卵石和砂岩骨料碱活性分析及混凝土综合性能

Alkali Activity Experimental Analysis of Pebble and Sandstone Aggregate and Comprehensive Properties of Concrete

为分析西藏某大型水利水电工程用天然卵石和开挖砂岩骨料的碱-骨料反应危害,采用岩相法和砂浆棒法快速法对骨料碱活性进行检测,研究掺II级粉煤灰的抑制效果;并评价卵石、砂岩骨料混凝土的综合性能。结果表明:卵石、砂岩均为具有潜在危害性反应的碱活性骨料,含有数量不等的碱-硅反应活性组分微晶质至隐晶质石英;单掺II级粉煤灰有效抑制卵石、砂岩碱活性的最低掺量分别为25%和30%。采用“P·O 42.5水泥+20%II级粉煤灰”的策略可有效抑制卵石、砂岩骨料的碱-硅反应,且两种骨料均可用于制备C25W6F200标号混凝土,混凝土性能满足设计要求。

In order to analyze the alkali-aggregate reaction hazards of natural pebble aggregate and excavated sandstone aggregate to be used in a large-scale water conservancy and hydropower project in Tibet,the alkali activity of aggregates is detected by lithofacies method and accelerated mortar bar method,and the inhibition effect of mixing grade II fly ash is studied.And the comprehensive properties of pebble or sandstone aggregate concrete are also evaluated.The results show that,both pebbles and sandstones are all alkali active aggregates with potential harmful reactions,and contain varying amounts of alkali-silicon reactive components,microcrystalline or cryptocrystalline quartz.The minimum dosages of single-doped grade II fly ash to effectively inhibit the alkali activity of pebble and sandstone are 25%and 30%,respectively.The alkali-silica reaction of pebble or sandstone aggregate can be effectively inhibited by using the strategy of“P·O 42.5 cement+20%grade II fly ash”.Both kinds of aggregates can be used to prepare C25W6F200 concrete,which meets the performance requirements.