Fiber-reinforced cementitious composites

A method for reinforcing a cementitious composite material comprising silicon, the method comprising the steps of:

• exposing a fibrous hydrocarbon polymer fiber reinforcing agent having greater than 50% carbon atoms on an outer surface to a population of charged, halogenated silicon molecules in a gaseous plasma, in the presence of a material that traps free halogen ions, at an energy level and for a time sufficient to implant a sufficient number of the halogenated silicon molecules onto the surface of the reinforcing agent so that the exposed reinforcing agent has between 10 and 100% silicon atoms, between 0 and 10% halogen atoms, between 10 and 90% oxygen atoms and less than 80% carbon atoms on the surface;
• incorporating the exposed reinforcing agent at a concentration of less than 10% by volume into the cementitious composite material;
• and
• curing the cementitious composite for a time sufficient to chemically link the exposed reinforcing agent to the cement by Si--O--Si linkages.