Fast-setting natural cement/NHL mortar for marine masonry in splash, tidal and submerged zones.
What it is
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Dry, ready-mixed blend of Prompt Natural Cement, NHL 5, and selected natural sands.
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Engineered for accelerated set to mitigate tidal washout while keeping overall binder strength modest for compatibility with weaker historic masonry.
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No Portland cement and no synthetic polymers.
Performance at a glance
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Working/open time: ~74 minutes at 17 °C (site conditions govern). Plan lifts and access so you can compact and finish promptly.
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Setting behaviour: Rapid initial grip with early resistance to washout; full strength develops with proper curing.
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Breathability & compatibility: More sympathetic than strong PC-rich mixes; helps avoid edge-spalling on soft stone/brick while delivering the set speed needed in tidal work.
Choose LP6 for tidal/splash or submerged repairs where fast set is critical.
Choose Roundtower Marine L4 for above-water, cement-free, slower-setting work prioritising maximum vapour permeability.
Typical uses
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Quay and harbour walls, coping stones, revetments, bridge abutments, lock chambers and culverts.
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Bedding and pointing to freshwater or saltwater masonry where washout risk is present.
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Conservation and renovation where a low-to-moderate strength marine mortar is preferred over rigid PC mixes.
Coverage & yield
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25 kg → Approx14.5 L fresh mortar.
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Roughly approx 1.5 m² of joint at 10 mm depth (actual yield varies with joint width/depth and substrate texture).
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On-site trials recommended for project-specific consumption.
Application essentials
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Prep: Rake out defective joints to sound arrises; remove salts/bio-growth; pre-dampen.
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Mix: Add clean water gradually to a cohesive, plastic consistency; avoid over-watering. Remix briefly if rested; discard material that has begun to set.
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Place/Finish: Compact fully to the back of the joint; form the required profile once the mortar starts to firm.
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Curing & Protection: Shield from direct rain, sun, drying winds and active washout until initial set; continue gentle curing thereafter.
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Temperature window: Use between +5 °C and +30 °C (consider wind-chill/radiant heat). Avoid if freezing is forecast during early cure.
Colour & batching
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Natural, pigment-free buff-tan. Final tone varies with exposure and curing. Custom colours are not available; for colour-critical projects, request guidance on curing and order sufficient material from the same batch.
Packaging, storage & safety
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25 kg polythene-lined paper bags; palletised for handling/storage.
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Store cool, dry, off the ground; rotate stock (oldest first).
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Safety: Contains lime/cement; avoid skin/eye contact and dust inhalation. Use appropriate PPE.
