*Corresponding Author e-mail: Abstract The Effect of Mineral Admixtures on Alkali-Silica Reaction in Concrete Yousef ZANDI 1 Metin HUSEM 2 1 Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, IRAN 2 Department of Civil Engineering , Karadeniz Technical University, Trabzon, TURKEY Zandi@iaut.ac.ir This paper presents theoretical and applied information in the feld of alkali-aggregate reactivity (AAR) in concrete. The aspects discussed include basic concepts of the reaction and expansion mechanisms, conditions conducive to the development and the sustainability of AAR in concrete, feld and laboratory investigation programs for evaluating the potential alkali-reactivity of concrete aggregates, selection of preventive measures against AAR, and the management of structures affected by AAR. Lithium Nitrate 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 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. In this study Effective recommendations to produce durable concrete resistant to ASR are proposed for the new concrete structures. Keywords: Alkali-Aggregate Reaction, Inhibitor, Slag, Silica Fume, Test Concrete Siliceous, Silica INTRODUCTION Historical Background ASR was frst identifed and technically described in 1940 in California [1], A great deal of research effort has been directed to understand the mechanism of this deterioration process [2], [3] and [4] and to develop appropriate preventive measures [5], [6], [7], [8] , [9] and [10]. The problem has been a subject of interest for research workers since that time. There have been numerous international conferences on alkali-silica reactivity in concrete. Hobbs, 1988 [17]; Swamy, 1992 [18] and West, 1996 [19] present useful information about the subject in their books. Chemical Reaction There are mainly three types of AAR found in concrete. These arealkali-silica reactionalkali-silicate reaction andalkali- carbonate reactionAlkali-silica reaction is a reaction between alkali hydroxides and free silica in aggregate form a alkali-silica gel [11], [12], [13], [14], [15] and [16],. SiO 2 + 2NaOH + H 2 O Silica Alkali Water Alkali-silicate reaction is the same as alkali-silica reaction except that in this case the reactive constituent is not free silica present in the combined form of phyllosilicates. Alkali-carbonate reaction occurs in concrete when alkalis react with certain dolomitic lime stones containing clay. Reaction causes cracks allowing water to enter which causes the clay to swell and disrupt the aggregate. Majority of the structures affected by AAR is found due to alkali-silica reaction. Alkali-silicate and alkali-carbonate reaction is relatively rear. Alkaline components of cement chemically react with existing silica/silicates in certain types of aggregates. The reaction product is an expansive gel. If the relative humidity of the concrete exceeds about 70%, Silica Gel will react with water and produce an expanded material. Since concrete members are internally restrained, the produced expansion will cause tensile stress and subsequent cracking of the concrete. ASR Crack Diagnostic and Effecting Time ASR cracks have normally with a mapped (pattern) shape, which make them different from other crack types (Figs. 1 and 2) In a concrete pavement, where the width is small in comparison to its length, the higher restraining effect in the width direction causes the general trend of the cracks to be longitudinal (Fig. 2). The required time for ASR deterioration has been declared to be 7 to10 years for moderately reactive condition. For highly reactive material it can be started as early as fve years. The new AASHTO Uranyl Uranium Acetate Internatıonal Journal of Natural and Engineering Sciences 6 (2) : 1-5 , 2012 ISSN: 1307-1149, E-ISSN: 2146-0086, www.nobel.gen.tr Received : November 20, 2011 Accepted : December 28, 2011