Mapei Mapegrout Thixotropic Zero

Mapei Mapegrout Thixotropic Zero is a ready-mixed powdered mortar composed of high-strength cements, selected aggregates, special additives and synthetic fibres.

Best Uses

Mapei Mapegrout Thixotropic Zero is suitable for the surface repair of deteriorated concrete structures on both vertical and horizontal surfaces.

Some application examples include:

• Repairing deteriorated areas of concrete, corners of pillars and beams, edges of balconies damaged by the oxidation of reinforcing steel
• Reconstruction of reinforcing rod covers in reinforced concrete structures
• Smoothing surface defects, such as gravel nests, new casting joints, holes created by formwork spacers, exposed rods, etc
• Filling of rigid joints
• Repair of surfaces subjected to heavy abrasion (canals, industrial floors, ramps, etc.)
• Smoothing of diaphragm walls and tunnels
• Repairing viaducts for highways, roads and railways

When mixed with water, Mapegrout Thixotropic Zero becomes an easily workable mortar with high thixotropic properties that can be applied on vertical surfaces without sagging even in great thicknesses and with no need for formwork. If Mapegrout Thixotropic Zero is prepared by only adding water, it must be cured under damp conditions in order to guarantee that the product expansive properties develop completely and correctly. Unfortunately, it is not easy to guarantee that these conditions are created on site.

However, to guarantee that the expansive properties of Mapegrout Thixotropic Zero are carried out in the open air, 0.25% of Mapecure SRA, a special additive which has the property of reducing both plastic and hydraulic shrinkage, may be used to great advantage when added to the mix. Mapecure SRA has a very important role to play, in guaranteeing better curing of mortar. Also, when mixed with Mapegrout Thixotropic Zero, it may be considered a technologically advanced system, in that the additive has the capacity of slowing down evaporation of the water and of promoting the development of hydration reactions.

Basically, Mapecure SRA behaves like an internal curing agent and, thanks to its interaction with some of the main components which make up the cement, it helps to reduce shrinkage by between 20% and 50% compared with the standard values of the product without the additive. This will obviously lead to a reduced risk of cracking.

Once hardened, Mapegrout Thixotropic Zero has the following properties:

• Very high flexural and compressive strength
• Modulus of elasticity, coefficient of thermal expansion and permeability to water vapour similar to those of high quality concrete
• Waterproof
• High adhesion to old concrete, provided it has been soaked with water beforehand, and also to reinforcing rods, especially if they have been treated with Mapefer or Mapefer 1K Zero
• High resistance to abrasion.

Application

Composition of mix:

• 100 kg of Mapegrout Thixotropic Zero
• 15.5-16.5 kg of water
• 0.25 % of Mapecure SRA (optional)

Preparing the substrate
Remove deteriorated, detached and contaminated concrete until a solid, resistant, and rough substrate is obtained. Any previous restoration work and any other coatings that are not perfectly adherent must be removed using suitable equipment (mechanical breakers, hydro-scarification, etc.).  Clean the concrete from residues of previous milling operations, and the reinforcement rods from dust, rust, cement slurry, grease, oil, paint, and other harmful materials, by sandblasting and treating with high pressure water. After preparation, the concrete surface to be repaired must be visibly clean and rough, with a roughness of no less than 5 mm, and with the inert fraction open and completely exposed to allow the mortar to properly set and adhere to the sub-layer.

Treat reinforcement rods with Mapefer or Mapefer 1K Zero, according to the procedure illustrated in the relative Technical Data Sheet for each product. Wait until Mapefer or Mapefer 1K Zero has dried. Saturate the substrate with water. Before carrying out repairs with Mapegrout Thixotropic Zero, wait until excess water has evaporated. If necessary, use compressed air to help remove excess water. The substrate must be saturated with water but with a dry surface.

Preparing the mortar
Pour the amount of water required into a cement mixer to obtain the consistency required (15.5-16.5% of the weight of powdered mortar). Start the concrete mixer and slowly and continuously pour Mapegrout Thixotropic Zero into the water. If improved open-air curing of the mortar is required, add Mapecure SRA to the final mix at a dosage of 0.25% by weight of the mortar (0.25 kg every 100 kg of Mapegrout Thixotropic Zero). Mix for 1-2 minutes, checking the homogeneity of the mix while scraping any unmixed powder off the sides of the mixer; remix for another 2-3 minutes.

Depending on the quantity being prepared, a mortar mixer or a drilling machine with a stirrer attachment can be used. The mixing must be carried out at low speed to avoid entraining an excess of air into the mix. Mapegrout Thixotropic Zero has a pot life of about 1 hour at +20°C. 

Applying the mortar
The application is carried out by trowel or putty knife without formwork even on vertical surfaces and ceilings for thicknesses from 10 mm to 50 mm per layer. Without confining, Mapegrout Thixotropic Zero can only be applied in thicknesses greater than 3 cm if the surface has been roughened and reinforcing rods have been placed, taking care to apply at least 2 cm of cover to the reinforcement. Smaller thicknesses can be applied without reinforcing rods as long as the substrate is sufficiently rough to be able to counter the expansion.

Mapegrout Thixotropic Zero may also be applied by spray with a suitable worm-screw or piston-type mortar pump with a separate mixing unit; continuous-feed type rendering machines are unsuitable. Apply Mapegrout Thixotropic Zero after treating the reinforcing rods with Mapefer or with Mapefer 1K Zero. When a further coat of Mapegrout Thixotropic Zero is necessary, it must be applied before the previous one has completely set (not more than 4 hours at +23°C). The repair process is complete when a smoothing coat of Mapefinish and a coat of Elastocolor Paint have been applied.