| Alkali aggregate reaction (AAR) is one of the important factors to affect the durability of concrete structures. It has caused deterioration/damage of concrete structures and large money consumption around the world in past decades. Alkali-silica reaction (ASR) is the important and universal type of AAR . It has always been a hot topic in area of AAR study to avoid ASR expansion. Much work shows that replacing part of cement with some type of SCMS, such as fly ash (PFA), slag and silica fume etc., not only can delay or suppress ASR, but also has important meanings on saving resources and protecting environment. SCMS especially PFA are now widely used internal and abroad. However, there is no reliable method for assessing the effectiveness of PFA and other SCMS in suppressing ASR expansion. Based on testing aggregate reactivity, the method of assessing the effectiveness of PFA compares the sample expansion before and after the PFA added. It cannot solve the problem whether in some construction project have danger of ASR and how design the concrete to ensure the security of the project. By adopting similar parameter with field concrete, Concrete Prism method (ASTM C1293) was considered as the most reliable method to evaluate the potential reactivity of aggregates. However, the period of testing is too long to meet project requirement in many conditions. By storing the mortar-bar in 1mol/L NaOH solution at 80℃, Accelerating Mortar-Bar method(ASTM C1260) was considered as the more quick method to evaluate the potential reactivity of aggregates. In order to develop reliable and rapid method for assessing the effectiveness of PFA in suppressing ASR expansion, we combine the advantages of two methods and select moderate and potential reactivity aggregates which were appraised with several testing methods and largely used in real project as standard aggregate. A lot of work has been done and the main results are summarized as follows. i ) Identification of alkali reactivity of aggregate and correlation of methods.The alkali reactivity of siliceous gravel, Wujing(WJ) sandstone and Zhejiang(ZHJ) sandstones etc. were examined by Petrographic, Chinese Autoclaving Method, Chinese accelerating Mortar-Bar Method and Accelerating Mortar-Bar Method. It was found that siliceous gravel was moderate reactivity, where WJ sandstone was low reactivity, ZHJ sandstone was potential reactivity. It was also found that these testing methods had correlation each other. Chinese Autoclaving Method and Chinese accelerating Mortar-Bar had good relation for they using the similar parameters, such as single graded fine aggregate and various cement-aggregate ratio. ii) Effect of alkali level of concrete on ASR expansion and the suppressing effect of PFA. ASR expansion behavior and the suppressing effect of PFA on ASR expansion of siliceous gravel at different alkali levels is studied. Results show that ASR expansion of gravel increased greatly when concrete alkali is 5.5Kg/m3. Considered reaction rate and international experiences in ASR studying, it is suitable to select 6.6Kg/m3 as assessing method's alkalinity. iii) Suppressing effect and the type of reactive aggregate. It has been studied that the effect of PFA on suppressing the expansion of concrete prisms with siliceous gravel, WJ sandstone and ZHJ sandstone. Results show that the suppressing effect of PFA on ASR expansion is closely related with the type of reactive aggregate, difference in the alkali reactivity of aggregate lead to differences of the minimum amount of PFA needed to control expansion. iv) Storage environment and the suppressing effect of PFA. The suppressing effect of PFA on ASR expansion in 1mol/L NaOH solution at 80℃and moist at 40℃ were respectively studied. It was found that these data had good relationship between expansion value of 0.04% at 28 days in 1mol/L NaOH solution at 80℃ and expansion value of 0.04% at 3 months in moist at 40℃ or 0.06% at 6 months. However, the final testing period and expansion value sh...
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