Prestressed textile reinforced cement composites: Fid-Bau Portal

Prestressed textile reinforced cement composites

Krüger, M. / Reinhardt, H.W.

Nowadays textile reinforcement is used in several applications. However, cement composites have been reinforced up to now with un-tensioned textiles, so the full tensile strength of the textile is only used after concrete cracking, this is not economically viable. In direct pre-stressing the high tensile strength of the textiles can already be used in the un-cracked state. The advantages are the higher stiffness of the composite element as well the impermeability with respect to liquids and gases. Among other things different possibilities and devices for pre-stressing textile layer structures are discussed. On the basis of some tests to the bearing capacity of textile layered bi-axial pre-stressed thin concrete elements, the pros and cons of pre-stressing are discussed. Finally in conclusion some fields of application are pointed out. Pre-stressing of AR-glass-textiles result in a higher stiffness and higher load in the ultimate limit state. Also the maximum crack width is very low up to the ultimate limit state, which has a positive effect upon its impermeability and possible self-healing of concrete. One problem, which occurred during the experiments, was the low durability up to 24 h of the used un-coated AR-glassrovings. Only very low pre-stressing loads could be applied, so the textile reinforcement was nearly not activated in the un-cracked state of the concrete. Pre-stressing of textiles does have some advantages. However resultant problems do occur. Pullout tests show that the different finishes of the analysed fibres have a high effect upon the bond. With regard to the low bond particularly of Carbon or Aramid fibres, there should be thought regarding the use of an epoxy-resin or coating. Another advantage in using an epoxy-resin is, that the nodes were fixed at their crossing points and second the rovings could probably be pre-stressed with a higher load. Pre-stressed textile reinforcement in concrete has several advantages, but there is the need for further research to make it practicable. Also it must be stressed, that it would not replace steel reinforcement, rather it will be an alternative to steel reinforcement or will make new fields of application possible.