must never contact dry cement — batching discipline at the plant is required
- It supplements, but does not replace, adequate cover, low w/c ratio and proper curing
Selection & best practice
Add ShaliPlast CI to the gauging water or directly into the mixer with the water — never onto dry cement. On ready-mix jobs it can be dosed into the transit mixer at the point of discharge with adequate remixing. Where multiple admixtures are in play, introduce each one separately into the mix; do not pre-blend them in the same container. Run laboratory and site trials across the 0.4–2% (by weight of cement) range, checking setting time against the retardation the pour can tolerate — the deeper the rebar and the poorer the concrete quality, the higher the dose typically needed, but never exceed the trial-established figure. If an air-entraining agent is in the mix, reduce its dose and confirm air content afresh, because ShaliPlast CI amplifies its effect. Store drums sealed, under shed, away from heat; shelf life is 12 months unopened.
Specifications
| Form and colour | Brownish liquid |
| Density | 1.04 – 1.08 g/cc |
| pH | Minimum 6 |
| Chloride content | Nil |
| Dosage | 0.4 – 2% by weight of cement (fix by trial) |
| Application temperature | 5 – 45°C |
| RCPT (treated concrete) | 500 – 700 coulombs, depending on concrete grade |
| Standards referenced | ASTM G109, ASTM G3, ASTM G1, ASTM C1582, JIS Z 1535 |
| Packing and shelf life | 20 L and 200 L drums; 12 months unopened |
Industry use cases
Marine & Ports
Berthing structures, jetty piles and seawater intakes live in the harshest chloride exposure there is. Dosing ShaliPlast CI at the batching plant builds corrosion resistance into every pour from day one.
Bridges & Highways
Decks, piers and crash barriers on coastal corridors and salt-treated routes gain a second line of defence behind the cover concrete, delaying the onset of chloride-induced corrosion.
Coastal Real Estate
Basements, rafts and pile caps in the saline groundwater belts of Mumbai, Chennai and Kochi benefit from inhibitor-dosed concrete where later access for remediation is impossible.
Parking Structures
Multi-level car parks collect vehicle-borne salts on every slab. An inhibitor admixture protects top-mat reinforcement that membranes and sealers alone often fail to save.
Industrial Plants
RCC around cooling towers, CETPs and chemical process areas faces chloride-laden spray and atmospheres; inhibitor-dosed mixes stretch maintenance intervals on hard-to-shut-down assets.
Frequently asked questions
What is the dosage of ShaliPlast CI?
Will it delay the setting of my concrete?
Can I use it along with a superplasticiser?
Can it stop corrosion in an already-built structure?
Which cements does it work with?
What pack sizes are available and how long does it keep?
How we position STP ShaliPlast CI
ShaliPlast CI slots naturally into a complete STP durability package: pair it with the ShaliPlast range of water-reducing and superplasticising admixtures for the same mix design, and turn to STP’s RestoFix repair and rehabilitation systems where corrosion damage has already set in. For projects whose specification names a calcium nitrite inhibitor, Space Arc also stocks Fosroc Conplast CN as a direct alternative — talk to us and we will match the product to your durability spec, exposure class and budget.
Fosroc Conplast CN — Specifiers who want a calcium nitrite inhibitor with a defined litres-per-cubic-metre dosage scaled to the expected chloride loading often standardise on Conplast CN, especially where the tender names nitrite-type chemistry.
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