Fast-setting natural cement mortar for aggressive marine environments above and below the waterline (incl. tidal/scour zones).
What it is
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Dry, ready-mixed Prompt Natural Cement with selected natural sands — no Portland cement, no synthetic polymers, no lime (so no carbonation required).
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Engineered for medium strength with an accelerated set, balancing durability, adhesion and flexibility in harsh saltwater exposure.
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One of our most specified marine mortars for seawater and saltwater canals where washout and scouring are concerns.
Performance at a glance
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Working/open time: ~50 minutes at 17 °C (ambient & suction dependent).
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Fast initial set reduces tidal washout; high adhesion lowers debonding risk.
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Naturally sulphate-resistant PNC chemistry; shrinkage risk minimised compared with many rapid-set alternatives.
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May be mixed with clear seawater (free of silt/biological contamination) when potable water access is constrained.
Compare:
• Need a similar fast-set but lower strength? Choose Roundtower Marine P10.
• Need a fast-set with NHL binder? Choose Roundtower Marine LP6 / LP8.
• Need cement-free, slower set above water? Choose Roundtower Marine L4.
Suitable applications
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Pointing and bedding of quay/harbour walls, bridge abutments, revetments, coping stones, lock chambers and culverts in fresh or saltwater.
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Tidal and splash zones demanding robust durability and strong early resistance to washout/scour.
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Conservation/renovation where a moderate, not brittle strength profile is desirable.
Coverage & yield
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25 kg → Approx14.5 L fresh mortar.
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Roughly 1.5 m² of joint at 10 mm depth (yield varies with joint width/depth and substrate texture).
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On-site trials recommended to confirm 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 to a cohesive, plastic consistency; do not over-water. Discard material that has begun to set.
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Place/Finish: Compact fully to the back of the joint; profile once the mortar firms.
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Curing & protection: Shield from frost, rain, direct sun, drying winds and washout through initial set; maintain gentle curing thereafter.
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Temperature window: +5 °C to +30 °C (consider wind-chill/radiant heat). Avoid use if freezing is forecast during early cure.
Colour & batching
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Natural, pigment-free tan; final tone varies with exposure and curing. Custom colours not available.
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For colour-critical work, request curing guidance and order sufficient material from a single batch.
