Mapei Lamposilex - Ultra Fast Set Plugging Mortar

Health & Safety Recommendations

Read the label and the safety data sheet before use. Wear appropriate PPE including protective gloves and eye protection, and ensure adequate ventilation in confined spaces such as basements, sumps and service chambers.

Avoid contact with eyes and prolonged skin contact. Do not ingest. Wash hands thoroughly after handling. In case of contact with eyes, rinse immediately and seek medical advice.

Keep out of reach of children. Do not expose unopened containers to direct sunlight or excessive heat. The product contains no added chlorides; nevertheless, comply with all local regulations and site-specific risk assessments. Dispose of wastes and empty packaging responsibly in accordance with local legislation.

Substrate Suitability

Mapei Lamposilex – Ultra Fast Set Plugging Mortar is designed for sealing live water leaks and stopping infiltration under pressure in rigid, mineral substrates. Suitable bases include sound concrete, dense masonry, stone and cementitious screeds where the substrate is stable, clean and free from contaminants.

It is intended for rigid joints, cracks and through-holes in structures such as basements, tunnels, subways, lift pits, tanks, canals, sewers and other hydraulic or below-grade constructions. It is not suitable for movement joints, deformable substrates, flexible interfaces, or as a substitute for an elastic joint sealant.

For final system waterproofing, Lamposilex may be used as a localised plug prior to subsequent cementitious tanking or membrane installation as specified.

Surface Preparation

Identify the leak path and mechanically open cracks or holes to form a dovetail profile, ensuring the wider part is towards the interior of the structure. The minimum external dimensions should be approximately 20mm in width and 20mm in depth to provide adequate mechanical key.

Remove any incoherent, degraded or loose material and laitance, and clean the cavity thoroughly. Clear all dust and debris using compressed air. Thoroughly wet the substrate with clean water until it is saturated. Before sealing, allow excess, unabsorbed water to evaporate so that the cavity is saturated but surface-dry; use compressed air or a sponge to remove standing water.

This saturated surface-dry condition promotes optimal bond and reduces rapid suction during the ultra-fast set.

Mixing

Prepare only the quantity that can be placed within one minute, as the product is a rapid setting plugging mortar.

While stirring, pour 1kg of Lamposilex into a container holding 280g of clean water and mix manually with a trowel until a smooth, lump-free paste is obtained. For dosing by volume, mix 2.5 parts Lamposilex with 1 part water.

Do not add lime, cement or gypsum, and do not retemper once the mix begins to stiffen. At approximately +20°C no special measures are required. In hot weather keep the powder shaded, avoid sun-warmed containers and use very cold mixing water to maintain workable time.

In low temperatures use water at around +20°C and store the material in a heated room; setting and curing are delayed at low temperatures.

Application Method

For stopping active water leaks, mould the fresh Lamposilex into a plug resembling a tapered cork. Wait a few seconds until the mix begins to warm and thicken, then press it firmly into the crack, hole or penetration, working against the flow and ensuring full contact with the dovetailed sides of the cavity. Hold the plug under steady pressure for two to three minutes until set.

When dealing with multiple leak points, start at the top and work down so that the hydrostatic pressure above is reduced as you proceed. Once the leak has been arrested and the plug has set, trim any excess material flush using an abrasive wheel or sanding disc.

For waterproof sealing of rigid joints, pack the fresh mix into the prepared chase with a trowel or float immediately after mixing, consolidating thoroughly. Keep the surface damp for the first fifteen to twenty minutes to avoid flash drying. After localised plugging, and once the surface is stable, proceed with any wider waterproofing system specified for the structure.

Coverage

The theoretical yield is approximately 1.8 kg of Lamposilex per litre (one dm³) of cavity volume. As a practical guide, a typical 20 mm by 20 mm dovetailed chase consumes about 0.72 kg of Lamposilex per linear metre.

Actual consumption will vary with cavity geometry, irregularities, wastage and workmanship; allow a sensible on-site contingency.

Drying Time

At approximately +20°C Lamposilex sets in about two minutes when correctly mixed and placed. Maintain hand pressure on active leak plugs for two to three minutes to ensure a secure set. Very high early compressive and flexural strength is achieved after roughly thirty minutes, allowing early resistance to hydraulic forces.

Setting and early strength development are temperature dependent; higher temperatures accelerate reaction, while lower temperatures slow it. Keep the surface damp for fifteen to twenty minutes after placement, particularly in warm, dry or windy conditions.

Limitations

Do not add lime, cement, gypsum or any other binders or admixtures. Do not overwater or retemper once the mix has begun to set. Do not apply to dusty, oily or weak substrates; prepare to sound, clean mineral material only.

Lamposilex is not suitable for movement or expansion joints and should not be used as a flexible sealant or as a fairing or skim coat. Do not leave unopened drums exposed to direct sunlight before use, and avoid placing or storing the product on hot surfaces.

In hot weather use very cold mixing water and work in the shade; in cold weather condition the material and water to around +20°C. Always follow best practice for confined-space working when applying in chambers, pits or tunnels.

Cleaning

Before it hardens, Lamposilex can be removed from tools and equipment with clean water. Once set, residues must be removed by mechanical means such as scraping or grinding.

Prevent contamination of adjacent finishes by masking or pre-wetting where appropriate, and clean spillages immediately due to the ultra-fast setting nature of the mortar.

Other Information

Mapei Lamposilex – Ultra Fast Set Plugging Mortar is a rapid setting, rapid hardening hydraulic binder specifically formulated to stop water leaks, including leaks under pressure, in below-grade and hydraulic structures.

It contains no chlorides and complies with the conditions of Annex XVII to Regulation (EC) No. 1907/2006 (REACH), item 47. Store unopened containers in a cool, dry location, protected from direct sunlight and frost. Use only clean water for mixing.

For best results, combine the instant leak-stopping plug with a compatible waterproofing system where long-term, full-area tanking is required. Always consult the current technical data sheet and material safety data sheet for definitive guidance, site-specific advice and compliance information.

Q) What is Mapei Lamposilex and what problem does it solve?

A) Mapei Lamposilex – Ultra Fast Set Plugging Mortar is a rapid-setting, rapid-hardening hydraulic binder formulated specifically to stop live water leaks, including leaks under pressure, in concrete and other mineral substrates. Supplied as a pre-blended powder based on high-strength cements and special admixtures, it is mixed with clean water to produce a mouldable paste that you can pack directly into cracks, holes and rigid joints. It sets in about two minutes, develops very high early compressive and flexural strength, and becomes waterproof and water-repellent once cured. Because it works against negative hydrostatic pressure, Mapei Lamposilex allows operatives to arrest infiltration immediately, safeguard adjacent finishes and services from washout, and stabilise structures so that subsequent waterproofing systems can be applied under controlled conditions. It contains no chlorides and is intended to be used exactly as supplied without additional binders or fillers.

Q) Where can Mapei Lamposilex be used, and which types of projects benefit most?

A) Mapei Lamposilex is designed for urgent leak-stopping in below-grade and hydraulic structures where ordinary mortars are washed out or too slow to react. Typical applications include basements, lift pits, tunnels and subways, where negative water pressure is common; water-retaining or water-excluding assets such as tanks, canals, culverts, chambers and spillways; manholes, sewers and drainage infrastructure suffering infiltration or exfiltration; and rigid construction details like wall-to-slab junctions, cold joints and pipe penetrations. It is equally useful during emergency response when unexpected leaks threaten to flood work areas or damage services, allowing a quick stabilisation before wider remedial works. By delivering an immediate plug that resists ongoing hydraulic action, the product shortens downtime, protects adjacent materials, and creates a dependable localised seal ahead of full-area tanking slurries, crystalline coatings or membranes specified for long-term waterproofing.

Q) Can Mapei Lamposilex really stop leaks under pressure, and how does it work in practice?

A) Yes. Mapei Lamposilex is engineered to perform under active water pressure by combining ultra-fast setting kinetics with high early mechanical strength. On contact with water, its hydraulic binders activate rapidly to create a thixotropic paste that can be hand-formed and pressed into the leak path. The recommended dovetail cavity and firm manual pressure generate mechanical interlock while the mortar hydrates. Within roughly two minutes it sets hard enough to resist washout; within about thirty minutes it reaches very high early compressive and flexural strength, allowing it to withstand ongoing hydrostatic forces and incidental vibration. Because you work against the flow and hold the plug in place as it warms and stiffens, the material keys tightly into sound mineral substrate and forms a dense, waterproof barrier. This behaviour distinguishes Mapei Lamposilex from general-purpose mortars, which typically need dry conditions or longer curing times and are vulnerable to being eroded before they gain strength.

Q) Which substrates and joints are suitable for Mapei Lamposilex, and what should be avoided?

A) Mapei Lamposilex is intended for sound, rigid, mineral bases such as concrete, dense masonry, stone and cementitious screeds. It is ideal in rigid junctions (for example wall-to-slab joints), daywork or cold joints, blow-holes, honeycombed areas, and through-holes around rigid penetrations where a fast, strong plug is required. It is not suitable for movement or expansion joints, deformable substrates, flexible interfaces, or as a substitute for elastic sealants—these conditions require products that accommodate movement rather than resist it. Avoid dusty, oily, friable or contaminated surfaces; weak material must be cut back to a solid, clean substrate. Do not use on gypsum, timber, plastics, or highly porous, soft materials that cannot provide mechanical interlock. As a rule, if the base cannot be mechanically prepared to a sound, mineral surface with a defined dovetail geometry, it is not an appropriate candidate for Mapei Lamposilex without additional remedial measures.

Q) How should I prepare the leak area before applying Mapei Lamposilex?

A) Preparation is crucial to achieve a secure, durable plug. First, trace the precise leak path and mechanically open cracks or holes into a dovetail profile so the cavity is wider inside the structure than at the face. A practical minimum is about 20 mm width by 20 mm depth, but enlarge as needed to remove all weak or contaminated material and to create sound shoulders for mechanical keying. Remove laitance, friable edges and any soft, degraded concrete. Clean thoroughly and blow out dust with compressed air. Saturate the substrate with clean water until fully wetted, then allow surface water to dissipate so the cavity is in a saturated surface-dry (SSD) condition—this limits suction, improves bond and helps the ultra-fast set hydrate correctly. Where multiple leaks exist, plan the sequence before mixing so you can work efficiently from the top down, reducing hydrostatic head on lower plugs as you proceed.

Q) What is the correct mixing ratio for Mapei Lamposilex and how much should I mix at once?

A) Mix only what you can place within about one minute because Mapei Lamposilex sets in roughly two minutes at around +20°C. By weight, add 280 g of clean water to 1 kg of powder (approximately 28% water), mixing by hand with a trowel until you achieve a smooth, lump-free paste. By volume, a guide ratio is 2.5 parts powder to 1 part water. Do not add lime, Portland cement, gypsum or other binders, and never retemper once the mix begins to thicken—discard and prepare fresh material instead. In hot conditions keep the powder shaded and use very cold mixing water to maintain workable time; in cold conditions store materials at around +20°C and use water at approximately +20°C to promote reliable early strength development. Use clean containers and tools to avoid contamination, and keep mixed batches small to ensure you can mould and place the plug promptly.

Q) How do I apply Mapei Lamposilex to an active water leak and how long should I hold it?

A) After preparing the SSD cavity, mix a small batch and quickly form the paste into a tapered plug, like a cork. Wait a few seconds as the mass warms and stiffens, then press it firmly into the leak path, working against the flow to drive the material into the dovetail and expel water. Maintain steady hand pressure for two to three minutes until initial set. For multiple leaks, always start at the top and work down so each successful plug reduces the head and flow impacting the next. Once the leak has been arrested and the plug is firm, trim any excess material flush with an abrasive wheel or sanding disc when appropriate. For rigid chases along joints, pack the fresh mix in with a trowel, consolidating fully, and keep the surface damp for the first fifteen to twenty minutes to prevent flash drying. After localised plugging, proceed with any specified full-area waterproofing once the area is stable.

Q) How fast does Mapei Lamposilex set and when does it achieve usable strength?

A) At approximately +20°C, Mapei Lamposilex sets in about two minutes, provided the correct water ratio and SSD substrate are observed. You should hold hand pressure on active leak plugs for two to three minutes to ensure the mortar locks in place. Very high early compressive and flexural strength develops after roughly thirty minutes, enabling the repair to resist ongoing hydraulic forces, incidental vibration and early service effects. Temperature affects kinetics: higher temperatures accelerate set and shorten working time; lower temperatures delay set and early strength gain. To manage this, use cold mixing water and shade materials in hot weather, and condition both powder and water to around +20°C in cold environments. Maintaining slight dampness on the surface for fifteen to twenty minutes after placement helps avoid surface flash-off, especially in warm, dry or windy conditions.

Q) How much Mapei Lamposilex will I need and how can I estimate consumption on site?

A) The theoretical yield of Mapei Lamposilex is approximately 1.8 kg per litre (one dm³) of cavity volume. To estimate consumption for a simple dovetailed chase, multiply width × depth × length to get volume, then multiply by 1.8 to convert to kilograms. As a practical guide, a typical 20 mm × 20 mm chase consumes about 0.72 kg per linear metre (0.02 m × 0.02 m × 1 m = 0.0004 m³ ≈ 0.4 litres; 0.4 × 1.8 = 0.72 kg). Real-world usage will vary with irregular geometry, enlargement at the defect, wastage and workmanship, so allow a sensible contingency. When plugging discrete holes or penetrations, calculate the approximate cavity volume after proper cutting-back rather than the visible surface opening. Because the product has a very short working time, it is efficient to prepare several small batches rather than one large mix that risks setting before placement.

Q) What limitations apply to Mapei Lamposilex and when should I choose a different solution?

A) Mapei Lamposilex is a specialist plugging mortar for rigid, localised leak-stopping; it is not a flexible joint sealant, movement-joint filler, skim coat or fairing compound. Do not use it where differential movement is expected or where the substrate is deformable. It must not be modified with lime, Portland cement, gypsum or other admixtures, and it should never be over-watered or retempered after stiffening. Application to dusty, oily, contaminated or weak substrates will compromise performance—mechanical preparation to a sound, clean, mineral surface is essential. Do not rely on it as the sole, full-area waterproofing measure where comprehensive tanking or negative-side waterproofing is specified; instead, use it to arrest leaks ahead of the main system. Finally, avoid exposing unopened containers to direct sunlight or excessive heat, and manage hot/cold weather working as recommended to maintain predictable set and strength development.

Q) Can Mapei Lamposilex be overcoated, and how does it fit within a wider waterproofing system?

A) Yes. Mapei Lamposilex is commonly used as the first step in a broader remediation strategy: plug localised leaks quickly, then proceed with the specified full-area waterproofing once conditions are stable. After the plug has set and early strength has developed, surfaces can be prepared as required for cementitious tanking slurries, crystalline treatments or membrane systems appropriate to the structure and service conditions. The product’s waterproof, water-repellent nature helps prevent further washout at defect points while you undertake coatings or lining works. Always follow the data sheets for the subsequent system regarding substrate moisture, profile, curing intervals and compatibility. Good sequencing—plug, stabilise, then waterproof—delivers reliable, long-term watertightness.

Q) What practical hints and troubleshooting tips will improve results with Mapei Lamposilex?

A) Work small and fast: prepare the cavity fully before mixing, then make compact batches you can place within a minute. Shape the plug slightly larger than the opening so it compresses into the dovetail, and wait a few seconds as the mix warms before pressing it home—this helps avoid premature washout. Start at the highest leak point and progress downward. Maintain steady pressure for two to three minutes, resisting the instinct to check underneath the plug too soon. Keep the surrounding surface damp for fifteen to twenty minutes, particularly in warm or windy conditions. In hot weather, cool the water and keep the powder shaded; in cold weather, warm both to around +20°C. Never add extra water to re-soften stiffening material—discard and mix fresh. If seepage persists around the edges, enlarge the cavity to sound material and re-plug; chasing thin, superficial cracks rarely succeeds without proper dovetailing.

Q) How should Mapei Lamposilex be stored, and how do I clean tools and surrounding areas?

A) Store unopened containers of Mapei Lamposilex in a cool, dry location, protected from direct sunlight, excessive heat and frost to preserve reactivity and predictable set times. Keep bags or tubs sealed until use to prevent moisture uptake. Organise the work so the pack is not left open in humid or wet environments. Clean tools and equipment with clean water immediately after use—before the mortar hardens. Once set, residues are tenacious and require mechanical removal by scraping or grinding, so prompt cleaning saves time and consumables. Protect adjacent finishes by masking or pre-wetting where appropriate, and wipe spillages immediately given the product’s ultra-fast set. Dispose of waste mortar and empty packaging responsibly in accordance with local regulations and site rules; do not wash unset material into drains or watercourses.

Q) What health and safety precautions apply when using Mapei Lamposilex, especially in confined spaces?

A) Read the label and safety data sheet before use and follow site-specific risk assessments. Wear appropriate PPE including protective gloves and eye protection; long sleeves and waterproof footwear are sensible when working around active leaks. Avoid contact with eyes and prolonged skin contact, and do not ingest. Ensure adequate ventilation in basements, pits and chambers; manage lighting and safe access where water is present. Wash hands thoroughly after handling and before breaks. In case of eye contact, rinse immediately and seek medical advice. Keep the product out of reach of children. Good housekeeping—dry footing, tidy hoses and secure tools—reduces slip and trip risks during urgent leak-stopping operations.

Q) How does Mapei Lamposilex compare to ordinary rapid-set mortars for emergency leak repairs?

A) Ordinary rapid-set mortars often require relatively dry conditions, longer working times and protection from flowing water until they have developed strength; under active hydrostatic pressure they can wash out or erode at the interface. Mapei Lamposilex is purpose-built as a plugging mortar for live leaks: it mixes to a hand-mouldable consistency, sets in about two minutes, and achieves very high early strength within roughly thirty minutes, allowing it to resist ongoing water pressure soon after placement. Its recommended dovetail preparation and hand-pressure placement are tailored to create mechanical interlock in rigid substrates, while its waterproof, water-repellent nature after cure provides a dense local barrier that complements subsequent tanking. In short, where speed, early strength and resistance to active flow are critical, Mapei Lamposilex offers a more reliable, repeatable solution than general rapid-set mortars.

Q) What environmental and regulatory considerations support the use of Mapei Lamposilex on infrastructure projects?

A) Mapei Lamposilex supports responsible specification by combining performance with compliance. It is formulated without added chlorides, reducing corrosion risk to embedded steel when used correctly, and it complies with Annex XVII to Regulation (EC) No. 1907/2006 (REACH) – All. XVII, item 47. Because the product is supplied pre-blended under factory control, on-site variability is reduced, supporting quality assurance and traceability demanded on civil and utility projects. From a practical standpoint, the ability to arrest leaks instantly can minimise water loss, prevent contamination of adjacent materials and limit emergency pump-outs, thereby reducing waste and disruption. As always, pair the leak-stopping plug with a properly designed full-area waterproofing solution and follow local environmental and asset-owner protocols for installation and return to service.

Q) What common mistakes should be avoided when using Mapei Lamposilex, and how can I ensure consistent success?

A) The most frequent errors are inadequate preparation, over-watering and slow working. Cutting only a superficial groove instead of a true dovetail leaves little shoulder for mechanical keying and invites edge seepage—always open to sound material with at least about 20 mm width and depth, larger if the defect demands it. Measure water accurately (about 280 g per kilogramme of powder) and mix by hand to a cohesive paste; sloppy mixes reduce strength and washout resistance. Never retemper partially set material—discard and make a fresh, small batch. Plan the sequence before mixing and work from the top down so each plug reduces pressure on the next. Maintain steady pressure for two to three minutes and keep the surface slightly damp for fifteen to twenty minutes post-placement to avoid flash-drying. Finally, integrate Mapei Lamposilex into a full waterproofing strategy rather than relying on plugs alone where comprehensive tanking is required.

Technical Data Sheet

Safety Data Sheet