Dr. Fixit Pidiproof LW+
Pidilite’s IS 2645:2003-compliant integral liquid waterproofing compound — 200 ml per cement bag makes concrete and plaster denser, more cohesive and far less permeable to water.
What is it?
An integral liquid waterproofing compound (Dr. Fixit code 101) built from surface-active plasticising agents, polymers and additives, dosed into concrete, mortar or plaster at batching.
Where is it used?
Basements, roof slabs and screeds, water tanks and water-retaining structures, external plastering, bathrooms and balconies, sumps and drains.
Why use it?
It cuts water permeability through the full concrete section while keeping setting time and compressive strength within IS 2645:2003 limits — waterproofing that cannot delaminate.
How is it applied?
200 ml per 50 kg bag of cement, added to the final portion of gauging water — never to the dry mix — then mixed a further two minutes before placing.
About Dr. Fixit Pidiproof LW+
Dr. Fixit Pidiproof LW+ is the most widely specified integral waterproofing admixture on Indian sites, and for a simple reason: it fixes waterproofing at the batching stage rather than after the concrete has already gone wrong. The wine-red, free-flowing liquid combines surface-active plasticisers with polymers and additives. Dosed at 200 ml per 50 kg bag of cement, it makes the mix noticeably more cohesive, prevents segregation and bleeding, and produces hardened concrete or plaster that resists water penetration through its entire depth. Because the protection is cast into the material itself, there is no membrane to puncture and no coating to peel.
Space Arc Engineering stocks Pidiproof LW+ across the full Pidilite pack range — from 200 ml sachets for retail plaster work up to 100-litre drums for RMC and project batching — with supply across Delhi NCR and pan-India dispatch. As an authorised distributor we source directly through Pidilite’s Construction Chemicals Division, so contractors get genuine, in-date material with batch traceability, alongside dosage guidance for site-mixed and plant-mixed concrete.
The technical insight
Concrete leaks mainly through capillary pores left behind by excess mixing water and through bleed channels formed as that water migrates upward. Pidiproof LW+ attacks both routes. Its surface-active plasticising fraction improves workability at a given water content, letting the site hold the water-cement ratio down — fewer interconnected capillaries form in the first place. The polymer fraction then works within the cement matrix, refining the pore structure and making the fresh mix cohesive enough to suppress segregation and bleeding. The practical result shows up in the IS 2645:2003 test regime: water permeability passes, while setting time and compressive strength remain within specification limits — meaning the waterproofing benefit costs nothing structurally. A chloride content of just 0.03% keeps it safe for reinforced and prestressed work, and the denser, more cohesive cover concrete gives embedded steel measurably better protection against corrosion. It is worth being precise about the mechanism: LW+ is a water-reducing, cohesion-improving admixture rather than a pore-blocking hydrophobe, so the permeability reduction is downstream of a denser cement paste, not of a barrier sitting inside it. That is why dosage discipline, a low water-cement ratio and curing quality matter as much as the admixture itself.
Where it is used
- Basement rafts, walls and foundation concrete below ground level
- Roof slabs and waterproof screeds on terraces
- Overhead and underground water tanks and other water-retaining structures
- External plastering and rendering exposed to driving rain
- Bathrooms, toilets and balcony slabs in residential buildings
- Sumps, drains and utility pits
- Swimming pool shells and surrounds
- Retaining walls in contact with damp earth
- Columns, beams and footings where cover-concrete quality drives rebar corrosion protection
- Podium and terrace slabs cast ahead of a topical waterproofing coat
Key advantages
- Reduces water permeability of concrete and mortar, verified against IS 2645:2003
- Waterproofs the full section — nothing to delaminate, puncture or wear off
- Improves workability of the fresh mix, aiding compaction at low water-cement ratios
- Makes the mix cohesive, preventing segregation and bleeding during placement
- Very low chloride content (0.03%) and denser cover concrete protect rebar from corrosion
- Reduces shrinkage crack development in both plaster and concrete
- Setting time and compressive strength stay within specification limits — no structural penalty
- Liquid form disperses uniformly in gauging water with no special equipment
Limitations & considerations
- Not a standalone answer at construction joints, tie-holes and cracks — these paths need waterstops, sealants or membrane treatment separately
- Must never be added to the dry cement-aggregate mix; dosing discipline into the gauging water is essential
- Exceeding the recommended dosage is expressly prohibited by the manufacturer and can compromise the mix
- Cannot rescue a poor mix — a high water-cement ratio or bad compaction will still leak
- Meant for new concrete and mortar only; it does not repair or bridge cracks in existing leaking structures
- The permeability benefit only materialises with proper curing — 7–10 days of conventional curing is the practical minimum, and skimped curing erodes much of it
- Site variables — cement brand, aggregate grading and batching accuracy — influence the outcome as much as the admixture does
- Highly alkaline liquid (pH 11.0–14.0), so gloves and goggles are mandatory during handling
Selection & best practice
Follow the batching sequence on the datasheet exactly. Charge cement and aggregates into the mixer per the mix design and blend dry for 1–2 minutes. Add 75–80% of the mixing water and mix for 2–3 minutes. Stir the measured dose of Pidiproof LW+ — 200 ml per 50 kg bag of cement — into the remaining gauging water, add this to the mixer, and mix for a further 2 minutes before placing concrete or applying plaster. Keep the water-cement ratio as low as workability allows; the admixture’s plasticising action is there to help you do exactly that. Never tip the product onto dry cement and aggregate, and never increase the dosage beyond the recommendation. Cure the placed concrete or plaster for at least 7–10 days by conventional methods — integral waterproofing does not replace curing, and poor curing erodes much of the permeability benefit you paid for. Wear rubber gloves and safety goggles while handling; if skin contact occurs, wash with plenty of water.
Specifications
| Form / Appearance | Free-flowing liquid, wine red |
| Specific gravity @ 25°C | 1.04 – 1.09 |
| Non-volatile content | 13.5 – 14.5% |
| pH value | 11.0 – 14.0 |
| Chloride content | 0.03% (IS 2645:2003) |
| Water permeability | Passes IS 2645:2003 |
| Setting time | Within IS 2645:2003 limits |
| Compressive strength | Meets IS 2645:2003 standard limits |
| Dosage | 200 ml per 50 kg bag of cement |
| Pack sizes | 200 ml, 1 L, 5 L, 10 L, 20 L, 100 L |
| Shelf life | 2 years in sealed pack, stored cool and dry |
Industry use cases
Residential Construction
Builders dose LW+ into roof slabs, bathroom sunken portions and external plaster across group-housing projects, cutting dampness complaints during the defect-liability period at a few rupees per bag of cement.
Water-Retaining Structures
OHTs, underground sumps and STP tanks gain a denser, low-permeability concrete core; applicators then add a cementitious coating internally so joints and tie-holes are covered too.
Commercial Basements
Raft and retaining-wall pours for office and retail basements use LW+ plant-dosed through 100-litre drums, giving uniform full-depth protection where membrane repair after backfilling is impossible.
Infrastructure & Utilities
Drains, culverts, utility pits and pump chambers benefit from cohesive, segregation-free concrete that stands up to continuous ground moisture without a separate applied system.
Repair & Renovation Plastering
Waterproof re-plastering of rain-exposed façades and parapets uses LW+ in the mortar to reduce shrinkage cracking and slow water ingress through the render.
Frequently asked questions
What is the correct dosage of Pidiproof LW+ per bag of cement?
Does it reduce the strength or delay the setting of concrete?
Can I use it in plaster as well as concrete?
Is Pidiproof LW+ alone enough to waterproof a roof or water tank?
Is it safe for reinforced concrete?
What pack sizes does Space Arc supply, and what is the shelf life?
What pack size should I buy for a single bathroom slab versus a full roof pour?
How we position Dr. Fixit Pidiproof LW+
Pidiproof LW+ is the batching-stage layer of a waterproofing system, not the whole system. Within the Dr. Fixit family, combine it with Pidifin 2K for the internal faces of water tanks, Newcoat for exposed terraces needing an elastomeric membrane, and Pidicrete URP where SBR-modified repair mortars or bonding slurries are involved. If your project specification calls for an integral waterproofer from a different approvals list, Space Arc also supplies Fosroc Conplast WP90 as a direct equivalent, and Sika’s Plastocrete range for RMC-dosed applications — talk to us about which datasheet matches your consultant’s spec before you pour.
Fosroc Conplast WL — Where a project’s specification already runs on Fosroc’s admixture range, or a leaner 125–200 ml dosage window is preferred, Conplast WL is a genuine IS 2645:2003-compliant integral waterproofing admixture that Space Arc also supplies as an authorised Fosroc distributor — a real alternative on different plasticiser chemistry, not a like-for-like clone.
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