APPLICATION OF BETEC MORTARS AT LOW TEMPERATURES
The application range of cement based products is usually +5°C. A few BETEC products, however, can be ap-plied below this temperature. The water/cement factor of BETEC mortars fluctuates around 0.30. This value is extremely low in comparison with various other mortar brands. This value implies that the water content in BETEC mortar is only used for the chemical reaction with cement, i.e. relatively little water, which could lead to freezing, is left in the capillary pores. BETEC’s high fluidity is achieved with the use of high quality plasticizers and liquefiers, contrary to other materials in which a higher water/cement factor is used, which affects the fluidity. Because of the excessive use of this transport water these materials are much more likely to result in freezing of the sub-mould, because water expands when it freezes.
Processing of BETEC mortars at temperatures below +5°C (DIN 1045):
Because of the delay in the hydration (hardening) process during low temperatures or frost the concrete needs to be protected from heat loss, freezing and dehydration.
In principle the above-mentioned BETEC mortars can be processed down to -5°C. However, a number of (win-ter) measures need to be imposed .
Required temperature of prepared mortar during processing:
- With air temperatures between +5°C and -3°C the mortar temperature must not drop below +10°C during processing
- With the air temperature below -3°C the mortar temperature must not drop below +20°C during processing
- The mortar temperature must not exceed +30°C during processing.
- The concrete processing base must always be free from snow and ice
- Concrete damaged by frost must be removed
- If necessary the mixing water must be heated (see table)
- Limit heat loss in applied mortar, for instance as follows:
1. Cover and insulate fresh mortar in contact with outside air using insulation blankets (it is advisable to keep some space (air) between the cover and concrete surface / wooden shuttering will usually provide sufficient protection providing the temperature is not too low – steel shuttering may require extra insulation).
2. Use heated shuttering.
3. Remove shuttering at a later date.
4. (Pre)heat the structure using heaters or infrared heaters. It should be noted, however, that heaters can generate hot, dry air flows. In that case measures should be taken to prevent the concrete from drying out locally; sudden cooling when the heat supply is switched off should also be prevented.
In general it would seem that when the material has reached a tensile strength of 5 N/mm2, it will be resistant to frost and further drops in temperature will not inflict any damage.
It is advisable to store the material in heated conditions so that the water needs less heating.
Tabel 1: Mixture temperature to achieve a specific fresh mortar temperature.
PREPARATION WATER TEMPERATURE
^ = Temperature dry mortar ^ =Temperature fresh mortar
This information sheet covers the use of moulding mortars; however, some other Betec mortars can be used in accordance with the above mentioned measures down to -5°C, ask our technical department.