STP ShaliPlast SP PQC
A chloride-free, naphthalene-based superplasticizer built specifically for pavement quality concrete, giving slip-form paving crews the workability and water reduction that PQC mixes demand.
What is it?
A high-range water-reducing admixture from STP based on sulphonated naphthalene polymers (SNF), supplied as a brown liquid that disperses instantly in the mixing water and carries a nil chloride content.
Where is it used?
Pavement quality concrete for national highways and expressways, airport aprons and runways, slip-form paved roads, industrial hardstandings and heavy-duty floor slabs.
Why use it?
It reduces mixing water by 15-20% at the same workability, so PQC mixes reach the target strength and durability without the bleed, segregation or high water-cement ratio that plague under-dosed paving concrete.
How is it applied?
Added to the mixing water or the wet mix at the batching plant at the dosage established by trial; never dry-dosed onto aggregate and never added to dry cement.
About STP ShaliPlast SP PQC
STP ShaliPlast SP PQC sits in a narrow but demanding niche: it is a superplasticizer formulated around the specific rheology that pavement quality concrete needs. PQC is not ordinary structural concrete. It is placed by slip-form or fixed-form pavers in continuous runs, it must hold a controlled slump long enough to consolidate under a vibrating screed, and it has to develop the flexural strength that IRC and MORTH specifications call for on highway and airfield work. A general-purpose plasticizer often overshoots on flow or bleeds under the paver; ShaliPlast SP PQC is tuned to the middle ground where the concrete stays cohesive yet fully compactible.
Chemically it belongs to the sulphonated naphthalene polymer (SNF) family, the same proven high-range water-reducer class used across Indian infrastructure for decades. It arrives as a brown liquid that is instantly dispersible in water, which makes batching straightforward at busy paving plants. Its defining commercial feature is that it is chloride-free: for pavements that carry reinforcement, dowel bars, tie bars and embedded steel, a nil-chloride admixture removes one of the classic drivers of long-term corrosion. That combination of PQC-specific behaviour and clean chemistry is why specifiers reach for it on road and runway packages rather than a bulk-market plasticizer.
The technical insight
SNF superplasticizers work by electrostatic dispersion. The long sulphonated naphthalene molecules adsorb onto the surface of cement grains and impart a strong negative charge, so the particles repel each other instead of flocculating into water-trapping clumps. Freeing that trapped water is what lets the mix flow at a much lower water content, which is the whole game in PQC: a lower water-cement ratio means a denser paste, higher flexural and compressive strength, lower permeability and better abrasion resistance under traffic. Because ShaliPlast SP PQC delivers 15-20% water reduction, a paving mix can hit its strength target while keeping the free-water and paste volume low enough to resist plastic shrinkage cracking and edge slump during slip-forming. The electrostatic mechanism also acts fast and cleanly, so the admixture improves cohesion and finishability without the sticky, over-retarded behaviour that would stall a continuous paving train.
Where it is used
- Dry lean concrete and pavement quality concrete for national highways and expressways
- Slip-form paved concrete carriageways and continuous paving trains
- Airport runway, taxiway and apron concrete carrying heavy wheel loads
- Industrial yard concrete, container depots and heavy-duty hardstandings
- Reinforced and dowelled rigid pavements where a nil-chloride admixture is mandatory
- High-strength precast paving elements and kerb units
- Ready-mix supply to road projects needing controlled, cohesive workability
- Ground floor and warehouse slabs requiring low water-cement ratio and abrasion resistance
Key advantages
- Cuts mixing water by 15-20% at equal workability, lowering the water-cement ratio and lifting flexural and compressive strength
- Nil chloride content, so it is safe for reinforced, dowelled and tie-bar pavements without adding corrosion risk
- Formulated specifically for PQC rheology – cohesive enough to resist bleed yet fully compactible under a paver
- Compatible with slip-form and fixed-form paving methods
- Proven SNF chemistry with a long track record on Indian highway and airfield infrastructure
- Brown liquid that disperses instantly in water, giving consistent, error-free batching at high-throughput plants
- Denser, less permeable concrete that improves durability and abrasion resistance under traffic
- Supports mix designs written to IRC and MORTH pavement specifications
Limitations & considerations
- It is a water reducer and workability aid, not a set retarder – in hot weather or long haul distances a separate retarder or ShaliPlast SP may be needed to hold slump
- Naphthalene-based admixtures give a shorter workability window than polycarboxylate (PCE) types, so a distant plant-to-paver cycle can outrun the slump life
- Overdosing can cause bleeding, segregation or excessive retardation; the correct dose must be fixed by site trial with the actual cement and aggregates
- Performance shifts with cement chemistry, temperature and admixture combinations, so results from one mix should not be assumed for another
- It reduces water demand but does not by itself entrainment air or protect against freeze-thaw; a separate air-entrainer is required where that is specified
Selection & best practice
Always establish the dosage by laboratory and field trial using the project’s own cement, aggregates and target flexural strength rather than a generic figure; for SNF plasticizers the working range under IS 9103 typically falls around 0.3-1.5% by mass of cement, but the paving mix design governs. Add ShaliPlast SP PQC to the mixing water or to the wet mix in the pan, never to dry cement or dry aggregate, and allow full mixing time so it disperses uniformly. Do not exceed the trial dosage chasing extra flow – overdosing is the usual cause of bleed and retardation on paving jobs. Keep an eye on plant-to-paver haul time and ambient temperature; on long hauls or hot afternoons, pair it with a retarding admixture so the slump survives to the paver. Store the drums under cover, protected from direct sun and frost, keep them sealed to prevent evaporation, and stir before use if the container has stood for a long period. Confirm compatibility whenever it is combined with any other admixture, and consult the STP TDS and MSDS for handling and safety before use.
Specifications
| Product type | High-range water-reducing admixture (superplasticizer) for PQC |
| Chemical base | Sulphonated naphthalene polymers (SNF) |
| Appearance | Brown liquid, instantly dispersible in water |
| Chloride content | Nil (chloride-free) |
| Water reduction | 15-20% at equal workability |
| Primary application | Pavement quality concrete for roads, highways and runways |
| Admixture standard | SNF high-range water reducer, IS 9103 / ASTM C494 admixture family |
| Specification context | Suited to IRC and MORTH pavement quality concrete requirements |
| Dosage | Established by trial (SNF plasticizer range typically 0.3-1.5% by mass of cement per IS 9103) |
Industry use cases
Highways & expressways
On slip-form paved carriageways, the admixture lets the PQC mix flow and consolidate under the paver at a low water-cement ratio, so the pavement reaches its specified flexural strength and durability.
Airports
For runway, taxiway and apron concrete carrying heavy aircraft loads, the 15-20% water reduction produces the dense, low-permeability, high-strength concrete these pavements demand.
Industrial pavements
Container yards, logistics hardstandings and heavy-duty floor slabs benefit from the tighter water-cement ratio, giving better abrasion resistance and less cracking under wheel traffic.
Reinforced rigid pavements
Where pavements carry dowel bars, tie bars or reinforcement, the nil-chloride formulation delivers workability without introducing chlorides that could corrode embedded steel.
Ready-mix & precast
RMC plants supplying road projects and precast paving units get consistent, cohesive workability and reliable batching from a liquid that disperses instantly in the mix water.
Frequently asked questions
What makes ShaliPlast SP PQC different from an ordinary superplasticizer?
Is it chloride-free, and why does that matter for pavements?
What dosage should we use?
How is it added to the mix?
Does it retard the set or hold slump on long hauls?
Which standards and specifications does it suit?
How we position STP ShaliPlast SP PQC
ShaliPlast SP PQC is the paving-specific member of STP’s ShaliPlast admixture range. Where a project needs a general high-range water-reducing-cum-retarding admixture for structural or ready-mix concrete rather than pavements, STP ShaliPlast SP (formerly ShaliCon 537) is the natural companion, and for next-generation polycarboxylate performance and extended slump retention on long hauls, look at STP’s ShaliPlast PCE range. On the curing side, pair PQC placement with an STP membrane curing compound such as ShaliCure to protect the fresh surface. Space Arc also stocks equivalent SNF and PCE superplasticizers from Fosroc, Sika, MC-Bauchemie and Master Builders Solutions, so if a specification is written around another brand’s admixture we can cross-supply a genuinely matched product with the supporting data sheet.
Fosroc Conplast SP430 — Choose the Fosroc SNF superplasticizer when the project specification is written around Conplast SP430 or the Fosroc admixture system, or when a single-source Fosroc supply chain is preferred across the concrete package.
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