Influence of mechanically treated carbon fibre additives on structure formation and properties of autoclaved aerated concrete

This work deals with investigations on effect of chemically and thermally resistant carbon fibre (CF) additives of various mechanical treatment on structure formation and properties of autoclaved aerated concrete (AAC). It was established that various methods of CF crushing, such as mixing with sand pulp, chopping, grounding, milling in dry way, milling in wet way cause different fineness of disintegrated CF particles and that along with increase in fineness, the crystallinity of AAC binding material is growing what leads to the following: increase in compressive strength by 6–22%; after exposure at temperature of 700 °C, decrease in thermal deformation by 5–20%; decrease in mass loss by 7–20%. Upon addition of mechanically not treated CF of 0.1%, the flexural strength increases by 29% versus that of AAC without CF additive. The effect of added mechanically treated CF on flexural strength is less than that of not treated CF. Due to increased CF fineness, the flexural strength increment drops from 21% to 4%. Basing on the results obtained, one can draw a conclusion that CF particles resulted in mechanical treatment have an activated surface and can serve as nuclei of crystallization during the hardening of AAC binding material, which contains a mechanically treated CF additive, thus causing increase in crystallinity of hardened binding material and, consequently, improved performance of AAC.

► Carbon fibre additives act as nuclei during the autoclave hardening of aerated concrete.
► Size of carbon fibre additives depends on the way of their mechanical treatment.
► The higher is amount of small carbon fibre particles the higher is degree of crystallinity.
► The higher is degree of crystalinity, the better are properties of autoclaved aerated concrete.