STATISTICAL EVALUATION OF LONG-TERM DURABILITY CHARACTERISTICS OF CELLULOSE FIBER-REINFORCED CEMENT COMPOSITES

Relatively low-cost and energy-efficient materials with desirable short-term mechanical properties can be obtained using cellulose fibers as cement reinforcement. There are, however, concerns regarding the long-term performance of cellulose fiber reinforced cement composites; some natural fibers tend to disintegrate in the alkaline environment of cement. The growth of cement hydration products within the hallow cellulose fibers may also lead to excessive fiber-matrix bonding and brittle failure after exposure to natural weathering. This paper presents the results of a comprehensive experimental study concerned with the long-term performance of cellulose fiber reinforced cement composites subjected to accelerated wetting-drying and hot-water soaking conditions. An experimental program was developed based on the statistical method of factorial factorial design. The variables of the experimental study were: 1) cellulose fiber type (softwood and hardwood); 2) fiber mass content (4 and 8 percent); 3) partial substitution of cement with pozzolans (30 percent fly ash or 15 percent silica fume); 4) aging conditions (aged and unaged); and 5) silica sand content (silica sand-cement ratio = 0.5 and 1.0). The composites were manufactured using a batch-type slurry-dewatering technique. Statistical methods of factorial analysis of variance were used to derive reliable conclusions, in the light of random experimental errors, regarding the effects of different variables on the flexural performance of cellulose fiber reinforced cement composites.