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Weber Saint-Gobain - Official website of the company

webercem mortar CP

webercem mortar CP
webercem mortar CP

Product Benefits

● Levelling rough surfaces of concrete ● Rendering and building up thicknesses over low cover to steel reinforcement ● Patch repairs to concrete bridge abutments, parapets, beams and crossheads ● Filling-in of core holes, small voids and shutter tie holes ● For tunnels, car parks, bridges, and marine structures such as jetties where cathodic protection is to be used as a preventative treatment ● For vertical and horizontal surfaces ● Suitable for external and internal surfaces

Low-resistivity, polymer-modified, Highways Agency Class M patching mortar and render for cathodic protection.

Product Features

About this Product

webercem mortar CP is a pre-batched, single-component mortar needing only mixing with water to produce a render with low resistivity, suitable for patch repairs on concrete structures where cathodic protection systems are to be used.

Conforms to BS EN 1504-3 as a Class R4 repair product.

Features and Benefits

  • Good bond to concrete - damp or wet
  • Durable - does not crack or craze when applied and properly cured
  • Easy to use - can be mixed by hand or mechanically
  • Easy to apply - can be applied easily with a spray pump or by trowel without slumping
  • Easy to finish - good smooth finish obtainable with a float or sponge. Provides a cohesive and level surface suitable for overcoating. 
  • Complies with Highways Agency ClassM mortar specification - contains more than 400 kg/m3 of ordinary Portland cement to BS 12, the maximum size of aggregate does not exceed 2 mm, the total chloride ion content is less than 0·1% of cement, the resistivity at 28 days saturation is between 5 kΩcm and 15 kΩcm.

Technical Services

weber's Customer Services Department has a team of experienced advisors available to provide on-site advice both at the specification stage and during application. Detailed specifications can be provided for specific projects or more general works. Site visits and on-site demonstrations can be arranged on request.

Technical helpline
Tel: (01525) 722110
Fax: (01525) 718988

Sales Contact

weber products are distributed throughout the UK through selected stockists and distributors. For UK sales enquiries and overseas projects, contact Weber's Sales office.

Sales office
Tel: (01525) 722100
Fax: (01525) 718988


Send or download the documents

You can either send the documents to an email address, or download it

Preparation & Application


All substrates must be sound, cohesive, free of loose matter, oil, grease and dust.

Concrete surfaces must be adequately prepared by use of scabbling, grit blasting, high pressure water jetting, needle gunning or other appropriate means to provide an adequate mechanical key for the mortar.

Old concrete surfaces contaminated with oil or grease require suitable preparation. New concrete must be cured effectively for at least 14 days or as directed by the engineer using an approved curing method not including use of a permanent curing membrane.

Fill voids with webercem mortar CP mixed to a stiffer mortar consistency and allow to cure.

The perimeter of each area where webercem mortar CP is to be applied must be cut back square. Feather edging is not permitted. Use temporary battens or a wet mortar thickness gauge to ensure that the correct thickness of mortar is applied. Thoroughly dampen the area with clean water before applying webercem mortar CP.


Water additions (per 25 kg bag)
As a repair mortar and for core hole filling: 2·75 to 3·0 litres
For bondcoat and for pumping: 3·25 litres
For hand application as a render: 3·0 to 3·25 litres

For hand application
Mix webercem mortar CP in a forced action mixer or in a clean bucket using a paddle and a slow speed drlll for at least 2 min. at a speed not exceeding 500rpm. For small quantities less than 2 kg, mixing by hand using a spatula is permissible.

For machine application
Use a Putzmeister P11 or similar machine. Machine mix the mortar for at least 2 mins using not more than 3.25 litres of clean water per 25kg bag.

Useable time after mixing: 60 min at 20°C.


Temperature range of application: +5°C to +35°C. Do not apply on frozen surfaces or when frost is expected within 24 hours unless special precautions are taken to protect the substrate and the finished work from falling below 5°C. Do not traffic until 4 days after application.

Hand application: as a render
Apply an initial bondcoat with a plaster float to a thickness of about 2 mm pressing well onto the damp substrate, then immediately apply the first layer of webercem mortar CP to the required thickness not exceeding 10 mm in total. Leave a rough surface suitable for subsequent bonding of the second coat which should be applied as soon as the first layer has hardened sufficiently to support the second layer (approx 4 hours at 20°C).

Hand application: as a patching mortar
Apply an initial bondcoat with a plaster float to a thickness of about 2 mm pressing well onto the damp substrate, then immediately apply the first layer of webercem mortar CP mixed to a stiffer consistency to the required thickness: up to 20 - 30 mm per layer on vertical surfaces, up to 15mm on soffts (see Size of Repairs Table below). Any subsequent layers ofwebercem mortar CP should be applied not later than 24 hours after the previous layer (at 20°C).

Machine application
Apply the mixed webercem mortar CP by spray pump to the required thickness (max. 10 mm in one pass) and level off with a screeding bar. When applying a total thickness of 20 mm in 2 layers, leave the first layer 'as screeded', before applying the second layer as soon as the first layer is firm enough to support it.

Apply 2nd layer of webercem mortar CP after 4 hours and within 24 hours at 20°C.

A sponge may be used for a slighly textured finish. Finish off with a float for a smooth finish but over-trowelling can lead to surface crazing.

Immediately after completion of finishing and thereafter for the curing period, the mortar shall be protected against harmful effects of weather, including rain, rapid temperature changes, frost and from drying out. The method of curing shall prevent loss of moisture from the mortar. The curing time shall be three days at 20°C.

Packaging, Health & Safety


webercem mortar is supplied in a 25 kg bag.

Coverage / Yield

One bag will yield approx. 12 litres.

Storage and Shelf Life

When stored unopened in a dry place at temperatures above 5°C, shelf life is 6 months from date of manufacture.

Health and Safety

Contains cement (Contains chromium (VI). May produce an allergic reaction). Harmful by inhalation. Irritating to eyes and skin. Keep out of the reach of children. In case of contact with eyes, rinse immediately with plenty of water and seek medical help. After contact with skin, wash immediately with plenty of soap and water. Wear suitable protective clothing, gloves and eye/face protection.

For further information, please request the Material Safety Data Sheet for this product.