The preparation of modified polypropylene fiber used for concrete crack resistance: Fid-Bau Portal

The preparation of modified polypropylene fiber used for concrete crack resistance

Wang, Y.M. / Ni, J.H. / Pan, X.Q. / He, Y.

Unreinforced concrete is a highly economical building material where compressive strength is concerned. Its disadvantages lie in its limited tensile strength, tendency to shrinkage-cracking, brittleness and unsatisfactory flexural strength. It is therefore advisable to improve the concrete so as to compensate for the disadvantages of reinforced concrete. Since polypropylene (PP) has excellent physical, mechanical and chemical properties, such as absolutely inert and stable, not corrode, non-magnetic and non-conductive etc. it has been rather widely used in concrete materials. However, the modified PP fibre with microvoids produced by transformation of Beta to Alpha crystal has a good tendency to improve cracking behaviour. PP chip was premixed with quinacridone dyestuff E3B at weight of 0.1 % base on the PP weight and melted cut into chip. The relative content of Beta-form (K) was calculated according to Tuner-Jones. A Perkin-Elmer 7 series thermal analyser was used for the Differential Scanning Calorimetry (DSC). Experiments were performed at the heating rate of 20 degrees C per minute. Furthermore density measurements, mercury porosimetry, as well as SEM investigations were carried out. The spinning temperature has no significant influence on the K value. An increase of spinning speed from 3.25 to 70 m/min results in a decrease of K value from 0.95 to nearly zero. With an increase of spinning draft (from 5.45 to 120) the K value also increases from 0.47 to 0.82. An increase of heat setting temperature from 30 to 130 degrees C results in a decrease of K value from 0.0551 to 0.0008.