| Cementitious materials are excellent candidates to replace materials that are currently used in residential applications, such as siding, roofing tile, backerboard and paneling systems, because they can be made to be strong, durable, environmentally friendly and cost effective. Plain cementitious materials, however, tend to be brittle, with low tensile strength and strain capacity. Special processing techniques, such as extrusion, can be used to overcome these weaknesses. These high-performance fiber-reinforced cementitious composites (HPFRCC) are ductile, have a high tensile strength and can exhibit a strain-hardening response under loading. Despite the many positive attributes of extruded composites, their use is not widespread in North America. Two main issues that are limiting the adoption of extrusion-based manufacturing by industry are the subject of this thesis: constructability and processing.; It would be desirable if HPFRCC can be nailed in the same way as wood composites. To produce nailable composites, a rational test methodology has been developed. A dynamic nailing test is used, to account for the rate sensitivity of cementitious materials. The nailing performance of extruded composites is compared with commercially-available materials, which are known to be nailable. Results from this analysis are presented, highlighting material parameters that influence nailing. Existing fracture mechanics and cavity expansion models are utilized to explain the role of the fiber reinforcement and the matrix in the nailing performance. Based on these findings, materials are extruded with lightweight fillers. These lightweight composites demonstrate excellent nailing performance, comparable to wood-based materials.; The fresh state characteristics of extruded materials are extremely sensitive to the processing aids used. These aids enable the production of high quality, cost-effective products, with minimal defects. Currently, relatively expensive cellulose ethers are used to control extrudability. The use of alternate, less expensive, binders is explored. The effect of the binders on the fresh state properties of extruded systems are evaluated using two existing models: the Benbow-Bridgewater model and capillary rheology. The results indicate that clay binders can be used to partially replace cellulose ethers and that capillary rheology is effective at characterizing the fresh state properties of cementitious paste systems. |
