Influence of different PVA fibres on the crack behaviour of foamed cement paste

Foamed cementitious materials are highly porous materials with low density, low compressive and bending strengths, caused by their high porosity. Due to the small strength and the scatter of the properties the material is not commonly considered as a load bearing material. The aim of this work is to improve the mechanical properties and to reduce the variability of the properties of foamed concrete while keeping its favourable physical properties. To achieve the main goal of this research fibres are added to the foamed cement paste to improve the mechanical properties, specifically the compressive and bending strengths at the macroscopic level. The crack patterns are analyzed by sectioning after impregnation with fluorescent epoxy resin. Emphasis is on fracture mechanisms in various foamed concretes. The varied parameters are the material density of the foamed concrete (with various amounts of foam), the w/c-ratio, fibre content and fibre size. The main result is that, in particular the flexural strength and ductility of foamed concrete can be improved significantly by adding fibres, achieving a bending strength a factor 5 higher than commonly observed values for plain mixtures without fibres.