Breathable to fully waterproof mortars for marine masonry — from splash-zone repointing to submerged, high-pollution environments. Our Roundtower Marine range combines Prompt Natural Cement (OPC-free), natural hydraulic lime (where specified), and selected sands to deliver fast set times, excellent adhesion, and long-term durability in freshwater and seawater—all while matching the strength and permeability your substrate actually needs.
Why choose Roundtower for marine work?
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Right strength, right permeability: From highly vapour-permeable above-water mortars to water-resistant and fully waterproof options for tidal and submerged zones.
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Fast set, reduced washout: Engineered working times (≈45–74 minutes at ~17 °C) help you beat the tide and minimise scour.
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OPC-free chemistry: No Portland cement; inherently sulphate-resistant, polymer-free, and designed for compatibility with historic masonry.
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High adhesion & flexibility: Low debonding risk and less brittleness than many conventional rapid-set mixes of similar strength.
Which product, when?
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L4 – Above-water, breathable & capillary-active. Slowest set, lowest strength in the range that contains NHL only (cement-free).
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LP6 / LP8 – Fast-set NHL + Prompt Natural Cement hybrids. Choose LP6 for lower strength; LP8 for NHL5-grade strength with quick set.
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P10 – Low–medium strength natural cement. Rapid set, higher compressive strength than NHL5 and lower capillary uptake; great tidal all-rounder.
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P15 – Medium strength, high adhesion. Popular for seawater/saltwater canals; rapid set and robust durability.
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P30 – Water-resistant (not fully waterproof). Limited vapour permeability, rapid strength gain for aggressive tidal exposure.
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P50 – Fully waterproof. Rapid set and early strength where zero permeability is required.
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P60 – Waterproof + chemical resistance. Highest strength, lowest absorption; suited to polluted harbours, wastewater assets, acid/alkali exposure.
Typical applications
Quay and harbour walls, bridge abutments, revetments, coping stones, lock chambers and culverts; splash/tidal and submerged zones; conservation repointing where strength must remain sympathetic to original fabric; industrial and wastewater settings (P60).
Key benefits at a glance
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Fast working times to match tides and access windows
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OPC-free, polymer-free binders
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Natural sulphate resistance (Prompt Natural Cement)
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High adhesion and reduced shrinkage risk
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Available in natural buff/tan finishes (pigment-free)
