چكيده به لاتين
Preplaced Aggregate Concrete (Also Prepacked Concrete, Two-Stage Concrete) is reffered to a kind of concrete in which coarse aggregate materials preplaces into formwork and the sand-cement mortar with special mix design is subsequently injected to fill the voids imprisoned between the coarse aggregate particles. This method is commonly used to repair dams, bridge columns and damaged structures. As a new approach, another application of PrePlaced Aggregate Concrete is to transform the ballasted railway tracks into slab tracks, Because the coarse aggregate is placed formerly in the site, so it can be easily transform into slab track using sand-cement mortar injection. For implementing this method in Iranian railway network, using concrete admixtures is highly essential due to the limitations existed for track closure and maintaining the ballast into railway bridges and tunnels. In the present thesis, after reviewing the related literature, laboratory tests on mortar including compressive and flexural strength, fluidity time and mortar setting time, and on concrete including cubic and cylindrical compressive strength with ultrasonic non-destructive test performed and separately proposed. Eventually, the best mortar mixture design for injecting into the ballast layer is presented using statistical analysis. Basing on the tests, the best mortar mixture design belongs to one whose which the cement content is 850 kg/m3, w/c ratio of 0.35 and silica fume content of 10% of cement weight. Relating to the proposed mixture design, 28-day compressive strength of mortar and concrete determined approximately as 76 and 53 MPa, respectively.
