The present invention relates to a fiber-reinforced cement based or cementitious material, and process for making, where the reinforcing fiber is a chemically treated cellulose or non-cellulose fiber. The fiber reinforced cementitious material includes (i) cement, (ii) optionally, sand, aggregate, or sand and aggregate, and (iii) chemically treated fibers having a polyvalent cation content of from about 0.1 weight percent to about 5.0 weight percent based on the dry weight of the treated fibers. The present invention further provides for a fiber reinforced cementitious material having a weak acid content of from about 0.5 weight percent to about 10 weight percent based on the dry weight of the treated fibers.