粉煤灰对ASR的抑制及有效性评估

EFFECTIVENESS OF FLY ASH ON SUPPRESSING ASR EXPANSION AND ITS EVALUATION

以中国快速砂浆棒法为基础 ,分别研究了在 40 ,60 ,80℃养护条件下低钙粉煤灰对硅质砾石、沸石化珍珠岩和石英玻璃碱硅酸反应 (alkalisilicareaction ,ASR)膨胀的抑制作用。讨论了集料碱活性、养护温度对粉煤灰抑制ASR效果的影响和建立粉煤灰及其它矿物外加剂抑制ASR有效性评估方法的技术路线和问题。结果表明 :粉煤灰抑制ASR的效果与集料碱活性和养护温度密切相关。一定养护温度下 ,集料活性越大 ,抑制效果越差 ;对特定活性集料 ,养护温度越高 ,抑制效果越差。粉煤灰对不同集料和同种集料不同养护温度下ASR膨胀抑制效果差异 ,主要与ASR历程有关 ,即与集料ASR本身特性有关。特定集料和养护条件下粉煤灰对ASR膨胀的抑制效果不能简单推广至其它种类不同的集料和养护条件。粉煤灰抑制ASR有效性应根据工程评价目的和要求分别确定。

The use of mineral admixture as partial replacement for portland cement in concrete is an effective means for controlling expansion due to (alkali silica reaction, ASR). However, reliable standard method for testing the effectiveness of mineral admixtures to prevent ASR has not been established. In order to develop a reliable method for testing the effectiveness of fly ash in controlling ASR, the suppression effect of low calcium fly ash on the ASR expansion occurred in siliceous gravel, zeolite perlite and silica glass at the curing conditions of 40℃, 60℃ and 80℃ were studied respectively based on Chinese accelerated mortar bar method. The effects of the reactivity of aggregate and curing temperatures on the effectiveness of fly ash on suppressing ASR expansion and the technique for assessing the effectiveness of fly ash and other mineral admixtures are discussed. Results show that the suppressing effect of fly ash on ASR expansion is strongly depended on the alkali reactivity of aggregate and conserving temperature. The higher the alkali reactivity and curing tempe rature are, the lower the suppressing effect is to get. The dependence of the suppressing effect of fly ash on alkali reactivity and conserving temperature is attributed to the different ASR behaviors for various aggregates and at various temperatures. The suppressing effect of fly ash on certain reactive aggregate at certain conserving conditions can not be simply extended to other aggregates and conditions. Methods for testing the effectiveness of fly ash and other mineral admixtures against ASR should be established according to application objectives. Correlation of result based on assessing method and long term performance of concrete needs further study.