Mitigation of alkali–silica expansion in pulp fiber–mortar composites

The physical and microstructural effects of kraft pulp, thermomechanical pulp, and polypropylene fibers for restraining expansion due to alkali–silica reaction are investigated through expansion measurements, environmental scanning electron microscopy, and energy dispersive spectroscopy. This preliminary research revealed that thermomechanical pulp fibers are more effective at reducing expansion due to alkali–silica reaction than kraft pulp and polypropylene fibers. It is shown that the open lumen of the TMP fibers, and to some degree, the kraft pulp fibers, serves as a reservoir for alkali–silica gel, potentially minimizing internal expansive pressures. Furthermore, increases in the fiber volume fraction and fiber–cement bond strength (accomplished through extended initial moist curing) decreased expansion for all composites.