Trade Journals for the Concrete Industry

High-performance concretes and ultra-high-performance concretes (UHPC) are attracting increasing interest worldwide due to their excellent mechanical properties and durability, resulting in an ever wider range of applications. The special properties of UHPC result from a very low water/binder ratio (w/b ratio  0.25) and a high packing density. However, a disadvantageous effect of the high-density and almost capillary-pore-free microstructure of the UHPC is that temperature stresses of 250 °C lead to damage to the microstructure or to explosive failure. An increase in thermal resistance to temperatures above this critical temperature is achieved by using regenerated cellulose (CR) fibres. These fibres decompose and form a cavity system, so that thermal resistance is ensured even under cyclic stress. One application for this is cement-bonded oven slabs for large bakeries. Conventional cementitious oven slabs are made of normal concrete (C30/37), have a thickness of 13 to 30 mm and a length/width of up to 2.85/1.25 m. A higher durability of the optimised oven slab can result in environmental and economic advantages, so that the thermally stable UHPC was adapted to existing factory conditions in close cooperation with the cooperation partner Schaub Backofenplatten.