A ready mixed natural cement, water-resistant mortar suitable for aggressive freshwater and saltwater applications requiring a robust level of durability, reduced risk of debonding and resistance to sulphates. Available in a 25kg bag.
£16.99 £20.39 inc VAT
In stock
Estimated lead time is 3-5 business days
Cornerstone Marine P15 (previously known as Harbour Mix) is a dry ready mixed natural cement mortar for marine building and pointing work of water-bearing masonry above and below the water level in aggressive marine environments. One of our most popular marine products, Marine P15, is frequently chosen for seawater and saltwater canals. Available with two finishes, a coarse tan finish as standard or medium by request.
As part of the Cornerstone Marine range for building and pointing water-bearing masonry, this ready-mixed natural hydraulic lime and natural cement mortar for aggressive marine environments.
Manufactured by Cornerstone using Prompt Natural Cement and natural sands and free of synthetic polymers to create a high-performance mortar which provides an additional level of durability for aggressive marine environments. Featuring no Portland Cement, Marine P15 offers additional flexibility and reduced risk of shrinkage cracking than typical mortars designed for water-bearing masonry but remains remarkably durable. Available as standard with Prompt Natural Cement.
Well-suited for applications in aggressive marine environments, which require a mortar with a medium level of strength but with an accelerated set.
With a diverse range of lime-based products, Cornerstone defies the standard one-size-fits-all approach, providing refined solutions to tackle each project effectively. Their products can be found on prestigious buildings worldwide, blending innovation with tradition to meet evolving industry needs.
As with any natural product, variations in colour, texture and shape may occur. In addition, images may vary slightly from actual products due to these natural variations and screen resolution. For the best consistency, ensure to acquire a sufficient amount of material with your order to avoid batch-to-batch variation.
Suitable for external use, where the binder strength is appropriate for the host background or surface.
Relevant for marine building and pointing work applications above and below the water level, including aggressive tidal environments that would benefit from a robust level of durability, reduced risk of debonding and resistance to sulphates. Appropriate for various project types, including conservation and renovation.
While Marine P15 is entirely natural in colour and absent of any pigments, the environmental conditions and curing process will affect the final colour achieved. As such, we are unable to create custom colours for this product. For colour-sensitive projects, our team can provide guidance on curing methodology.
A 25kg bag will produce approximately 14.5 litres of mortar and fill roughly 1.5m² of joint at a depth of 10mm. Can conveniently be mixed with clear seawater free of biological, silt and sand contamination. The width and depth of the joint will influence this estimation. On-site trials are advised for the best yield indication for your specific project.
Supplied in 25kg polythene-lined and colour and batch-code paper bags for easy identification on-site and palletised for ease of transport, storage, and handling.
The working or open time of Marine P15 is variable depending on environmental temperatures. Do not use in temperatures below 5°C or above 30°C, or if freezing conditions are predicted within the following few weeks, including wind chill. We always advise following best practices for curing and protecting natural cement mortars. Protect from adverse environmental conditions, including frost, rain, direct sunlight and drying winds.
See the Technical Data and Documentation section for detailed product information, application guidance, and datasheets. Always review any available documents before use. Each project is unique, always seek professional advice before undertaking a project.
When working with lime, an alkaline material, always ensure you wear the appropriate PPE. Browse our range of tools and PPE to get started.
Store in indoor covered and dry conditions, protected from environmental conditions, including water, damp or frost and clear from the ground. Always reseal packaging if product is still present.
Do not use in temperatures below 5°C or above 30°C, or if freezing conditions are predicted within the following few weeks, including wind chill. We always advise following best practices for curing and protecting fresh lime renders and plasters. Protect from adverse environmental conditions, including frost, rain, direct sunlight and drying winds.
Brand
Cornerstone
Binder
Natural Cement
Colour
Tan
Material
Natural Cement, Natural Sands
Work
Pointing, Building, Bedding
Use
External
Application
Manual
Mix Ratio
1:2
Aggregate
5mm down sharp washed flint sand
Coverage
A 25kg bag covers approx. 1.5m2 for pointing applications at a 10mm depth
Yield
A 25kg bag yields approx. 14.5 liters
Set Time
Approx. 50 minutes at 17oC
Strength
21.8 Nmm 2 as a mean measurement with a w/c ratio of 0.64. *Not a guaranteed minumum
Always read any available datasheets and documentation before use.
Stock Quantities and Lead Times
Stock quantities and lead times are estimated and may differ or increase based on the order size and shipping method. If your timeline is sensitive, get in touch with the team.
Palletforce
Pallet orders with Palletforce Economy are typically dispatched from Cornish Lime within 1-2 business days, providing your item is in stock and not made-to-order. Once dispatched, Palletforce will deliver your order within 3-5 business days, depending on your location. Please ensure that your site can accommodate articulated lorries or similar-sized vehicles.
Local Delivery
The Cornish Lime team provides local delivery with a 18-tonne vehicle with a crane to assist with unloading. You will be contacted by phone to arrange delivery and ensure your site can accommodate our vehicle.
APC Parcel Courier
Orders shipped by APC parcel courier are typically shipped the next business day and arrive within 2-3 business days, providing your item is in stock and not made-to-order. APC will contact you via email with delivery information, and orders can be tracked on the APC website.
Premium or Expedited Service
For a premium or expedited delivery service, please get in touch to discuss if this option is available for your order.
For further information, see our delivery information page.
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