چكيده به لاتين
Abstract:
Pre-placed aggregate concrete refers to concrete, which at first coarse aggregate is applied to concreting lacation, and then by injection of mortar under atmospheric pressure, the mortar goes into the empty space between aggregates and becomes Pre-placed aggregate concrete. This method is used in large-scale concrete bricks, such as the construction of dams, the pier of bridges, etc. It is also used to repair concrete structures where part of them has been damaged. 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. In this thesis, by reviewing existing standards for the use of PrePlaced Aggregate Concrete and other countries' experiences in using this method on the railways
, as well as reviewing the papers available in this field, the information vacuum has been identified and by designed and constructed using the appropriate laboratory equipment for injection into The railtrack and the design and carrying out of the relevant tests have obtained the susceptibility of PrePlaced Aggregate concrete with ballasts aggregate to three factors: water-to-cement ratio, sand grading and ballast grading at the age of 1, 3 and 28 days, and Has been achieved the optimal values of each of these factors In the mixing plan. The design of the experiments is based on a "two-level factor design". This means that the highest possible level and the lowest possible level for each of the three factors were considered, and all combinations of these two levels were tested for three factors (eight mix designs) at three ages (a total of 24 experiments). Finally, in addition to observing the behavior and the sensitivity of the compressive strength to the change in each of the three factors mentioned, the combination with water to cement ratio is 0.35, the group 1of ballast grouping and the Greater granulation of the sand with a compressive strength of 1 days, 7.09 MPa, 3 days 17.48 MPa and 28 days, 24.57 MPa, has gained as the best combination with the highest compressive strength, of course with attention to the constant consideration of other variables that are effective in the mixing scheme.
Keywords: pre-coated concrete, slab, mortar injection, mixing design
