پديد آورندگان :
توكلي، حميدرضا نويسنده استاديار دانشكده‌ي مهندسي عمران، دانشگاه صنعتي نوشيرواني، بابل Tavakoli, H.R , صدر ممتازي، علي نويسنده دانشيار دانشكده ي مهندسي عمران دانشگاه گيلان sadr momtazi, A , لطفي عمران، اميد نويسنده دانشجوي دكتري دانشكده‌ي مهندسي عمران، دانشگاه گيلان Lotfiomran, O , بيگي ، مرتضي حسينعلي نويسنده استادياردانشكده‌ي مهندسي عمران، دانشگاه صنعتي نوشيرواني، بابل Beygi , M , فلاح تبار، مسعود نويسنده دانشجوي كارشناسي ارشد دانشكده‌ي مهندسي عمران، دانشگاه صنعتي نوشيرواني بابل Fallahtabar, M
كليدواژه :
الياف , بتن خودتراكم , جذب انرژي , چقرمگي , نانوسيليس
چكيده لاتين :
Self-compacting concrete (SCC) is a new class of high performance concrete that can spread readily into place under its own weight and fill restricted sections, as well as congested reinforcement structures, without the need for mechanical consolidation and without undergoing any significant separation of material constituents. The use of SCC can improve productivity in structural applications such as repairs, and facilitate the filling of restricted sections. Such concrete has been widely used to facilitate construction operations, especially in sections presenting particular difficulties in casting and vibration, such as the bottom sides of beams, girders, and slabs. Workability requirements for successful casting of SCC include high deformability, passing ability, and proper resistance to segregation. Deformability refers to the ability of SCC to flow into and completely fill all spaces within the formwork, under its own weight. Deformability is the property most commonly associated with SCC and provides justification for acceptance of the technology.
In recent years, progress in concrete technology has made it possible to produce SCC, which is of more workability and durability than normal vibrated concrete (NVC). A remarkable problem in concrete elements is its low energy dissipation and, thus, its high brittleness. Although SCC has higher strength than (NVC), observing its stress-strain curve reveals that the declining segment of the curve is almost vertical and no considerable strain softening is detected, which causes sudden brittle fracture in the structure. Studies show that addition of different fibers does not fundamentally change the behavior of the concrete prior to its maximum stress, while it greatly improves the concrete post-cracking behavior. This method positively influences other properties of the concrete including toughness, fracture energy and flexural strength. On the other hand, in the past two decades, application of nano-technology has significantly revolutionized human knowledge. Using nano-silica particles as a product of pozolanic reaction can strongly improve the permeability of concrete by increasing the transition layer of fiber and cement matrix. Thus, concrete, having the properties of both self compacting concrete and fiber reinforced concrete with strengthened micro matrices, can improve the fabrication of durable structures at a high performance level. In this research, the combined effects of nano-silica particles and fiber type (steel, polypropylene and glass) on toughness, fracture energy, flexural strength, and rheological behavior (L-box, slump flow and T50) of self-compacting concrete were evaluated.For this purpose, forty mixtures in an A, B, C and D series, representing 0, 2, 4 and 6 percent of nano-silica particles, replacing cement content, were cast. Each series involved three different fiber types and content; 0.2, 0.3 and 0.5% volume for steel fiber, 0.1, 0.15 and 0.2% volume for polypropylene fiber and, finally, 0.15, 0.2 and 0.3% volume for glass fiber. The results show that the combined usage of the optimum percent of fiber and nano-silica particles will improve the toughness, fracture energy and flexural strength of self-compacting concrete.
