Sika Intraplast Z
Powder expanding admixture that makes site-batched cement grout swell before it sets, closing shrinkage gaps in cable ducts, anchor pockets and cavity fills.
What is it?
A ready-to-use grey powder admixture that you add to site-batched cement grout. It generates a fine, even distribution of inert hydrogen gas bubbles, so the grout expands slightly before setting instead of shrinking away from the surfaces it is meant to fill.
Where is it used?
Grouting of post-tensioning and prestressing cable ducts, filling cavities in rock and loose soil, and general injection work where a dense, void-free fill matters. Widely specified by contractors and PT specialists across Delhi NCR and pan-India projects.
Why use it?
Ordinary cement grout bleeds and shrinks as it sets, leaving voids that trap water and expose steel. Intraplast Z counteracts that with controlled plastic-stage expansion, reduced bleed and prolonged workability, giving a fuller, more durable fill.
How is it applied?
Dosed at 1-2% by weight of cement and dry-mixed into the grout (water-cement-Intraplast Z, or sand-cement-admixture-water where sand is used), then pumped and placed within 15 minutes of mixing to capture the full expansion.
About Sika Intraplast Z
Sika Intraplast Z is one of the older, more trusted names in cable-duct and cavity grouting, and it earns that reputation by doing one job reliably: making a site-batched cement grout expand a little instead of shrinking as it hardens. It arrives as a grey, free-flowing powder that is non-toxic, non-flammable and free of chlorides or other corrosive ingredients, so it can sit against prestressing steel without setting up the conditions for rust. You add it straight into the grout mix at the batching stage, which suits the reality of Indian sites where grout is proportioned by the bag rather than delivered ready-mixed.
What sets it apart from a straightforward plasticiser is the expansion mechanism. As the fresh grout hydrates, the admixture releases a large number of very fine, evenly spread gas bubbles that gently swell the mix before it stiffens. That swelling pushes grout into the corners of a duct or cavity and holds it in intimate contact with the surrounding steel or substrate, while the same fine pore structure lends the set grout good frost resistance. It is a specialist product, and Sika is clear on that point: mixing method, cement type, water content and temperature all influence how much it expands, so it belongs in the hands of crews who understand prestressing and injection grouting.
The technical insight
The core of Intraplast Z is a gas-generating expansion system rather than a metallic or chemical filler. Once the powder meets the wet, alkaline cement paste, it reacts to liberate tiny quantities of inert hydrogen, which nucleate as an extremely regular, densely distributed field of micro-bubbles throughout the grout. Because the gas forms while the grout is still plastic, the mix swells slightly and stays swollen against the duct or cavity walls, compensating for the plastic settlement and bleed that would otherwise open a gap at the top of a pour. Crucially the reaction is timed to the plastic phase, which is exactly why placement must happen within about 15 minutes of mixing; leave it longer and the grout begins to set before the expansion can do its work. The admixture also acts on the water demand of the mix, letting crews hold a controlled water-cement ratio in the 0.40-0.45 range for prestressed work while suppressing bleed, so the hardened grout is denser and better bonded to the strand it protects. Because there is no metallic iron in the formulation, there is nothing inside the grout to later corrode, stain or expand from rust.
Where it is used
- Grouting of post-tensioning and prestressing cable ducts
- Injection filling of cavities and fissures in rock
- Consolidation and filling of loose or open soil formations
- General void filling where a dense, non-shrink cement grout is required
- Bedding and gap-filling grout for structural elements
- Corrosion-protective grouting around embedded prestressing wires
- Site-batched injection grout for repair and rehabilitation cavities
Key advantages
- Causes the grout to expand before setting, compensating plastic settlement and shrinkage
- Reduces bleeding, so water does not separate and collect at the top of the pour
- Prolongs workability, giving crews more time to pump and place
- Lets you cut gauging water while keeping the mix pumpable, for a denser set grout
- Chloride-free and non-corrosive, safe against prestressing steel
- No metallic iron content, so nothing inside the grout can rust, stain or expand later
- Fine, regular pore structure lends the hardened grout good frost resistance
- Simple dry powder that dispenses straight into a site batch
Limitations & considerations
- It is a specialist product intended for crews experienced in prestressing and injection grouting, not a general-purpose additive
- Expansion is sensitive to mixing procedure, cement type, water and sand content, and temperature, so results vary if the mix is not controlled
- Cement containing fly ash can affect the amount of expansion achieved
- Grout must be placed within about 15 minutes of mixing, or the expansion benefit is lost
- For important work, preliminary site trials are needed to confirm the right mix and procedure
- It aids grout performance but is not a stand-alone product; grout quality still depends on correct cement, water and workmanship
Selection & best practice
Fix the grout mix design first, then dose Intraplast Z at 1-2% by weight of cement to suit the job. For plain cement grout the preferred sequence is water, then cement, then the admixture; where sand is included, batch sand, cement, admixture and finally water. For prestressed work a mixing time of about 4 minutes with a water-cement ratio of 0.40-0.45 gives reliable results, and sand is generally not added. Mix mechanically to disperse the powder fully, then place and pump the grout within 15 minutes so the plastic-stage expansion is captured inside the duct or cavity rather than lost in the bucket. Keep the flow continuous while injecting to avoid trapping air. On any critical structure, run a preliminary site trial with the actual cement and conditions to confirm expansion and workability before the main pour, and always read the current Safety Data Sheet before handling. Clean tools with water immediately after use; once set, the grout comes off only by mechanical means.
Specifications
| Product type | Expanding grout admixture (powder) |
| Base / mechanism | Gas-generating; releases inert hydrogen micro-bubbles |
| Appearance / colour | Grey powder |
| Recommended dosage | 1-2% by weight of cement |
| Water-cement ratio (PT work) | 0.40-0.45 |
| Placement time | Within 15 minutes of mixing |
| Chloride content | Chloride-free, non-corrosive |
| Shelf life | 12 months from date of production, unopened |
| Storage | Dry conditions, original sealed packaging, out of direct sunlight |
Industry use cases
Bridges & Flyovers
Grouting of post-tensioning cable ducts so the strand is fully encased and protected against corrosion, with no shrinkage voids at duct crowns.
Infrastructure & Tunnelling
Injection grouting to fill fissures in rock and consolidate loose soil ahead of or behind tunnel and foundation works.
High-Rise & Prestressed Buildings
Duct grouting on post-tensioned floor slabs and transfer beams where a dense, void-free fill is critical to long-term durability.
Dams & Water-Retaining Structures
Cavity and cable-duct grouting where reduced bleed and a frost-resistant pore structure improve the durability of the set grout.
Repair & Rehabilitation
Site-batched injection grout for filling cavities and gaps during strengthening and remedial works on ageing structures.
Frequently asked questions
How much Sika Intraplast Z do I add to the grout?
How does it make the grout non-shrink?
Is it safe to use around prestressing steel?
How soon must the grout be placed after mixing?
Can I add sand to the mix?
What is the shelf life and how should it be stored?
How we position Sika Intraplast Z
Sika Intraplast Z is the right call when your grout is site-batched and the priority is controlled expansion for cable-duct and cavity work. Within the Sika family, pair it with Sika grouting and PT systems for the strand and anchorage side of the job, and consider Sika ready-mixed cementitious grouts where a pre-blended non-shrink grout is preferred over batching from scratch. If you would rather use a pre-packaged flowable grout for baseplates and equipment foundations, our Fosroc Conbextra GP2 or high-strength Conbextra HF are natural alternatives. For expanding admixtures specifically, the closest counterpart is Fosroc Cebex 100 (below).
Fosroc Cebex 100 — A specifier standardised on the Fosroc system, or one who wants a stated unrestrained expansion figure for site-batched grout, may prefer Cebex 100 as the directly equivalent plasticising expanding grout admixture.
Related Concrete Admixtures products
Source Sika Intraplast Z for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.