About Sika Sika-101h

Sika-101h is one of those products that quietly does the heavy lifting on a waterproofing scope without adding a separate membrane trade to the programme. It is a grey cementitious powder loaded with crystalline-active compounds, and its whole value proposition is that it becomes part of the concrete rather than sitting on top of it. Mixed with water it brushes on as a slurry; dusted onto a green slab it works as a dry shake; batched into the mix it acts as an integral admixture. Whichever route the site chooses, the same chemistry is at work, and the product conforms to IS 2645, which is the reference most Indian consultants and clients look for on a waterproofing submittal.

For engineers dealing with tanks, basements, tunnels and treatment plants, the practical appeal is that Sika-101h handles both positive and negative side water pressure. That matters on jobs where you cannot always get to the water-bearing face, such as a basement raft where the ingress is from outside but the only accessible surface is the internal one. Because the active compounds migrate into the capillary network and are re-activated by moisture, the treated concrete can also self-heal fine cracks that open up later in service. It stays vapour-permeable, carries no added chloride and is non-toxic, so it suits reservoirs and water-retaining structures where a rigid, breathable, in-depth seal is preferable to a film that can blister or debond.

The technical insight

The mechanism is diffusion-driven crystallisation, not surface film-forming. When Sika-101h contacts the moisture and free lime naturally present in concrete, its reactive compounds migrate along the capillary tracts and precipitate insoluble crystalline deposits inside those pores and voids. Those crystals progressively choke the capillary network from the bottom upwards, so the path water would normally travel is physically blocked within the concrete mass rather than bridged by a coating. This is why the product resists negative-side pressure: the seal lives inside the section, so water pushing from the far face still meets a blocked capillary. It also explains the timeline. Sika India records very low water penetration under 5 bar to EN 12390-8, but the crystal growth depends on concrete grade, cover, porosity and available free lime, so a minimum of 28 days of in-service exposure is recommended for the system to develop fully. The same dormant chemistry gives the self-sealing behaviour: when a hairline crack later admits water, residual compounds re-activate and crystallise to re-close the path.

Where it is used

• Internal and external waterproofing of RCC water tanks and overhead reservoirs
• Basement rafts and retaining walls where only the negative (internal) face is accessible
• Swimming pool shells and balancing tanks requiring a breathable, non-toxic seal
• Tunnels, underground subways and cut-and-cover structures
• Underground and podium car park decks and their retaining structures
• Sewage treatment and effluent treatment plant tanks and channels
• Integral waterproofing of RCC when dosed into the concrete at batching
• Dry-shake surface hardening-cum-waterproofing of green horizontal slabs

Key advantages

• Waterproofs against both positive and negative hydrostatic pressure from a single product
• Crystalline action seals hairline cracks and can re-activate to self-heal fine cracks later in service
• Becomes an integral, homogeneous part of the concrete rather than a debondable surface film
• Three application routes – slurry coat, dry shake or integral admixture – from one bag
• Vapour-permeable, so the structure can still breathe
• No added chloride and non-toxic, suitable for potable-adjacent and water-retaining structures
• Conforms to IS 2645, easing consultant and client approval on Indian projects
• Supports a faster construction schedule by removing a separate membrane trade

Limitations & considerations

• Full crystalline development needs a minimum of about 28 days of moisture exposure, so it is not an instant seal
• Performance depends on concrete quality, cover, porosity and free lime – it works with sound concrete, not as a fix for badly made concrete
• Must not be applied over old rendered substrates, and honeycombing must first be repaired with polymer-modified mortar
• Requires diligent curing – protect from rain, strong wind and direct sun for at least 24 hours and cure at least 5 days
• Application is restricted to a +10 C to +40 C ambient and substrate temperature window
• As an integral admixture it can cause slight set retardation depending on mix design and dosage

Selection & best practice

Specifications

Industry use cases

How we position Sika Sika-101h

Within the Sika range, pair Sika-101h with a flexible cementitious topping such as SikaTop Seal 107 where movement or a smoother finished surface is wanted, or specify SikaTop-107 Seal IN when a potable-water clearance is the deciding factor; for structures relying on integral protection, Sika-1 remains the classic waterproofing admixture. Across our other brands, Space Arc supplies comparable crystalline and cementitious systems from Dr. Fixit, MC-Bauchemie and STP, so we can match whatever a consultant has named in the specification. As authorised distributors and applicators across Delhi NCR and Pan-India, we can also advise on the right combination of admixture, slurry and coating for a given water head and exposure.

Related Waterproofing products

View all Waterproofing products →