Preventing Alkali-Silica Reactivity (ASR) in Concrete Bridges and Pavements

Alkali-Silica reactivity in concrete is one of the major causes of concrete deterioration throughout the world. This phenomenon is due to reaction between certain types of Silica/Silicates aggregates and the existing alkali materials (NaOH or KOH) in concrete.The produced material (SilicaGel) is an expansive substance when absorbs water and hence its subsequent excessive tensile stress will cause cracking of the concrete.Different types of reactive silica aggregates were selected to make the experimental concrete specimens according to ASTM-C-1260 and C-227 for the accelerated ASR tests.Lithium Nitrate (LiNO3) inhibitor in the form of liquid solution was used in the concrete mix as an admixture to prevent ASR. This substance will react with silica gel and produces a non-expansive material when absorbing water to prevent cracking. In addition to Lithium inhibitor, ground granulated furnace slag, a well-known cement substitution pozolan was used in the specimens as a less expensive material. Silica fume as a cement replacement material was also used to observe its ASR inhibiting effect. Slag and silica fume have a lower Alkali content in comparison to ordinary portland cement and can reduces the rate of ASR. Effective recommendations to produce durable concrete resistant to ASR are proposed for the new concrete structures. For the existing ASR affected structures, the diagnostic methods to identify ASR are given

کلیدواژه ها:

Alkali-Silica Reactivity ، Inhibitor ، Slag ، Silica Fume ، siliceous ، silica