Effect of alkali-silica reaction expansion on mechanical properties of concrete

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Fen Bilimleri Enstitüsü, Türkiye

Tezin Onay Tarihi: 2013

Öğrenci: ALKAN HAFÇI

Danışman: LUTFULLAH TURANLI

Özet:

Alkali-silica reaction (ASR) is a chemical deterioration process which arises in concrete due to reactive aggregate from its constituent, sufficient alkalis from cement or external resources and humidity about 85%. ASR gel, formed by the reaction, absorbs water and expands so that it causes expansion and cracking in concrete. ASR has detrimental effects on mechanical properties of concrete. Therefore, ASR which is a long and a constantly progressive reaction may become a threat to the safety of concrete structures. This experimental study focuses on two main subjects. The first one is the effect of ASR on mechanical properties of concrete, which are compressive strength, flexural strength, splitting tensile strength, modulus of elasticity and pullout strength at expansion of over 0.04 % and the second one is the impact of the type of specimen on ASR expansion, which differs as prism, cube, and cylinder. Concrete specimens in different types for tests include not only fine river sand, a reactive aggregate, but also coarse limestone, a non-reactive aggregate. As known, some standards like ASTM C1293 and Canadian CSA–A23.2-14A, describe aggregates causing expansion more than 0.04% in concrete within 1 year as potentially deleteriously reactive. Firstly, immediately after the expansion of the specimens, exposed to ASR exceeded 0.04%, the mechanical tests were performed on both them and the control specimens. Secondly, the specimens, exposed to ASR for longer time, were tested at expansion of over 0.10% to investigate ASR effect on mechanical properties. The investigation results confirm that expansion of over 0.04% in concrete from ASR caused losses in mechanical properties of concrete at different rates. With higher expansion, losses increase significantly especially in flexural strength and pullout strength of concrete. Moreover, higher rate of expansion in prisms than cubes at any time and cylinders proves that the type of specimen has an important role on rate of ASR expansion according to results.