بررسي آثار مواد پوزولاني بر دوام بتن هاي خودمتراكم

Evaluation of Durability of Self-consolidating Concrete

چكيده- بتن خودمتراكم مي تواند به عنوان يكي از بتن هاي نويني مطرح شود كه بدون جداشدگي سنگ دانه يا آب انداختگي و بدون نياز به عمل تراكم، قابليت پركنندگي فضاهاي خالي ميان آرماتورها را دارد. اين نوع بتن به دليل قابليت هاي صنعتي و اقتصادي مي تواند به كمك مواد پوزولاني كه خود نقش مهمي در افزايش مقاومت و دوام سازه هاي بتني دارند، ساخته شود. اين مقاله، نتايج مطالعات آزمايشگاهي روي ويژگي هاي بتن تازه، انتشار يون كلرايد و نفوذ پذيري نمونه هاي بتن هاي پوزولاني خود متراكم را در مقايسه با بتن هاي بدون پوزولان و بتن معمولي ارايه مي دهد دوده ي سيليس ، پوزولان هاي پوميس و خاكستر پوسته برنج، مواد پوزولاني است كه در اين پژوهش جايگزين سيمان و موادپركننده (فيلر) شدهاند. آزمايشهاي گوناگوني، مانند نفوذ يون كلرايد، جذب آب مويينه، نفوذ آب و مقاومت الكتريكي. روي نمونههاي نام برده انجام شده است . نت ايج آزمايش ها نشان مي دهند كه بتن هاي خودمتراكم حاوي پوزولان به طور محسوسي مقدار نفوذ يون كلرايد و نفوذ آب را كاهش ميدهد.

Abstract: Self-consolidating concrete (SCC) has been used increasingly over the last two decades, especially in the pre-cast concrete industry because of its ability to consolidate without vibration even in congested areas. The development of SCC mixture design has been driven mostly by private companies who desired to utilize advantages of SCC. Consequently, there exists limited public information regarding the performance of SCC mixtures. In addition, SCC can be characterized as flowing concrete without segregation and bleeding, capable of filling spaces and dense reinforcement. Further it should be able to flow through, and completely fill the form without vibration. Due to the technical and economic advantages that can be accrued by the use of pozzolans, they play an important role when added to Portland cement by usually increasing the mechanical strength and durability of concrete structures. This paper present, an experimental study on the properties of different self-consolidating concrete mixes containing three types of pozzolanic materials in comparison with SCC mixtures without any pozzolanic materials and conventionally vibrated concrete mixtures. Silica fume, pumice powder and rice husk ash were used for both cement and filler replacements. Various experiments such as slump-flow, J-ring, L-box, V-funnel and sieve segregation resistance were investigated for fresh concrete. Further, compressive strength, water and chloride-ion permeability and capillary water absorption at various days were carried out to determine the properties of self-consolidating concretes. The test results indicated that pozzolanic materials such as RHA and VP can be used to produce SCCs. Regarding the strength properties, the test results showed that the 270-day compressive strength of ordinary SCC is about 70 MPa, while SCC mixtures containing SF, RHA and VP have strengths more than 90, 77 and 76 MPa, respectively. In addition, the results proved that artificial and natural pozzolans enhanced the durability of SCC and reduced the penetration, significantly. For instance, adding 15% pumice and 7% silica fume in the SCC specimen reduced the water depth at 90 days by 19% and 54%, respectively.