Highly isotactic polypropylene (PP) is currently studied as a cement-reinforcement fiber that could potentially be substituted for asbestos because of its resistance to prolonged high-temperature curing. The higher the isotacticity of the PP fiber is, the higher the tensile modulus and breaking strength of the cured fiber are. The PP fiber that exhibits a isotacticity of 99.6% (XI) and draw ratio of 6.0 retains a tensile modulus of 4.23 GPa, even after high-temperature curing at 175 degrees C for 5 h. PP fiber is cut into 6-mm lengths and dispersed throughout a cement mixture to prepare a reinforced cement composite. The mixture is cured in an autoclave at 175 degrees C for 5 h. The Charpy impact strength and flexural strength of the obtained cement composite tends to increase with increasing PP isotacticity. (C) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 981-988, 2013