摘要
The composition and structure of the inter facial zone between aggregate and paste of Portland cement as well as the orientation coefficient of portlandite ( Icn ) were preliminarily studied by XRD and SEM methods. The main products in the zone are C -S-H gel, portlandite, AFt and pores, micro-cracks as welt as unhydrated portland cement clinker particles. Potlandite not only grows well but exists in orientating forms, and near the interface it exists in a state parallel to the surface of aggregate by its (001) lattice plane. Icn rises with the increase of cement water ratio (w/c) and the development of the cement hydration. The higher the w/c, the more the pores and micro-cracks in the zone. w/c bears an exact relation to the decrease of bond strength. Icn, is decreased when 5. 0% silica fume is added to cement. Bond strengths at early ages are reduced by adding 0. 5% FDN (one kind of water-reducing admixture) due to the retarded hydration of cement, but they will increase continually and become greater than those of other samples after 28 days.
The composition and structure of the inter facial zone between aggregate and paste of Portland cement as well as the orientation coefficient of portlandite ( Icn ) were preliminarily studied by XRD and SEM methods. The main products in the zone are C -S-H gel, portlandite, AFt and pores, micro-cracks as welt as unhydrated portland cement clinker particles. Potlandite not only grows well but exists in orientating forms, and near the interface it exists in a state parallel to the surface of aggregate by its (001) lattice plane. Icn rises with the increase of cement water ratio (w/c) and the development of the cement hydration. The higher the w/c, the more the pores and micro-cracks in the zone. w/c bears an exact relation to the decrease of bond strength. Icn, is decreased when 5. 0% silica fume is added to cement. Bond strengths at early ages are reduced by adding 0. 5% FDN (one kind of water-reducing admixture) due to the retarded hydration of cement, but they will increase continually and become greater than those of other samples after 28 days.
