High temperature durability of fiber reinforced high alumina cement composites

The effect of high temperature exposure on the durability of fiber-reinforced composite materials based on high alumina cement is studied. A combination of X-ray diffraction- and thermal analyses of hydrated phases shows a simultaneous presence of all principal hydrates (CAH(10), C(2)AH(8), C(3)AH(6), AH(3)) in significant amounts during the whole 2-28 days hydration period. The application of basalt aggregates and basalt fibers is found to improve significantly the high-temperature durability, in a comparison with the cement paste. The residual values of compressive and bending strength of the most successful mix with the combination of longer and shorter basalt fibers in a 90:10 ratio are 50% and 34%, respectively, after 1000 degrees C exposure. The fiber reinforced composite material with the most favorable mechanical properties exhibits also the highest resistance to water and water vapor transport and the lowest water vapor adsorption after 1000 degrees C pre-heating, which correlates well with its lowest amount of pores bigger than 100 nm. The thermal conductivity and specific heat capacity of all analyzed composites show a significant increase with the increasing moisture content; the differences between the values in dry and water saturated state are up to 100% and 65%, respectively. The thermal strain of all studied materials is almost linear within the whole 20-1000 degrees C range, with the basalt fibers being able to decrease it by up to 7% at 1000 degrees C. (C) 2018 Elsevier Ltd. All rights reserved.