Chen Mingxiang

The mechanical properties of polypropylene fiber reinforced concrete

The compressive, shear strengths and abrasion-erosion resistance as well as flexural properties of two polypropylene fiber reinforced concretes and the comparison with a steel fiber reinforced concrete were reported. The exprimental results show that a low content of polypropylene fiber (0.91 kg/m3 of concrete) slightly decreases the compressive and shear strengths, and appreciably increased the flexural strength, but obviously enhances the toughness index and fracture energy for the concrete with the same mix proportion, consequently it plays a role of anti-cracking and improving toughness in concrete. Moreover, the polypropylene mesh fiber is better than the polypropylene monofilament fiber in improving flexural strength and toughness of concrete, but the two types of polypropylene fibers are inferior to steel fiber. All the polypropylene and steel fibers have no great beneficial effect on the abrasion-erosion resistance of concrete.

Experimental research on performances of dry-grinding fine cement for grouting

The performances of dry-grinding fine cemenT (DFC) in grouting procedure were experimentally studied. The measurement of its fineness and simulated test for injectability showed that this DFC could be used to inject rock mass with micro-fissure. In order to improve the grouting quality, the water-cement ratio and discarding time of slurry should be controlled precisely. If the water-cement ratio is over 2∶1 in slurry that is made from DFC, it is not suitable to grout. Finally, the influence of different mixing times on strength of hydrated cement made from the DFC is explained by microstructure analysis with SEM.