Lightweight Mortar Based on Blended Cement and Waste Cellulose Fibers Exposed to High Temperature

This article presents research focusing on the analysis of lightweight polymer–cement mortar using combined impact-echo (IE) and computed tomography (CT) methods after exposure to extreme temperatures. Lightweight mortar based on blended cement and waste cellulose fibers was developed for this purpose. The mortar consisted of a polymer–cement matrix (60% Portland cement, 40% blast furnace slag and polymer modifier) and porous aggregate (expanded clay with grain size from 0 to 2 mm) including other minor components (superplasticizer) and admixtures (silica fume). Mortars with two types of dispersed reinforcement based on waste cellulose (G-500T and G-700T) in amounts ranging from 0.5 to 1.5 kg/m3 were analyzed. The materials were tested at the age of 28 days upon exposure to 20 °C (storage in laboratory conditions), 600 °C, 800 °C and 1000 °C. Aside from IE and CT, the outputs were supplemented by testing basic physical and mechanical parameters (strength, volume changes, etc.), as well as microstructure analysis, specifically testing of microcracks using SEM. The purpose of the CT and SEM was confirmation of cracks, specifically microcracks (including their character and areas of appearance), along with possible anomalies occurring during high-temperature stress of polymer–cement composites.