Response of Refractory Cement Based Composite to Gradual Temperature Loading

This paper deals with the experimental study of the response of refractory concrete mixture to gradual thermal loading, up to 1000 °C. A binding system based on calcium aluminate cement (CAC) modified by the partial replacement of metakaolin was used. Short ceramic fibers were applied in a dose of 4% by volume in the studied mixture. Material transformations due to thermal loading were monitored in terms of residual mechanical, fracture and basic physical properties-compressive strength, flexural strength, fracture energy, dynamic modulus of elasticity, and bulk density in the study. The results obtained corresponded well with the mineral transformations monitored using the thermogravimetric analysis performed on the binder paste. Residual values of compressive and flexural strength were approximately 40% of the initial values after exposure to a temperature of 1000°C; however, the dominant part of the total loss was monitored up to 400°C, due to decomposition of the hydrates. Fiber employment contributed considerably to the resistance against thermal loading up to 400°C, which was demonstrated by the fracture energy results (a loss of 25% was monitored). An additional increase of the temperature load led to micro crack propagation, which was obvious in the results of dynamic modulus of elasticity determination, in which the short fiber incorporation was noticeably limited

Hygric Properties of Lime-cement Plasters with the Addition of a Pozzolana

AbstractThere are more than seven billion people currently living on the Earth and the demands of population are rising. Lime and cement are parts of most building materials, so their global consumption grows. Therefore, it is necessary to think both economically and ecologically, and search for a suitable alternatives and replacements. This study is aimed at an investigation of the influence of pozzolana as the third binder component on basic physical characteristics and hygric properties of lime-cement plasters. Results show that with the increasing amount of pozzolana in the mixture the open porosity goes down. This is accompanied by a liquid water absorption decrease. Also diffusion parameters are somehow worsened, as the water vapour diffusion resistance factor increases

RESIDUAL PROPERTIES OF FIBER-REINFORCED REFRACTORY COMPOSITES WITH A FIRECLAY FILLER

The aim of our study was to develop a composite material for industrial use that is resistant to the effect of high temperatures. The binder system based on aluminous cement was modified by adding finely-ground ceramic powder and metakaolin to reduce costs and also to reduce adverse effects on the environment due to high energy consumption for cement production. Additives were applied as a partial aluminous cement replacement in doses of 10, 20 and 30% by weight. The composites were evaluated on the basis of their mechanical properties and their bulk density after gradual temperature loading. The influence of basalt fibers and modifications to the binder system were studied at the same time. Basalt fibers were applied in doses of 0.5% and 2.0% by volume. The results confirmed the potential of the mineral additives studied here for practical applications, taking into account the residual mechanical parameters after thermal loading. The addition of ceramic powder reduced the bulk density by 5% for each 10% of cement substitution, but the residual values were very similar. The bulk density and the compressive strength were reduced when basalt fibers were applied, and the flexural strength was significantly increased in proportion to the fiber dosages. Metakaolin seems to be a more suitable additive than the ceramic powder that was applied here, because there was a significant increase in the mechanical parameters and also in the residual values of all properties that were studied