The Influence of the Silica Fume Content on the Mechanical Behavior and Fracture Toughness of the Portland Cement Concrete Applied on the Rigid Road Pavement.

Reference Presenter Authors
09-114 Joamir Henrique da Silva Silva, W.S.(Universidade Federal de Santa Catarina); Silva, J.H.(Universidade Federal do Rio Grande do Norte); The concrete is a ceramic compound type, characterized by a quasi-brittle mechanical behavior. Its physical and mechanical properties are established by its microstructure, the water/cement ratio, aggregate size and shape and by the use of modifiers like silica fume, which may improves the mechanical strength and durability of cement Portland concretes. The rigid road pavements are shortly used in Brazil, which demand the enlargement of the research and development, including materials, processing and physics and mechanical properties. In this work is studied the relationship between the addition of different amounts of silica fume (0, 3, 6, 9 and 12%) relative to the cement mass and mechanical behavior (resistance to axial compression, tensile strength in bending and KICVM fracture toughness Chevron notch "short-rod" tests), and physical properties (specific gravity, absorption and void index) of Portland cement concrete applied in road rigid pavements. The materials are analyzed by XRF, XRD and SEM techniques. The mechanical tests were performed at 7 and 28 days of concrete age. The technologic characteristics of all specimens were determined by the slump test value defined by technologic demand of the road operational execution, fixed at 50 +/- 10 mm values. The growth of the silica fume content reduced the values of absorption index (a reduction in the porous volume) and caused the improvement in the values of flexural tensile strength, axial compressive strength and fracture toughness. Moreover, in all of the concrete types, the minimum values of fctMk surpass the technical value required by rigid pavements. These improvements of the mechanical behavior and in the physical properties are associated to physical and chemical effects promoted by silica addition in the concrete structure, characterized by a pores volume reduction and by a strengthening of matrix/aggregate interface, as demonstrated by SEM fractography analysis.
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