About Fosroc Conplast WP90

Fosroc Conplast WP90 Powder is a traditional integral waterproofing admixture for concrete and cement mortar. It is supplied as a fine, white, ready-to-use powder that is blended directly into the dry mix on site. Rather than coating a surface from the outside, WP90 works inside the matrix: its fine particles fill the natural capillary pores and voids left in the cement paste as it hydrates, reducing the interconnected pore network through which water travels. The result is a denser, less permeable concrete or mortar that resists the slow passage of moisture. For Indian projects this is one of the most widely specified and cost-effective entry points into waterproofing because it relies on a method site teams already understand: a measured powder added to an ordinary mix, with no special plant, primers or curing regime beyond good concreting practice. Conplast WP90 conforms to IS:2645-2003, the Indian Standard for integral cement waterproofing compounds, and is certified by the Bureau of Indian Standards (BIS), which makes it acceptable for government, PWD and CPWD-type specifications that call for an IS:2645 product. It is compatible with all cements, including Portland Pozzolana Cement (PPC), so it slots into the OPC and PPC mixes common across the country. The product carries no particular effect on compressive strength and conforms to IS:2645-2003 for initial and final set, so designers do not have to compensate the mix design for its use. Space Arc Engineering, an authorised Fosroc distributor serving Delhi NCR and pan-India, supplies WP90 in both 1 kg and 25 kg packs so it suits everything from a single-room repair to a full basement raft pour.

The technical insight

Conplast WP90 is a pore-filling (or pore-blocking) waterproofer, which is a distinct mechanism from the hydrophobic and crystalline approaches in Fosroc’s range. Concrete is permeable mainly because of the interconnected capillary pores left when excess mix water evaporates. WP90’s fine inert and reactive powder fractions physically pack into and bridge these capillaries, lowering the effective permeability so the TDS reports very low permeability to water compared with a reference sample containing no waterproofer. Because it is a pore-filler rather than a set accelerator or retarder, it conforms to IS:2645-2003 limits for setting time and chloride content and does not materially change the compressive strength of the concrete or mortar. A practical consequence worth understanding is that integral waterproofing reduces permeability but does not turn concrete into a membrane: WP90 makes a sound, well-compacted, low water-cement-ratio mix more watertight, but it cannot seal honeycombing, cold joints, shrinkage cracks or poorly vibrated pours. The Fosroc TDS itself flags that where bleeding or segregation is hard to control, or in mass pours demanding maximum compaction and water tightness, the liquid compound Conplast X421IC is preferred. WP90 therefore performs best as one layer of a properly detailed waterproofing strategy alongside correct mix design, compaction, curing and movement-joint treatment.

Where it is used

• Reducing permeability of structural concrete in basement rafts, retaining walls and water-retaining structures
• Waterproofing roof slabs and the screeds laid over them
• Water tanks and reservoirs where a denser, less permeable concrete or render is required
• External plastering of roofs, balconies and parapets exposed to rain
• Plastering of basements, tanks and external masonry walls
• Bathroom, toilet and balcony sunk-slab and screed concrete in residential construction
• General sand/cement mortar and render where lower water absorption is wanted

Key advantages

• BIS certified and conforms to IS:2645-2003, satisfying government and PWD/CPWD-type specifications
• Simple, familiar dry-mixing application that needs no special plant or skilled applicator
• Compatible with all cements, including Pozzolana (PPC) cements
• No particular effect on compressive strength of concrete or mortar
• Conforms to IS:2645-2003 for initial and final setting time, so mix design need not be altered
• Improves workability of the mix
• Very low water permeability compared with an untreated reference sample
• Non-toxic and non-flammable, with a straightforward safety profile
• Economical entry-level waterproofing supplied in both small 1 kg and bulk 25 kg packs
• 12-month shelf life in unopened packs under normal warehouse storage

Limitations & considerations

• It is a permeability reducer, not a membrane; it cannot bridge cracks, cold joints or honeycombing
• Effectiveness depends entirely on good concreting: low water-cement ratio, proper compaction and curing are essential
• Not the best choice for mass pours or mixes prone to bleeding/segregation, where Conplast X421IC liquid is recommended instead
• Does not provide crack-healing like crystalline admixtures (e.g. Conplast Crystalline)
• Cannot waterproof structures already suffering active leakage or moving cracks on its own
• Provides no resistance to chemical attack, hydrostatic pressure through defects, or structural movement
• Being a powder, requires accurate site dosing and thorough dry-mixing to perform as intended

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Conplast WP90

Conplast WP90 is Fosroc’s traditional, value-oriented integral waterproofing powder, best understood as the entry point in a tiered range. For liquid integral waterproofing, Fosroc offers Conplast WL, and for mass pours or mixes prone to bleeding the TDS itself points to Conplast X421IC; for crack-healing performance, Conplast Crystalline grows pore-blocking crystals and self-seals fine cracks. Against the broader Indian market, WP90 competes with powder integral compounds such as Dr. Fixit Pidiproof LW+ (liquid) and Pidicrete-type ranges from Pidilite, Sika’s Sika Waterproofing Mortar admixtures and WT-200 P powders, MYK Laticrete / MBCC (Master Builders) integral admixtures, and STP (Shalimar) integral waterproofers. Honestly, all of these IS:2645-class products do a similar job and none replace a properly detailed membrane where one is required; WP90’s edge is Fosroc’s BIS certification, all-cement compatibility and the trust of a long-established brand backed by local technical support. Specify WP90 when the requirement is an economical, BIS-certified permeability reducer for sound concrete and mortar; step up to a liquid compound, crystalline admixture or a dedicated membrane system as the hydrostatic head, crack risk or pour complexity increases.

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