FRACTURE-BEHAVIOR OF HARDENED CEMENT PASTE INCORPORATING MINERAL ADDITIONS

Various powder materials have been added on the hydration of cement to improve its mechanical and chemical properties. Industrial waste or b y-product powder is consumed in large quantities as aggregates or hydr aulic reactants. In the present study, hardened cement pastes (HCP) we re prepared with ordinary portland cement containing fine powder consi sting of isotropic graphite or glass waste to investigate their micros tructure and mechanical properties. Fracture behavior was investigated by compact tension, by which the fracture energy and fracture toughne ss of a specimen were obtained. The amount of calcium hydroxide and Ca /Si molar ratio of C-S-H were constant in spite of being mixed with gr aphite. Graphite powder did not take part in the hydration of cement. An improvement in fracture toughness and a remarkable plastic behavior were observed because of the dispersion of graphite particles. On the other hand, glass waste powder reacting with alkaline solution in the pores resulted in decreasing the Ca/Si molar ratio of C-S-H. Similar behavior was observed in a mixture of cement and fine blast furnace sl ag. Bending and compressive strength increased, but-fracture toughness decreased. The lower elastic fracture energy in HCP containing reacti ve fine powder facilitated crack propagation and enlarged the fracture surface.