Fosroc Conplast WP100
A chloride-free, powder-based integral waterproofing admixture that blocks capillary pores and makes concrete and mortar hydrophobic from the inside out.
What is it?
Fosroc Conplast WP100 is a free-flowing white powder integral waterproofing admixture based on organic fatty acid salts, blended with hydrophobic materials and plasticising agents that work inside the cement matrix rather than as a surface coating.
Where is it used?
Added at the batching stage into structural and precast concrete, sand:cement renders, floor screeds, mortars and plasters, basements, roof slabs and water-retaining structures across Delhi NCR and Pan-India projects.
Why use it?
It reduces concrete permeability throughout the mass, controls efflorescence and moisture movement, and keeps working even if the surface is later chipped or abraded, unlike applied films or coatings.
How is it applied?
Dosed by weight of cement (typically around 1.0%-2.0%) and added as a dry powder directly into the mix during batching, without introducing extra water into dry or semi-dry mixes.
About Fosroc Conplast WP100
Fosroc Conplast WP100 is an integral waterproofing admixture supplied as a free-flowing white powder based on organic fatty acid salts. It belongs to Fosroc’s well-established Conplast range of concrete admixtures, the same family that includes the liquid integral waterproofers Conplast WL and Conplast WL Xtra and the reactive Conplast Crystalline. Where those products are dosed as liquids, WP100 is engineered specifically as a powder so it can be introduced into dry, semi-dry and conventional wet mixes without adding any extra water, an important advantage in screeds, precast units and tile-bedding mortars where the water-cement ratio is tightly controlled. When the powder is blended into a cement-based mortar or concrete, it does two things at once. First, the hydrophobic fatty-acid components line and block the fine capillary pores that naturally form as cement hydrates, so the hardened matrix resists the passage of water and water-borne salts. Second, the plasticising fraction in the blend improves the efficiency of mixing water, allowing the same workability to be achieved at a lower water-cement ratio, which by itself produces a denser, less permeable concrete. The combined effect is a material that resists moisture ingress from the surrounding environment and reduces internal moisture movement through the section. A defining feature for Indian site conditions is that Conplast WP100 is chloride free, which means it can be used safely in reinforced and pre-stressed concrete and alongside sulphate-resisting cements without any risk of accelerating reinforcement corrosion. Because the protection is integral, it is not lost if the surface is later cut, drilled or abraded, a common failure mode for surface-applied waterproofing films. For Space Arc Engineering’s customers, WP100 is positioned as the cost-effective, dependable first line of integral waterproofing for everyday RCC and mortar work where a powder dosing format suits the mix and the site logistics.
The technical insight
The chemistry of Conplast WP100 is built on organic fatty acid salts that are essentially metallic soaps. When dispersed through fresh cement paste they react with the calcium-rich hydration products to deposit a water-insoluble, hydrophobic layer along the walls of the capillary pore network. This does not seal the concrete in the way a membrane does; instead it changes the contact angle of water at the pore surface so that capillary suction, the main driver of water rising and moving through hardened concrete, is strongly reduced. Equally important is the secondary plasticising action. By allowing the desired slump or workability to be reached at a lower water content, WP100 lowers the water-cement ratio, and since permeability in concrete rises sharply with water-cement ratio, this densification contributes as much to water-tightness as the hydrophobic pore-blocking does. The product carries a chloride content rated Nil to BS 5075, confirming it adds no chlorides to the mix. Because it is powder, dosing accuracy and thorough dry blending matter: the admixture must be measured by weight of cement and dispersed uniformly during mixing rather than dumped in one spot. It is compatible with all types of Portland cement and with cement-replacement materials such as fly ash (PFA), GGBFS and microsilica, but admixtures should be added separately to the mix and never pre-blended together. Crucially, WP100 is a quality-enhancer, not a substitute for sound concrete practice: a minimum cement content of around 300 kg/m3, well-graded aggregates, proper compaction and adequate curing remain prerequisites, and water-stops must still be detailed at construction joints and between floor bays.
Where it is used
- Integral waterproofing of structural and precast RCC elements
- Sand:cement renders and external plaster requiring reduced water penetration
- Floor screeds where extra mix water cannot be tolerated
- Mortars and plasters for masonry and bedding
- Basement walls and rafts subject to soil moisture and water tables
- Roof slabs and terraces requiring mass waterproofing
- Water-retaining structures such as tanks, sumps and reservoirs
- Concrete exposed to mildly aggressive, water-borne chemicals
Key advantages
- Chloride free, safe for reinforced, pre-stressed and sulphate-resisting cement concrete
- Powder form adds no extra water, ideal for screeds and dry/semi-dry mixes
- Reduces permeability throughout the full mass of concrete and mortar
- Integral protection is retained even if the surface is later damaged or abraded
- Plasticising action lowers water-cement ratio and improves compressive strength at equal workability
- Controls efflorescence and reduces pigment leaching in coloured mortars
- Compatible with all Portland cements and with PFA, GGBFS and microsilica
- No membranes or separate surface waterproofers required
Limitations & considerations
- Will not make poor-quality concrete waterproof, sound mix design and workmanship are essential
- Not a substitute for water-stops at construction joints and floor bays
- Requires accurate batching by weight and thorough dispersion in the mix
- Overdosing (around double the intended rate) can increase retardation and workability
- Does not bridge cracks or seal structural movement, it is a mass-densifying admixture not a coating
- Good curing is essential, particularly if an overdose has occurred
- Cement content of roughly 300 kg/m3 minimum is needed for effective performance
- For potable-water or heavy chemical exposure, confirm suitability against the current local Fosroc India datasheet
Selection & best practice
Always establish the optimum dosage by trial mixes using the actual job materials and site conditions, taking the published 1.0%-2.0% by weight of cement only as a starting guide. Measure the powder accurately by weight, add it separately from any other admixture, and disperse it thoroughly during mixing, never pre-blend admixtures together before they go into the mix. Maintain a minimum cement content of about 300 kg/m3, use well-graded aggregates, and combine WP100 with correct water-stop detailing at all construction joints and between floor bays. Follow good curing practice with water spray or wet hessian, especially where an overdose may have occurred, and store the product below 35 degrees C in dry warehouse conditions, using stock within its shelf life. For mix-critical or warranty-backed work, cross-check the dosage and properties against the current Fosroc India technical data sheet for Conplast WP100 before finalising the design.
Specifications
| Product type | Integral waterproofing admixture (powder) |
| Chemical basis | Organic fatty acid salts (hydrophobic blend with plasticising agents) |
| Form / appearance | Free-flowing white powder |
| Chloride content | Nil (to BS 5075) |
| Typical dosage | 1.0% – 2.0% by weight of cement (confirm by trial mix) |
| Minimum cement content recommended | 300 kg/m3 |
| Cement compatibility | All Portland cements; compatible with PFA, GGBFS and microsilica |
| Effect of overdose | Approx. double dose may increase retardation and workability |
| Standard referenced | BS 5075 (chloride content) |
Industry use cases
Residential & Commercial Basements
Dosed into raft and retaining-wall concrete to cut capillary water ingress from high water tables common in Delhi NCR sub-soil, reducing damp and efflorescence without relying solely on external membranes.
Roofing & Terraces
Added to roof-slab and screed concrete to provide mass waterproofing that survives foot traffic and surface wear, where a chipped membrane would otherwise leak.
Water-Retaining Structures
Used in tanks, sumps and reservoir walls to lower permeability through the section, complementing water-stops at joints for watertight construction.
Precast & Manufactured Concrete
Suits factory mixes because the powder form maintains a controlled low water-cement ratio while improving water-tightness of the finished units.
External Renders & Plaster
Blended into sand:cement renders on facades to resist rain penetration and control pigment leaching and efflorescence in exposed elevations.
Frequently asked questions
Is Fosroc Conplast WP100 chloride free and safe for reinforced concrete?
What is the dosage of Conplast WP100?
How is WP100 different from liquid integral waterproofers like Conplast WL?
Does Conplast WP100 replace a waterproofing membrane?
Can WP100 be used with fly ash, GGBFS or PPC?
What are the storage conditions and shelf life?
How we position Fosroc Conplast WP100
Within Fosroc’s own range, Conplast WP100 sits as the powder option in the integral waterproofing family. Choose WP100 when the mix cannot tolerate extra water (screeds, precast, semi-dry mortars); choose the liquids Conplast WL or Conplast WL Xtra for conventionally batched site concrete and plaster where per-bag liquid dosing is simpler; and step up to Conplast Crystalline when a reactive, self-sealing crystalline technology is specified for demanding water-retaining or below-grade structures. Against competitor integral waterproofers, WP100 competes with Sika’s integral admixtures (such as the Sika WT / Sika-1 family), MBS (MYK Schomburg) integral compounds, Dr. Fixit’s powder and liquid integral waterproofers (e.g. LW+ and powder grades), and STP (Bharat Petroleum’s Pidilite-adjacent / STP Ltd) integral products. Its strengths versus these are the chloride-free fatty-acid chemistry, the genuine no-added-water powder format, and the credibility of the Fosroc brand and technical support. As an authorised Fosroc distributor for Delhi NCR and Pan-India, Space Arc Engineering supplies Conplast WP100 with genuine-stock assurance and application guidance, and can advise where a crystalline, liquid, or membrane-backed solution would be a better fit for a given structure.
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