Wastepaper Fibers in Cementitious Composites

Abstract

The use of cellulose fibers, reclaimed from wastewater from paper recycling, as reinforcement in cementitious building products is discussed. An experimental program is based on the development of a material composed of Portland cement mixed with sludge produced by the treatment of wastewater from a paper recycling plant. This sludge is composed primarily of cellulose fibers and Kaolinitic clay. The primary obstacle in the development of a mixing process is the problem of achieving an intimate mixing of the fibers and the cement, as the fibers tend to coalesce and form soft inclusions in the hardened mass. This problem is overcome by introducing the cement in to the sludge prior to chemical or mechanical dewatering, followed by vibratory and pressure dewatering of the cement/sludge slurry. Optical and electron microscope photographs clearly indicate the differences between mixing techniques. Physical properties of the resulting mass are measured as a function of varying mix proportions and mixing techniques. Compressive strength on the order of 10.3 MPa (1,500 psi), and tensile strength on the order of 2.8 MPa (400 psi) have been obtained.