The effect of the addition of polypropylene fibres on the properties of corundum refractory concretes with a low cement content and an addition of aluminium phosphate

The effect of the addition of polypropylene fibres to the corundum concretes containing both high-aluminate cement and aluminium phosphate on the compactness, gas-permeability and pore distribution has been investigated. The mercury porosimetry test results revealed that concretes with the addition of polypropylene fibres, as compared with concretes containing no fibres, exhibit microstructure with an increased quantity of pores of a diameter of about 17 μm, which corresponds in approximation to the fibre diameter and is comparable to AlPO4-containing concretes and to concretes containing aluminate cement only. Specimens of the AlPO4-containing concrete with no fibre addition have lower gas-permeability at temperatures of 110 and 300 °C, as compared to specimens of concrete with aluminate cement only. For both concretes with the polypropylene fibre addition, a similar gas-permeability and its increase with the increase in heating temperature were reported. This is caused most probably by burning out of the fibres creating a micro-channels system in the concrete, which facilitates the gas flow. For these concretes, an increase in the volume of pores is also observed after heating at a temperature of both 110 °C, and 1500 °C.