بررسی مشخصات مکانیکی بلند مدت (3 ساله) بتن حاوی سنگ دانه ی بازیافتی و پوزولان‌های زئولیت و میکروسیلیس

از مسائل مطرح در زمینه‌ی استفاده از سنگ‌دانه‌ی بازیافتی و پوزولان‌های جایگزین سیمان، عملکرد بلندمدت آن‌هاست. به‌منظور بررسی مسئله‌ی کنونی، با استفاده از یک نوع درشت‏دانه‌ی بازیافتی و دو نوع پوزولان (میکروسیلیس و زئولیت)، در مجموع 12 طرح اختلاط طراحی و ساخته شد. بررسی نتایج عملکرد مکانیکی نشان داد که تا سن 28 روز، استفاده از میکروسیلیس و زئولیت باعث بهبود مقاومت‏های فشاری و کششی به ترتیب 11- 17 و 2 -33 درصد شد، اما در بلندمدت اثر پوزولان‏های مصرفی کاهش یافت و به 2- 10 و 5- 8 درصد رسید. همچنین داده‏های درصد جذب آب و عمق نفوذ آب نشان داد که استفاده از میکروسیلیس تاثیر بیشتری برای بهبود خواص دوامی بتن حاوی سنگ‌دانه‌ی بازیافتی نسبت به زئولیت دارد، اما خواص دوامی همچنان ضعیف‌تر از نمونه‌ی بدون سنگ‌دانه‌ی بازیافتی است.

assessing long term (3 year) mechanical properties of recycled aggregate concrete containing zeolite and silica fume

using recycled concrete aggregate as a sustainable solution has been the subject of much research in recent years. the use of recycled aggregate has led to a reduction in the quality of concrete, according to various studies. a promising approach to enhance the concrete properties of recycled aggregate concrete involves the use of pozzolans as supplementary cementitious materials. in this study, cement was replaced by silica fume in 8% of the specimens, while in other specimens, cement was replaced by zeolite in 15%. natural aggregate was substituted with recycled concrete aggregate in varying proportions of 30%, 50%, and 100%. subsequently, various mechanical and durability tests were conducted to evaluate the properties of each specimen. compressive and tensile tests were carried out to assess the mechanical properties of the specimens. the tests revealed that specimens containing recycled aggregate exhibited inferior properties compared to natural aggregate concrete. over the long term (3 years), the specimens containing recycled aggregate also displayed lower compressive strength. specimens containing silica fume demonstrated higher compressive strength in the short term when used with natural aggregate concrete but showed similar performance over the 3 year period. in specimens containing recycled aggregate, silica fume had a more pronounced effect, leading to higher compressive strength in the short term but similar or reduced strength over the 3 year period. a similar trend to that observed in compressive strength was found in splitting tensile strength. as the percentage of recycled aggregate replacement increased, tensile strength decreased. the use of silica fume increased splitting tensile strength, even over the 3 year period. on the other hand, using zeolite did not result in a significant change, and specimens exhibited similar or reduced compressive strength over the 3 year period. in general, it can be inferred that the use of supplementary cementitious materials can enhance mechanical properties in the short term. however, durability tests, including water penetration depth and water absorption percentage, demonstrated almost the opposite trend. this suggests that the use of supplementary cementitious materials generally has a negative impact on concrete properties in the long term.