MM Surface Repair Mortars. Accelerator for Cold Weather Working
Cold Weather Working
In this instance cold weather working means temperatures of less than 50C but more than 10C and where the ambient temperature will not drop below 10C for at least 12 hours but may also not rise above 50C in the same period.
Precautions for Use
Accelerators should be used with care.
Do not over or under-dose mortars.
Use the correct amount of accelerator to the correct amount of mix water for the whole mix.
The Accelerator must only be added to the mix water in accordance with the data provided here.
Dosing
Determining the correct amount of accelerator to use as follows.
| Surface Repair Mortar Kilos | Nominal Water Content mL | Accelerator Content mL |
| 1 | 180 | 10 |
| 2.5 | 450 | 25 |
| 6.25 | 1125 | 62.5 |
| 12.5 | 2250 | 125 |
| 25 | 4500 | 250 |
Water content may vary slightly depending on the final mix consistency required and or the depth colour used to achieve the desired result, however the amount of accelerator per Kilo of material should remain the same for the given weight of repair mortar. Deep reds, very strong yellows and very dark colours require higher pigment loads and therefore will use more mix water, the amount of accelerator should be determined by the weight of the product and the final water demand tempered to achieve the desired consistency.
Mixing
Mix in accordance with standard mixing practice.
Preparation of Backgrounds
Never apply MM Surface Repair Mortars on frozen or saturated backgrounds.
Check background suction and adjust by dampening as required to achieve a good suction bond.
On very low suction backgrounds use MM Bond Enhancer, either added to the mortar on site in accordance with the stated dosage or factory produced, within the mortar.
Mechanical keying can help to overcome inadequacies in suction bonds.
With an accelerated set, comes additional chemical shrinkage stress that could result in detachment with the background if the suction is higher or lower than ideal.
Where accelerators are being used, greater emphasis on mechanical keying, cramps and anchorages should be introduced.
Protection of New Work
Protect new work from direct rainfall, saturation, rapid drying and freezing.
Curing New Work in Cold Weather
Avoid wet curing, keep immediate area surrounding new work damp, never wet for the first 12 hours only, allow to dry out under covers for at least 24 hours.
Rate of Set
The initial rate of set of an accelerated repair mortar is approximately twice as fast as an unadulterated standard repair mortar at an ambient temperature of 100C. Pot life will not exceed 1 hour. Do not re-temper accelerated mixes after 1 hour. Discard unused mortar.
Mortar with accelerator mixed into it will reach 72 hours strength at 24 hours and 7-day strength at 72 hours. Freeze thaw resistance will be achieved in 24 hours.
Frost damage is a result of water within the matrix of the mortar being irreversibly disrupted by the expansion of water at freezing, new work has a water content added at the mixing stage, as this begins to dry out, and during the curing period, the work should not be allowed to become saturated by rain as this will likely result in the mortar pores becoming inundated and at a higher risk of damage from expanding ice forming within the pores of the mortar at or below 00C. Keep fresh new work insulated.