Properties of Short Fiber Reinforced Cement Paste for Concrete Tubes Produced by a Centrifugation Method

Abstract

This paper describes how concrete tubes are usually produced by a centrifugation method using steel bar reinforcements. It explains how the reinforcement of concrete with steel bars is expensive, susceptible to corrosion, and leads to rather thick and heavy structural elements. The application of short fiber reinforced cement (FRC) or mortar is a suitable alternative. This paper presents the development and evaluation of a suitable FRC for this particular application. First, the cement matrix was optimized for use in a conventional casting forming process. A mixture of ultra-fine cement and ordinary Portland cement improves the rheological properties of the fresh mixture and results in a very dense cement matrix with excellent mechanical properties. This optimized cement matrix was then reinforced with different kinds of carbon and polymeric fibers such as PVA and PP. Hereby, the carbon fibers primarily increase the flexural and tensile strength of the material, where the polymer fibers tend to improve the ductility of the cement matrix. Furthermore, the influence of water-reducing agents, of different constituents (microsilica, filler, sand), and the mixing process on the mechanical properties were studied. The mechanical properties were found to depend also on the curing conditions of the hydrated samples. The microstructure and the fiber-matrix interface were investigated by Environmental Scanning Electron Microscope (ESEM). In a further test series, the mixtures were optimized with regard to the flow properties needed for the centrifugation process. The mechanical properties and the microstructure were investigated. As a result, this work shows the possibility to apply the FRC for industrial production of centrifuged tubes.