【作者】 白银；

【导师】 丁建彤；

【作者基本信息】 南京水利科学研究院 ， 材料学， 2009， 硕士

【摘要】 锦屏一级水电站为一等工程,根据成勘院的初步调研,坝址附近料场砂岩骨料是碱活性岩石,可能导致坝体混凝土发生碱骨料反应破坏,存在潜在威胁。本论文研究了锦屏砂岩骨料碱活性及其抑制问题,主要结论如下:（1）砂岩骨料为具有潜在危害性反应的碱-硅反应（ASR）活性骨料;在本文试验中,砂岩骨料不存在“最劣比”现象,砂岩与大理岩组合骨料仍然具有较高的碱活性。（2）Ⅰ级粉煤灰与Ⅱ级粉煤灰相比,对砂岩ASR的抑制效果没有明显差异;包括CaO含量8%左右的平凉Ⅰ级灰和Ⅱ级灰在内的9种备选粉煤灰,在30%掺量下都可以有效抑制砂岩ASR;考虑到锦屏砂岩碱活性的波动,抑制ASR所需粉煤灰的掺量宜不低于35%。（3）粉煤灰的单个化学成分与粉煤灰抑制ASR的效果没有显著相关性。用化学成分因子C_FA来表征粉煤灰的化学特性更合理,根据砂浆棒快速法28d试验结果回归得出的C_FA表达式为:当C_FA≤0.400时,粉煤灰掺量30%左右可以有效抑制锦屏一级砂岩骨料的ASR;当C_FA＞0.400时,则需要更大的掺量。在粉煤灰掺量为30%时,其矿物组成对抑制效果没有明显影响;用非晶态SiO₂和非晶态Al₂O₃分别取代C_FA中的SiO₂总量和Al₂O₃总量并没有使相关系数提高。粉煤灰的细度对抑制ASR效果有影响,但不及化学成分影响明显;用比表面积与C_FA组合而成的物化因子C可以综合地反映粉煤灰物理、化学特性对抑制ASR效果的影响,C的表达式为:（4）在80℃、1mol/L NaOH并且Ca（OH）₂饱和的溶液中,粉煤灰的火山灰活性被严重激发,导致快速砂浆棒法测试的粉煤灰抑制效果明显高于60℃快速混凝土棱柱体法测试结果。粉煤灰中除了约占20%左右的莫来石不能被溶解以外,其余成分都可以溶解,因此,粉煤灰的化学成分对抑制ASR效果的影响要比矿物组成的影响大。粉煤灰在热碱液浸泡下,主要生成P型沸石和C-S-H凝胶。生成P型沸石有利于抑制ASR;生成C-S-H凝胶对强度有较大贡献,但是对抑制ASR没有明显作用。（5）采用碱活性骨料作为混凝土原料时,人工砂中引入的碱活性石粉以及引气剂引入的气泡对ASR膨胀有一定“自免疫”作用,可减少40%～80%的ASR膨胀率。从这个角度而言,现有室内试验方法高估了大坝混凝土中的ASR风险。（6）锂渣粉可以有效抑制砂岩ASR,但需要分离锂渣粉自身引起的微膨胀。改性沸石复合粉在掺量30%以上时,可以有效抑制锦屏砂岩的ASR,但是抑制效果不及粉煤灰显著。HLC-ASW型高效减水剂对ASR有一定的抑制效果,约为20%,明显优于普通萘系高效减水剂。更多还原

【Abstract】 In the thesis, some questions are studied about suppressing the alkali-silica reaction （ASR） of the sandstone aggregate to be used in the dam concrete for the Jinping-ⅠHydroelectric Project. The conculsions are summarized as follows:（1） Sandstone aggregate and sandstone-marble combination aggregate are alkali-silica reactive and indicative of potentially deleterious expansion, no "passimum" phenomenon was observed.（2） There was no difference between ClassⅠand ClassⅡfly ash on suppressing ASR. All the 9 fly ashes from Jinping-ⅠHydroelectric Project could effectively suppress ASR of sandstone at 30% replacement level, including Pingliang ClassⅠand ClassⅡfly ash with CaO content about 8%. Considering the difference between dam concrete and normal concrete and the variation of the reactivity of sandstone, the safe replacement level of fly ash is suggested to be no less than 35%.（3） There is no remarkable relationship between any chemical composition of fly ash and the suppressing effect on ASR. As the criteria for selecting proper fly ash source, the chemical index C_FA is more reasonable than the CaO content or alkali content. The formula of C_FA is:If C_FA is below 0.40, the fly ash at 30% replacement level can effectively inhibit the ASR of sandstone used in the Jinping-ⅠHydroelectric Project, and if C_FA is above 0.40, more fly ash would be needed.At 30% replacement level, there is no remarkable relationship between mineralogical composition of fly ash and the suppressing effect on ASR. Replacing the SiO₂ and Al₂O₃ content in C_FA by amorphous SiO₂ and amorphous Al₂O₃ content didn’t increase the relativity.The fineness of fly ash influences the suppressing effect on ASR, but not as obviously as C_FA. The physical-chemical index C made up of C_FA and specific surface area can reflect the influence of physical and chemical quantities of fly ash on suppressing effect on ASR. The formula of C_FA is:（4） Fly ash would be terriblely activated in 80℃, 1mol/L NaOH and saturated Ca（OH）₂ solutions so that the suppressing effect on ASR tested by AMBT was much better than the effect tested by ACPT.Most compositions of fly ash could dissolved except mullite which makes up about 20% of total fly ash by weight, this phenomenon can explain why the influence of chemical compositions is bigger than that of mineralogical compositions.The main productions of fly ash in hot alkaline solution are P zeolite and C-S-H gel. P zeolite is beneficial to suppressing ASR. C-S-H gel can improve the strength of mortar, but no influence on ASR.（5） If reactive aggregate is used in dam concrete, the reactive stone powder brought in with fine aggregate and the air bubbles entrained by AEA will reduce ASR expansion greatly. The overall effect of these self-immunity mechanisms of dam concrete is the reduction of ASR expansion by 40% to 80%. So ASR expansion in real dam concrete structures is not as serious as observed in standard tests.（6） Ground lithium slag can efficiently suppress ASR, but it will cause early expansion of mortar or concrete, this expansion should be separated when testing the suppressing effect. Composite powder can effectively inhibit the expansion due to ASR at 30% or more replacement level. HLC-ASW type superplasticizer can reduce about 20% of expansion due to ASR, which is much better than normal naphthalene type superplasticizers.更多还原