MasterSeal® 551 Cementitious Waterproof Coating | MCT CHEMICALS | MASTER BUILDER SOLUTIONS

MasterSeal 551 is a flexible, two-component, acrylic-modified cementitious waterproofing coating for concrete and masonry. This elastomeric, reinforced coating is applied by brush, roller, or trowel to waterproof and resurface various construction materials. Once cured, the 2mm thick MasterSeal 551 membrane can accommodate movements up to 0.5mm, or up to 1.2mm when reinforced with 100% virgin polypropylene woven fabric.

RECOMMENDED USES

MasterSeal 551 is ideal for:

• Waterproofing of roofs, decks, balconies, etc.
• Water-retaining structures subject to movement
• Basement waterproofing
• Protecting concrete from water, carbonation, and de-icing salts

FEATURES AND BENEFITS

• Protection Against Carbonation: A 1mm coating offers an anti-carbonation barrier equivalent to over 80cm of concrete.
• Waterproof: Suitable for both internal and external waterproofing.
• Excellent Adhesion: Bonds effectively to both porous and non-porous surfaces.
• Flexible: Handles thermal movement in concrete structures.
• Suitable for Potable Water Contact: Can be used for lining concrete water tanks.
• Vapor Permeable: Repels water while allowing concrete to breathe, preventing osmosis.
• Compatible with Moist Surfaces: Can be applied to concrete as soon as 24 hours after pouring, providing immediate protection.
• Durable: Can withstand occasional foot traffic.

STANDARDS

• BS 1881 Part 208: 1996 – I.S.A.T.
• DIN 1048 water penetration test

APPLICATION GUIDELINES

Proper substrate preparation is crucial for optimal performance. Surfaces should be structurally sound, with a direct tensile strength greater than 1.5 MPa (measured via pull-off tester at a load rate of 100N/s), clean, and free from laitance, loose particles, oil, grease, old coatings, curing compounds, or any other contaminants. Mechanical wire brushing may be needed for small areas.
Before priming, use MasterEmaco repair mortars to fill holes and smooth out irregularities.

MIXING

MasterSeal 551 is supplied in pre-measured units. Mix on-site using clean containers. Slowly add the powder to the liquid and mix with a slow-speed drill (300rpm) fitted with a suitable paddle. Mix only as much as can be used within one hour.

APPLICATION

Do not apply to dry concrete. Saturate the surface with clean water before applying while it is still damp (saturated surface dry). Use a short, stiff-bristled brush or roller for application, and trowel as needed. For large depressions (6-10mm), use less gauging liquid to achieve the desired consistency. If multiple coats are required, apply the second or subsequent coats after the previous one has dried.