بررسي خواص مقاومتي و دوام در برابر نفوذ يون كلريد بتن‌هاي توانمند سه جزيي حاوي سرباره‌ي كوره‌ي آهن‌گدازي و دوده‌ي سيليسي

MECHANICAL AND DURABILITY PROPERTIES OF TERNARY CONCRETES CONTAINING BLAST FURNACE SLAG AND SILICA FUME

اين نوشتار با هدف بررسي امكان ارتقا خواص بتن‌هاي حاوي سرباره‌ي توليد داخل كشور از طريق كاربرد توام آن با دوده‌ي سيليسي (مخلوط سه‌جزيي) انجام شده است. مخلوط‌هاي سه‌جزيي مورد مطالعه حاوي 15، 30، و 50 درصد سرباره به همراه 5/2، 5، و 5/7 درصد دوده‌ي سيليسي بوده‌اند. علاوه‌بر خواص مقاومتي، خواص دوام مخلوط‌ها از طريق آزمايش تعيين مقاومت الكتريكي و آزمايش‌هاي تسريع‌شده‌ي تعيين مقاومت بتن در برابر نفوذ يون كلر شامل روش‌هاي RCPT و RCMT بررسي شده است. نتايج نشانگر اين است كه اثر استفاده‌ي توام از سرباره و دوده‌ي سيليسي در بهبود روند كسب مقاومت مخلوط‌هاي دوجزيي حاوي سرباره‌ي محدود بوده است و بستگي به مقدار سرباره در مخلوط دارد. ليكن استفاده از مخلوط‌هاي سه‌جزيي باعث ارتقا قابل‌توجه دوام در تمام سنين مي‌شود. با استفاده از تركيب مناسب سرباره و دوده‌ي سيليسي دستيابي به خواص مناسب مقاومت و دوام در سن 28 روز و ارتقا بسيار قابل توجه دوام درازمدت امكان‌پذير است.

In this paper, the potential of using a combination of the blast furnace slag of an Isfahan steel work, and silica fume to achieve concrete with high durability and appropriate rate of strength gain has been investigated. The performance of the ternary concrete is compared with control and binary mixes. The binary concrete studied includes mixes containing slag at cement replacement levels of 15, 30 and 50 percent, and mixes containing silica fume at cement replacement levels of 2.5, 5, 7.5 and 10 percent. The ternary concrete includes a combination of silica fume and slag at various cement replacement levels. The w/b ratio and total cementitious material content was kept constant for all mixes at 0.38 and 420 Kg/m3, respectively. Concrete mixes were evaluated for compressive strength, electrical resistance, rapid chloride permeability (ASTM C1202 RCPT test) and rapid chloride migration (AASHTO TP64 RCMT test), at various ages up to 180 days. Combined use of silica fume and slag resulted in reduced water demand, compared to mixes containing silica fume. Using ternary mixes, it was also possible to reduce water demand compared to the control concrete. Use of slag at a 15% replacement level of cement did not cause a considerable reduction in strength properties. For slag at 30% and 50% replacement levels of cement, strength properties were considerably lower than control at all ages.The results show that simultaneous use of silica fume has only a moderate effect in improving the slow rate of strength gain of binary mixes containing slag. Therefore ternary mixes with high slag content have considerably lower strength than control at all ages. The durability of ternary mixes, even at the age of 28 days, was better than the control mix, and the problem of the lower durability of binary mixes containing slag at 28 days can, thus, be overcome through the use of ternary mixes. At later ages, ternary mixes have excellent durability and can even outperform binary mixes containing equal amounts of silica fume. Using an appropriate combination of slag and silica fume, it is possible to obtain ternary mixes with 28 day strength comparable to the control mix, and with considerably improved durability, particularly in the long term.