SINGLE COMPONENT SULPHATE AND CHLORIDE RESISTANT, FIBRE-REINFORCED MORTAR FOR THE REPAIR OF CONCRETE

Preparing the substrate
Remove all degraded and/or loose concrete until a sound and solid substrate is achieved.

Where necessary clean the concrete and reinforcing steel by sweep blasting or other approved mechanical methods, to remove all dirt, any corrosion products, cement laitance, grease, oil, any previous coatings and other deleterious elements.

Any previous repairs that are no longer thoroughly bonded must also be removed.

Pre-soak the substrate with clean, potable grade water to obtain a saturated surface dry (SSD) condition.

Preparing the mortar
Pour into the mixer or a rust-free mixing vessel, the pre-gauged amount of potable grade water needed to obtain the required consistency.
Application Litres of water
per 25 kg bag
Trowel 2.75 – 3.25
Spray 3.25 – 3.75
Start the mixer and slowly add the complete bag of SpECbuild MC500 Fibre to the water, in a continuous flow;

Mix for 1 to 2 minutes; check to make sure the mix is well blended. Scrape any unmixed powder from the bottom and the sides of the mixer. Mix again for a further 2 to 3 minutes;

Depending on the amount of mixed material required, a mortar mixer or a slow speed heavy duty drill with an appropriate mixing paddle may also be used. Mix at low speed (300 rpm) to avoid entraining air;

Avoid mixing manually as this may adversely affect several of the mortars characteristics, including mechanical strength, shrinkage, impermeability, etc;

SpECbuild MC500 Fibre can be applied at a minimum thicknesses of 20 mm up to 60 mm in a single layer. Additional buildup can be achieved subject upon the repair area geometry, location and roughness of the concrete substrate.

Reinforcement Steel Preparation
For repairing concrete elements damaged due to reinforcement corrosion, it is recommended to use mechanical means of abrasion in order to remove the corrosion deposits from the exposed reinforcement prior to coating with SpECcoat Zn25.

APPLICATION
Hand Application
SpECbuild MC500 Fibre may be applied by trowel to vertical surfaces in layers up to 60 mm thick, or for overhead applications in layers up to 30 mm thick, without the use of formwork. Where higher buildup of SpECbuild MC500 Fibre is required, leave the surface of the previous layer in a rough condition, allow to harden, then wet the surface with water, prior to applying the second layer.

Spray Application
SpECbuild MC500 Fibre can be spray applied using a suitable piston or worm-screw type rendering machine, such as a Turbosol or Putzmeister. Do not use a continuous mixing type rendering machine.

Precautions to be observed during application
In hot working conditions the following precautions should be taken:
· Avoid direct exposure to sunlight for stored material and also mixing equipment;
· Prior to use, the product must be stored in a shaded area out of direct sunlight;
· Use cool water for mixing;
· Avoid application during the hottest time of the day and/or in direct sunlight;
· Mix only sufficient material that can be applied using available labour and equipment;

At low temperatures, prepare the mix with water heated to approx. +20°C.

Curing
In accordance with good concrete practice, all exposed surfaces of SpECbuild MC500 Fibre must be immediately cured after application, using wet hessian covered with polythene sheeting; failure to cure the open surfaces can cause the formation of cracks due to plastic shrinkage, especially in hot and/or windy climatic conditions; SpECcure WE should also be considered.

Spray water onto the surface of the application within the first 8-12 hours and repeat the operation for at least the first 48 hours. As an alternative, after finishing the application of the material, apply a coat of curing membrane such as SpECcure WE or SpECcure AC. Film forming curing membranes can impair the adhesion of subsequent finishes