Technical Paper
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permeability decreases (Figure 8) while the strength increases (Figure 9). Also with MP20 the permeability decreases however, even after 30 days it keeps a much higher level than the MP20-free castable. The cold crushing strength increases somewhat more slowely with MP20 but nevertheless, it increases from 60 MPa after 1 day up to more than 100 MPa after 30 days.
Figure 7: DSC of CAC70-RA (1:1) pastes with and without MP20
Figure 10: Permeability as function of curing temperature (24h)
Impact of curing temperature on permeability While the AS10 formulation shows very low 110ºC-permeability after curing at 5 and 20ºC (24h, 100% rH) its even lower for the sample cured at 35ºC (Figure 10). With MP20 the permeability is for all curing temperatures more than 10 times higher than the MP20-free mixes.
Figure 8: Permeability evolution as function of curing time (20ºC)
Figure 11: Temperature at which 2/3 of water is removed from cubes of different sizes
Impact of sample size on dry-out behaviour Figure 9: Strength evolution as function of curing time (20ºC)
Impact of curing time on permeability and strength
Castable samples of AM6 and AM6-MP20 have been cured over a period of 30 days at 20ºC, 100% rH. With increased curing time, the castable
Cubes of three different dimensions and cured for 24h (20ºC, 100% rH) have been heated with a rate of 300 K/h. Figure 11 shows the temperature in the center of the castable at which 2/3 of the initially added water have been removed from the sample. While the removal temperature increases with the sample size for the MP20-free castables it remains almost constant in the range between 120 and 140ºC for all 3 tested MP20-containing castables. Without MP20 the A15 formulation shows the highest water removal temperature and the 12x12x12 cm3
cube exploded during the test 20 ENGINEER THE REFRACTORIES
November 2017 Issue
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