Traditional good practice on site is essential. We recommend that all site practice is in accordance with the recommendations of the Code of Practice for use of masonry. BS 5628-3:2005. The following points are of importance:
Health & Safety: Wet mortar, concrete and screed are abrasive and alkaline. They can cause alkali burns, which are not felt until after the damage has been done. Non porous protective clothing should be used. Where contact occurs, whether directly or through saturated clothing, wash immediately.
Cover mortar in tubs to avoid contamination from site debris and adverse weather.
Do not use trowel ready mortar after its 'Use By' date which is printed on the face of the delivery ticket, or after the mortar has begun to harden. Please advise us if you should encounter any problems..
Workability is enhanced by the inclusion of air entrainment, which reduces the water requirement, making hardened trowel ready mortar more resistant to freeze-thaw attack by frost. Not more that 5 litres of water per tub may be added to restore consistency, whilst the mortar is still retarded and easily workable.
Freshly laid masonry should be protected from wind and sun, for instance with a waterproof sheet or damp hessian. This will avoid the mortar drying out too fast before the slow chemical reaction of hardening (which needs moisture) is completed.
Freshly laid masonry should be protected from driving rain and any frost with a waterproof sheet or damp hessian allowing an air gap between the covering and the masonry. This will avoid the wet mortar being washed away by the rain, or being subject to freeze-thaw attack by the frost, while the slow chemical reaction of hardening is completed.
It has been the practice with some brick types to sometimes lightly wet the bricks (ducking) to offest moisture being sucked too quickly from the wet mortar into the brick, which can result in reduced adhesion. However, this is not now generally recommended. We suggest the brick manufacturer is consulted if the practice is being considered.
The use of trowel ready mortar with wet engineering bricks should be avoided, as there may be too little suction to permit good results. Satisfactory results can usually be obtained with dry engineering bricks.
For further information please contact our Mortars & Screeds Customer Service Team on 01652 680000