Surface-Fluorinated Fibers in Cementitious Mixtures

Control of cracking and failure mode by means of postcracking ductility. 

Change in the rheology or flow characteristics ofthe cementitious mixture in the fresh state. 

Improved durability on exposure to freeze-thaw cycling, especially synthetic fibers. 

To improve the interfacial bonding between the PP fiber and a cementitious matrix, commercially available PP fibers with different geometries were fluori-nated and the effect evaluated with regard to crack control, impact resistance (AC1 Committee 544 Report), and water absorption (ASTM C-948).M,34a In all cases, as seen in Table 16.13, fluorination improved the induced properties. 

It is well known that addition of PP fibers to concrete increases water absorption. It is, however, interesting to note that with fluorinated fibers, the water absorption is very similar to unfilled concrete, suggesting an improvement in wettability and chemical adhesion between fiber and matrix. 

Concrete is an inherently brittle material with low tensile strength and strain capacities. Its brittle characteristics lead to easy nucleation and propagation of cracks, thus restricting its range of applications. To address this deficiency, fibers of different materials such as asbestos, glass, metal, and synthetics are used as additives, with the following results  

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