Flat R4

Structural R4-class, rapid-setting, shrinkage compensated, thixotropic, fiber-reinforced, mortar, applied in a single layer from 3 to 40 mm thick, for repairing and smoothing concrete

Product Description

Flat R4 is a one-component, thixotropic mortar with very low emission of volatile organic compounds made from special hydraulic binders, fine selected aggregates, synthetic poly acrylonitrile fibers, synthetic polymers and special admixtures. After mixing with water, the product forms a mortar with good workability. It is applied by trowel in a single layer from 3 to 40 mm thick to repair and smooth over concrete. Flat R4 hardens without shrinking and is characterized by its excellent adhesion to concrete substrates. After hardening, Flat R4 has the following characteristics:
• Excellent bond strength to both old concrete
• High dimensional stability and, therefore, low risk of cracking
• Thermal compatibility to freeze/thaw cycles
• Low permeability to water.

Field of Application

• Rapid repair work on deteriorated concrete beams, pillars, buffer walls, cornices, edges of balconies and structural members and elements that require the use of mortar with high mechanical performance characteristics.

• Quickly smoothing over surface defects in cast concrete, such as deep gravel clusters, spacer holes, second pours, etc. before painting the surface.

• Repairs and structural strengthening of concrete.

• Repairing precast concrete members and elements.

• Repairs to concrete damaged by rusty reinforcing bars due to carbonation.

Product Details

Product identity

Class according to EN 1504-3: R4
Type: PCC
Consistency: powder
Color: grey
Maximum diameter of aggregate (EN 1015-1) (mm): 0.4
Bulk density (kg/m³): 1,200
Dry solids content (%): 100
Ion chloride content (%): ≤ 0.05


Flat R4 is supplied in:
– 25 kg paper bags


The consumption is approximately 1.5kg/m2 at 1 mm thickness.

Application Procedure

Preparation of the substrate

• Remove all deteriorated and loose concrete to form a solid, rough and strong substrate. Any areas previously repaired and which are not perfectly bonded must also be removed.
• Remove all dust, rust, cement laitance, grease, oil and paint from the concrete and reinforcement rods by sandblasting or hydro-sandblasting.
• Treat reinforcement rods with Ferroprimer 1K or 2K, according to the procedure given in the Technical Data Sheet of product.
• Saturate the substrate with water.
• Before carrying out repairs, wait until excess water has evaporated.

Preparing the product

Pour approximately 5.5 liters of clean water into a container and slowly add a 25 kg bag of Flat R4 while mixing. Carefully mix the blend for several minutes then remove any powder which has stuck to the sides and bottom of the container. Add more water to obtain the consistency required without exceeding the recommended amount, approximately 6-6.5 liters. Mix again for several minutes to form a well-blended, plastic consistency, lump-free mixture. Flat R4 remains workable for around 15 minutes at +10°C to +25°C.

Applying the product

Apply a layer of mortar from 3 to 40 m thick with a trowel or putty knife; no formwork is required. As soon as the mortar starts to set, tamp the surface with a sponge float. The waiting time required before carrying out this operation depends on surrounding weather conditions. To paint and protect the surface, apply a coat of an elastomeric product or an acrylic product.